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Phaeohyphomycotic Rhinitis Caused by Bipolaris hawaiiensis in a Horse
Journal of Equine Veterinary Science 82 (2019) 102798
Contents lists available at ScienceDirect
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Case Report
Phaeohyphomycotic Rhinitis Caused by Bipolaris hawaiiensis in a Horse Rebecca M. Legere a, *, Anne A. Wooldridge a, Maninder Sandey b, R. Reid Hanson a, Robert Cole a a b
Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 April 2019 Received in revised form 30 July 2019 Accepted 23 September 2019 Available online 1 October 2019
This case represents the first reported case of Bipolaris hawaiiensis infection in an equid, and its aggressive clinical course. This case provides important descriptive and prognostic information for horses diagnosed with phaeohyphomycotic rhinitis. A 19-year-old American Quarter Horse mare was presented for second opinion of stertor and exercise intolerance of four-month duration. Endoscopy revealed generalized, proximal nasal edema, and computed tomography identified a soft tissue mass eroded through the rostral nasal bone. Biopsy of the mass was identified as a fungal granuloma caused by B. hawaiiensis resulting in chronic invasive fungal rhinitis. Treatment options were limited because of invasive infection, financial constraints, fungal sensitivity results, and published accounts of in vivo behavior of the organism. The infection progressed, resulting in euthanasia. In this case of equine phaeohyphomycosis, B. hawaiiensis was likely traumatically introduced into the patient’s nasal cavity. Its aggressive nature in an apparently immunocompetent patient is noteworthy, in the face of surgical debridement and attempted medical therapy. Therapeutic decisions were challenging in this case based on limited in vivo efficacy data in equids, pharmacokinetic challenges with available antifungal agents, and client-driven limitations regarding management of airway restriction. Published by Elsevier Inc.
Keywords: Phaeohyphomycosis Bipolaris hawaiiensis Aerosolized voriconazole Fungal osteomyelitis Fungal rhinitis
1. Background Phaeohyphomycosis is an uncommon opportunistic subcutaneous and systemic infection caused by a wide variety of dematiaceous fungi that develop as black molds in culture and as darkwalled (brown), polymorphous fungal elements in tissue. The pigmentation is due to the presence of melanin, which may act as a virulence factor. These are ubiquitous environmental organisms that cause opportunistic infections in both immune-competent and immune-compromised individuals and lead to a variety of syndromes based on the degree of invasiveness and site of infection [1]. In this case, Bipolaris hawaiiensis was the causative agent. It has
Animal welfare/ethical statement: This report describes a clinical experience. No submission to an ethics committee was required. The owner signed a standard consent form. Conflict of interest statement: The authors declare no conflicts of interest. * Corresponding author at: Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, 1500 Wire Rd., Auburn, AL, 36833, USA. E-mail address: [email protected] (R.M. Legere). https://doi.org/10.1016/j.jevs.2019.102798 0737-0806/Published by Elsevier Inc.
been well documented in humans to cause opportunistic infections of the skin, eyes, respiratory tract, and less commonly, deeper tissues and systemic infections. Reports of equine infections caused by a closely related agent Bipolaris spicifera are limited to superficial ophthalmic and dermatologic infections, which have been responsive to local therapy [2e4]. To the author’s knowledge, this case represents the first report of an infection by B. hawaiiensis in an equid. 2. Case Presentation 2.1. Case History A 19-year-old 568 kg (1,250 lb) American Quarter Horse mare was referred for evaluation of chronic stertor without history of nasal discharge or cough. Stertorous breathing and increased respiratory effort were first observed four months before presentation, and the noise was worsened by excitement and exercise. A course of corticosteroid therapy was administered (dexamethasone, 40 mg [0.07 mg/kg] intramuscularly every 24 hours, with dose tapered
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over 14 days). There was a partial response to this treatment, in that respiratory noise and effort were decreased, but were not completely normal. After discontinuing corticosteroids, clinical signs returned and continued to worsen, prompting referral for workup for the persistent stertor.
reflected over the site of the mass, revealing a friable, pink soft tissue mass that extended full thickness between the subcutaneous tissue on the dorsal aspect of the nasal bone through the bone to the nasal mucosa. Tissue was obtained for culture and histopathology, and the site was debrided to visually normal bony margins dorsally, ventrally, and laterally, and to the septum medially. The skin was closed, and a pressure bandage was placed.
