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Avian pathogenic flagellated enteric protozoa
Avian Pathogenic Flagellated Enteric Protozoa Robert Clipsham, D VM
Endoparasitism continues to be a significant factor in avian health care for both clinicians and aviculturists. The motile enteric protozoal parasites comprise a fairly finite but markedly significant group of potential and active pathogens whose presence require accurate diagnosis and treatment. Several organisms in this group are considered to be endemic in various groups or species of birds and are common enough to warrant routine investigation, both on acquisition as well as during annual reexamination. Perhaps more significant, in the general picture of avian health and disease, is the role of these unicellular, motile parasites as sentinel organisms whose presence dictates a review of their relationship to the overall medical management of the bird(s) in question.
T ~ z oe subject of pathogenic flagellated protoal infections in avian species tends to diverge in its definition and/or recognition in regard to host(s), specific parasitic genera, and/ or species a n d t h e i r i n h e r e n t d e g r e e of pathogenicity, making the issue controversial at both the academic and clinical levels. Further complicating the subject is the disparity of documented evidence published on specific parasites in exotic and pet birds, as those that are predominantly reported are in domestic fowl. Many times the reports by clinicians of various pet and/or aviary bird cases involving flagellates are anecdotal, where multiple diseases often coexist. Furthermore, the exact identification of a specific genus and species is difficult or impossible owing to limitations in the on-site laboratory used, leading to misinterpretation or generalized reference to the presence of a "Giardia-like" organism. Con-
trolled studies in exotic and/or avicuhural subjects are substantially unavailable at this time. This report will focus on the clinically important aspects of the various flagellates, as well as bring forth some known varieties of relevant parasites that are often not considered by the practitioner. The amoebae and ciliates are also included as a matter of practicality because they are phylogenetically related and constitute a very small group of potential and actual pathogens for avians. F u r t h e r m o r e , their identification as a differential diagnosis is of consequence for the outcome of a case. A reasonable summary of the current philosophy concerning this class of parasites for the avian practitioner will help to put the specifics detailed here in perspective. 1-a The presence of flagellates does not always constitute a disease process: 9 flagellated parasitic disease is the combined result of host resistance, immune status, parasite load and pathogenicity of the parasite; 9 many parasites appear to require concurrent infection from bacteria, viruses, and yeasts; 9 general health s u p p o r t in the f o r m o f proper diet, stress reduction, sanitation, and sound management will do more to prevent parasitic disease than pharmaceutical intervention in the greater scheme; 9 flagellates generally require a wet environment to persist in their motile form; consistent washing and drying of living facilities will enhance control; and 9 the presence of parasitic disease is a vigorous indication for a review of avicultural management and on going preventative health measures.
From Thousand Oaks, CA. Address reprint requests to Robert Clipsham, DVM, Exotic Medicine and Management Consultant, 560 N Moorpark Rd, Suite 168, Thousand Oaks, CA 91360. Copyright 9 1995 by W.B. Saunders Company 1055-937X/95/0403 -000255.00/0
Since the discovery by Antony van Leeuwenhook during the 17th Century (Eimereria stiedae from a rabbit gallbladder in 1674 and Giardia lamblia from van Leeuwenhook's personal case of diarrhea in 1681) some 65,000 species of protozoa have been described, many by sophisticated biochemical processes, such as
Copyright 9 1995 by W.B. Saunders Company Key words: Protozoa, flagellates, enteritis, avian, ciliates, amoeba.
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Seminars in Avian and Exotic Pet Medicine, Vol 4, No 3 (July), 1995: pp 112-125
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antigenic structure (Table 1). The following material will focus on the pertinent anatomical structures of the pathogenic flagellates, ciliates and amoebae as they relate to presence, host location, disease signs, and treatment.
Locomotion 4,s Flagellates use a whiplike flagella composed of a central axoneme and an outer sheath. The structure arises from a kinetosome in the cytoplasm. T h e flagellum may pass posteriorly along the body freely or be attached to the body along its entire length or at several points to form an undulating membrane. The number of flagella may vary from one to eight. Flagella may be temporarily present in some developmental stages of specific ciliates. Ciliates use cilia, which are essentially tiny flagella with the same internal structural anatomy as true flagellates. The ciliophora may be Table 1. Classification4:
Subkingdom: Protozoa Zoomastigophorasid (flagellates) K inetoplastorida B odonorina Bodonidae P leuromonas Retortamonadorida Chilomastix Cochlostomatorida Cochlosoma Diplomonado~ida Giardia, Hexamita, Spironucleus Trichomonadorida Monocercomonadidae Histomonas, monocercomonas 7u Trichomonas, Tritrichomanas, Tetratrichomonas, P entatrichomonas Phylum: Ciliophora (ciliates) Class: K inetofragminop horasida Subclass: Vestibuliferasina Family: Balantidiidae Genera: Balantidium, Tetrahymena Sarcodina (amoebae) Subphylum: Lobosasida Class: Order: Amoebrdorida Tubulinorina Suborder: Genera: Amoeba, Endolimax, Entamoeba Acanthopodorina Suborder: Genera: Acanthamoeba, Hartmannella Schizopyrenorida Order: Genus: Vahlkampfia Class: Order: Suborder: Family: Genus: Order: Genus: Order: Genus: Order: Genera: Order: Family: Genera: Family: Genera:
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in large numbers, arranged in rows and beat synchronously, or may be more specialized in arrangement and fused into organelles, such as tufts (cirrus), membranelles (fusion of two or more rows), or an undulating membrane (formed by the longitudinal fusion of a cilia
rOW). Amoebae move by pseudopods, which are temporary organelles of locomotion formed and retracted as needed. There are four types of pseudopods: lobopods, filopods, myxopods, and anopods. Furthermore, locomotion may be described for the fashion characteristic for the parasite in question, such as smooth, gliding, bending, snapping, jerky, or twisting. These motions when observed under the microscope may be helpful or essential in correct parasite identification.
Reproduction 4's Reproduction for the protozoa under consideration may be sexual or asexual. The most common type of asexual reproduction is binary fission with a simple division of the parent cell splitting into two daughter organisms. This type of reproduction is used by flagellates and amoebae. Ciliates use a form of sexual reproduction termed conjugation where two individuals temporarily fuse and donate a haploid pronucleus, each after dividing their micronuclei several times. The ciliates then separate and an internal nuclear reorganization then follows. Some protozoa form cysts, which occurs when the organism forms a thick wall around itself for environmental resistance purposes. The motile, vegetative form of a protozoan is termed a trophozoite.
Flagellated Protozoan Parasites The private avian clinician will be most experienced with Giardia, Trichomonas, or Hexamita, depending on the avian species seen most often during normal case loads. Many times the inability to rapidly diagnose a parasitic disease leads to the random use of antiflagellate prescriptions and a hindsight review based on a therapeutic diagnosis. Often this is because of the decision to avoid invasive procedures in
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the event that no organisms are being shed or a lack o f awareness o f the availability o f alternative diagnostic methods. It is the intent o f this section to e n c o u r a g e avian veterinarians to e x p a n d their diagnostic base, visual identification capacity, and, foremost, an appreciation o f the disease complex, which includes all the basic c o m p o n e n t s o f s o u n d h u s b a n d r y a n d m a n a g e m e n t whose oversight are usually the real culprits leading u p to the diagnosis o f endoparasitism. Failure to p u r s u e the first three items will most likely result in a persistence o f the greater cause.
Giardia
Name: Giardia lamblia. (Synonyms): G lamblia, G intestinalis, G enterica, G duodenalis, Cercomonas intestinalis, Lamblia intestinalis, Megastoma entericum. T h e controversy as to w h e t h e r all host species for Giardia infection are subject to G lamblia and, t h e r e f o r e , d i f f e r e n t cases of separate host species are only n o t e d in their d i f f e r e n c e by individual host species n o m e n c l a t u r e or whether, in fact, separate species o f Giardia specifically infect each host type still remains as subject o f debate. 4'6-s T h e view c u r r e n t l y gaining p r e d o m i n a n c e is that only t h r e e species exist (G duodenalis, G agilis (amphibia), and G muris) and the traditionally held host specific names and infectivity restrictions are m o r e a matter o f custom and convenience (eg, G equi, G boris, G canis, G cati, G caviae) r a t h e r t h a n owing to a biological basis. F u r t h e r m o r e , e x p e r i m e n t a l cross-infectivity have only been partially successful, and strains o f G cati, G caviae, and G intestinalis are antigenicaUy the same. 9 Additionally, m o r p h o l o g ical studies o f the various strains show that only G muris has any distinct physical differences o f the strains reviewed. 4 Despite the incidence o f 3.9% in h u m a n fecal examination surveys, 1~ not all positive cases showed evidence o f disease, and only a small n u m b e r showed chronic diarrhea, 4 thereby emphasizing the disparity between infection and disease n o t e d in avians and small animals. Box identified Giardia associated with enteritis in parakeets and mortality in nestlings in
1981 and designated the organism Giardia duodenalis race psittaci. Identification T h e trophozoite is elliptical and symmetrical, the anterior end being b r o a d and the posterior end pointed. A large sucking disc for adhesion is present o n the ventral face and the dorsal aspect 'is c o n v e x . Eight flagella are present as f o u r pairs, two nuclei are present anteriorly, and the a p p e a r a n c e is c o m m o n l y r e f e r r e d to as "monkey-faced." Cysts have two or f o u r nuclei in a paracentral location and are slightly egg shaped. 4'5'11
Diagnosis T h e trophozoites can be identified by their classic shape and "falling leaf ''12 or u n d u l a t i n g motion. T h e trophozoites can be d e m o n s t r a t e d on fresh, warm feces, but quickly die (within one hour). It is r e c o m m e n d e d to use a saline m o u n t with the feces concentrated no m o r e than would allow for n e w s p a p e r print to be read t h r o u g h the smear and the slide scanned within 3 minutes for the best results b e f o r e significant cooling o f the specimen occurs. 4 Because the passage o f trophozoites may be intermittent and in variable quantities, multiple smears may be r e q u i r e d and at least 20 highdry fields reviewed for each smear. Cysts may be difficult to identify, especially for those not familiar with their anatomy. T h e cysts may be confused with yeasts because they are above the same d i a m e t e r (10 to 14 ~ m x 8 to 10 p,m) but do not have the central elementary body present in giardial cysts. T h e use o f Lugols or D'Antoni's aqueous iodine solutions o n f r e s h s m e a r s o r i r o n - h e m a t o x y l i n , trichrome, or carbolfuchsin stain dried smears will aid in the accurate identification o f Giar-
dia.4,5,12.13 T h e concentration o f cysts using standard sugar or salt solutions is ineffective (eg, sodium nitrate-Fecasol; Evsco Pharmaceuticals, Buena, N J) owing to the distortion or disruption o f their cell walls. 4'5'~1 Saturated zinc sulfate flotation is the technique o f choice for these cysts. 4'5'~ An alternative m e t h o d uses a gauze filter to strain the suspect fecal sample and then centrifuge the filtered fluid at 1,200 to 1,500 r p m for 10 minutes in o r d e r to con-
Pathogenic Flagellated Enteric Protozoa
centrate any cysts present before microscopic examination. 11 T h e use of an enzyme-linked immunosorbent assay (ELISA) test for G lamblia fecal antigen is considered by m a n y parasitologists to be more sensitive than fecal smears or stains owing to the intermittent nature of trophozoite and cyst shedding, the location of infections being p r e d o m i n a n t l y in the small intestine, and the tendency for scant stools from birds in the advanced stage of disease on presentation. T h e use of the test is controversial because it was developed in England for humans, and specific testing on avians has not been extensively pursued, l'la'a2 A study in dogs 14 f o u n d the fecal ELISA to be less sensitive than zinc floatation, more difficult to conduct, and more expensive than the traditional zinc flotation test. T h e 96% specificity results published are for h u m a n studies only. A series of three zinc floatations is currently considered to be a superior test protocol for dogs. m5 Fecal ELISA testing should not be ruled out, but sole reliance on this technique may p r o d u c e falsenegatives. Controlled studies are needed to establish the reliability of this test in different avian hosts.
