- Email: [email protected]
Peritonitis, as a Result of a Retrograde Postoperative Incisional Infection
Accepted Manuscript Case report: Peritonitis, as a result of a retrograde postoperative incisional infection Christine T. Lopp, DVM, Cathleen A. Mochal-King, DVM, MS, DACVS
PII:
S0737-0806(15)00489-X
DOI:
10.1016/j.jevs.2015.07.017
Reference:
YJEVS 1921
To appear in:
Journal of Equine Veterinary Science
Received Date: 16 May 2015 Revised Date:
17 July 2015
Accepted Date: 24 July 2015
Please cite this article as: Lopp CT, Mochal-King CA, Case report: Peritonitis, as a result of a retrograde postoperative incisional infection, Journal of Equine Veterinary Science (2015), doi: 10.1016/ j.jevs.2015.07.017. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Case report: Peritonitis, as a result of a retrograde postoperative incisional infection
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C. T. Lopp, DVM and C. A. Mochal-King, DVM, MS, DACVS
3 Christine T. Lopp, DVM, Department of Clinical Sciences, College of Veterinary Medicine, Mississippi
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State University, P.O. Box 6100, Mississippi State, MS 39762; Telephone: 336-944-1565; Fax: 662-
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325-0243; Email: [email protected]
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Cathleen A. Mochal-King, DVM, MS, DACVS, Department of Clinical Sciences, College of Veterinary
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Medicine, Mississippi State University, P.O. Box 6100, Mississippi State, MS 39762; Telephone: 662-
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325-1400; Fax: 662-325-0243; Email: [email protected]
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key words: incisional infection, peritonitis, medical maggot, cecum
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Corresponding author:
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Christine T. Lopp, DVM
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Department of Clinical Sciences
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College of Veterinary Medicine, Mississippi State University
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P.O. Box 6100, Mississippi State, MS 39762
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Telephone: 336-944-1565
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Fax: 662-325-0243
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Email: [email protected]
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ACCEPTED MANUSCRIPT Abstract:
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An eight-year-old Quarter horse x Walking horse cross mare was referred for treatment of septic
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pedal osteitis and subsequently developed a cecal impaction which was resolved surgically. Post-
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operative enteritis and incisional drainage developed in the short-term post-operative period.
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One month post-operatively, the mare developed an acute septic peritonitis with Streptococcus
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equi zooepidemicus that was likely a sequela to the incisional infection. Systemic antibiotic
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therapy and peritoneal lavage was instituted, however, repeated culture and sensitivity of the
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abdominal fluid revealed a multi-drug resistant Escherichia coli. In the face of antibiotic treatment
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failure, medical grade Phaenicia sericata larvae were placed into the abdomen to be used as a
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biological debriding agent. Clinical improvement was seen for 6 weeks, until the mare was
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euthanized due to a small intestinal strangulating lesion. Additionally, this case report is a
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description of the novel use of medical maggots in the treatment of a multi-drug resistant
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peritonitis in a horse.
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Case report: peritonitis, as a result of a retrograde postoperative incisional infection
1. Introduction: Septic peritonitis is a complication following abdominal surgery and
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typhylotomy in horses and typically results in polymicrobial sepsis, predominantly with gram negative enteric bacteria 1,2,3. The overall prevalence of septic peritonitis following colic surgery is reported to be 3.1% 3 to 11% 4. Wound complication rates following a single initial
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laparotomy vary from 7.4% 5 to as high as 37% 6, with higher rates of wound suppuration
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reported in horses that had caecal or large colon obstruction, enterotomy6,7, or post-
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operative peritonitis3. Abdominal contamination and peritonitis may lead to prolonged
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incisional drainage, however little evidence exists in the literature that supports septic
ACCEPTED MANUSCRIPT peritonitis as a result of a retrograde postoperative incisional infection. Formation of
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extraperitoneal incisional abscesses following colic surgery has been reported in 3 horses,
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however in these cases the abscesses invaded the rectus abdominis muscle and did not
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penetrate into the peritoneum8. This report describes the surgical and postsurgical
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management of an 8-year-old Quarter Horse x Walking horse cross mare which developed a
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septic peritonitis likely resulting from an ascending incisional infection. Additionally, this
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case report describes the novel, off-label use of medical grade maggots as a biological
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debriding agent in the treatment of a multidrug resistant peritonitis in a horse.
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2. Case Report
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2.1 History: An 8-year-old Quarter Horse x Walking horse cross mare initially presented for
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chronic septic pedal osteitis in the left forelimb and was treated with surgical debridement of
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the distal phalanx under general anesthesia. Perioperative antibiotics with cefazolin (11mg/kg
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bwt i.v, q8h)a and gentamicin (GentaFuse; 6.6 mg/kg bwt i.v.)b were given. Following recovery
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from anesthesia, the mare was maintained on flunixin meglumine (Banamine; 1.1 mg/kg bwt,
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i.v., q12h)c and lidocaine hydrochloride (Lidocaine 2% Inj; 0.05 mg/kg/min)d, and butorphanol
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(Torbugesic; 0.01-0.02 mg/kg bwt i.v. or i.m.)e was given as needed for additional analgesia. An
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intravenous regional limb perfusion was performed with cefazolin and morphine (Morphine
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Sulfate Injection)f at the time of surgery and then repeated 2 days later.
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Two days following her surgical debridement of P3, the mare was observed to show mild to
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moderate colic signs (decreased appetite, reduced fecal output, increased recumbency,
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inappetance, infrequent rolling) and was subsequently diagnosed with a cecal impaction on
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rectal palpation. The mare was initially treated with intravenous and enteral fluids, however
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due to unrelenting pain, surgical intervention was elected.
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2.2 Surgical procedure: Antimicrobial therapy with cefazolin and gentamicin was maintained.
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The patient was premedicated with xylazine (AnaSed; 1.1 mg/kg bwt i.v.)g and butorphanol.
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ACCEPTED MANUSCRIPT General anesthesia was induced with ketamine (Ketaset; 2.2 mg/kg bwt i.v.)h and
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diazepam(Diazepam injection; 0.05 mg/kg bwt i.v.)i, and maintained with isofluorane (Isoflurane;
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1.5-3%)j and oxygen(5 L/min). A routine 30 cm ventral midline celiotomy was performed which
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revealed a markedly enlarged cecum filled with hard ingesta. The cecal apex was exteriorized,
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isolated with laparotomy sponges, and draped with a sterile plastic sheet. A routine typhlotomy
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was performed. Ingesta was removed by lavaging the cecum with water administered using a
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nasogastric tube and bilge pump inserted through the typhlotomy site. The typhlotomy was
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closed with 2-0 Polydioxanone suture using a simple continuous pattern, which was oversewn
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with 2-0 polydioxanone in a Cushing pattern. The cecum was lavaged with sterile 0.9% saline
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solution, containing 500 mg Gentamicin/L and 5x10^6 IU potassium penicillin (PfizerPen) k, prior
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to being replaced into the abdomen. The surgeons replaced gowns and gloves, re-draped the
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surgical field, and lavaged the abdomen with 5 L sterile 0.9% saline solution which was removed
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by suction. Gross contamination during or after the typhlotomy was not appreciated and
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therefore abdominal drains were not deemed necessary. A final liter of sterile 0.9% saline
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solution containing 500 mg gentamicin/L and 5x10^6 IU potassium penicillin was left in the
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abdomen. The linea alba was sutured with No. 3 Polygalactin 910 in 3 segments using a simple
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continuous pattern and the subcutaneous tissue was apposed with 2-0 Polydioxanone suture
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using a simple continuous suture pattern. The skin was apposed with stainless steel staples. The
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incision was protected during recovery by the placement of an adherent absorbent dressing
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(Telfa pad). After recovery, a clean belly bandage, consisting of sterile cotton padding held in
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place with adhesive bandage material (elastikon), was placed to protect the incision site from
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external contamination.
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2.3 Postoperative course: Recovery from anesthesia was uneventful and post-operative
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antibiotic therapy was continued with cefazolin (11 mg/kg bwt i.v., q8h) and gentamicin (6.6
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mg/kg bwt i.v., q24h) in the immediate post-operative period, however 48 hours after surgery,
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the patient developed anterior enteritis, as evidenced by an elevated temperature (103.4°F),
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ACCEPTED MANUSCRIPT moderate signs of endotoxemia, significant volumes of serosanguinous nasogastric reflux, and
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segmental intramural edema and thickening of the small intestine (4.5-9 mm) (Image 1 and
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Image 2). The horse was treated with continuous infusion i.v. of balanced polyionic fluids,
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lidocaine hydrochloride (0.05 mg/kg/min), metoclopramide (Metoclopramide; 0.04 mg/kg/hr)l ,
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and partial parenteral nutrition (lactated ringers solution containing 500mL of 50% dextrose, and
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500 mL of aminosyn (Aminosyn II 10%) m) at 0.5-1 L/hr, for 4.5 days. Polymyxin B (Polymyxin B
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for injection; 5000 u/kg bwt i.v., q8h) n and sodium heparin (Heparin; 40 u/kg bwt sub cut., q8h)o
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were administered for 2 days. Enrofloxacin (Baytril 100; 7.5 mg/kg bwt i.v., q24h) p was
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administered for 5 days for treatment of anterior enteritis. Nasogastric reflux ceased after 48
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hours of enrofloxacin therapy.