2.2. Clinical Findings and Initial Evaluation On presentation, the mare was bright, alert, responsive, and in excellent body condition. Respiratory noise was audible with each breath during inspiration and expiration, with the restrictive sound focused in the nasal region. No nasal discharge or coughing were present, but air flow was slightly reduced from the right nostril. Facial contour showed a symmetrical, raised bony ridge bridging the dorsal aspect of the nasal bone at the level of the nasoincisive notch, with no history of trauma or abrasion of the site. Upper airway endoscopic examination findings were uniform swelling of the rostral portions of the right and left dorsal and ventral nasal passages. The passages were pale pink and appeared edematous, without signs of plaques, masses, or other visible lesions (Fig. 1A). Standing computed tomography (CT) examination findings were a circular, 2.5-cm soft tissue attenuating mass in the right dorsal nasal passage, with erosion of the right maxilla (nasal bone) with soft tissue swelling external to the nasal bone (Fig. 2A). Additional CT findings were diffuse thickening of the mucosal soft tissues of the nasal septum and turbinates, evident bilaterally in the nasal passages, with associated decreased air column (Fig. 2B and 2C). Surgical debridement of the mass was performed under standing sedation to debulk and to obtain a diagnosis. A skin flap was
2.3. Diagnosis Impression smears from the excised tissue with potassium hydroxide preparation revealed fungal hyphae. Histological examination of the nasal turbinates revealed a severe, diffuse, suppurative to pyogranulomatous rhinitis. The mucosal epithelium was multifocally eroded, and the underlying submucosa was infiltrated by moderate numbers of lymphocytes, plasma cells, neutrophils, and macrophages (Fig. 3A). There was no evidence of osteomyelitis in the examined sections; however, there was evidence of new bone formation. The nasal cavity contained a superficial serocellular exudate composed of abundant necrotic cellular debris, fibrin admixed with degenerate neutrophils, and large numbers of variably pigmented, occasionally branched, 5- to 7-mm wide and Gomori Methenamine Silverepositive fungal hyphae. (Figs. 3A, 3B, and 3C). The hyphae contained thick-walled vesicular swellings and prominent constrictions at their septations (chlamydoconidia) (Fig. 3C). Based on the fungal morphology and pigmentation, findings were consistent with a phaeohyphomycotic rhinitis. Margins of the lesion could not be identified in the examined sections, as multiple smaller fragments from the excised
Fig. 1. Tissue progression: (A) Endoscopy of the right nasal passage at presentation, with diffuse edema of soft tissues; (B) endoscopy after 12 weeks, with complete occlusion and progression in the face of localized and then systemic therapy; (C) Three firm masses (arrows) that acutely developed on the nasal bone caudal to the original surgical site (star) at 6 weeks after presentation; (D) lateral skull radiograph at 6 weeks after presentation, indicating three sites of bony lysis and periosteal reaction underlying the firm masses (arrows) that developed caudal to the original surgery site (star).
R.M. Legere et al. / Journal of Equine Veterinary Science 82 (2019) 102798
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Fig. 2. Computed tomography: (A-C) Taken at presentation. (D-F) Taken at 12 weeks after presentation. (A and D) Rostral nasal passage at the nasoincisive notch, with thickening of soft tissues at presentation and marked progression 12 weeks later, reducing diameter of the airway. Bony lysis at the site of fungal granuloma (arrow) where the soft tissue mass had eroded through the nasal bone. (B and E) At the level of the second premolar, bony lysis was present at presentation (arrow) and improved 12 weeks later. However, progression of nasal septum and turbinate thickening has reduced the diameter of the airway at 12 weeks after presentation. (C and E) At the rostral maxillary sinus, thickening of the ventral nasal septum was seen at presentation. Significant progression of septal thickening has obliterated the ventral air passages and significantly decreased the air column of the ventral and middle nasal meatus.
tissue were submitted. However, pyogranulomatous inflammation and fungal invasion were present throughout all examined tissue sections. Fungal culture was positive for heavy growth of a Bipolaris species, with morphology consistent with B. hawaiiensis. Fungal sensitivity results (Table 1) indicated that fluconazole and amphotericin B would likely be ineffective, and itraconazole and voriconazole were the only viable antifungal treatment options, based on reported MIC90 values. The MIC90 was considered the minimal concentration of the antimicrobial agent that inhibited growth of 90% of isolates of the specific fungal agent. 2.4. Case Progression More aggressive surgical debridement with a nasal septum resection was considered to remove some of the infected tissue and provide a larger airway; however, the owner declined. Due to high costs of systemic doses of noncompounded itraconazole and voriconazole, therapy was attempted with local injections of injectable voriconazole (VFEND), a thermal-responsive biogel (Therma-vert) (Best Pet RX, New York, NY, USA 10128) prepared with 0.25% dexamethasone, 4% itraconazole, and 1.3% voriconazole to deliver a slow-release depot of drug at the site of infection, and nebulized voriconazole (Vfend powder for solution (Pfizer, Inc New York, NY,
USA 100174) reconstituted to 6.25 mg/mL delivered using a nebulizer [Flexi-neb] (Jiffy Steamer Equine Division, Union City, TN, USA 38261) in 20 mg doses q 8 hours). Systemically, the mare was treated with organic iodide salt product (EDDI salt) (Vedco, Inc St. Joseph, MO, USA 64507), containing 9.2% ethylenediamine dihydroiodide (1 mg/kg EDDI). The mare responded to this treatment for approximately 2 weeks, but then respiratory noise and effort became more pronounced. A tapering course of dexamethasone was instituted to attempt to improve airway patency, which may have accelerated the progression of disease. Within 1 month of diagnosis, multiple bony ridges appeared on the nasal bone caudal to the surgical site, which were not painful but were growing rapidly (Fig. 1C). Radiographic findings were multifocal osteomyelitis of the maxillary bone with an aggressive pattern of lysis and proliferation and elevation of the overlying periosteum (Fig. 1D). Repeated standing CT indicated progression of bony lysis on the left side of the nasal bone. Aggressive surgical debulking with a nasal septum resection was again discussed with the same concerns of inability to remove all of the infected tissue and declined by the owner because of invasiveness of the procedure. The owner elected to proceed with a temporary tracheostomy and administration of systemic voriconazole (VFend tablets [Pfizer, Inc New York, NY, USA 100174] at 4 mg/kg orally once daily) for a limited period of time
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Fig. 3. Histopathology: (A and B) Histopathological examination of the nasal turbinates revealed marked pyogranulomatous rhinitis with multifocal areas of necrosis (N) containing numerous variably pigmented fungal organisms (arrow). H&E stain 3A (100x) and (3B) 400x; (C) Fungal hyphae were 5e7 mm wide (arrows), Gomori Methenamine Silver (GMS)positive with thick-walled vesicular swellings and prominent constrictions (arrow head) at their septations (chlamydoconidia). GMS stain (400 x).