Clinical Signs T h e most c o m m o n reason for presentation is a chronic enteritis accompanied by one or more of the following signs: weight loss, vomition, ruffled feathers, lethargic, or anorexia. Mortality can be acute (with or without signs) or of a chronic nature in a flock and reach 20% to 50% if u n t r e a t e d in a timely fashion.11'12'16'17 A m a l a b s o r p t i o n / m a l d i g e s t i o n syndrome has been identified with chronic giardiasis and is believed to be secondary to the attachment of massive numbers of trophozoites via their adhesion discs to the villi of the proximal gut. A shifting leg lameness and rough feather coat is believed to be caused by a vitamin E deficiency in cockatiels and budgies manifested as white muscle disease. 11,12'ls'm Dry, flaky dermatitis and a dermal hypersensitivity has been well described for the cockatiel and budgie and is believed to be possible for any psittacine species. 12'ls'm Documentation in other avian groups, such as poultry or ratites, is not f o u n d at this time in the literature.
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Hematology findings may show an elevated eosinophil count, but this finding is not consistent. 11,12,i7-19 Some authorities are skeptical of the association between endoparasitism a n d eosinophilia in avians being as close a relationship as in mammals. 9~ Leading authorities on giardiasis in small animals report the association between Giardia and a circulating eosinophilia to be essentially nil. 6-s Eosinophilia in avians is, at least partly, species specific and not generally associated with parasitic invasions. Avian eosinophils are associated with hypersensitivity and more research is required to further define the relationship in hypersensitivity reactions. 2~ Microbiological cultures may show concurrent bacterial infections, and some researchers believe that the additional stress of bacterial infections are necessary as precursors or as commensurates for parasitic disease signs to occur. This may account for a lack of disease in Giardia-positive birds or clinical resolution of g i a r d i a l - i n f e s t e d b i r d s with a n t i b a c t e r i a l drugs.l,3,11,12,17 Fudge reported an acute bacterial hepatitis secondary to Giardia in a cockatiel.16 Necropsy specimens should have their small gut epithelium scraped and examined via saline smear and stained preparation as well as submitting full sections of gut for histopathology on the event of negative-direct examination.
Parasite Location D u o d e n u m , j e j u n u m , ileum.
Treatment T h e imidazole group has been used traditionally, but the withdrawal of many of this group from the food animal industry owing tO suspected or proven links to carcinogenesis has significantly reduced the choices available. Metronidazole (Flagyl; Searle, Chicago, IL) at 25 to 30 mg/kg SID for 10 days orally has been r e c o m m e n d e d . 1'11 Some patients have been d o c u m e n t e d by the author to routinely require 14, and even up to 30, days of continuous treatment at 25 mg/kg BID to clear the organisms from fecal smears in cockatiels and
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budgies. T h e use o f water-based t r e a t m e n t has b e e n prescribed at 250 m g per 0.25 to 1.0 L as a drinking source. 12'21 Because o f very p o o r palatability, t r e m e n d o u s variability in d i f f e r e n t species' daily water intake (which may also be highly seasonally influenced), and the potential for central nervous system toxicity in some species, this is a p o o r r o u t e o f administration. Injectable metronidazole (Flagyl; SCS Pharmaceuticals, Chicago, IL) at 15 to 50 mg/kg IM as a one time use has been f o u n d to be apparently clinically safe, but the relapse as n o t e d by positive trophozoite and cyst shedding 3 to 4 weeks postinjection makes this a questionable solution. ~2,19,22 Recently, studies have shown albendazole (Valbazen; SKB, Westchester, PA) at 25 mg/lb BID PO for 2 days in dogs and the same dose for 5 days in cats to be m o r e effective than m e t r o n i d a z o l e (94% effective v 67%). 6 This d r u g may provide a safer and m o r e effective alternative to that o f Flagyl for many species, but m o r e investigation is needed. 15 Febendazole (Pancur; Hoechst-Roussell, Somerville, N J) has also been shown to clear giardial cysts in 3 days at 50 mg/kg in controlled studies using six dogs. s'15 T h e author's personal experience in using febendazole in cockatiels with giardiasis has b e e n similar to the results r e p o r t e d in dogs. Carnidazole (Spartrix; Wildlife Labs, Fort Collins, CO) has been r e c o m m e n d e d at 20 mg/ kg as a single t r e a t m e n t as well. 12 It is o f interest to note that a geographical difference exists in the United States, and West Coast clinicians r e p o r t a h i g h e r incidence and m o r e difficulty resolving Giardia cases in both avians as well as small mammals. 6-8'22'23 It is theorized that a variance in pathogenicity exists between strains.
Species Affected B u d g ies , 1-~' 11' 12' 16-19 cockatiels, 1-3,11,i2,16-19 lovebirds, 11,12,24 G r e y - C h e e k e d Parakeets, 11,12 conures, 12 a m a z o n p a r r o t s , T M m a c a w s , 11'12 c o c k a t o o s , l l , 12 toucans,12,16,1s, 25 finches, 25 Galliformes,11 anseriformes,11 Ostriches,3,2.11 Emus, 3'27 as well as native N o r t h A m e r i c a n birds (herons, avocet, shrike, Black-Winged Kite). 16
Trichomonas Name: Trichomonas gallinae. (Synonyms): T gallinarum, T columbae, T halli, T hepaticum, T diversa.
Identification T h e body is roughly elongated or p i r i f o r m and plastic. F o u r anterior flagella are present, and a narrow ~axostyle p r o t r u d e s posteriorly and no free trailing flagellum is present, as in m a n y trichomonads o f mammals. A short undulating m e m b r a n e extends for only a p o r t i o n o f the body and does not trail. Cysts d o not O c c u r . 4'5
Diagnosis Direct saline smears o f lesions o f the u p p e r digestive tract, sinuses, and liver will show largely clear, highly motile trophozoite organisms with t h e i r t y p i c a l j e r k y , s p i r a l motion. 4'11'29 Culturing o f the organism is possible with several types o f media m a n u f a c t u r e d for T foetus *'4'~~ or h u m a n patients. Post m o r t e m analysis can show nondigestive tract loci in addition to the classic, cheesy, yellow abscesses o f the o r o p h a r y n x and u p p e r esophagus. 4'5'29 Organisms can be f o u n d residing in the liver, lung air sacs, serosa o f the intestines, heart, pancreas, and sinuses, as well as less c o m m o n sites in the spleen, kidneys, trachea, and bone marrow. 4'5'31'~2 Stains o f dried smears or tissue impressions using Wrights, Heidenhain's iron-hematoxylin, Bodian Silver impregnation, and Schoudinn's stains are practical for trophozoite identification.