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Incisional drainage was noted 5 days after the celiotomy (Image 3) at which point the skin
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staples around the points of suppuration were removed to facilitate drainage and a hernia belt
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with sterile cotton padding adjacent to the incision was placed to allow for daily bandage
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changes. Incisional ultrasound showed a hypoechoic area in the subcutaneous tissues at the
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cranial aspect (2 cm caudal to the cranial extent of the incision) and at the middle aspect of the
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incision (4 cm caudal to the caudal draining site). Palpation of the incision with sterile gloves
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revealed no defect in the abdominal wall, however through palpation of the cranial half of the
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incision purulent material could be expressed from the drainage sites. Enrofloxacin was
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discontinued after 5 days of treatment. Chloramphenicol (Viceton)q, (Chloramphenicol
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Palmitate oral suspension; 50 mg/kg bwt per os, q8h) r administration was initiated after
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discontinuing enrofloxacin. Chloramphenicol was selected due to the culture and sensitivity
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patterns of the Streptococcus uberis from her pedal osteitis with a sensitivity of less than 4
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mcg/mL. Chloramphenicol treatment was continued for an additional 20 days to treat the
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incisional drainage as well as the pedal osteitis.
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ACCEPTED MANUSCRIPT For a period of 4 weeks, the horse showed clinical signs of improvement and could have been
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discharged to the care of her owners, however, she remained at the hospital for boarding during
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her period of post-operative stall confinement. The area of solar debridement over P3 showed
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progression of healthy granulation tissue and solar cornification, and the patient’s lameness
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(grade 3/5) was not noticeable at the walk. The abdominal incision site continued to drain a
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moderate amount of slightly yellow-tinged purulent fluid until day 25 post celiotomy, at which
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point the incisional drainage abruptly lessened until it was essentially 2 small spots seen on the
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belly bandage over a 2-3 days period.
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At 31 days post laparotomy, the patient acutely developed signs of severe septic peritonitis
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(temperature 106, and HR 120 bpm), depression, had mild ataxia and muscle weakness, and was
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hesitant to walk. Nasogastric intubation yielded 10 L net reflux, and abdominal ultrasound
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revealed a mild amount of free peritoneal fluid. An abdominocentesis was aseptically
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performed approximately 10 cm to the left of midline, using a (10 inch) bitch catheter, to avoid
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potential contamination from the incision and to minimize the risk of enterocentesis in case the
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cecum had formed an adhesion on midline. Grossly purulent fluid, with a nucleated cell count of
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125,750 cells/uL, was obtained in a steady stream from a depth of approximately 8 inches and
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cultured a pure growth of Streptococcus equi zooepidemicus.
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The horse was administered 1000 mg prednisolone sodium succinate(Solu-Delt-Cortef)s i.v. and
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7.2% saline solution (2 ml/kg bwt i.v.) followed by continuous infusion i.v. of balanced polyionic
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fluids, lidocaine hydrochloride (0.05 mg/kg/min), metoclopramide (0.04 mg/kg/hr), and partial
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parenteral nutrition (lactated ringers solution containing 500mL of 50% dextrose, and 500 mL of
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aminosyn) at 0.5-1 L/hr, for 4 days. Polymyxin B (5000 u/kg bwt i.v., q8h) was administered for 2
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days. Potassium penicillin (22000 u/kg bwt i.v., q6h) and gentamicin (6.6 mg/kg bwt i.v., q24h)
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were administered for 14 days.
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ACCEPTED MANUSCRIPT Inadequate clinical progress was made over the first 2 days of treating the peritonitis closed
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(persistent fevers, elevated heart rate, and progressive abdominal distention), therefore a left
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flank laparotomy was made and two ventral abdominal drains were placed to facilitate
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peritoneal lavage. The abdomen was lavaged daily with 10 L balanced polyionic fluids containing
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potassium penicillin and heparin. Abdominal fluid was sampled from the drains daily and
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evaluated for clinical improvement until day 5 when the patient’s cell count improved at which
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time the drains were removed. Following removal of the drains, the horse’s condition plateaued
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and then started to decline steadily with increasing amounts of abdominal fluid distention and
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development of cyclic fevers. Two days following drain removal, abdominocentesis was
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repeated (Day 40) and submitted for culture. Culture revealed Escherichia coli, which showed
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marked resistance to multiple antibiotics, with the exception of tetracycline. The antimicrobial
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treatment of potassium penicillin and gentamicin was discontinued at this time and
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oxytetracycline therapy was initiated due to the sensitivity results. A 6.6 mg/kg bwt i.v., q12h
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dose of oxytetracycline was chosen initially to try to minimize the rapid die-off of gram-negative
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bacteria and thus hope to reduce the amount of endotoxin released. The mare was pretreated
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with polymyxin B (5000 u/kg bwt i.v., q8h) to help bind and inactivate endotoxins predicted to
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be released following the initiation of oxytetracycline (Liquamycin, LA-200) t.
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Despite the low dose oxytetracycline and pretreatment with polymyxin B, a 24-48 hours period
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of endotoxemia was encountered which caused a transient period of ileus (lack of auscultable
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gastrointestinal borborygmi and mild to moderate nasogastric reflux) and also resulted in
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rotational deviation of P3 from the dorsal hoof wall on her left front foot (the same foot affected
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with pedal osteitis). After 3 days of low dose oxytetracycline, the endotoxemia seemed to have
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resolved, however the patient’s abdomen became further distended with peritoneal fluid and
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the cyclic fevers were no longer regressing. The oxytetracycline dose was increased (10 mg/kg
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bwt i.v., q12h) which resulted in initial improvement (reduction in fevers and less abdominal
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fluid), however, after the second dose, the mare developed watery diarrhea, and the dose was
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ACCEPTED MANUSCRIPT reduced back to the 6.6 mg/kg bwt i.v., q12h. Weight loss during this time period was estimated
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to be about 80 kg, and bloodwork revealed an anemia of chronic disease.
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The mare was moved into an isolation stall due to her multi-drug resistant infection, which
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limited her progressive monitoring with the ultrasound. Ultrasound evaluation of the abdomen
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during this time frame revealed the progression of a 4-7 mm thickness fibrin layer coating the
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serosal surface of the abdominal organs diffusely (Image 4). Given the mare’s static response to
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oxytetracycline, profound antimicrobial resistance of the E.coli, and the marked fibrin formation
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visible on ultrasound, a novel form of treatment was sought to reduce bacterial load and reduce
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fibrin adhesion formation.
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On day 56 post-celiotomy, the most cranial and dependent abdominal drain was replaced and
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the abdomen was lavaged with 5L LRS and allowed to empty by gravity. Approximately 3000
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disinfected Phaenicia sericata larvae (Medical Maggots) u were introduced into the abdomen via
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the abdominal drain and the drain was removed (Image 5). A belly bandage was placed over the
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open drain site with porous materials to allow a vent for oxygen passage into the abdomen as
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well as a portal for maggot self-extraction.
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24 hours after the first application of medical maggots into the abdomen, the mare had her first
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24 hour period without a fever since the initial onset of peritonitis. Incidentally, there was a
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dramatic increase in the number of flies in the mare’s isolated/completely enclosed stall, and
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when the abdominal lavage was repeated 4 days later, no maggots were recovered. Ultrasound
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evaluation revealed marked reduction in the fibrin layer in a 10 cm radius from the site of
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maggot introduction (Image 6), however, areas more remote to the drain portal continued to
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show fibrinous adhesion formation. Cytology results indicated marked reduction in inflammatory
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response, with a decrease in nucleated cell count from 186,000/uL to 1400/uL.
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ACCEPTED MANUSCRIPT Serial abdominal ultrasonography revealed progression and consolidation of an abscess capsule
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visible on the right ventral abdomen that extended caudodorsally toward the base of the cecum
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and craniomedially toward the ventral midline incision (Image 7). A second application of
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medical maggots was performed on day 87, through a new portal placed directly into the
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abscess in the right ventral flank region. Repeated ultrasound indicated reduction in the size of
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the abscess where the maggots had been inserted (Image 8).
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The patient continued to improve clinically, with resolution of fevers, improved appetite, and
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weight gain. After approximately 4 weeks on intravenous oxytetracycline, perivascular irritation
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necessitated a switch from intravenous to oral medications thus oxytetracycline was
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discontinued and doxycycline (Doxycycline powder; 10 mg/kg bwt per os, q12h)v was initiated.