because of budget. Four weeks after the temporary tracheostomy and systemic voriconazole therapy, both nasal passages were completely occluded (Fig. 1B), and more bony deformation was present grossly on the nasal bone. CT imaging of the head indicated progression of soft tissue thickening in the rostral nasal passages (Fig. 2D), as well as expansion of the turbinates of the nasal passages and nasal septum (Fig. 2E and 2F), causing nearly complete obstruction of the airway. Due to the progression and poor prognosis, the owners elected euthanasia at home.
2.5. Postmortem Findings A full necropsy was not performed, but a large, full thickness sample of the nasal mucosa was obtained postmortem by the primary care veterinarian and submitted for histopathology. There was diffuse moderate lymphocytic and neutrophilic rhinitis with multifocal submucosal gland hyperplasia. Numerous fungal
Table 1 Antifungal sensitivity results for the cultured Bipolaris hawaiiensis, from initial excisional biopsy. Antifungal Medication
Cutoff (ug/mL)
MIC90 value (ug/mL)
Fluconazole Ketoconazole Itraconazole Voriconazole Amphotericin B
>256 0.064 0.19 0.023 0.38
16 N/A 0.5 1 0.25
organisms with morphology consistent with B. hawaiiensis were present in the superficial serocellular nasal exudate. Despite medical therapy with systemic voriconazole, the fungal agent was actively proliferating in the tissues of the nasal mucosa, with evidence of mucin as well as inflammatory cell populations, resulting in markedly thickened mucosa and progressive airway constriction. 3. Discussion and Conclusions This presentation represents a case of chronic, locally invasive phaeohyphomycotic rhinitis. This has been well described in humans with B. hawaiiensis, but not in veterinary patients [5]. In the reported case, there was significant soft tissue swelling and thickening of the nasal mucosa bilaterally, distant from the focal fungal lesion, which was consistent with marked local tissue inflammation in reports of chronic fungal rhinosinusitis in multiple species, including people and cattle [1,6,7]. Both the initial surgical biopsy samples and postmortem samples of the nasal mucosa, at which time generalized mucosal thickening had progressed and completely occluded the airway, confirmed the presence of fungal hyphae and mucin within the tissues. This is consistent with invasive fungal rhinitis, which is characterized by tissue penetration with granulomatous inflammation and fungal hyphae identified within the mucosa and invasive bone lesions [8]. In immunosuppressed patients, this follows a very rapid clinical course and results in significant morbidity [5]. Chronic invasive rhinitis is seen in humans with apparently normal immune function or mild immune suppression [5]. There was clear evidence of
R.M. Legere et al. / Journal of Equine Veterinary Science 82 (2019) 102798
lysis through the nasal bone and thickening of the cartilage within the nasal passages and septum observed on CT. Histopathology showed no evidence of osteomyelitis in the examined tissues; however, there was indication of new bone formation, and limited sample quantity and quality may have impacted the ability to detect osteomyelitis. Bone expansion with allergic fungal rhinosinusitis is typically secondary to pressure necrosis by spaceoccupying mucin and tissue filling and expanding out of sinus cavities, as opposed to the locally invasive bony lesions seen clinically in the current case. Progression of superficial infections to invasive multifocal infections is reported for other veterinary phaeohyphomycotic infections, but not Bipolaris. Superficial infections of the skin by Bipolaris are more common in humans and aquatic animals [9,10] and are typically easily resolved with medical therapy. Reports of dermatologic infections by closely related dematiaceous fungi in immunocompetent horses describe superficial or nodular infections, which have been resolved by topical treatments or surgical resection alone [2e4]. Progression to multifocal osteomyelitis has been reported in two dogsdone case of an infection of the tibia moving onto the femur (suspected to be hematogenous [11]) and another as a progression from the subcutaneous space to the underlying ribs [12]. The immune status of the first canine case was unknown, but the dog with progression to the ribs was suspected to be immunosuppressed secondary to corticosteroids administered systemically for initial management of the dermatologic lesion. Human cases with this reported progression are typically immunosuppressed, except when the lesion is eroding into the cranial cavity to the brain, which is driven by the fungal agents’ tropism for neurologic tissue. This process is considered more common in immunocompetent patients [1]. In this