Clinical Signs T h e disease is p r e d o m i n a n t l y one f o u n d in y o u n g birds in the p r i m a r y host, the domestic pigeon (Columba livia domestica), but very little host restriction is noted. 2 T h e incidence o f disease and/or diagnosis is h i g h e r in England, Europe, and Australia over that o f N o r t h A m e r ica. 2 Birds o f prey that feed on doves and pigeons easily become infected via ingestion o f contaminated birds, and the condition is referred to as "frounce." O t h e r species can become * In pouch TF, Biomed Diagnostics, San Jose, CA, 800-9646466
Pathogenic Flagellated Enteric Protozoa
infected through the ingestion of contaminated water sources, facilities, and carrier state of parents feeding altricial chicks. 4'5'16'31-a5 It is estimated that 80% to 90% of adult pigeons are infected and that squabs are immediately infected by affected parents via crop milk transfer as well as subsequent fecal transmission. Disease conditions vary from nonapparent carrier status to poor weight gain to the presence of open-mouthed respiration, emaciation, pasted vents, ruffled plumage, weakness, lethargy, anorexia, and death. 16 The strain of Trichomonas involved is probably the single most relevant feature in assessing pathogenicity potential b e y o n d mere infection. Velogenic strains tend to create the diphtheritic membranes of "wet canker" often seen in cases of high mortality. Mesogenic strains are often associated with the classic caseated abscesses of the upper gastrointestinal tract and oropharyngeal regions. Lentogenic strains often produce no visible lesions. Deep tissue lesions (eg, liver, peritoneum, spleen) are associated with velogenic strains and are aggravated by stress, overcrowding, and poor sanitation. Stabler 36 identified the Jones' Barn (J.B.) strain as being the most pathogenic and was noted to retain its pathogenicity through 300 serial passages in pigeons. 5 Gross lesions must be differentiated from vitamin A deficiency squamous metaplasia, poxvirus, candidiasis, and bacterial abscessation. 4,5,35
Because no cysts are produced by the trophozoites, direct contact for infection must be achieved before drying of the organism occurs. Necropsies in psittacines have shown lesions in the musculature of the neck (budgies), 32 esophageal and tracheal abscesses (BlueFronted Amazon Parrot), 31 and lungs (Nanday Conure and Yellow-Naped Amazon Parrots). ~a
Anatomical Location Predominantly upper gastrointestinal tract, with above-referenced variable sites for velogic strains. Some references indicate an antigenic and/or anatomical difference in upper (T gallinae) and lower (T gaUinarium) gut tract species where T gaUinae has an undulating membrane for three quarters of its length, whereas T gallinarum has a membrane the full length of the body, plus a free trailing portion. 5"16'19 Newer
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references dispute these differences as being inconsequential or nonexistent. 4'28
Treatment Traditionally, like those pharmaceuticals for giardiasis, the imidazoles are highly effective against trichomonas infections. Since the removal of all agricultural flock use forms of the imidazole group in the United States, only metronidazole and carnidazole remain as available agents. Metronidazole has been recommended at 5 mg/100 g of body weight added to feed, 29 16.5 mg/kg PO BID for 5 days for infected raptorsY 50 mg/kg BID PO for 5 days in columbiforms, 3~ and 10 to 30 mg/kg BID PO for 10 days in psittacines. 11'33 Injectable metronidazole at 10 mg/kg IM has been recommended at SID frequency 37 as well as BID protocol. 3~ Water use of metronidazole for flock treatment of trichomoniasis has the significant drawbacks of poor palatability, variable water intake, settling out of solution in water bowls, variable water intake according to species, and weather variability and potential toxicity. Metronidazole has been reported to be toxic in finchesY C a r n i d a z o l e tablets have been recommended from 5 mg and 10 mg PO once depending on body size 3~ to 100 mg/kg PO once for adults 37 in affected pigeons according to various authors. No attempts to use ablendazole or febendazole against trichomoniasis (as in giardiasis) have been reported to the author's knowledge. Resistance to treatment with both oral and injectable metronidazole at an unknown dose for trichomonas in cockatiels has been reported in the literature. 3s Methods of prevention include culling of affected members of the flock, 28 evaluating for the presence of lentogenic tvichomonas, which prevents the infection of birds with disease causing strains, 4'5'a4 sanitation, 4'5'34 and the use of an injection of plasma from an infected bird .4 Freezing of infected carcasses before being fed to raptors will prevent infection.
Species Affected Pigeons and doves, 4'5'11'12'16'18"19'34'35'39'4~ poultry,4,5,l 1,16,28,4I raptors,16,19,31,39,42,43 budgies, 11,12,16,18,19,26,33,39,40,44 cockatiels,11,33, 42
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lovebirds, 24 Blue-Fronted Amazons, 31 YellowNaped Amazons, 33 Nanday C o n u r e s Y canaries,2,16,19,26,29,40,42,45 finches,8,16,17,19,26,29,40,42 and ratites. 3'46-48 Other related organisms have been reported to be associated with disease in avians. They include tritrichomonas in chickens, turkeys, and possibly ducks (T eberthi), 4'5'28'49 Tetratrichomonas in gallinaceous birds (T gallinarium), 4'5'28'49 geese (T anseris), 4 ducks (T anatis), 4 and Pentatrichomonas in fowl (T gallinarum). 4'5'28 Most of these parasites are nonpathogenic unless the conditions of captivity or poor husbandry culminate to warrant treatment as part of a corrective program.
Histomonas Name: Histomonas meleagridis. Identification H meleagridis is pleomorphic, has four life stages, and the structure is based on the stage observed. 1. Invasive stage--Found in early liver and cecal lesions. This form is actively ameboid with pseudopods. The cytoplasm is basophilic with an outer zone of clear ectoplasm and is approximately 8 to 17 ixm wide. 2. Vegetative stage--Found at a slightly more advanced stage postinvasion. The organism is slightly larger (12 to 21 Ixm long) and is slightly less active than stage 1. The organisms are often found packed at the center of lesions. 3. Resistant stage--Not truly resistant. Found singly or grouped with an acidophilic cytoplasm containing small globules. 4. Flagellated f o r m - - F r e e swimming and found in the cecal lumen. Body is ameboid and 5 to 30 p~m wide. Cytoplasm is clear and may contain bacteria or food particles. A single nucleus and a single flagellum are present. Occasionally, two flagella may be present. A related form, H Wenrichi (also known as Parahistomonas wenrichi), has four flagella but is nonpathogenic and must be differentiated from H meleagridis.
Disease Signs The disease is predominantly one found in gatlinaceous birds, especially turkeys, whereas in other species it is considered to be less p a t h o g e n i c or even an i n c i d e n t a l f i n d ing. 4'5'11'16'40'41'47'50-52 The organism affects birds of all ages, but the intensity, course, and mortality varies with age. Poults less than 3 weeks old are resistant, but from 3 to 12 weeks of age, mortality can reach 100%. Death generally occurs within 2 to 3 days of clinical signs. Older birds show more chronic morbidity and recovery can occur. The initial signs of weakness, drowsiness, and droopy head and tail feathers is followed by a sulphur-colored diarrhea after the 21-day incubation period. 4'5'2s On post mortem, the principal lesions are found in the ceca and liver. Cecal mucosa first shows pinpoint ulcers, which enlarge and eventually coalesce. Cecal perforations followed by peritonitis are possible. The mucosal lining thickens and becomes increasingly necrotic, producing a foul exudate that can consolidate to form a tightly bound cecal plug. T h e affected cecum subsequently becomes highly enlarged. Hepatic lesions are pathognomonic, being circular, yellow to greenish at the necrotic sites, and depressed. These depressions vary in diameter and are generally up to 1 cm (or more) and extend deeply into the parenchyma. Lesions may also be located in the kidney, spleen, mesentery, and lungs as areas of circular, white necrotic foci. Affected birds are often emaciated, have classic yellow diarrhea, and may exhibit bloody droppings; turkeys often have cyanotic skin of the head (hence, the term "Blackhead") presumably caused by poor circulation.
Anatomical Locations Liver, cecum, and to a lesser extent, kidney, spleen, mesentery, and lung.
Diagnosis Fecal smears may show trophs in an advanced state of disease. Cecal scrapings taken from a freshly killed bird while still warm is the most expeditious manner for rapid diagnosis using a saline mount. Cultures of histomonads
Pathogenic Flagellated Enteric Protozoa
can be accomplished using fresh tissue samples harvested at necropsy, and macerating them into modified Dwyers medium for later identification. 2a Histopathology is required for diagnosis of the nonflagellated tissue phases, and the tissues of choice are cecal wall and liver. Other organs showing gross lesions should be included. Histomonads at this stage must be differentiated from giant cells, macrophages, and yeasts using H & E or periodic acid-Schiff stains. Liver samples will show classic hepatocellular necrosis with extensive numbers of lymphocytes and macrophages and moderate populations of heterophils. The organisms may be found in the periphery of lesions. 4'5'2s White blood counts have been noted at levels of up to 70,000 leukocytes/mm3 at 10 days postinfection but return to normal by 21 days postinfection. Aspartate a m i n o t r a n s f e r a s e (AST) (SGOT) a n d lactic d e h y d r o g e n a s e (LDH) levels increase as livers become increasingly affected. Bilirubinuria occurs later in the process of hepatic involved birds. Those birds only having cecal lesions (eg, chickens) will exhibit decreased AST, LDH, and other enzyme levels suggesting impaired liver functions. 28
Epidemiology This parasite is ubiquitous in chickens and is one of the foremost infectious diseases of concern in the turkey industry. The most frequent form of infection is by ingestion of the infected eggs of the cecal worm Heterakis gallinarum and remains the most prominent reservoir for histomiasis in birds. Infected cecal worm eggs can remain viable for up to 2 years. It is essentially impossible to run turkeys or other susceptible gallinaceous fowl with chickens on the same range without contacting a flock disease problem. The same is assumed for other species of avians, including exotic fowl and free range mixed collections, in which infection has not been documented, but such a susceptibility exists for the host in question. 4'5'11'19'28'4~ Direct transmission of the trophozoites is possible by ingestion if the organism is not allowed prolonged exposure to the environment. Direct ingestion of infected tissues is also a possible route of exposure and is relevant to
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those species known to practice cannibalism, such as pheasants and cockatoos. Establishment of histomoniasis also requires the presence of commensal bacteria, especially E coli and Clostridium perfringens, among others. Experimental efforts in gnotobiotic turkeys produced clinical signs in only one of 12 subjects and 0 mortality. 5s Prevention is best established by keeping vector species, such as chickens, game fowl, quail, and pheasants separated from other avians. 4'5'28 The practice of keeping mixed collections with quail, pheasants, and exotic jungle fowl on the floors of aviaries as scavengers is to be highly discouraged. Wire-floored, dropthrough aviaries, concrete floors, and high level sanitation are the other fundamental aspects of control and/or preventi0n. 4'5'28'54'55 Reinfection is not possible owing to the immunity produced in recovered birds. 4'5 Injection of serum from recovered birds did not protect against infection. 4
Treatment As with other flagellate infections, the imidazoles are recommended and largely unavailable at the current time. This has created substantial concern for the turkey and game bird industries. Metronidazole, carnidazole nifursol, and furazolidone are recommended for treatment.