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The mare continued to do well for 2 weeks until she became acutely and severely colicky. Rectal
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examination, in conjunction with ultrasonography was highly suggestive of a strangulating small
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intestinal lesion. Repeat laparotomy was declined by the owner and the mare was euthanized
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on day 98, due to unrelenting pain.
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2.4 Post mortem findings: Necropsy revealed strangulation/incarceration of approximately 8
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feet of distal jejunum by a fibrous band of adhesions in the left inguinal region. The necropsy
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also revealed a very well defined fibrous capsule of the abdominal abscess tracking from the
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cranial aspect of the ventral midline incision up into the abdomen and wrapping caudally
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towards the body of the cecum (Image 9). Upon further evaluation of the abscess, no purulent
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material was present. The typhlotomy site was not involved in the abscess and there was no
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evidence of eosinophilic granulomatous inflammation or residual maggots within the abdomen
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at necropsy.
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ACCEPTED MANUSCRIPT 3. Discussion:
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Cecal impactions are a serious and not infrequent complication of patients hospitalized with
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musculoskeletal disease9,10,11, and can rapidly result in cecal rupture despite medical
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management2,11,12. Surgical intervention has a reported short-term survival rate of 82%9 to
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95%11, which is greater than or comparable to that of medical management9,11, however surgery
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involving cecal disorders have been associated with increased incidence of peritonitis and
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incisional suppuration6,13,14 likely due to direct trauma to the incisional tissue during
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manipulation and the anatomic positioning of the cecum often results in the typhlotomy being
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mere inches from the abdominal incision, making contamination highly likely.
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Surgical site infection is a common and important complication that occurs in 7.4%5 to 37%6 of
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horses undergoing abdominal surgery for acute gastrointestinal disease, with the two most
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common sources of contamination being flora of the gastrointestinal tract or superficial
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contamination of the wound from skin bacteria or environmental contaminants13. Suggested
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risk factors include use of polyglactin 910 to close the linea alba, trauma to the incisional edges,
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endotoxemia on admission, contamination with intestinal content during surgery, repeat
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celiotomy, and poor anesthetic recovery. Reported sequelae to incisional drainage is herniation,
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incisional dehiscence, and evisceration15,16.
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Reported causes of postoperative peritonitis include intestinal infarction and necrosis of a
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segment of the gastrointestinal tract before or after surgical intervention, contamination during
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surgery, or leakage from the anastomosis or enterotomy site17,18. The most common reported
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pathogens isolated from horses with peritonitis include E. coli, Staphylococcus, Streptococcus,
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Rhodococcus, Bacteroides, Clostridium, and Fusobacterium spp18.
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While many of the same risk factors and bacterial isolates seem to be shared between peritonitis
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and incisional infection, there is lack of evidence in previous literature to support a causal
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ACCEPTED MANUSCRIPT relationship between these two conditions15. In this case report, the acuteness and severity of
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the onset of clinical signs of septic peritonitis combined with the pure growth of Streptococcus
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equi zooepidemicus, a common commensal organism of the equine epidermis, led to suspicions
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that this case of peritonitis had resulted from an ascending incisional infection and internal
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abscess formation that had subsequently ruptured internally once the external drainage tracts
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had sealed over with granulation tissue. This explanation seems supported by the post mortem
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finding of the abscess track that was directly leading from the incision site. It is speculated that
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the incisional drainage may have communicated with an extraperitoneal incisional abscess,
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similar to the cases reported by Rubio Martinez et al,8 which, when the granulation tissue had
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sealed the drainage spots, built up pressure enough to break through the peritoneum and
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disseminate into the abdomen. To the authors’ knowledge this is the first reported case of an
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ascending incisional infection documented as causing a septic peritonitis in a horse.
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Serial ultrasound evaluation of the abdomen during the treatment of peritonitis in this horse
254
revealed the progression of a fibrin layer coating the serosal surface of the abdominal organs
255
diffusely. Given the patient’s static response to oxytetracycline, marked antimicrobial resistance
256
of the E.coli, and the marked fibrin on ultrasound, a novel form of treatment was sought to
257
reduce bacterial load and reduce fibrin adhesion formation.
258
Up until the 1940’s maggot therapy was used commonly by human surgeons for controlling soft
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tissue infections and as an adjunct to surgical resection for osteomyelitis. The advent of modern
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antibiotics and improved surgical techniques drastically reduced the use of these “tiny
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surgeons”, but they are still FDA approved for the debridement of non-healing necrotic skin and
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soft tissue wounds. Due to their seemingly distasteful nature of consuming necrotic tissue,
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fibrin, and bacteria, medical maggots seem to have become reserved for treatment of wounds
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that are not responsive to conventional treatment or that have multi-drug resistant bacterial
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infections. As part of their role as debriding agents, maggots secrete potent proteolytic enzymes
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ACCEPTED MANUSCRIPT that have significant anti-microbial activity against bacteria such as Staphylococcus,
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Streptococcus, Pseudomonas, and Escherichia coli, causing breakdown of biofilm formation and
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making the wound environment unsuitable for bacterial colonization19,20.
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In human medicine, medical maggots are most commonly used on pressure sores, venous ulcers,
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neuropathic foot ulcers, and non-healing traumatic or postsurgical wounds, however reported
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off-label applications include the use of maggots to debride areas in the pleural and peritoneal
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spaces21. In equine medicine, medical maggots are most often used in conjunction with surgical
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debridement as a non-traumatic, minimally invasive means of removing necrotic tissue from an
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extensive foot infection involving deeper structures of the foot such as the coffin bone, collateral
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cartilages, distal interphalangeal joint, and navicular bursa20,22. Other more rare case reports of
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their use include debridement of necrotic tissues in cases of supraspinus bursitis, abdominal
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wound dehiscence, chronic infected leg wounds, soft tissue abscesses, and one case with a
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MRSA infection over an internal fixation device used to stabilize a fracture20. To the authors’
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knowledge, no literature exists documenting the use of medical maggots within a body cavity of
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a horse. After consultation with Monarch Labs, it was decided to use a dose of 3000 maggots,
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the same dose that had been used in the cases of human peritonitis and pleuritis. The usual
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dose of disinfected larvae is 5-10 maggots per square cm of wound surface area; however
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consultation with the laboratory revealed that doses of 16000 maggots had been reported to
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cause myiasis and hepatic encephalopathy in sheep, and thus maximal doses of 6000 larvae per
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application cycle were recommended.
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The risks associated with use of medical maggots are not well reported due to limited use,
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however, one must consider the potential risks of the treatment such as myiasis, eosinophilic
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granulomatous reaction, failure of the maggots to survive and grow within the abdomen,
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inadequate debridement of the fibrinous material dispersed throughout the abdomen, and
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failure to recover all maggots from the abdominal cavity at the end of the treatment cycle. A
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ACCEPTED MANUSCRIPT relatively conservative dose of Phaenicia sericata larvae was used to minimize the risk of myiasis
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and degree of eosinophilic inflammation. At necropsy, no evidence of inappropriate tissue
293
consumption or eosinophilic response was seen. In this case report, no maggots were recovered
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from the abdominal lavage 5 days after application, which raises concern about failure of the
295
maggots to survive within the abdominal cavity or loss of maggots within the abdomen. After
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consultation with Monarch Labs, it was decided to leave the ventral drain portal open as a vent
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to allow oxygen access for the Phaenicia sericata larvae and also to act as a portal for self-
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extraction once the larvae were satiated, as is in accordance with their natural life cycle. This is
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similar to how the medical maggot treatments were carried out in human thoracic and
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peritoneal cavities and was thought to be appropriate for larvae placement within the equine
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peritoneal cavity. It is possible that the larvae died upon instillation into the abdominal cavity
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and their bodies were resorbed, however, the lack of eosinophilic granulomatous reaction at
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necropsy does not suggest this. At the time of maggot implantation, the mare was being housed
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in a completely confined concrete isolation building with controlled airflow into and out of the
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stall. For the week following administration of the Phaenicia sericata larvae, there was an
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exponential increase in the number of flies within the stall which could not be accounted for by
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external migration alone. The other option for maggot administration is to apply the maggots
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into the body cavity while still contained within a porous fabric bag (Biobag System). This allows
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debridement via proteolytic enzyme secretion, but greatly limits the phagocytosis of fibrinous
310
material and the ability of the larvae to migrate to more confined areas of contamination. The
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benefit of application of maggots within a porous bag would be that it assures that there will be
312
no loss of larvae within the cavity and might have also been a way to quantify larval survival
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within the abdomen. However, larval bag placement was deemed less appropriate for this case
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because it was felt that the bagged larvae would be less efficacious in debridement of the entire
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abdomen, the bag might act as an irritant to cause more serosal adhesion formation, and would
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also require a more invasive surgical procedure for retrieval. It is entirely plausible that the
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ACCEPTED MANUSCRIPT improvement in the mare’s clinical status was due to the treatment with prolonged tetracycline
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administration, however, the decision to add maggot therapy was made in response to a
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suspected treatment failure at the low dose oxytetracycline (further peritoneal fluid distension
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and cyclic fevers) and intolerance of the higher dose of oxytetracycline (diarrhea). The authors
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feel confident in saying that the maggots caused no harm and likely contributed positively to the
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treatment of the peritonitis if only by facilitating the continued treatment with low dose
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oxytetracycline.