case, the horse did not have overt evidence of immune suppression based on clinical signs and blood work. However, the corticosteroid therapy that was used initially by the primary care veterinarian and then later after diagnosis to attempt to improve nasal passage patency in the face of respiratory difficulty may have caused immune suppression that contributed to progression. After identifying B. hawaiiensis as the causative agent, medical management decisions for this horse were based on published data on the fungus, primarily in human literature, as well as the fungal culture and sensitivity. As with all phaeohyphomycoses, in vitro sensitivity does not perfectly translate into in vivo efficacy because of issues with fungal virulence factors and limited bioavailability of many systemic antifungal medications. Ketoconazole and fluconazole have limited to no reported efficacy against Bipolaris, which was confirmed on the fungal sensitivity results from the cultured agent [1,13,14]. Amphotericin B was frequently recommended as systemic therapy against Bipolaris before the advent of azole antifungals; however, fungal sensitivity results showed likely resistance, and concerns for toxicity made this drug less appealing [13,15]. Itraconazole and voriconazole were considered the most appealing therapeutic options in this case because of their relative clinical safety, reported efficacy in the literature, and apparent sensitivity of the cultured agent to these drugs [1,13,14]. In this case of equine phaeohyphomycosis, B. hawaiiensis was likely traumatically induced into the patient’s nasal cavity, which resulted in chronic invasive fungal rhinitis. The original source of this agent is unknown, as there was no history of trauma at the site, and no evidence of external wounds or mucosal plaques within the nasal passage. Rhinitis and sinusitis caused by phaeohyphomycotic agents are typically associated with inhaled pathogens, followed by mucosal infection and invasion into deeper tissues. In this case, the location of the soft tissue and bone pathology suggests an original
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introduction from the rostral portion of the interior of the nasal cavity, with progression outward through the nasal bone and expansion caudally through the septum. Inoculation of the local tissues may have occurred through a healed wound, as there was a slow onset of clinical signs before presentation and several months before that with limited daily observation of the horse, or by penetration of a contaminated foreign body, such as an inhaled grass awn. Pasture grasses in the Southeast United States, especially Bermuda grass, can be infected with multiple Bipolaris species (including B. hawaiiensis) that cause variable plant pathologies and phaeohyphomycotic infections in herbivorous animals, and this represents a plausible route for inoculation of the patient [16,17]. Its aggressive nature in an apparently immunocompetent patient is noteworthy, in the face of surgical debridement and attempted medical therapy. Therapeutic decisions were challenging in this case based on limited in vivo efficacy data in equids, pharmacokinetic challenges with available antifungal agents, and client-driven limitations regarding management of airway restriction. Caution should be exercised in the use of corticosteroids in the management of invasive fungal disease, especially when antifungal treatment may be delivered at subtherapeutic doses or for inadequate duration. To the authors’ knowledge, this is the first report to describe the clinical course of an invasive infection by B. hawaiiensis in a horse.
References [1] Chowdhary A, Meis JF, Guarro J, de Hoog GS, Kathuria S, Arendrup MC, et al. ESCMID and ECMM joint clinical guidelines for the diagnosis and management of systemic phaeohyphomycosis: diseases caused by black fungi. Clin Microbiol Infect 2014;20(Suppl 3):47e75. [2] Genovese LM, Whitbread TJ, Campbell CK. Cutaneous nodular phaeohyphomycosis in five horses associated with Alternaria alternata infection. Vet Rec 2001;148:55e6. [3] Jennings JE. Phaeohyphomycosis due to pyrenophora phaeocomes and drechslera nobleae in an appaloosa mare. Can Vet J 2016;57:431e3. [4] Kaplan W, Chandler FW, Ajello L, Gauther R, Higgins R, Cayouette P. Equine phaeohyphomycosis caused by drechslera spicifera. Can Vet J 1975;16:205e8. [5] Castelnuovo P, De Bernardi F, Cavanna C, Pagella F, Bossolesi P, Marone P, et al. Invasive fungal sinusitis due to bipolaris hawaiiensis. Mycoses 2004;47: 76e81. [6] Conti Diaz IA, Vargas R, Apolo A, Morana JA, Pedrana G, Cardozo E, et al. Mycotic bovine nasal granuloma. Rev Inst Med Trop Sao Paulo 2003;45: 163e6. [7] Naclerio RM, Bachert C, Baraniuk JN. Pathophysiology of nasal congestion. Int J Gen Med 