Species Affected Chickens, 4'5'28 turkeys, 4.5,11,16,19,40,41,47,50-52,54 peafowl,41 quail, 4'5'28'5~ chukar partridges, 4'5'28 guinea fowl,4'5"35'42 ruffled grouse, 4'5'28 palawan peacock pheasant, 51 assorted "zoo birds", 5l and ratites. 3,40,47
Pleuromonas Name: Pleuromonas jaculans. Identification The body is slightly ameboid. Two flagella are present and are located on opposite poles of the organism. The anterior flagella is short and may be rolled into a ring-like structure. The posterior flagella is at least two to three times the length of the body and is relatively large in diameter. The cysts are spherical. 56
Robert Clipsham
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Disease Signs Assumed to be enteritis depending on host immune status, host species tolerance, and total numbers of parasites. Primary source of infection is listed as stagnant water. Anatomical Location: Ceca. Species Affected: Chicken.
Monocercomonas Name: Monocercomonas gallinarium. 4'5 (Synonyms): trichomastix and eutrichomastix. May be a degenerate form of Tritrichomonas eberthi. Identification Unicellular body is pirilorm with a bluntly rounded anterior end. The four flagella are found on the leading edge with three flagella pointed forward and the fourth trailing backwards. No undulating membrane is present. No cysts are formed.
Disease Signs Possibly associated with enteritis, but pathogenicity is assigned to the species associated with this organism. Total numbers and host resistance are probably similarly relevant to disease presence, as in other flagellate infections. Anatomical Location: Ceca. Species Affected: Reported in chickens.
Hexamita Name: Hexamita meleagridis. Now renamed Spironucleus meleagridis. Other species include S columbae (also known as Hexamita columbae, Octomitus columbae) in pigeons. 4'5'16 S intestinalis in ducks. 4 Identification This flagellate is piriform in shape with a less r o u n d e d anterior end than most other flagellates in avians, is smaller than Giardia at 9 • 3 ~Lm, has no suction disc, and swims in a smooth, linear fashion. 4'5'1~'2s It has eight prominent flagella, four anterior, one project-
ing down each side and two trailing from the posterior. No cysts are formed and reproduction is by longitudinal binary fission.4
Disease Signs Spironucleosis is referred to classically as infectious catarrhal enteritis when f o u n d in poults. Weight loss, chronic diarrhea, poor feather coat, lethargy, and death are described for both fowl and other groups of avians, including psittacines. 4"5'1t'16 Affected individuals remain fairly bright and maintain an appetite and vocalization until shortly before death, unlike many other protozoal enteric diseases. The incubation is reported to be 4 to 7 days and the disease is largely found in juvenile birds. 35
Anatomical Location Duodenum and small intestine, with same incidence noted in the cecum and bursa.
Diagnosis Saline smears of loose stools taken directly from warm droppings may demonstrate the active trophs. 57 The small size, large number of flagella, and linear locomotion are important differences from Giardia and trichornonas. S columbae can be readily demonstrated on asymptomatic pigeon fecal mounts from infected birds. Necropsy efforts should include scrapings from the small intestine, particularly the jejun u m and d u o d e n u m . The small bowel will characteristically show poor muscle tone of the gut loops plus thin, foamy contents. 4'5'28 The disease incidence of this parasite is extremely low in comparison with most other flagellates.49 Only 10 cases were reported in domestic birds in the United States in 1986 versus a 2-million annual loss to the turkey industry alone from Histomoniasis. 2s An increasing awareness of this organism and its presence in Europe and Australia may change the clinical appreciation for this parasite and its impact on aviculture.
Treatment Most drugs are ineffective against S meleagridis. Those drugs approved for meat and egg-producing fowl include chlortetracycline,
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Pathogenic Flagellated Enteric Protozoa
furazolidone, and butynorate with no degree of efficacy reported. 2s Prevention is the same standard sanitation, disinfection, species separation, and good husbandry practices recommended for all livestock and avicultural operations. The use of wire floors and elimination of stagnant water is the most efficient means of eliminating transmission. 4,5,28
Species Affected Domestic turkeys,4'5'16'28 Rio Grande Turkey, 51 pheasant, 4,5,28 quail, 4,5,28 partridge,4.5, m,zs,S7,58 budgies,16 cockatiels,iX Splendid Grass Parakeets,11 lories,11 and King Parrots. 44
Cochlosoma Name: Cochlosoma anatis. Cochlosoma sp (unnamed species). Identification Members of this genus have an oval body (6-12 • 4-7 ~m) with a broad anterior pole and a narrowly rounded posterior. Six flagella of unequal length arise from the front end, two of them trailing. A large sucking organ is present on the anterioventral surface covering one third to one half of the body length. A slender, fibrillar axostyle is present also. The movement is described as being erratic and jerky with horizontal rotation, but no spiraling action like Giardia. 4'5'29 Cysts are reported for C anatis with an oval shape by one author. 5 Longitudinal binary fission is reported as being the mode of reproduction by a more current source. 4
Disease Signs Dehydration, yellow to green malodorous droppings, maldigestion, fading of fledglings, and mortality is reported in passerines. 27'45 Catarrhal enteritis has been documented in turkeys with C anatis. Necropsy shows lesions similar to spironucleosis. 4'5
Anatomical Location Small intestine, large intestine, ceca and cloaca.4,5,29,45
Diagnosis Saline smears from fresh feces or scrapings of gut mucosa on necropsy.
Treatment Dimetridazole and ronidazole are reported to be of value in the literature. 29'45 It is postulated that metronidazole would be an acceptable substitute in the face of the lack of availability of the first two drugs at this time. Carnidazole and metronidazole have been recommended by one authority based on good resolution of signs in psittacines.1
Species Affected Domestic ducks, 4"5 wild ducks, 4'5 turkeys, 5 and Australian Finches. 29'45 Also reported to be present in wild psittacines in Australia. 59 It is reported to be apathogenic in Bengalese and Japanese Finches who may act as the vector source for other finches when acting as surrogate parents. Factors common to other protozoal infections, such as immune status, age, sanitation, and stress, probably influence host susceptibility.
Chilomastix Name: Chilomastix gaUinarum. Chilomastix sp (unnamed species). Identification The body is asymmetrically piriform (6 to 24 • 3 to 10 ~m) and plastic with a substantial cytostomal groove at the anterior end. There are three anteriorly directed flagella and a short fourth flagellum, which undulates in the cytostomal cleft along the body wall. Cysts are formed and are lemon shaped. The fibrils of the trophozoite persist in the cystic form. Cysts are rare in fecal smears compared with other cyst-producing protozoa.
Disease Signs This organism is considered to be slightly pathogenic and found with regularity in the ceca of normal chickens and turkeys on routine examination. 4 Enteritis of a nonspecific character is assumed to be associated with those individuals sustaining the s t a n d a r d
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Robert Clipsham
stresses of poor diet mismanagement or immunoinsufficiency.
Anatomical Location Ceca and large intestine.
Diagnosis Direct fecal saline smear on warm droppings and mucosal scrapings of the large 'intestine.
Species Affected Ratites appear to have the only significant incidence of confirmed diagnosis of B coli at this time. 1-3'46'48 It is assumed that the overgrowth of this organism is primarily an indicator of other preexisting disease and should serve as an activator for a more detailed investigation of health status and m a n a g e m e n t practices.
Tetrahymena
Treatment None is listed in the literature reviewed.
Names: T. pyriforms. 4
Species Affected
Identification
Chicken, 4'41 t u r k e y , 4'5'41 ducks, 4'5 and geese. 4
A smaller ciliate (40 to 60 • 15 to 30 ~m) than B coli with a piriform body and uniformly distributed cilia.
Ciliated Protozoan Parasites: Balantidium Name: Balantidium coli. (Synonyms) B sui, B wenrichi. Identification The body is oval and extremely large in comparison with the previously described flagellates (30 to 150 • 25 to 120 pxm). A sausage or bean-shaped macronucleus and the associated micronucleus are evident. Many vacuoles containing food, bacteria, and red blood cells are present. The rows of cilia are obvious along the lateral margins, and the method of locomotion is a smooth gliding via the rhythmic motion of the rows of cilia.
Disease Signs Rare, but reported as dysentery and diarrhea, or present in cases of enteritis. 1"3'46 It is ordinarily a commensal in the hind gut, especially the cecum, where it digests starch and bacteria.l~
Disease Signs Nonspecific. Found only in birds with vitamin A deficiency.
Anatomical Locations Digestive tract, infraorbital sinuses and conjunctiva.
Diagnosis Direct smears of affected tissues.
Treatment Vitamin A and antibiotics, as indicated.
Species Affected Only documented in chickens to date. This is a free-living organism and is frequently used in protozoal research. It is a facultative parasite of man and thereby assumed to be potentially in contact with captive avians. More investigation into the many species of captive kept exotic avian species is warranted.
Anatomical Location
Amebic Protozoal Parasites (Table 2)
Large intestine.
Very few of this large group (subphylum Sarcodina) are pathogenic for animals. The few documented reports are of significance because they serve as important differentials and as significant indicators for mismanagement in captive operations for aviculturists.
Treatment None prescribed. Treatment for predisposing factors and other disease processes present is the recommended therapeutic approach.