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Subjectively, the authors feel that the use of medical maggots as a debriding agent was
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efficacious in reducing fibrinous adhesions in the immediate area of application; however, the
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maggots did not migrate as far from the site of administration as was hoped. It is speculated
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that a greater surface area might have been able to be debrided by either using a larger dose
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(6000 maggots) or by administering smaller doses of maggots at multiple sites around the
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abdomen. It is also speculated that earlier administration of the medical maggots may have
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improved their efficacy, as the fibrinous adhesions would have been less well established. No
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deleterious effects were seen as a result of either maggot application, but further studies are
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warranted to determine an appropriate dose and administration distribution, and expected
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efficacy of intraperitoneal maggot debridement therapy.
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Manufacturers’ addresses:
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a SAGENT Pharmaceuticals, Inc., Schaumburg, Illinois, USA
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b Sparhawk Laboratories, Inc., Lenexa, Kansas, USA
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c Intervet Inc., Merck & Co. Inc. Whitehouse Station, New Jersey, USA
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d Hospira, Inc, Lake Forest, Illinois, USA
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e Fort Dodge Animal Health, a division of Wyeth, Pfizer Inc, New York, New York, USA
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f West-Ward, Eatontown, New Jersey, USA
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g Akorn, Inc., Decatur, Illinois, USA
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ACCEPTED MANUSCRIPT h Boehringer Ingelheim Vetmedica, Inc., St. Joseph, MO, USA
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i Hospira, Inc., Lake Forest, Illinois, USA
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j Piramal Healthcare Limited, Digwal Village, Andhra Pradesh, India
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k Roerig, division of Pfizer, Inc., New York, New York, USA,
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l Teva Parenteral Medications, Inc, Irvine, California, USA
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m Hospira, Inc, Lake Forest, Illinois, USA
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n X-GEN Pharmaceuticals Inc., Big Flats, New York, USA
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o SAGENT Pharmaceuticals, Inc, Schaumburg, Illinois, USA
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p Bayer Healthcare LLC, Animal Health Division, Shawnee Mission, Kansas, USA
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q Bimeda, Inc, Le sueur, Minnesota, USA
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r Wedgewood Pharmacy, Swedesboro, New Jersey, USA
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s Pharmacia & Upjohn Co., Division of Pfizer Inc, New York, New York, USA
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t Zoetis Inc, Kalamazoo, Michigan, USA
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u Monarch Labs, Irvine, California, USA
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v Wedgewood Pharmacy, Swedesboro, New Jersey, USA
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Image Legend:
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Image 1 and Image 2: (day 3 post-celiotomy) This longitudinal image of a small intestinal loop,
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located in the left ventral flank region, demonstrates a wall that is thickened and edematous,
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consistent with anterior enteritis. Note there is scant amount of free peritoneal fluid and the serosal
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surfaces of the intestine appear smooth.
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Image 3: (day 8) Copious drainage soaking through the belly bandage from draining sites at the
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cranial (black arrow) and middle (blue arrow) aspects of the incision line. Digital pressure on the
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incision line caudal to the draining sites resulted in expression of approximately 10 mL of purulent
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material. The incision site was cleaned daily with 4% chlorhexidine and saline and the belly bandage
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changed daily.
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surfaces of the small intestine and body wall in the left ventral abdomen.
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Image 5: (day 56) Approximately 3000 medical grade maggots were instilled into the abdomen via
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the left ventral abdominal drain portals.
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Image 6: (day 81) Left ventral abdomen at the site of the cranial drain portal, 25 days after the first
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medical maggot therapy. There is a mild amount of free peritoneal fluid, but the fibrin lining the
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intestine is no longer identifiable.
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Image 7: (day 87) Encapsulated abscess in the right ventral flank region between the body wall and
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cecum. This window was used for the site of the second medical maggot application.
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Image 8: (day 96) Right ventral flank portal site, 7 days after the second application of medical
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maggots.
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Image 9: Necropsy revealed a well-defined abdominal abscess that tracked from the cranial aspect of
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the ventral midline incision (arrow) up into the abdomen and wrapped caudally towards the body of
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the cecum. Note the body is in left lateral recumbency.
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[1] Hawkins JK, Bowman KF, Roberts M. Peritonitis in horses. J Am Vet Med Assoc 1993; 203:284
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[2] Smith LCR, Payne RJ, Boys Smith SJ, Bathe AP, and Greet TRC. Outcome and long-term follow-up
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of 20 horses undergoing surgery for caecal impaction: A retrospective study (2000-2008). Equine
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Vet J. 2010; 42: 388-392.
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[3] Mair TS1, Smith LJ. Survival and complication rates in 300 horses undergoing surgical treatment
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of colic. Part 2: Short-term complications. Equine Vet J. 2005; 37(4):303-9.
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ACCEPTED MANUSCRIPT [4] Driscoll, N., Baia, P., Fischer, A. T., Brauer, T. and Klohnen, A. Large colon resection and
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anastomosis in horses: 52 cases (1996–2006). Equine Veterinary Journal 2008; 40: 342–347
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[5] Freeman, D.E., Hammock, P., Baker, G.J., Foreman, J.H., Schaeffer, D.J., Richter, R.-A., Inoue, O.,
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and Magid, J.H. Short- and long-term survival and prevalence of post operative ileus after small
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intestinal surgery in the horse. Equine vet. J., Suppl. 2000; 32, 42-51
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[6] Phillips, T.J. and Walmsley, J.P. Retrospective analysis of the results of 151 exploratory
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laparotomies in horses with gastrointestinal disease. Equine vet. J. 1993; 25, 427-431
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[7] Honnas, C.M. and Cohen, N.D. Risk factors for wound infection following celiotomy in horses. J.
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am. vet. med. Ass. 1997; 2100, 78-81
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[8] Rubio Martinez L.M., Cribb N.C., and Koenig J.B. Extraperitoneal incisional abscess formation
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after colic surgery in 3 horses. Equine Vet. Educ. 2012; 24, 109-115
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[9] Aitken, M.R., Southwood, L.L., Ross, B.M., and Ross, M.W. Outcome of surgical and medical
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management of cecal impaction in 150 horses (1991-2011). Vet Surg. 2014; doi: 10.1111/j.1532-
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950X.2014.12286.x
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[10] Roberts, C.T., and Slone, D.E. Caecal impactions managed surgically by typhlotomy in 10 cases
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(1988-1998). Equine vet. J., Suppl. 2000; (32) 74-76
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[11] Plummer A.E., Rakestraw P.C., Hardy J., and Lee R.M. Outcome of medical and surgical
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treatment of cecal impaction in horses: 114 cases (1994-2004). JAVMA. 2007; 231, 1378-1385
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[12] Dart A.J., Dowling B.A., and Hudgson D.R. Cecal disease. Equine vet. Educ. 1999; 11, 182-188
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[13] Ingle-Fehr J.E., Baxter G.M., Howard R.D., Trotter G.W., and Stashak T.S. Bacterial Culturing of
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Ventral Median Celiotomies for Prediction of Postoperative Incisional complications in Horses. Vet.
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Surg. 1997; 26, 7-13
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ACCEPTED MANUSCRIPT [14] Kobluk CN, Ducharme NG, Lumsden JH, et al. Factors affecting incisional complication rates
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associated with colic surgery in horses: 78 cases (1983-1985). J Am Vet Med Assoc 1989; 195:639-
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642
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[15] Freeman D.E., Rotting A.K., and Inoue O.J. Abdominal Closure and Complications. Clinical
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Techniques in Equine Practice. 2002; 1, 174-187
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[16] French N.P., Smith J., Edwards G.B., and Proudman C.J. Equine surgical colic: risk factors for
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postoperative complications. Equine vet. J. 2002; 34, 444-449
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[17] Hillyer M.H., Wright C.J. Peritonitis in the horse. Equine vet. Educ. 1997; 9, 136-142
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[18] Hardy J., Rakestraw P.C. Postoperative Management for Colics. Clinical Techniques in Equine
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Practice. 2002; 1, 188-197
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[19] Jones G., Wall R. Maggot-therapy in veterinary medicine. Research in veterinary Science. 2008;
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85, 394-398
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[20] Lepage O.M., Doumbia A., Perron-Lepage M.F., and Gangl M. The use of maggot debridement
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therapy in 41 equids. Equine vet. J. 2012; 44, 120-125
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[21] Sherman R.A., Shapiro C.E., Yang R.M. Maggot Therapy for Problematic Wounds: Uncommon
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and Off-label Applications. Advances in Skin & Wound Care. 2007; 20, 602-610
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[22] Morrison S.E. How to Use Sterile Maggot Debridement Therapy for Foot Infections of the Horse.