2010;3:47e57. [8] deShazo RD, O’Brien M, Chapin K, Soto-Aguilar M, Gardner L, Swain R. A new classification and diagnostic criteria for invasive fungal sinusitis. Arch Otolaryngol Head Neck Surg 1997;123:1181e8. [9] Costa Sidrim JJ, Carvalho VL, Branco de Souza Collares Maia DC, Nogueira Brilhante RS, de Meirelles AC, Negrao Silva CP, et al. Bipolaris hawaiiensis as an emerging cause of cutaneous phaeohyphomycosis in an antillean manatee trichechus manatus manatus. Dis Aquat Org 2015;113:69e73. [10] Seyedmousavi S, Guillot J, de Hoog GS. Phaeohyphomycoses, emerging opportunistic diseases in animals. Clin Microbiol Rev 2013;26:19e35. [11] Lomax LG, Cole JR, Padhye AA, Ajello L, Chandler FW, Smith BR. Osteolytic phaeohyphomycosis in a German shepherd dog caused by Phialemonium obovatum. J Clin Microbiol 1986;23:987e91. [12] Guillot J, Garcia-Hermoso D, Degorce F, Deville M, Calvie C, Dickele G, et al. Eumycetoma caused by Cladophialophora bantiana in a dog. J Clin Microbiol 2004;42:4901e3. [13] da Cunha KC, Sutton DA, Fothergill AW, Cano J, Gene J, Madrid H, et al. Diversity of bipolaris species in clinical samples in the United States and their antifungal susceptibility profiles. J Clin Microbiol 2012;50:4061e6. [14] Revankar SG, Sutton DA. Melanized fungi in human disease. Clin Microbiol Rev 2010;23:884e928. [15] Revankar SG. Dematiaceous fungi. Mycoses 2007;50:91e101. [16] Manamgoda DS, Rossman AY, Castlebury LA, Crous PW, Madrid H, Chukeatirote E, et al. The genus bipolaris. Stud Mycol 2014;79:221e8. [17] Pratt RG. Variation in occurrence of dematiaceous hyphomycetes on forage bermudagrass over years, sampling times, and locations. Phytopathology 2005;95:1183e90.
Contents lists available at ScienceDirect
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Case Report
Phaeohyphomycotic Rhinitis Caused by Bipolaris hawaiiensis in a Horse Rebecca M. Legere a, *, Anne A. Wooldridge a, Maninder Sandey b, R. Reid Hanson a, Robert Cole a a b
Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 April 2019 Received in revised form 30 July 2019 Accepted 23 September 2019 Available online 1 October 2019
This case represents the first reported case of Bipolaris hawaiiensis infection in an equid, and its aggressive clinical course. This case provides important descriptive and prognostic information for horses diagnosed with phaeohyphomycotic rhinitis. A 19-year-old American Quarter Horse mare was presented for second opinion of stertor and exercise intolerance of four-month duration. Endoscopy revealed generalized, proximal nasal edema, and computed tomography identified a soft tissue mass eroded through the rostral nasal bone. Biopsy of the mass was identified as a fungal granuloma caused by B. hawaiiensis resulting in chronic invasive fungal rhinitis. Treatment options were limited because of invasive infection, financial constraints, fungal sensitivity results, and published accounts of in vivo behavior of the organism. The infection progressed, resulting in euthanasia. In this case of equine phaeohyphomycosis, B. hawaiiensis was likely traumatically introduced into the patient’s nasal cavity. Its aggressive nature in an apparently immunocompetent patient is noteworthy, in the face of surgical debridement and attempted medical therapy. Therapeutic decisions were challenging in this case based on limited in vivo efficacy data in equids, pharmacokinetic challenges with available antifungal agents, and client-driven limitations regarding management of airway restriction. Published by Elsevier Inc.
Keywords: Phaeohyphomycosis Bipolaris hawaiiensis Aerosolized voriconazole Fungal osteomyelitis Fungal rhinitis
1. Background Phaeohyphomycosis is an uncommon opportunistic subcutaneous and systemic infection caused by a wide variety of dematiaceous fungi that develop as black molds in culture and as darkwalled (brown), polymorphous fungal elements in tissue. The pigmentation is due to the presence of melanin, which may act as a virulence factor. These are ubiquitous environmental organisms that cause opportunistic infections in both immune-competent and immune-compromised individuals and lead to a variety of syndromes based on the degree of invasiveness and site of infection [1]. In this case, Bipolaris hawaiiensis was the causative agent. It has
Animal welfare/ethical statement: This report describes a clinical experience. No submission to an ethics committee was required. The owner signed a standard consent form. Conflict of interest statement: The authors declare no conflicts of interest. * Corresponding author at: Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, 1500 Wire Rd., Auburn, AL, 36833, USA. E-mail address: [email protected] (R.M. Legere). https://doi.org/10.1016/j.jevs.2019.102798 0737-0806/Published by Elsevier Inc.