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Table 2. Amebic Protozoal Parasites Names
Host
1. Pathogenic Entamoeba anatis (E histolytic group) 4 2. Nonpathogenic Entamoeba gallinarum (E coli group) 4'~ Acanthamoeba polyphaga Hartmanella vermiformis Valkampfia enterica Endolimax gregariniformis
Duck Duck, chicken, turkey, guinea fowl, goose Pigeon, turkey Turkey Turkey Chicken, turkey, guinea fowl, pheasant, goose, duck, heron, owl, various wild avians
p a t h o g e n i c enteric p r o t o z o a l parasites affecting avian species. It b e c o m e s readily e v i d e n t that m o s t o f these o r g a n i s m s are o p p o r t u n i s t s o r s e c o n d a r y i n v a d e r s o f c o m p r o m i s e d o r imm a t u r e birds u n d e r c o n d i t i o n s o f less t h a n optimal m a n a g e m e n t a n d h u s b a n d r y . P e r h a p s the m o s t significant c o n c l u s i o n that the a t t e n d ing avian v e t e r i n a r i a n m i g h t d r a w is t h a t t h e t r u e scope o f the c u r r e n t h e a l t h p r o b l e m is multifactorial a n d p r e s e n t s an o p p o r t u n i t y to e d u c a t e the client. P r e v e n t i o n is usually b o t h a long-standing effort and reward once the s h o r t - t e r m n e e d s h a v e b e e n rectified with the a p p r o p r i a t e diagnostics a n d medication.6 ~
Identification T h e t r o p h o z o i t e is plastic, m o v e s by m e a n s o f p s e u d o p o d s , a n d has n o cilia o r flagella f o r t h e s p e c i e s r e l e v a n t to a v i a n s . C y s t s a r e f o r m e d . T h e r e a d e r is r e f e r r e d to the references n o t e d f o r a m o r e extensive d e s c r i p t i o n o f each f o r m . T h e basic issue o f n o t e h e r e is r e c o g n i t i o n o f these o r g a n i s m s a n d their potential f o r p a t h o genicity, especially in a b e r r a n t hosts, which are p o o r l y d o c u m e n t e d to date. 28'4t'48 W h e t h e r these parasites b e c a m e a n y g r e a t e r m a t t e r o f c o n c e r n will be b a s e d o n f u t u r e studies. W a r m fecal o r g u t c o n t e n t s m e a r s with saline, p h a s e c o n t r a s t m i c r o s c o p y , a n d / o r stained slides are o f t e n necessary to identify these variable-sized and relatively translucent parasites. 28 Tissue sections o n h i s t o p a t h o l o g y are also diagnostic. 52
References 1. 2. 3. 4. 5,
6. 7. 8. 9. 10.
11.
Anatomical Location P a t h o g e n i c f o r m s - - I n t e s t i n a l tract. A p a t h o g e n i c f o r m s - - I n t e s t i n a l tract, trachea.
12.
13.
Treatment M e t r o n i d a z o l e a n d v a r i o u s antibiotics to eliminate c o n c o m i t a n t e n t e r i c bacteria. 4'52
14.
Species Affected
15.
Ducks, ostriches, ratites. I'3,4A8
Conclusion T h e t h r u s t o f this p r e s e n t a t i o n has b e e n to p r e s e n t the diversity a n d c o m p l e x i t y o f motile,
16.
17.
Greiner E: Personal communication, 1995 Graham D: Personal communication, 1995 Stewart J: Personal communication, 1994 Levine ND: Veterinary Protozoology. Ames, IA, Iowa State University Press, 1985 Soulsby EJ: Helminths, Arthropods and Protoza of Domesticated Animals (ed 6). Baltimore, MD, Williams & Wilkins, CO, 1975 Tamms T: Personal communication, 1994 Ryan P: Personal communication, 1987 Barr S: Personal communication, 1995 Visvesara GS, Healy GR, Meyer EA: Giardiasis. J Protozool 27:38A, 1980 Jakubowski W, Hoff JC (eds): Waterborne transmission of giardiasis. US Environmental Protection Agency. EPA-600/9-79-001, 1979 Greiner E, Ritchie B: Parasites, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 1007-1029 Fudge A: Avian giardiasis: Syndromes, diagnosis and therapy: in Proceedings of Association of Avian Veterinarians, Miami, FL, 1985, pp 155-164 Dalhausen R: Detection of giardia.with carbol fuchsin stain. J Assoc Avian Vet 7:104-I05, 1993 Hall EJ, Rutgers HC, Batt RM: Evaluation of the peroral string test in the diagnosis of canine giardias. J Sm Anita Pract 29:177-183, 1988 Barr SC, Bowman DD: Giardiasis in dogs and cats. Compendium Cont Educ Prac Vet, 16:603-611, 1994 Keymer IF: Parasitic diseases, in Petrak ML (ed): Diseases of Cage & Aviary Birds. Philadelphia, PA, Lea & Febiger, 1982, pp 535-598 Rosskopf W, Woerpel R, Reed-Blake S, et al: Pet avian disease syndromes, in Proceedings of Association of Avian Veterinarians. Boulder, CO, 1985, pp 295-318
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18. Barnes H J: Parasites, in Harrison G, Harrison L (eds): Clinical Avian Medicine and Surgery. Philadelphia, PA, Saunders, 1986, pp 472-485 19. McCluggage D: Parasitology in caged birds, in Proceedings of Association Avian Veterinarians. Seattle, WA, 1989, pp 97-100 20. Gerlach H: Defense mechanism of the avian host, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Applications. Fortworth, FL, Wingers, 1994, pp 114-120 21. McDonald S: Personal communication, 1989 22. Ritchie G, Harrison G: Formulary, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Applications. Fortworth, FL, Wingers, 1994, pp 457-477 23. Joyner K: Personal communication, 1991 24. Dorrestein G, Marein H: Aviculture and veterinary problems in lovebirds, in Proceedings of Assoc of Avian Vet. Honolulu, HI, 1987, pp 243-261 25. Worell A: Management and medicine of toucans, in Proceedings of Association of Avian Veterinarians. Houston, TX, 1988, pp 253-262 26. Mac Whirter P: Passeriformes, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 1172-1199 27. Wade J: Ratite pediatric medicine and surgery, in Proceedings of the Association of Avian Veterinarians. New Orleans, LA, 1992, pp 340-353
37.
38. 39.
40. 41.
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43. 44.
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28. McDougald LR: Other protozoal diseases of the intestinal tract, in Calnek B, Barnes H J, Beard CW, et al (eds): Diseases of Poultry. Ames, IA, Iowa State University Press, 1991, pp 804-813 29. Clipsham R, Murray M: Small pets: Birds, rabbits and exotics, in Vet Post-Graduate Institute. Santa Cruz, CA, 1993
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30. E h r e n b e r g M, Rupiper D: Introduction to pigeon practice, in Proceedings of the Association of Avian Veterinarians. Reno, NV, t994, pp 203-211
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31. Garner M, Sturtevant F: Trichomoniasis in a Blue Fronted Amazon Parrot. J Assoc Avian Vet 6:17-20, 1992 32. Ward FP: Parasites and their treatment in birds of prey, in Fowler M (ed): Zoo and Wild Animal Medicine (ed 2). Philadelphia, PA, Saunders, 1986, pp 425429 33. Murphy J: Psittacine Trichomoniasis, in Proceedings of the Association of Avian Veterinarians. New Orleans, LA, 1992, pp 21-24 34. Rupiper D, Briggs K, Ehrenberg M: Management of trichomoniasis paramyxovirus-1 and salmonellosis in a pigeon loft, in Proceedings of the Association of Avian Veterinarians. Reno, NV, 1994, pp 241-247 35. Dorrestein JG, Sluis J Van der, Hage MH Van der: Diseases of pigeons with emphasis on racing pigeons, in Proceedings of the Association of Avian Veterinarians. Boulder, CO, 1985, pp 181-203 36. Stabler RM: T h e effect of Furazolidone on pigeon
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51. 52. 53.
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trichomoniasis due to T. gallinae. J Parasit 43:280-282, 1957 Richie B, Harrison G: Formulary, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 457-478 Curtis-Velasco M: Giardia-like organisms in cockatiels. J Assoc Avian Vet 4:206, 1990 Rosskopf wJ, Shindo MK: Crop disorders in pet avian species, in Proceedings of the Association of Avian Veterinarians. Nashville, TN, 1993, pp 263-267 Schwartz LD: Intestinal parasites in captive birds. Assoc Avian Vet Newsletter 4:66-69, 1983 Schales C, Schales K: Galliformes, in Harrison G, Harrison L, Richie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 1218-1236 Ramsay E, Drew M, j o h n s o n B: Trichomoniasis in a flock of budgies, in Proceedings of the Association of Avian Veterinarians. Phoenix, AZ, 1990, pp 309-311 Halliwell HH: Diseases of birds of prey. Vet Clin North Am (Small Anim Pract) 9:pp 541-568, 1979 Mc Whirter P: Avian practice in Australia, in Proceedings of Association of Avian Veterinarians. Seattle, WA, 1989, pp 46-56 Dorrestein, J Hage van Vander, Zwart P: Diseases of passerines, especially canaries and finches, in Proceedings of the Association of Avian Veterinarians. Boulder, CO, 1985, pp 53-70 Hanley RS, Woods LW, Stillian DJ, et al: Serpulinalike spirochetes and flagellated protozoa associated with a necrotizing typhlitis in the rhea (Rhea Americana), in Proceedings of the Association Avian Veterinarians. Reno, NV, 1994, pp 157-162 Stewart J: Ratites, in Harrison G, Harrison L, Richie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 1284-1326 Shivaprasad HL: Neonatal mortality in ostriches: An overview of possible causes, in Proceedings of the Association of Avian Veterinarians. Nashville, TN, t993, pp 282-293 Greve JH: Parasitic diseases, in Fowler M (ed): Zoo and Wild Animal Medicine (ed 2). Philadelphia, PA, Saunders, 1986, pp 234-251 Olsen GH: Common infectious and parasitic diseases of quail and pheasants, in Proceedings of the Association of Avian Veterinarians. Nashville, TN, 1993, pp 146-150 Schmidt RE, Hubbard GB: Atlas of Zoo Animal Pathology, vol 2. Boca Raton, FL, CRC Press, 1987 Smith HA, Jones TC, H u n t RD: Veterinary Pathology (ed 4). Philadelphia, PA, Lea & Febiger, 1972 Doll JP, Franker CK: Experimental histomoniasis in gnotobiotic turkeys. I. Infection and histopathology of the bacteria free host. J Parasit 49:411-414, 1963 Flammer K: Avicultural medicine of psittacine birds. Vet Clin North Am (Small Anim Pract) 14:381-401, 1984 Clubb SL, Flammer K: T h e avian flock, in Harrison G,
Pathogenic Flagellated Enteric Protozoa
Harrison L, Richie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 45-62 56. Martin CL, Robertson M: Further observations on the cecal parasites of fowls. J Micro Sci 57:53-81, 1911 57. Pennycott TW: Pigeon diseases--Results from a Scottish diagnostic laboratory, in Proceedings of the Association of Avian Veterinarians. Reno, NV, 1994, pp 231-239
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58. Zwart P: Pigeons and doves, in Fowler M (ed): Zoo and Wild Animal Medicine (ed 2). Philadelphia, PA, Saunders, 1986, pp 440-445 59. Fillopich L: Personal communication via D. Graham, 1995 60. Speer B: Avicultural medical management: An introduction to basic principles of flock medicine and the closed aviary concept. Vet Clin North Am (Small Anita Practice) 21:1393-1404, 1991
Endoparasitism continues to be a significant factor in avian health care for both clinicians and aviculturists. The motile enteric protozoal parasites comprise a fairly finite but markedly significant group of potential and active pathogens whose presence require accurate diagnosis and treatment. Several organisms in this group are considered to be endemic in various groups or species of birds and are common enough to warrant routine investigation, both on acquisition as well as during annual reexamination. Perhaps more significant, in the general picture of avian health and disease, is the role of these unicellular, motile parasites as sentinel organisms whose presence dictates a review of their relationship to the overall medical management of the bird(s) in question.