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Proc. Am. Ass. equine Practnrs. 2005; 51, 461-464
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We describe the potential progression of a ventral midline suppurative incisional wound into a septic peritonitis We describe the novel use of medical grade Phaenicia sericata larvae in the treatment of a multi-drug resistant peritonitis in a horse Medical grade Phaenicia sericata larvae caused no ill effects when placed into the peritoneal cavity
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PII:
S0737-0806(15)00489-X
DOI:
10.1016/j.jevs.2015.07.017
Reference:
YJEVS 1921
To appear in:
Journal of Equine Veterinary Science
Received Date: 16 May 2015 Revised Date:
17 July 2015
Accepted Date: 24 July 2015
Please cite this article as: Lopp CT, Mochal-King CA, Case report: Peritonitis, as a result of a retrograde postoperative incisional infection, Journal of Equine Veterinary Science (2015), doi: 10.1016/ j.jevs.2015.07.017. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Case report: Peritonitis, as a result of a retrograde postoperative incisional infection
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C. T. Lopp, DVM and C. A. Mochal-King, DVM, MS, DACVS
3 Christine T. Lopp, DVM, Department of Clinical Sciences, College of Veterinary Medicine, Mississippi
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State University, P.O. Box 6100, Mississippi State, MS 39762; Telephone: 336-944-1565; Fax: 662-
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325-0243; Email: [email protected]
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Cathleen A. Mochal-King, DVM, MS, DACVS, Department of Clinical Sciences, College of Veterinary
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Medicine, Mississippi State University, P.O. Box 6100, Mississippi State, MS 39762; Telephone: 662-
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325-1400; Fax: 662-325-0243; Email: [email protected]
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key words: incisional infection, peritonitis, medical maggot, cecum
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Corresponding author:
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Christine T. Lopp, DVM
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Department of Clinical Sciences
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College of Veterinary Medicine, Mississippi State University
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P.O. Box 6100, Mississippi State, MS 39762
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Telephone: 336-944-1565
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Fax: 662-325-0243
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Email: [email protected]
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ACCEPTED MANUSCRIPT Abstract:
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An eight-year-old Quarter horse x Walking horse cross mare was referred for treatment of septic
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pedal osteitis and subsequently developed a cecal impaction which was resolved surgically. Post-
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operative enteritis and incisional drainage developed in the short-term post-operative period.
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One month post-operatively, the mare developed an acute septic peritonitis with Streptococcus
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equi zooepidemicus that was likely a sequela to the incisional infection. Systemic antibiotic
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therapy and peritoneal lavage was instituted, however, repeated culture and sensitivity of the
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abdominal fluid revealed a multi-drug resistant Escherichia coli. In the face of antibiotic treatment
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failure, medical grade Phaenicia sericata larvae were placed into the abdomen to be used as a
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biological debriding agent. Clinical improvement was seen for 6 weeks, until the mare was
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euthanized due to a small intestinal strangulating lesion. Additionally, this case report is a
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description of the novel use of medical maggots in the treatment of a multi-drug resistant
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peritonitis in a horse.
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Case report: peritonitis, as a result of a retrograde postoperative incisional infection
1. Introduction: Septic peritonitis is a complication following abdominal surgery and
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typhylotomy in horses and typically results in polymicrobial sepsis, predominantly with gram negative enteric bacteria 1,2,3. The overall prevalence of septic peritonitis following colic surgery is reported to be 3.1% 3 to 11% 4. Wound complication rates following a single initial
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laparotomy vary from 7.4% 5 to as high as 37% 6, with higher rates of wound suppuration
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reported in horses that had caecal or large colon obstruction, enterotomy6,7, or post-
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operative peritonitis3. Abdominal contamination and peritonitis may lead to prolonged
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incisional drainage, however little evidence exists in the literature that supports septic
ACCEPTED MANUSCRIPT peritonitis as a result of a retrograde postoperative incisional infection. Formation of
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extraperitoneal incisional abscesses following colic surgery has been reported in 3 horses,
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however in these cases the abscesses invaded the rectus abdominis muscle and did not
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penetrate into the peritoneum8. This report describes the surgical and postsurgical
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management of an 8-year-old Quarter Horse x Walking horse cross mare which developed a
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septic peritonitis likely resulting from an ascending incisional infection. Additionally, this
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case report describes the novel, off-label use of medical grade maggots as a biological
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debriding agent in the treatment of a multidrug resistant peritonitis in a horse.
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2. Case Report
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2.1 History: An 8-year-old Quarter Horse x Walking horse cross mare initially presented for
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chronic septic pedal osteitis in the left forelimb and was treated with surgical debridement of
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the distal phalanx under general anesthesia. Perioperative antibiotics with cefazolin (11mg/kg
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bwt i.v, q8h)a and gentamicin (GentaFuse; 6.6 mg/kg bwt i.v.)b were given. Following recovery
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from anesthesia, the mare was maintained on flunixin meglumine (Banamine; 1.1 mg/kg bwt,
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i.v., q12h)c and lidocaine hydrochloride (Lidocaine 2% Inj; 0.05 mg/kg/min)d, and butorphanol
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(Torbugesic; 0.01-0.02 mg/kg bwt i.v. or i.m.)e was given as needed for additional analgesia. An
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intravenous regional limb perfusion was performed with cefazolin and morphine (Morphine
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Sulfate Injection)f at the time of surgery and then repeated 2 days later.
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Two days following her surgical debridement of P3, the mare was observed to show mild to
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moderate colic signs (decreased appetite, reduced fecal output, increased recumbency,
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inappetance, infrequent rolling) and was subsequently diagnosed with a cecal impaction on
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rectal palpation. The mare was initially treated with intravenous and enteral fluids, however
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due to unrelenting pain, surgical intervention was elected.
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2.2 Surgical procedure: Antimicrobial therapy with cefazolin and gentamicin was maintained.
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The patient was premedicated with xylazine (AnaSed; 1.1 mg/kg bwt i.v.)g and butorphanol.
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ACCEPTED MANUSCRIPT General anesthesia was induced with ketamine (Ketaset; 2.2 mg/kg bwt i.v.)h and
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diazepam(Diazepam injection; 0.05 mg/kg bwt i.v.)i, and maintained with isofluorane (Isoflurane;
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1.5-3%)j and oxygen(5 L/min). A routine 30 cm ventral midline celiotomy was performed which
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revealed a markedly enlarged cecum filled with hard ingesta. The cecal apex was exteriorized,
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isolated with laparotomy sponges, and draped with a sterile plastic sheet. A routine typhlotomy
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was performed. Ingesta was removed by lavaging the cecum with water administered using a
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nasogastric tube and bilge pump inserted through the typhlotomy site. The typhlotomy was
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closed with 2-0 Polydioxanone suture using a simple continuous pattern, which was oversewn
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with 2-0 polydioxanone in a Cushing pattern. The cecum was lavaged with sterile 0.9% saline
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solution, containing 500 mg Gentamicin/L and 5x10^6 IU potassium penicillin (PfizerPen) k, prior
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to being replaced into the abdomen. The surgeons replaced gowns and gloves, re-draped the
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surgical field, and lavaged the abdomen with 5 L sterile 0.9% saline solution which was removed
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by suction. Gross contamination during or after the typhlotomy was not appreciated and
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therefore abdominal drains were not deemed necessary. A final liter of sterile 0.9% saline
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solution containing 500 mg gentamicin/L and 5x10^6 IU potassium penicillin was left in the
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abdomen. The linea alba was sutured with No. 3 Polygalactin 910 in 3 segments using a simple
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continuous pattern and the subcutaneous tissue was apposed with 2-0 Polydioxanone suture
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using a simple continuous suture pattern. The skin was apposed with stainless steel staples. The
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incision was protected during recovery by the placement of an adherent absorbent dressing
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(Telfa pad). After recovery, a clean belly bandage, consisting of sterile cotton padding held in
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place with adhesive bandage material (elastikon), was placed to protect the incision site from
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external contamination.