been well documented in humans to cause opportunistic infections of the skin, eyes, respiratory tract, and less commonly, deeper tissues and systemic infections. Reports of equine infections caused by a closely related agent Bipolaris spicifera are limited to superficial ophthalmic and dermatologic infections, which have been responsive to local therapy [2e4]. To the author’s knowledge, this case represents the first report of an infection by B. hawaiiensis in an equid. 2. Case Presentation 2.1. Case History A 19-year-old 568 kg (1,250 lb) American Quarter Horse mare was referred for evaluation of chronic stertor without history of nasal discharge or cough. Stertorous breathing and increased respiratory effort were first observed four months before presentation, and the noise was worsened by excitement and exercise. A course of corticosteroid therapy was administered (dexamethasone, 40 mg [0.07 mg/kg] intramuscularly every 24 hours, with dose tapered
2
R.M. Legere et al. / Journal of Equine Veterinary Science 82 (2019) 102798
over 14 days). There was a partial response to this treatment, in that respiratory noise and effort were decreased, but were not completely normal. After discontinuing corticosteroids, clinical signs returned and continued to worsen, prompting referral for workup for the persistent stertor.
reflected over the site of the mass, revealing a friable, pink soft tissue mass that extended full thickness between the subcutaneous tissue on the dorsal aspect of the nasal bone through the bone to the nasal mucosa. Tissue was obtained for culture and histopathology, and the site was debrided to visually normal bony margins dorsally, ventrally, and laterally, and to the septum medially. The skin was closed, and a pressure bandage was placed.
2.2. Clinical Findings and Initial Evaluation On presentation, the mare was bright, alert, responsive, and in excellent body condition. Respiratory noise was audible with each breath during inspiration and expiration, with the restrictive sound focused in the nasal region. No nasal discharge or coughing were present, but air flow was slightly reduced from the right nostril. Facial contour showed a symmetrical, raised bony ridge bridging the dorsal aspect of the nasal bone at the level of the nasoincisive notch, with no history of trauma or abrasion of the site. Upper airway endoscopic examination findings were uniform swelling of the rostral portions of the right and left dorsal and ventral nasal passages. The passages were pale pink and appeared edematous, without signs of plaques, masses, or other visible lesions (Fig. 1A). Standing computed tomography (CT) examination findings were a circular, 2.5-cm soft tissue attenuating mass in the right dorsal nasal passage, with erosion of the right maxilla (nasal bone) with soft tissue swelling external to the nasal bone (Fig. 2A). Additional CT findings were diffuse thickening of the mucosal soft tissues of the nasal septum and turbinates, evident bilaterally in the nasal passages, with associated decreased air column (Fig. 2B and 2C). Surgical debridement of the mass was performed under standing sedation to debulk and to obtain a diagnosis. A skin flap was
2.3. Diagnosis Impression smears from the excised tissue with potassium hydroxide preparation revealed fungal hyphae. Histological examination of the nasal turbinates revealed a severe, diffuse, suppurative to pyogranulomatous rhinitis. The mucosal epithelium was multifocally eroded, and the underlying submucosa was infiltrated by moderate numbers of lymphocytes, plasma cells, neutrophils, and macrophages (Fig. 3A). There was no evidence of osteomyelitis in the examined sections; however, there was evidence of new bone formation. The nasal cavity contained a superficial serocellular exudate composed of abundant necrotic cellular debris, fibrin admixed with degenerate neutrophils, and large numbers of variably pigmented, occasionally branched, 5- to 7-mm wide and Gomori Methenamine Silverepositive fungal hyphae. (Figs. 3A, 3B, and 3C). The hyphae contained thick-walled vesicular swellings and prominent constrictions at their septations (chlamydoconidia) (Fig. 3C). Based on the fungal morphology and pigmentation, findings were consistent with a phaeohyphomycotic rhinitis. Margins of the lesion could not be identified in the examined sections, as multiple smaller fragments from the excised
Fig. 1. Tissue progression: (A) Endoscopy of the right nasal passage at presentation, with diffuse edema of soft tissues; (B) endoscopy after 12 weeks, with complete occlusion and progression in the face of localized and then systemic therapy; (C) Three firm masses (arrows) that acutely developed on the nasal bone caudal to the original surgical site (star) at 6 weeks after presentation; (D) lateral skull radiograph at 6 weeks after presentation, indicating three sites of bony lysis and periosteal reaction underlying the firm masses (arrows) that developed caudal to the original surgery site (star).
R.M. Legere et al. / Journal of Equine Veterinary Science 82 (2019) 102798
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Fig. 2. Computed tomography: (A-C) Taken at presentation. (D-F) Taken at 12 weeks after presentation. (A and D) Rostral nasal passage at the nasoincisive notch, with thickening of soft tissues at presentation and marked progression 12 weeks later, reducing diameter of the airway. Bony lysis at the site of fungal granuloma (arrow) where the soft tissue mass had eroded through the nasal bone. (B and E) At the level of the second premolar, bony lysis was present at presentation (arrow) and improved 12 weeks later. However, progression of nasal septum and turbinate thickening has reduced the diameter of the airway at 12 weeks after presentation. (C and E) At the rostral maxillary sinus, thickening of the ventral nasal septum was seen at presentation. Significant progression of septal thickening has obliterated the ventral air passages and significantly decreased the air column of the ventral and middle nasal meatus.