T ~ z oe subject of pathogenic flagellated protoal infections in avian species tends to diverge in its definition and/or recognition in regard to host(s), specific parasitic genera, and/ or species a n d t h e i r i n h e r e n t d e g r e e of pathogenicity, making the issue controversial at both the academic and clinical levels. Further complicating the subject is the disparity of documented evidence published on specific parasites in exotic and pet birds, as those that are predominantly reported are in domestic fowl. Many times the reports by clinicians of various pet and/or aviary bird cases involving flagellates are anecdotal, where multiple diseases often coexist. Furthermore, the exact identification of a specific genus and species is difficult or impossible owing to limitations in the on-site laboratory used, leading to misinterpretation or generalized reference to the presence of a "Giardia-like" organism. Con-
trolled studies in exotic and/or avicuhural subjects are substantially unavailable at this time. This report will focus on the clinically important aspects of the various flagellates, as well as bring forth some known varieties of relevant parasites that are often not considered by the practitioner. The amoebae and ciliates are also included as a matter of practicality because they are phylogenetically related and constitute a very small group of potential and actual pathogens for avians. F u r t h e r m o r e , their identification as a differential diagnosis is of consequence for the outcome of a case. A reasonable summary of the current philosophy concerning this class of parasites for the avian practitioner will help to put the specifics detailed here in perspective. 1-a The presence of flagellates does not always constitute a disease process: 9 flagellated parasitic disease is the combined result of host resistance, immune status, parasite load and pathogenicity of the parasite; 9 many parasites appear to require concurrent infection from bacteria, viruses, and yeasts; 9 general health s u p p o r t in the f o r m o f proper diet, stress reduction, sanitation, and sound management will do more to prevent parasitic disease than pharmaceutical intervention in the greater scheme; 9 flagellates generally require a wet environment to persist in their motile form; consistent washing and drying of living facilities will enhance control; and 9 the presence of parasitic disease is a vigorous indication for a review of avicultural management and on going preventative health measures.
From Thousand Oaks, CA. Address reprint requests to Robert Clipsham, DVM, Exotic Medicine and Management Consultant, 560 N Moorpark Rd, Suite 168, Thousand Oaks, CA 91360. Copyright 9 1995 by W.B. Saunders Company 1055-937X/95/0403 -000255.00/0
Since the discovery by Antony van Leeuwenhook during the 17th Century (Eimereria stiedae from a rabbit gallbladder in 1674 and Giardia lamblia from van Leeuwenhook's personal case of diarrhea in 1681) some 65,000 species of protozoa have been described, many by sophisticated biochemical processes, such as
Copyright 9 1995 by W.B. Saunders Company Key words: Protozoa, flagellates, enteritis, avian, ciliates, amoeba.
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antigenic structure (Table 1). The following material will focus on the pertinent anatomical structures of the pathogenic flagellates, ciliates and amoebae as they relate to presence, host location, disease signs, and treatment.
Locomotion 4,s Flagellates use a whiplike flagella composed of a central axoneme and an outer sheath. The structure arises from a kinetosome in the cytoplasm. T h e flagellum may pass posteriorly along the body freely or be attached to the body along its entire length or at several points to form an undulating membrane. The number of flagella may vary from one to eight. Flagella may be temporarily present in some developmental stages of specific ciliates. Ciliates use cilia, which are essentially tiny flagella with the same internal structural anatomy as true flagellates. The ciliophora may be Table 1. Classification4:
Subkingdom: Protozoa Zoomastigophorasid (flagellates) K inetoplastorida B odonorina Bodonidae P leuromonas Retortamonadorida Chilomastix Cochlostomatorida Cochlosoma Diplomonado~ida Giardia, Hexamita, Spironucleus Trichomonadorida Monocercomonadidae Histomonas, monocercomonas 7u Trichomonas, Tritrichomanas, Tetratrichomonas, P entatrichomonas Phylum: Ciliophora (ciliates) Class: K inetofragminop horasida Subclass: Vestibuliferasina Family: Balantidiidae Genera: Balantidium, Tetrahymena Sarcodina (amoebae) Subphylum: Lobosasida Class: Order: Amoebrdorida Tubulinorina Suborder: Genera: Amoeba, Endolimax, Entamoeba Acanthopodorina Suborder: Genera: Acanthamoeba, Hartmannella Schizopyrenorida Order: Genus: Vahlkampfia Class: Order: Suborder: Family: Genus: Order: Genus: Order: Genus: Order: Genera: Order: Family: Genera: Family: Genera:
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in large numbers, arranged in rows and beat synchronously, or may be more specialized in arrangement and fused into organelles, such as tufts (cirrus), membranelles (fusion of two or more rows), or an undulating membrane (formed by the longitudinal fusion of a cilia
rOW). Amoebae move by pseudopods, which are temporary organelles of locomotion formed and retracted as needed. There are four types of pseudopods: lobopods, filopods, myxopods, and anopods. Furthermore, locomotion may be described for the fashion characteristic for the parasite in question, such as smooth, gliding, bending, snapping, jerky, or twisting. These motions when observed under the microscope may be helpful or essential in correct parasite identification.
Reproduction 4's Reproduction for the protozoa under consideration may be sexual or asexual. The most common type of asexual reproduction is binary fission with a simple division of the parent cell splitting into two daughter organisms. This type of reproduction is used by flagellates and amoebae. Ciliates use a form of sexual reproduction termed conjugation where two individuals temporarily fuse and donate a haploid pronucleus, each after dividing their micronuclei several times. The ciliates then separate and an internal nuclear reorganization then follows. Some protozoa form cysts, which occurs when the organism forms a thick wall around itself for environmental resistance purposes. The motile, vegetative form of a protozoan is termed a trophozoite.
Flagellated Protozoan Parasites The private avian clinician will be most experienced with Giardia, Trichomonas, or Hexamita, depending on the avian species seen most often during normal case loads. Many times the inability to rapidly diagnose a parasitic disease leads to the random use of antiflagellate prescriptions and a hindsight review based on a therapeutic diagnosis. Often this is because of the decision to avoid invasive procedures in
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the event that no organisms are being shed or a lack o f awareness o f the availability o f alternative diagnostic methods. It is the intent o f this section to e n c o u r a g e avian veterinarians to e x p a n d their diagnostic base, visual identification capacity, and, foremost, an appreciation o f the disease complex, which includes all the basic c o m p o n e n t s o f s o u n d h u s b a n d r y a n d m a n a g e m e n t whose oversight are usually the real culprits leading u p to the diagnosis o f endoparasitism. Failure to p u r s u e the first three items will most likely result in a persistence o f the greater cause.
Giardia
Name: Giardia lamblia. (Synonyms): G lamblia, G intestinalis, G enterica, G duodenalis, Cercomonas intestinalis, Lamblia intestinalis, Megastoma entericum. T h e controversy as to w h e t h e r all host species for Giardia infection are subject to G lamblia and, t h e r e f o r e , d i f f e r e n t cases of separate host species are only n o t e d in their d i f f e r e n c e by individual host species n o m e n c l a t u r e or whether, in fact, separate species o f Giardia specifically infect each host type still remains as subject o f debate. 4'6-s T h e view c u r r e n t l y gaining p r e d o m i n a n c e is that only t h r e e species exist (G duodenalis, G agilis (amphibia), and G muris) and the traditionally held host specific names and infectivity restrictions are m o r e a matter o f custom and convenience (eg, G equi, G boris, G canis, G cati, G caviae) r a t h e r t h a n owing to a biological basis. F u r t h e r m o r e , e x p e r i m e n t a l cross-infectivity have only been partially successful, and strains o f G cati, G caviae, and G intestinalis are antigenicaUy the same. 9 Additionally, m o r p h o l o g ical studies o f the various strains show that only G muris has any distinct physical differences o f the strains reviewed. 4 Despite the incidence o f 3.9% in h u m a n fecal examination surveys, 1~ not all positive cases showed evidence o f disease, and only a small n u m b e r showed chronic diarrhea, 4 thereby emphasizing the disparity between infection and disease n o t e d in avians and small animals. Box identified Giardia associated with enteritis in parakeets and mortality in nestlings in
1981 and designated the organism Giardia duodenalis race psittaci. Identification T h e trophozoite is elliptical and symmetrical, the anterior end being b r o a d and the posterior end pointed. A large sucking disc for adhesion is present o n the ventral face and the dorsal aspect 'is c o n v e x . Eight flagella are present as f o u r pairs, two nuclei are present anteriorly, and the a p p e a r a n c e is c o m m o n l y r e f e r r e d to as "monkey-faced." Cysts have two or f o u r nuclei in a paracentral location and are slightly egg shaped. 4'5'11
Diagnosis T h e trophozoites can be identified by their classic shape and "falling leaf ''12 or u n d u l a t i n g motion. T h e trophozoites can be d e m o n s t r a t e d on fresh, warm feces, but quickly die (within one hour). It is r e c o m m e n d e d to use a saline m o u n t with the feces concentrated no m o r e than would allow for n e w s p a p e r print to be read t h r o u g h the smear and the slide scanned within 3 minutes for the best results b e f o r e significant cooling o f the specimen occurs. 4 Because the passage o f trophozoites may be intermittent and in variable quantities, multiple smears may be r e q u i r e d and at least 20 highdry fields reviewed for each smear. Cysts may be difficult to identify, especially for those not familiar with their anatomy. T h e cysts may be confused with yeasts because they are above the same d i a m e t e r (10 to 14 ~ m x 8 to 10 p,m) but do not have the central elementary body present in giardial cysts. T h e use o f Lugols or D'Antoni's aqueous iodine solutions o n f r e s h s m e a r s o r i r o n - h e m a t o x y l i n , trichrome, or carbolfuchsin stain dried smears will aid in the accurate identification o f Giar-
dia.4,5,12.13 T h e concentration o f cysts using standard sugar or salt solutions is ineffective (eg, sodium nitrate-Fecasol; Evsco Pharmaceuticals, Buena, N J) owing to the distortion or disruption o f their cell walls. 4'5'~1 Saturated zinc sulfate flotation is the technique o f choice for these cysts. 4'5'~ An alternative m e t h o d uses a gauze filter to strain the suspect fecal sample and then centrifuge the filtered fluid at 1,200 to 1,500 r p m for 10 minutes in o r d e r to con-
Pathogenic Flagellated Enteric Protozoa
centrate any cysts present before microscopic examination. 11 T h e use of an enzyme-linked immunosorbent assay (ELISA) test for G lamblia fecal antigen is considered by m a n y parasitologists to be more sensitive than fecal smears or stains owing to the intermittent nature of trophozoite and cyst shedding, the location of infections being p r e d o m i n a n t l y in the small intestine, and the tendency for scant stools from birds in the advanced stage of disease on presentation. T h e use of the test is controversial because it was developed in England for humans, and specific testing on avians has not been extensively pursued, l'la'a2 A study in dogs 14 f o u n d the fecal ELISA to be less sensitive than zinc floatation, more difficult to conduct, and more expensive than the traditional zinc flotation test. T h e 96% specificity results published are for h u m a n studies only. A series of three zinc floatations is currently considered to be a superior test protocol for dogs. m5 Fecal ELISA testing should not be ruled out, but sole reliance on this technique may p r o d u c e falsenegatives. Controlled studies are needed to establish the reliability of this test in different avian hosts.