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2.3 Postoperative course: Recovery from anesthesia was uneventful and post-operative
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antibiotic therapy was continued with cefazolin (11 mg/kg bwt i.v., q8h) and gentamicin (6.6
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mg/kg bwt i.v., q24h) in the immediate post-operative period, however 48 hours after surgery,
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the patient developed anterior enteritis, as evidenced by an elevated temperature (103.4°F),
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ACCEPTED MANUSCRIPT moderate signs of endotoxemia, significant volumes of serosanguinous nasogastric reflux, and
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segmental intramural edema and thickening of the small intestine (4.5-9 mm) (Image 1 and
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Image 2). The horse was treated with continuous infusion i.v. of balanced polyionic fluids,
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lidocaine hydrochloride (0.05 mg/kg/min), metoclopramide (Metoclopramide; 0.04 mg/kg/hr)l ,
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and partial parenteral nutrition (lactated ringers solution containing 500mL of 50% dextrose, and
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500 mL of aminosyn (Aminosyn II 10%) m) at 0.5-1 L/hr, for 4.5 days. Polymyxin B (Polymyxin B
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for injection; 5000 u/kg bwt i.v., q8h) n and sodium heparin (Heparin; 40 u/kg bwt sub cut., q8h)o
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were administered for 2 days. Enrofloxacin (Baytril 100; 7.5 mg/kg bwt i.v., q24h) p was
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administered for 5 days for treatment of anterior enteritis. Nasogastric reflux ceased after 48
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hours of enrofloxacin therapy.
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Incisional drainage was noted 5 days after the celiotomy (Image 3) at which point the skin
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staples around the points of suppuration were removed to facilitate drainage and a hernia belt
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with sterile cotton padding adjacent to the incision was placed to allow for daily bandage
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changes. Incisional ultrasound showed a hypoechoic area in the subcutaneous tissues at the
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cranial aspect (2 cm caudal to the cranial extent of the incision) and at the middle aspect of the
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incision (4 cm caudal to the caudal draining site). Palpation of the incision with sterile gloves
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revealed no defect in the abdominal wall, however through palpation of the cranial half of the
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incision purulent material could be expressed from the drainage sites. Enrofloxacin was
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discontinued after 5 days of treatment. Chloramphenicol (Viceton)q, (Chloramphenicol
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Palmitate oral suspension; 50 mg/kg bwt per os, q8h) r administration was initiated after
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discontinuing enrofloxacin. Chloramphenicol was selected due to the culture and sensitivity
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patterns of the Streptococcus uberis from her pedal osteitis with a sensitivity of less than 4
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mcg/mL. Chloramphenicol treatment was continued for an additional 20 days to treat the
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incisional drainage as well as the pedal osteitis.
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ACCEPTED MANUSCRIPT For a period of 4 weeks, the horse showed clinical signs of improvement and could have been
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discharged to the care of her owners, however, she remained at the hospital for boarding during
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her period of post-operative stall confinement. The area of solar debridement over P3 showed
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progression of healthy granulation tissue and solar cornification, and the patient’s lameness
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(grade 3/5) was not noticeable at the walk. The abdominal incision site continued to drain a
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moderate amount of slightly yellow-tinged purulent fluid until day 25 post celiotomy, at which
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point the incisional drainage abruptly lessened until it was essentially 2 small spots seen on the
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belly bandage over a 2-3 days period.
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At 31 days post laparotomy, the patient acutely developed signs of severe septic peritonitis
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(temperature 106, and HR 120 bpm), depression, had mild ataxia and muscle weakness, and was
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hesitant to walk. Nasogastric intubation yielded 10 L net reflux, and abdominal ultrasound
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revealed a mild amount of free peritoneal fluid. An abdominocentesis was aseptically
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performed approximately 10 cm to the left of midline, using a (10 inch) bitch catheter, to avoid
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potential contamination from the incision and to minimize the risk of enterocentesis in case the
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cecum had formed an adhesion on midline. Grossly purulent fluid, with a nucleated cell count of
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125,750 cells/uL, was obtained in a steady stream from a depth of approximately 8 inches and
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cultured a pure growth of Streptococcus equi zooepidemicus.
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The horse was administered 1000 mg prednisolone sodium succinate(Solu-Delt-Cortef)s i.v. and
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7.2% saline solution (2 ml/kg bwt i.v.) followed by continuous infusion i.v. of balanced polyionic
139
fluids, lidocaine hydrochloride (0.05 mg/kg/min), metoclopramide (0.04 mg/kg/hr), and partial
140
parenteral nutrition (lactated ringers solution containing 500mL of 50% dextrose, and 500 mL of
141
aminosyn) at 0.5-1 L/hr, for 4 days. Polymyxin B (5000 u/kg bwt i.v., q8h) was administered for 2
142
days. Potassium penicillin (22000 u/kg bwt i.v., q6h) and gentamicin (6.6 mg/kg bwt i.v., q24h)
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were administered for 14 days.
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ACCEPTED MANUSCRIPT Inadequate clinical progress was made over the first 2 days of treating the peritonitis closed
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(persistent fevers, elevated heart rate, and progressive abdominal distention), therefore a left
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flank laparotomy was made and two ventral abdominal drains were placed to facilitate
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peritoneal lavage. The abdomen was lavaged daily with 10 L balanced polyionic fluids containing
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potassium penicillin and heparin. Abdominal fluid was sampled from the drains daily and
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evaluated for clinical improvement until day 5 when the patient’s cell count improved at which
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time the drains were removed. Following removal of the drains, the horse’s condition plateaued
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and then started to decline steadily with increasing amounts of abdominal fluid distention and
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development of cyclic fevers. Two days following drain removal, abdominocentesis was
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repeated (Day 40) and submitted for culture. Culture revealed Escherichia coli, which showed
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marked resistance to multiple antibiotics, with the exception of tetracycline. The antimicrobial
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treatment of potassium penicillin and gentamicin was discontinued at this time and
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oxytetracycline therapy was initiated due to the sensitivity results. A 6.6 mg/kg bwt i.v., q12h
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dose of oxytetracycline was chosen initially to try to minimize the rapid die-off of gram-negative
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bacteria and thus hope to reduce the amount of endotoxin released. The mare was pretreated
159
with polymyxin B (5000 u/kg bwt i.v., q8h) to help bind and inactivate endotoxins predicted to
160
be released following the initiation of oxytetracycline (Liquamycin, LA-200) t.
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Despite the low dose oxytetracycline and pretreatment with polymyxin B, a 24-48 hours period
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of endotoxemia was encountered which caused a transient period of ileus (lack of auscultable
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gastrointestinal borborygmi and mild to moderate nasogastric reflux) and also resulted in
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rotational deviation of P3 from the dorsal hoof wall on her left front foot (the same foot affected
165
with pedal osteitis). After 3 days of low dose oxytetracycline, the endotoxemia seemed to have
166
resolved, however the patient’s abdomen became further distended with peritoneal fluid and
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the cyclic fevers were no longer regressing. The oxytetracycline dose was increased (10 mg/kg
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bwt i.v., q12h) which resulted in initial improvement (reduction in fevers and less abdominal
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fluid), however, after the second dose, the mare developed watery diarrhea, and the dose was
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ACCEPTED MANUSCRIPT reduced back to the 6.6 mg/kg bwt i.v., q12h. Weight loss during this time period was estimated
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to be about 80 kg, and bloodwork revealed an anemia of chronic disease.
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The mare was moved into an isolation stall due to her multi-drug resistant infection, which
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limited her progressive monitoring with the ultrasound. Ultrasound evaluation of the abdomen
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during this time frame revealed the progression of a 4-7 mm thickness fibrin layer coating the
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serosal surface of the abdominal organs diffusely (Image 4). Given the mare’s static response to
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oxytetracycline, profound antimicrobial resistance of the E.coli, and the marked fibrin formation
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visible on ultrasound, a novel form of treatment was sought to reduce bacterial load and reduce
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fibrin adhesion formation.
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On day 56 post-celiotomy, the most cranial and dependent abdominal drain was replaced and
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the abdomen was lavaged with 5L LRS and allowed to empty by gravity. Approximately 3000
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disinfected Phaenicia sericata larvae (Medical Maggots) u were introduced into the abdomen via
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the abdominal drain and the drain was removed (Image 5). A belly bandage was placed over the
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open drain site with porous materials to allow a vent for oxygen passage into the abdomen as
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well as a portal for maggot self-extraction.
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24 hours after the first application of medical maggots into the abdomen, the mare had her first
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24 hour period without a fever since the initial onset of peritonitis. Incidentally, there was a
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dramatic increase in the number of flies in the mare’s isolated/completely enclosed stall, and
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when the abdominal lavage was repeated 4 days later, no maggots were recovered. Ultrasound
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evaluation revealed marked reduction in the fibrin layer in a 10 cm radius from the site of
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maggot introduction (Image 6), however, areas more remote to the drain portal continued to
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show fibrinous adhesion formation. Cytology results indicated marked reduction in inflammatory
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response, with a decrease in nucleated cell count from 186,000/uL to 1400/uL.
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ACCEPTED MANUSCRIPT Serial abdominal ultrasonography revealed progression and consolidation of an abscess capsule
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visible on the right ventral abdomen that extended caudodorsally toward the base of the cecum
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and craniomedially toward the ventral midline incision (Image 7). A second application of
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medical maggots was performed on day 87, through a new portal placed directly into the
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abscess in the right ventral flank region. Repeated ultrasound indicated reduction in the size of
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the abscess where the maggots had been inserted (Image 8).