tissue were submitted. However, pyogranulomatous inflammation and fungal invasion were present throughout all examined tissue sections. Fungal culture was positive for heavy growth of a Bipolaris species, with morphology consistent with B. hawaiiensis. Fungal sensitivity results (Table 1) indicated that fluconazole and amphotericin B would likely be ineffective, and itraconazole and voriconazole were the only viable antifungal treatment options, based on reported MIC90 values. The MIC90 was considered the minimal concentration of the antimicrobial agent that inhibited growth of 90% of isolates of the specific fungal agent. 2.4. Case Progression More aggressive surgical debridement with a nasal septum resection was considered to remove some of the infected tissue and provide a larger airway; however, the owner declined. Due to high costs of systemic doses of noncompounded itraconazole and voriconazole, therapy was attempted with local injections of injectable voriconazole (VFEND), a thermal-responsive biogel (Therma-vert) (Best Pet RX, New York, NY, USA 10128) prepared with 0.25% dexamethasone, 4% itraconazole, and 1.3% voriconazole to deliver a slow-release depot of drug at the site of infection, and nebulized voriconazole (Vfend powder for solution (Pfizer, Inc New York, NY,
USA 100174) reconstituted to 6.25 mg/mL delivered using a nebulizer [Flexi-neb] (Jiffy Steamer Equine Division, Union City, TN, USA 38261) in 20 mg doses q 8 hours). Systemically, the mare was treated with organic iodide salt product (EDDI salt) (Vedco, Inc St. Joseph, MO, USA 64507), containing 9.2% ethylenediamine dihydroiodide (1 mg/kg EDDI). The mare responded to this treatment for approximately 2 weeks, but then respiratory noise and effort became more pronounced. A tapering course of dexamethasone was instituted to attempt to improve airway patency, which may have accelerated the progression of disease. Within 1 month of diagnosis, multiple bony ridges appeared on the nasal bone caudal to the surgical site, which were not painful but were growing rapidly (Fig. 1C). Radiographic findings were multifocal osteomyelitis of the maxillary bone with an aggressive pattern of lysis and proliferation and elevation of the overlying periosteum (Fig. 1D). Repeated standing CT indicated progression of bony lysis on the left side of the nasal bone. Aggressive surgical debulking with a nasal septum resection was again discussed with the same concerns of inability to remove all of the infected tissue and declined by the owner because of invasiveness of the procedure. The owner elected to proceed with a temporary tracheostomy and administration of systemic voriconazole (VFend tablets [Pfizer, Inc New York, NY, USA 100174] at 4 mg/kg orally once daily) for a limited period of time
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Fig. 3. Histopathology: (A and B) Histopathological examination of the nasal turbinates revealed marked pyogranulomatous rhinitis with multifocal areas of necrosis (N) containing numerous variably pigmented fungal organisms (arrow). H&E stain 3A (100x) and (3B) 400x; (C) Fungal hyphae were 5e7 mm wide (arrows), Gomori Methenamine Silver (GMS)positive with thick-walled vesicular swellings and prominent constrictions (arrow head) at their septations (chlamydoconidia). GMS stain (400 x).
because of budget. Four weeks after the temporary tracheostomy and systemic voriconazole therapy, both nasal passages were completely occluded (Fig. 1B), and more bony deformation was present grossly on the nasal bone. CT imaging of the head indicated progression of soft tissue thickening in the rostral nasal passages (Fig. 2D), as well as expansion of the turbinates of the nasal passages and nasal septum (Fig. 2E and 2F), causing nearly complete obstruction of the airway. Due to the progression and poor prognosis, the owners elected euthanasia at home.