Clinical Signs T h e most c o m m o n reason for presentation is a chronic enteritis accompanied by one or more of the following signs: weight loss, vomition, ruffled feathers, lethargic, or anorexia. Mortality can be acute (with or without signs) or of a chronic nature in a flock and reach 20% to 50% if u n t r e a t e d in a timely fashion.11'12'16'17 A m a l a b s o r p t i o n / m a l d i g e s t i o n syndrome has been identified with chronic giardiasis and is believed to be secondary to the attachment of massive numbers of trophozoites via their adhesion discs to the villi of the proximal gut. A shifting leg lameness and rough feather coat is believed to be caused by a vitamin E deficiency in cockatiels and budgies manifested as white muscle disease. 11,12'ls'm Dry, flaky dermatitis and a dermal hypersensitivity has been well described for the cockatiel and budgie and is believed to be possible for any psittacine species. 12'ls'm Documentation in other avian groups, such as poultry or ratites, is not f o u n d at this time in the literature.
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Hematology findings may show an elevated eosinophil count, but this finding is not consistent. 11,12,i7-19 Some authorities are skeptical of the association between endoparasitism a n d eosinophilia in avians being as close a relationship as in mammals. 9~ Leading authorities on giardiasis in small animals report the association between Giardia and a circulating eosinophilia to be essentially nil. 6-s Eosinophilia in avians is, at least partly, species specific and not generally associated with parasitic invasions. Avian eosinophils are associated with hypersensitivity and more research is required to further define the relationship in hypersensitivity reactions. 2~ Microbiological cultures may show concurrent bacterial infections, and some researchers believe that the additional stress of bacterial infections are necessary as precursors or as commensurates for parasitic disease signs to occur. This may account for a lack of disease in Giardia-positive birds or clinical resolution of g i a r d i a l - i n f e s t e d b i r d s with a n t i b a c t e r i a l drugs.l,3,11,12,17 Fudge reported an acute bacterial hepatitis secondary to Giardia in a cockatiel.16 Necropsy specimens should have their small gut epithelium scraped and examined via saline smear and stained preparation as well as submitting full sections of gut for histopathology on the event of negative-direct examination.
Parasite Location D u o d e n u m , j e j u n u m , ileum.
Treatment T h e imidazole group has been used traditionally, but the withdrawal of many of this group from the food animal industry owing tO suspected or proven links to carcinogenesis has significantly reduced the choices available. Metronidazole (Flagyl; Searle, Chicago, IL) at 25 to 30 mg/kg SID for 10 days orally has been r e c o m m e n d e d . 1'11 Some patients have been d o c u m e n t e d by the author to routinely require 14, and even up to 30, days of continuous treatment at 25 mg/kg BID to clear the organisms from fecal smears in cockatiels and
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budgies. T h e use o f water-based t r e a t m e n t has b e e n prescribed at 250 m g per 0.25 to 1.0 L as a drinking source. 12'21 Because o f very p o o r palatability, t r e m e n d o u s variability in d i f f e r e n t species' daily water intake (which may also be highly seasonally influenced), and the potential for central nervous system toxicity in some species, this is a p o o r r o u t e o f administration. Injectable metronidazole (Flagyl; SCS Pharmaceuticals, Chicago, IL) at 15 to 50 mg/kg IM as a one time use has been f o u n d to be apparently clinically safe, but the relapse as n o t e d by positive trophozoite and cyst shedding 3 to 4 weeks postinjection makes this a questionable solution. ~2,19,22 Recently, studies have shown albendazole (Valbazen; SKB, Westchester, PA) at 25 mg/lb BID PO for 2 days in dogs and the same dose for 5 days in cats to be m o r e effective than m e t r o n i d a z o l e (94% effective v 67%). 6 This d r u g may provide a safer and m o r e effective alternative to that o f Flagyl for many species, but m o r e investigation is needed. 15 Febendazole (Pancur; Hoechst-Roussell, Somerville, N J) has also been shown to clear giardial cysts in 3 days at 50 mg/kg in controlled studies using six dogs. s'15 T h e author's personal experience in using febendazole in cockatiels with giardiasis has b e e n similar to the results r e p o r t e d in dogs. Carnidazole (Spartrix; Wildlife Labs, Fort Collins, CO) has been r e c o m m e n d e d at 20 mg/ kg as a single t r e a t m e n t as well. 12 It is o f interest to note that a geographical difference exists in the United States, and West Coast clinicians r e p o r t a h i g h e r incidence and m o r e difficulty resolving Giardia cases in both avians as well as small mammals. 6-8'22'23 It is theorized that a variance in pathogenicity exists between strains.
Species Affected B u d g ies , 1-~' 11' 12' 16-19 cockatiels, 1-3,11,i2,16-19 lovebirds, 11,12,24 G r e y - C h e e k e d Parakeets, 11,12 conures, 12 a m a z o n p a r r o t s , T M m a c a w s , 11'12 c o c k a t o o s , l l , 12 toucans,12,16,1s, 25 finches, 25 Galliformes,11 anseriformes,11 Ostriches,3,2.11 Emus, 3'27 as well as native N o r t h A m e r i c a n birds (herons, avocet, shrike, Black-Winged Kite). 16
Trichomonas Name: Trichomonas gallinae. (Synonyms): T gallinarum, T columbae, T halli, T hepaticum, T diversa.
Identification T h e body is roughly elongated or p i r i f o r m and plastic. F o u r anterior flagella are present, and a narrow ~axostyle p r o t r u d e s posteriorly and no free trailing flagellum is present, as in m a n y trichomonads o f mammals. A short undulating m e m b r a n e extends for only a p o r t i o n o f the body and does not trail. Cysts d o not O c c u r . 4'5
Diagnosis Direct saline smears o f lesions o f the u p p e r digestive tract, sinuses, and liver will show largely clear, highly motile trophozoite organisms with t h e i r t y p i c a l j e r k y , s p i r a l motion. 4'11'29 Culturing o f the organism is possible with several types o f media m a n u f a c t u r e d for T foetus *'4'~~ or h u m a n patients. Post m o r t e m analysis can show nondigestive tract loci in addition to the classic, cheesy, yellow abscesses o f the o r o p h a r y n x and u p p e r esophagus. 4'5'29 Organisms can be f o u n d residing in the liver, lung air sacs, serosa o f the intestines, heart, pancreas, and sinuses, as well as less c o m m o n sites in the spleen, kidneys, trachea, and bone marrow. 4'5'31'~2 Stains o f dried smears or tissue impressions using Wrights, Heidenhain's iron-hematoxylin, Bodian Silver impregnation, and Schoudinn's stains are practical for trophozoite identification.