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The patient continued to improve clinically, with resolution of fevers, improved appetite, and
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weight gain. After approximately 4 weeks on intravenous oxytetracycline, perivascular irritation
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necessitated a switch from intravenous to oral medications thus oxytetracycline was
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discontinued and doxycycline (Doxycycline powder; 10 mg/kg bwt per os, q12h)v was initiated.
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The mare continued to do well for 2 weeks until she became acutely and severely colicky. Rectal
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examination, in conjunction with ultrasonography was highly suggestive of a strangulating small
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intestinal lesion. Repeat laparotomy was declined by the owner and the mare was euthanized
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on day 98, due to unrelenting pain.
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2.4 Post mortem findings: Necropsy revealed strangulation/incarceration of approximately 8
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feet of distal jejunum by a fibrous band of adhesions in the left inguinal region. The necropsy
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also revealed a very well defined fibrous capsule of the abdominal abscess tracking from the
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cranial aspect of the ventral midline incision up into the abdomen and wrapping caudally
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towards the body of the cecum (Image 9). Upon further evaluation of the abscess, no purulent
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material was present. The typhlotomy site was not involved in the abscess and there was no
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evidence of eosinophilic granulomatous inflammation or residual maggots within the abdomen
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at necropsy.
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ACCEPTED MANUSCRIPT 3. Discussion:
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Cecal impactions are a serious and not infrequent complication of patients hospitalized with
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musculoskeletal disease9,10,11, and can rapidly result in cecal rupture despite medical
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management2,11,12. Surgical intervention has a reported short-term survival rate of 82%9 to
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95%11, which is greater than or comparable to that of medical management9,11, however surgery
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involving cecal disorders have been associated with increased incidence of peritonitis and
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incisional suppuration6,13,14 likely due to direct trauma to the incisional tissue during
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manipulation and the anatomic positioning of the cecum often results in the typhlotomy being
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mere inches from the abdominal incision, making contamination highly likely.
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Surgical site infection is a common and important complication that occurs in 7.4%5 to 37%6 of
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horses undergoing abdominal surgery for acute gastrointestinal disease, with the two most
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common sources of contamination being flora of the gastrointestinal tract or superficial
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contamination of the wound from skin bacteria or environmental contaminants13. Suggested
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risk factors include use of polyglactin 910 to close the linea alba, trauma to the incisional edges,
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endotoxemia on admission, contamination with intestinal content during surgery, repeat
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celiotomy, and poor anesthetic recovery. Reported sequelae to incisional drainage is herniation,
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incisional dehiscence, and evisceration15,16.
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Reported causes of postoperative peritonitis include intestinal infarction and necrosis of a
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segment of the gastrointestinal tract before or after surgical intervention, contamination during
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surgery, or leakage from the anastomosis or enterotomy site17,18. The most common reported
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pathogens isolated from horses with peritonitis include E. coli, Staphylococcus, Streptococcus,
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Rhodococcus, Bacteroides, Clostridium, and Fusobacterium spp18.
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While many of the same risk factors and bacterial isolates seem to be shared between peritonitis
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and incisional infection, there is lack of evidence in previous literature to support a causal
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ACCEPTED MANUSCRIPT relationship between these two conditions15. In this case report, the acuteness and severity of
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the onset of clinical signs of septic peritonitis combined with the pure growth of Streptococcus
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equi zooepidemicus, a common commensal organism of the equine epidermis, led to suspicions
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that this case of peritonitis had resulted from an ascending incisional infection and internal
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abscess formation that had subsequently ruptured internally once the external drainage tracts
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had sealed over with granulation tissue. This explanation seems supported by the post mortem
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finding of the abscess track that was directly leading from the incision site. It is speculated that
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the incisional drainage may have communicated with an extraperitoneal incisional abscess,
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similar to the cases reported by Rubio Martinez et al,8 which, when the granulation tissue had
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sealed the drainage spots, built up pressure enough to break through the peritoneum and
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disseminate into the abdomen. To the authors’ knowledge this is the first reported case of an
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ascending incisional infection documented as causing a septic peritonitis in a horse.
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Serial ultrasound evaluation of the abdomen during the treatment of peritonitis in this horse
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revealed the progression of a fibrin layer coating the serosal surface of the abdominal organs
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diffusely. Given the patient’s static response to oxytetracycline, marked antimicrobial resistance
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of the E.coli, and the marked fibrin on ultrasound, a novel form of treatment was sought to
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reduce bacterial load and reduce fibrin adhesion formation.
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Up until the 1940’s maggot therapy was used commonly by human surgeons for controlling soft
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tissue infections and as an adjunct to surgical resection for osteomyelitis. The advent of modern
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antibiotics and improved surgical techniques drastically reduced the use of these “tiny
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surgeons”, but they are still FDA approved for the debridement of non-healing necrotic skin and
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soft tissue wounds. Due to their seemingly distasteful nature of consuming necrotic tissue,
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fibrin, and bacteria, medical maggots seem to have become reserved for treatment of wounds
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that are not responsive to conventional treatment or that have multi-drug resistant bacterial
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infections. As part of their role as debriding agents, maggots secrete potent proteolytic enzymes
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ACCEPTED MANUSCRIPT that have significant anti-microbial activity against bacteria such as Staphylococcus,
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Streptococcus, Pseudomonas, and Escherichia coli, causing breakdown of biofilm formation and
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making the wound environment unsuitable for bacterial colonization19,20.
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In human medicine, medical maggots are most commonly used on pressure sores, venous ulcers,
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neuropathic foot ulcers, and non-healing traumatic or postsurgical wounds, however reported
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off-label applications include the use of maggots to debride areas in the pleural and peritoneal
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spaces21. In equine medicine, medical maggots are most often used in conjunction with surgical
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debridement as a non-traumatic, minimally invasive means of removing necrotic tissue from an
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extensive foot infection involving deeper structures of the foot such as the coffin bone, collateral
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cartilages, distal interphalangeal joint, and navicular bursa20,22. Other more rare case reports of
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their use include debridement of necrotic tissues in cases of supraspinus bursitis, abdominal
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wound dehiscence, chronic infected leg wounds, soft tissue abscesses, and one case with a
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MRSA infection over an internal fixation device used to stabilize a fracture20. To the authors’
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knowledge, no literature exists documenting the use of medical maggots within a body cavity of
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a horse. After consultation with Monarch Labs, it was decided to use a dose of 3000 maggots,
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the same dose that had been used in the cases of human peritonitis and pleuritis. The usual
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dose of disinfected larvae is 5-10 maggots per square cm of wound surface area; however
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consultation with the laboratory revealed that doses of 16000 maggots had been reported to
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cause myiasis and hepatic encephalopathy in sheep, and thus maximal doses of 6000 larvae per
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application cycle were recommended.
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The risks associated with use of medical maggots are not well reported due to limited use,
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however, one must consider the potential risks of the treatment such as myiasis, eosinophilic
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granulomatous reaction, failure of the maggots to survive and grow within the abdomen,
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inadequate debridement of the fibrinous material dispersed throughout the abdomen, and
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failure to recover all maggots from the abdominal cavity at the end of the treatment cycle. A
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ACCEPTED MANUSCRIPT relatively conservative dose of Phaenicia sericata larvae was used to minimize the risk of myiasis
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and degree of eosinophilic inflammation. At necropsy, no evidence of inappropriate tissue
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consumption or eosinophilic response was seen. In this case report, no maggots were recovered
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from the abdominal lavage 5 days after application, which raises concern about failure of the
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maggots to survive within the abdominal cavity or loss of maggots within the abdomen. After
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consultation with Monarch Labs, it was decided to leave the ventral drain portal open as a vent
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to allow oxygen access for the Phaenicia sericata larvae and also to act as a portal for self-
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extraction once the larvae were satiated, as is in accordance with their natural life cycle. This is
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similar to how the medical maggot treatments were carried out in human thoracic and
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peritoneal cavities and was thought to be appropriate for larvae placement within the equine
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peritoneal cavity. It is possible that the larvae died upon instillation into the abdominal cavity
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and their bodies were resorbed, however, the lack of eosinophilic granulomatous reaction at
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necropsy does not suggest this. At the time of maggot implantation, the mare was being housed
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in a completely confined concrete isolation building with controlled airflow into and out of the
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stall. For the week following administration of the Phaenicia sericata larvae, there was an
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exponential increase in the number of flies within the stall which could not be accounted for by
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external migration alone. The other option for maggot administration is to apply the maggots
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into the body cavity while still contained within a porous fabric bag (Biobag System). This allows
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debridement via proteolytic enzyme secretion, but greatly limits the phagocytosis of fibrinous
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material and the ability of the larvae to migrate to more confined areas of contamination. The
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benefit of application of maggots within a porous bag would be that it assures that there will be
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no loss of larvae within the cavity and might have also been a way to quantify larval survival
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within the abdomen. However, larval bag placement was deemed less appropriate for this case
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because it was felt that the bagged larvae would be less efficacious in debridement of the entire
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abdomen, the bag might act as an irritant to cause more serosal adhesion formation, and would
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also require a more invasive surgical procedure for retrieval. It is entirely plausible that the
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ACCEPTED MANUSCRIPT improvement in the mare’s clinical status was due to the treatment with prolonged tetracycline
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administration, however, the decision to add maggot therapy was made in response to a
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suspected treatment failure at the low dose oxytetracycline (further peritoneal fluid distension
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and cyclic fevers) and intolerance of the higher dose of oxytetracycline (diarrhea). The authors
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feel confident in saying that the maggots caused no harm and likely contributed positively to the
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treatment of the peritonitis if only by facilitating the continued treatment with low dose
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oxytetracycline.