2.5. Postmortem Findings A full necropsy was not performed, but a large, full thickness sample of the nasal mucosa was obtained postmortem by the primary care veterinarian and submitted for histopathology. There was diffuse moderate lymphocytic and neutrophilic rhinitis with multifocal submucosal gland hyperplasia. Numerous fungal
Table 1 Antifungal sensitivity results for the cultured Bipolaris hawaiiensis, from initial excisional biopsy. Antifungal Medication
Cutoff (ug/mL)
MIC90 value (ug/mL)
Fluconazole Ketoconazole Itraconazole Voriconazole Amphotericin B
>256 0.064 0.19 0.023 0.38
16 N/A 0.5 1 0.25
organisms with morphology consistent with B. hawaiiensis were present in the superficial serocellular nasal exudate. Despite medical therapy with systemic voriconazole, the fungal agent was actively proliferating in the tissues of the nasal mucosa, with evidence of mucin as well as inflammatory cell populations, resulting in markedly thickened mucosa and progressive airway constriction. 3. Discussion and Conclusions This presentation represents a case of chronic, locally invasive phaeohyphomycotic rhinitis. This has been well described in humans with B. hawaiiensis, but not in veterinary patients [5]. In the reported case, there was significant soft tissue swelling and thickening of the nasal mucosa bilaterally, distant from the focal fungal lesion, which was consistent with marked local tissue inflammation in reports of chronic fungal rhinosinusitis in multiple species, including people and cattle [1,6,7]. Both the initial surgical biopsy samples and postmortem samples of the nasal mucosa, at which time generalized mucosal thickening had progressed and completely occluded the airway, confirmed the presence of fungal hyphae and mucin within the tissues. This is consistent with invasive fungal rhinitis, which is characterized by tissue penetration with granulomatous inflammation and fungal hyphae identified within the mucosa and invasive bone lesions [8]. In immunosuppressed patients, this follows a very rapid clinical course and results in significant morbidity [5]. Chronic invasive rhinitis is seen in humans with apparently normal immune function or mild immune suppression [5]. There was clear evidence of
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lysis through the nasal bone and thickening of the cartilage within the nasal passages and septum observed on CT. Histopathology showed no evidence of osteomyelitis in the examined tissues; however, there was indication of new bone formation, and limited sample quantity and quality may have impacted the ability to detect osteomyelitis. Bone expansion with allergic fungal rhinosinusitis is typically secondary to pressure necrosis by spaceoccupying mucin and tissue filling and expanding out of sinus cavities, as opposed to the locally invasive bony lesions seen clinically in the current case. Progression of superficial infections to invasive multifocal infections is reported for other veterinary phaeohyphomycotic infections, but not Bipolaris. Superficial infections of the skin by Bipolaris are more common in humans and aquatic animals [9,10] and are typically easily resolved with medical therapy. Reports of dermatologic infections by closely related dematiaceous fungi in immunocompetent horses describe superficial or nodular infections, which have been resolved by topical treatments or surgical resection alone [2e4]. Progression to multifocal osteomyelitis has been reported in two dogsdone case of an infection of the tibia moving onto the femur (suspected to be hematogenous [11]) and another as a progression from the subcutaneous space to the underlying ribs [12]. The immune status of the first canine case was unknown, but the dog with progression to the ribs was suspected to be immunosuppressed secondary to corticosteroids administered systemically for initial management of the dermatologic lesion. Human cases with this reported progression are typically immunosuppressed, except when the lesion is eroding into the cranial cavity to the brain, which is driven by the fungal agents’ tropism for neurologic tissue. This process is considered more common in immunocompetent patients [1]. In this case, the horse did not have overt evidence of immune suppression based on clinical signs and blood work. However, the corticosteroid therapy that was used initially by the primary care veterinarian and then later after diagnosis to attempt to improve nasal passage patency in the face of respiratory difficulty may have caused immune suppression that contributed to progression. After identifying B. hawaiiensis as the causative agent, medical management decisions for this horse were based on published data on the fungus, primarily in human literature, as well as the fungal culture and sensitivity. As with all phaeohyphomycoses, in vitro sensitivity does not perfectly translate into in vivo efficacy because of issues with fungal virulence factors and limited bioavailability of many systemic antifungal medications. Ketoconazole and fluconazole have limited to no reported efficacy against Bipolaris, which was confirmed on the fungal sensitivity results from the cultured agent [1,13,14]. Amphotericin B was frequently recommended as systemic therapy against Bipolaris before the advent of azole antifungals; however, fungal sensitivity results showed likely resistance, and concerns for toxicity made this drug less appealing [13,15]. Itraconazole and voriconazole were considered the most appealing therapeutic options in this case because of their relative clinical safety, reported efficacy in the literature, and apparent sensitivity of the cultured agent to these drugs [1,13,14]. In this case of equine phaeohyphomycosis, B. hawaiiensis was likely traumatically induced into the patient’s nasal cavity, which resulted in chronic invasive fungal rhinitis. The original source of this agent is unknown, as there was no history of trauma at the site, and no evidence of external wounds or mucosal plaques within the nasal passage. Rhinitis and sinusitis caused by phaeohyphomycotic agents are typically associated with inhaled pathogens, followed by mucosal infection and invasion into deeper tissues. In this case, the location of the soft tissue and bone pathology suggests an original
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introduction from the rostral portion of the interior of the nasal cavity, with progression outward through the nasal bone and expansion caudally through the septum. Inoculation of the local tissues may have occurred through a healed wound, as there was a slow onset of clinical signs before presentation and several months before that with limited daily observation of the horse, or by penetration of a contaminated foreign body, such as an inhaled grass awn. Pasture grasses in the Southeast United States, especially Bermuda grass, can be infected with multiple Bipolaris species (including B. hawaiiensis) that cause variable plant pathologies and phaeohyphomycotic infections in herbivorous animals, and this represents a plausible route for inoculation of the patient [16,17]. Its aggressive nature in an apparently immunocompetent patient is noteworthy, in the face of surgical debridement and attempted medical therapy. Therapeutic decisions were challenging in this case based on limited in vivo efficacy data in equids, pharmacokinetic challenges with available antifungal agents, and client-driven limitations regarding management of airway restriction. Caution should be exercised in the use of corticosteroids in the management of invasive fungal disease, especially when antifungal treatment may be delivered at subtherapeutic doses or for inadequate duration. To the authors’ knowledge, this is the first report to describe the clinical course of an invasive infection by B. hawaiiensis in a horse.
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