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Subjectively, the authors feel that the use of medical maggots as a debriding agent was
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efficacious in reducing fibrinous adhesions in the immediate area of application; however, the
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maggots did not migrate as far from the site of administration as was hoped. It is speculated
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that a greater surface area might have been able to be debrided by either using a larger dose
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(6000 maggots) or by administering smaller doses of maggots at multiple sites around the
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abdomen. It is also speculated that earlier administration of the medical maggots may have
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improved their efficacy, as the fibrinous adhesions would have been less well established. No
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deleterious effects were seen as a result of either maggot application, but further studies are
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warranted to determine an appropriate dose and administration distribution, and expected
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efficacy of intraperitoneal maggot debridement therapy.
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Manufacturers’ addresses:
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a SAGENT Pharmaceuticals, Inc., Schaumburg, Illinois, USA
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b Sparhawk Laboratories, Inc., Lenexa, Kansas, USA
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c Intervet Inc., Merck & Co. Inc. Whitehouse Station, New Jersey, USA
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d Hospira, Inc, Lake Forest, Illinois, USA
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e Fort Dodge Animal Health, a division of Wyeth, Pfizer Inc, New York, New York, USA
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f West-Ward, Eatontown, New Jersey, USA
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g Akorn, Inc., Decatur, Illinois, USA
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ACCEPTED MANUSCRIPT h Boehringer Ingelheim Vetmedica, Inc., St. Joseph, MO, USA
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i Hospira, Inc., Lake Forest, Illinois, USA
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j Piramal Healthcare Limited, Digwal Village, Andhra Pradesh, India
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k Roerig, division of Pfizer, Inc., New York, New York, USA,
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l Teva Parenteral Medications, Inc, Irvine, California, USA
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m Hospira, Inc, Lake Forest, Illinois, USA
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n X-GEN Pharmaceuticals Inc., Big Flats, New York, USA
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o SAGENT Pharmaceuticals, Inc, Schaumburg, Illinois, USA
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p Bayer Healthcare LLC, Animal Health Division, Shawnee Mission, Kansas, USA
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q Bimeda, Inc, Le sueur, Minnesota, USA
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r Wedgewood Pharmacy, Swedesboro, New Jersey, USA
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s Pharmacia & Upjohn Co., Division of Pfizer Inc, New York, New York, USA
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t Zoetis Inc, Kalamazoo, Michigan, USA
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u Monarch Labs, Irvine, California, USA
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v Wedgewood Pharmacy, Swedesboro, New Jersey, USA
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Image Legend:
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Image 1 and Image 2: (day 3 post-celiotomy) This longitudinal image of a small intestinal loop,
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located in the left ventral flank region, demonstrates a wall that is thickened and edematous,
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consistent with anterior enteritis. Note there is scant amount of free peritoneal fluid and the serosal
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surfaces of the intestine appear smooth.
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Image 3: (day 8) Copious drainage soaking through the belly bandage from draining sites at the
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cranial (black arrow) and middle (blue arrow) aspects of the incision line. Digital pressure on the
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incision line caudal to the draining sites resulted in expression of approximately 10 mL of purulent
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material. The incision site was cleaned daily with 4% chlorhexidine and saline and the belly bandage
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changed daily.
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ACCEPTED MANUSCRIPT Image 4: (day 47) Moderate amount of anechoic free peritoneal fluid and fibrin lining the serosal
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surfaces of the small intestine and body wall in the left ventral abdomen.
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Image 5: (day 56) Approximately 3000 medical grade maggots were instilled into the abdomen via
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the left ventral abdominal drain portals.
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Image 6: (day 81) Left ventral abdomen at the site of the cranial drain portal, 25 days after the first
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medical maggot therapy. There is a mild amount of free peritoneal fluid, but the fibrin lining the
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intestine is no longer identifiable.
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Image 7: (day 87) Encapsulated abscess in the right ventral flank region between the body wall and
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cecum. This window was used for the site of the second medical maggot application.
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Image 8: (day 96) Right ventral flank portal site, 7 days after the second application of medical
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maggots.
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Image 9: Necropsy revealed a well-defined abdominal abscess that tracked from the cranial aspect of
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the ventral midline incision (arrow) up into the abdomen and wrapped caudally towards the body of
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the cecum. Note the body is in left lateral recumbency.
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[1] Hawkins JK, Bowman KF, Roberts M. Peritonitis in horses. J Am Vet Med Assoc 1993; 203:284
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[2] Smith LCR, Payne RJ, Boys Smith SJ, Bathe AP, and Greet TRC. Outcome and long-term follow-up
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of 20 horses undergoing surgery for caecal impaction: A retrospective study (2000-2008). Equine
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Vet J. 2010; 42: 388-392.
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[3] Mair TS1, Smith LJ. Survival and complication rates in 300 horses undergoing surgical treatment
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of colic. Part 2: Short-term complications. Equine Vet J. 2005; 37(4):303-9.
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[5] Freeman, D.E., Hammock, P., Baker, G.J., Foreman, J.H., Schaeffer, D.J., Richter, R.-A., Inoue, O.,
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and Magid, J.H. Short- and long-term survival and prevalence of post operative ileus after small
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[6] Phillips, T.J. and Walmsley, J.P. Retrospective analysis of the results of 151 exploratory
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[7] Honnas, C.M. and Cohen, N.D. Risk factors for wound infection following celiotomy in horses. J.
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am. vet. med. Ass. 1997; 2100, 78-81
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[8] Rubio Martinez L.M., Cribb N.C., and Koenig J.B. Extraperitoneal incisional abscess formation
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after colic surgery in 3 horses. Equine Vet. Educ. 2012; 24, 109-115
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[9] Aitken, M.R., Southwood, L.L., Ross, B.M., and Ross, M.W. Outcome of surgical and medical
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treatment of cecal impaction in horses: 114 cases (1994-2004). JAVMA. 2007; 231, 1378-1385
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[12] Dart A.J., Dowling B.A., and Hudgson D.R. Cecal disease. Equine vet. Educ. 1999; 11, 182-188
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[13] Ingle-Fehr J.E., Baxter G.M., Howard R.D., Trotter G.W., and Stashak T.S. Bacterial Culturing of
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Ventral Median Celiotomies for Prediction of Postoperative Incisional complications in Horses. Vet.
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associated with colic surgery in horses: 78 cases (1983-1985). J Am Vet Med Assoc 1989; 195:639-
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[15] Freeman D.E., Rotting A.K., and Inoue O.J. Abdominal Closure and Complications. Clinical
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[16] French N.P., Smith J., Edwards G.B., and Proudman C.J. Equine surgical colic: risk factors for
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postoperative complications. Equine vet. J. 2002; 34, 444-449
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[17] Hillyer M.H., Wright C.J. Peritonitis in the horse. Equine vet. Educ. 1997; 9, 136-142
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[18] Hardy J., Rakestraw P.C. Postoperative Management for Colics. Clinical Techniques in Equine
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Practice. 2002; 1, 188-197
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[19] Jones G., Wall R. Maggot-therapy in veterinary medicine. Research in veterinary Science. 2008;
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85, 394-398
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[20] Lepage O.M., Doumbia A., Perron-Lepage M.F., and Gangl M. The use of maggot debridement
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therapy in 41 equids. Equine vet. J. 2012; 44, 120-125
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[21] Sherman R.A., Shapiro C.E., Yang R.M. Maggot Therapy for Problematic Wounds: Uncommon
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and Off-label Applications. Advances in Skin & Wound Care. 2007; 20, 602-610
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[22] Morrison S.E. How to Use Sterile Maggot Debridement Therapy for Foot Infections of the Horse.
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We describe the potential progression of a ventral midline suppurative incisional wound into a septic peritonitis We describe the novel use of medical grade Phaenicia sericata larvae in the treatment of a multi-drug resistant peritonitis in a horse Medical grade Phaenicia sericata larvae caused no ill effects when placed into the peritoneal cavity
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