Clinical Signs T h e disease is p r e d o m i n a n t l y one f o u n d in y o u n g birds in the p r i m a r y host, the domestic pigeon (Columba livia domestica), but very little host restriction is noted. 2 T h e incidence o f disease and/or diagnosis is h i g h e r in England, Europe, and Australia over that o f N o r t h A m e r ica. 2 Birds o f prey that feed on doves and pigeons easily become infected via ingestion o f contaminated birds, and the condition is referred to as "frounce." O t h e r species can become * In pouch TF, Biomed Diagnostics, San Jose, CA, 800-9646466
Pathogenic Flagellated Enteric Protozoa
infected through the ingestion of contaminated water sources, facilities, and carrier state of parents feeding altricial chicks. 4'5'16'31-a5 It is estimated that 80% to 90% of adult pigeons are infected and that squabs are immediately infected by affected parents via crop milk transfer as well as subsequent fecal transmission. Disease conditions vary from nonapparent carrier status to poor weight gain to the presence of open-mouthed respiration, emaciation, pasted vents, ruffled plumage, weakness, lethargy, anorexia, and death. 16 The strain of Trichomonas involved is probably the single most relevant feature in assessing pathogenicity potential b e y o n d mere infection. Velogenic strains tend to create the diphtheritic membranes of "wet canker" often seen in cases of high mortality. Mesogenic strains are often associated with the classic caseated abscesses of the upper gastrointestinal tract and oropharyngeal regions. Lentogenic strains often produce no visible lesions. Deep tissue lesions (eg, liver, peritoneum, spleen) are associated with velogenic strains and are aggravated by stress, overcrowding, and poor sanitation. Stabler 36 identified the Jones' Barn (J.B.) strain as being the most pathogenic and was noted to retain its pathogenicity through 300 serial passages in pigeons. 5 Gross lesions must be differentiated from vitamin A deficiency squamous metaplasia, poxvirus, candidiasis, and bacterial abscessation. 4,5,35
Because no cysts are produced by the trophozoites, direct contact for infection must be achieved before drying of the organism occurs. Necropsies in psittacines have shown lesions in the musculature of the neck (budgies), 32 esophageal and tracheal abscesses (BlueFronted Amazon Parrot), 31 and lungs (Nanday Conure and Yellow-Naped Amazon Parrots). ~a
Anatomical Location Predominantly upper gastrointestinal tract, with above-referenced variable sites for velogic strains. Some references indicate an antigenic and/or anatomical difference in upper (T gallinae) and lower (T gaUinarium) gut tract species where T gaUinae has an undulating membrane for three quarters of its length, whereas T gallinarum has a membrane the full length of the body, plus a free trailing portion. 5"16'19 Newer
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references dispute these differences as being inconsequential or nonexistent. 4'28
Treatment Traditionally, like those pharmaceuticals for giardiasis, the imidazoles are highly effective against trichomonas infections. Since the removal of all agricultural flock use forms of the imidazole group in the United States, only metronidazole and carnidazole remain as available agents. Metronidazole has been recommended at 5 mg/100 g of body weight added to feed, 29 16.5 mg/kg PO BID for 5 days for infected raptorsY 50 mg/kg BID PO for 5 days in columbiforms, 3~ and 10 to 30 mg/kg BID PO for 10 days in psittacines. 11'33 Injectable metronidazole at 10 mg/kg IM has been recommended at SID frequency 37 as well as BID protocol. 3~ Water use of metronidazole for flock treatment of trichomoniasis has the significant drawbacks of poor palatability, variable water intake, settling out of solution in water bowls, variable water intake according to species, and weather variability and potential toxicity. Metronidazole has been reported to be toxic in finchesY C a r n i d a z o l e tablets have been recommended from 5 mg and 10 mg PO once depending on body size 3~ to 100 mg/kg PO once for adults 37 in affected pigeons according to various authors. No attempts to use ablendazole or febendazole against trichomoniasis (as in giardiasis) have been reported to the author's knowledge. Resistance to treatment with both oral and injectable metronidazole at an unknown dose for trichomonas in cockatiels has been reported in the literature. 3s Methods of prevention include culling of affected members of the flock, 28 evaluating for the presence of lentogenic tvichomonas, which prevents the infection of birds with disease causing strains, 4'5'a4 sanitation, 4'5'34 and the use of an injection of plasma from an infected bird .4 Freezing of infected carcasses before being fed to raptors will prevent infection.
Species Affected Pigeons and doves, 4'5'11'12'16'18"19'34'35'39'4~ poultry,4,5,l 1,16,28,4I raptors,16,19,31,39,42,43 budgies, 11,12,16,18,19,26,33,39,40,44 cockatiels,11,33, 42
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lovebirds, 24 Blue-Fronted Amazons, 31 YellowNaped Amazons, 33 Nanday C o n u r e s Y canaries,2,16,19,26,29,40,42,45 finches,8,16,17,19,26,29,40,42 and ratites. 3'46-48 Other related organisms have been reported to be associated with disease in avians. They include tritrichomonas in chickens, turkeys, and possibly ducks (T eberthi), 4'5'28'49 Tetratrichomonas in gallinaceous birds (T gallinarium), 4'5'28'49 geese (T anseris), 4 ducks (T anatis), 4 and Pentatrichomonas in fowl (T gallinarum). 4'5'28 Most of these parasites are nonpathogenic unless the conditions of captivity or poor husbandry culminate to warrant treatment as part of a corrective program.
Histomonas Name: Histomonas meleagridis. Identification H meleagridis is pleomorphic, has four life stages, and the structure is based on the stage observed. 1. Invasive stage--Found in early liver and cecal lesions. This form is actively ameboid with pseudopods. The cytoplasm is basophilic with an outer zone of clear ectoplasm and is approximately 8 to 17 ixm wide. 2. Vegetative stage--Found at a slightly more advanced stage postinvasion. The organism is slightly larger (12 to 21 Ixm long) and is slightly less active than stage 1. The organisms are often found packed at the center of lesions. 3. Resistant stage--Not truly resistant. Found singly or grouped with an acidophilic cytoplasm containing small globules. 4. Flagellated f o r m - - F r e e swimming and found in the cecal lumen. Body is ameboid and 5 to 30 p~m wide. Cytoplasm is clear and may contain bacteria or food particles. A single nucleus and a single flagellum are present. Occasionally, two flagella may be present. A related form, H Wenrichi (also known as Parahistomonas wenrichi), has four flagella but is nonpathogenic and must be differentiated from H meleagridis.
Disease Signs The disease is predominantly one found in gatlinaceous birds, especially turkeys, whereas in other species it is considered to be less p a t h o g e n i c or even an i n c i d e n t a l f i n d ing. 4'5'11'16'40'41'47'50-52 The organism affects birds of all ages, but the intensity, course, and mortality varies with age. Poults less than 3 weeks old are resistant, but from 3 to 12 weeks of age, mortality can reach 100%. Death generally occurs within 2 to 3 days of clinical signs. Older birds show more chronic morbidity and recovery can occur. The initial signs of weakness, drowsiness, and droopy head and tail feathers is followed by a sulphur-colored diarrhea after the 21-day incubation period. 4'5'2s On post mortem, the principal lesions are found in the ceca and liver. Cecal mucosa first shows pinpoint ulcers, which enlarge and eventually coalesce. Cecal perforations followed by peritonitis are possible. The mucosal lining thickens and becomes increasingly necrotic, producing a foul exudate that can consolidate to form a tightly bound cecal plug. T h e affected cecum subsequently becomes highly enlarged. Hepatic lesions are pathognomonic, being circular, yellow to greenish at the necrotic sites, and depressed. These depressions vary in diameter and are generally up to 1 cm (or more) and extend deeply into the parenchyma. Lesions may also be located in the kidney, spleen, mesentery, and lungs as areas of circular, white necrotic foci. Affected birds are often emaciated, have classic yellow diarrhea, and may exhibit bloody droppings; turkeys often have cyanotic skin of the head (hence, the term "Blackhead") presumably caused by poor circulation.
Anatomical Locations Liver, cecum, and to a lesser extent, kidney, spleen, mesentery, and lung.
Diagnosis Fecal smears may show trophs in an advanced state of disease. Cecal scrapings taken from a freshly killed bird while still warm is the most expeditious manner for rapid diagnosis using a saline mount. Cultures of histomonads
Pathogenic Flagellated Enteric Protozoa
can be accomplished using fresh tissue samples harvested at necropsy, and macerating them into modified Dwyers medium for later identification. 2a Histopathology is required for diagnosis of the nonflagellated tissue phases, and the tissues of choice are cecal wall and liver. Other organs showing gross lesions should be included. Histomonads at this stage must be differentiated from giant cells, macrophages, and yeasts using H & E or periodic acid-Schiff stains. Liver samples will show classic hepatocellular necrosis with extensive numbers of lymphocytes and macrophages and moderate populations of heterophils. The organisms may be found in the periphery of lesions. 4'5'2s White blood counts have been noted at levels of up to 70,000 leukocytes/mm3 at 10 days postinfection but return to normal by 21 days postinfection. Aspartate a m i n o t r a n s f e r a s e (AST) (SGOT) a n d lactic d e h y d r o g e n a s e (LDH) levels increase as livers become increasingly affected. Bilirubinuria occurs later in the process of hepatic involved birds. Those birds only having cecal lesions (eg, chickens) will exhibit decreased AST, LDH, and other enzyme levels suggesting impaired liver functions. 28
Epidemiology This parasite is ubiquitous in chickens and is one of the foremost infectious diseases of concern in the turkey industry. The most frequent form of infection is by ingestion of the infected eggs of the cecal worm Heterakis gallinarum and remains the most prominent reservoir for histomiasis in birds. Infected cecal worm eggs can remain viable for up to 2 years. It is essentially impossible to run turkeys or other susceptible gallinaceous fowl with chickens on the same range without contacting a flock disease problem. The same is assumed for other species of avians, including exotic fowl and free range mixed collections, in which infection has not been documented, but such a susceptibility exists for the host in question. 4'5'11'19'28'4~ Direct transmission of the trophozoites is possible by ingestion if the organism is not allowed prolonged exposure to the environment. Direct ingestion of infected tissues is also a possible route of exposure and is relevant to
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those species known to practice cannibalism, such as pheasants and cockatoos. Establishment of histomoniasis also requires the presence of commensal bacteria, especially E coli and Clostridium perfringens, among others. Experimental efforts in gnotobiotic turkeys produced clinical signs in only one of 12 subjects and 0 mortality. 5s Prevention is best established by keeping vector species, such as chickens, game fowl, quail, and pheasants separated from other avians. 4'5'28 The practice of keeping mixed collections with quail, pheasants, and exotic jungle fowl on the floors of aviaries as scavengers is to be highly discouraged. Wire-floored, dropthrough aviaries, concrete floors, and high level sanitation are the other fundamental aspects of control and/or preventi0n. 4'5'28'54'55 Reinfection is not possible owing to the immunity produced in recovered birds. 4'5 Injection of serum from recovered birds did not protect against infection. 4
Treatment As with other flagellate infections, the imidazoles are recommended and largely unavailable at the current time. This has created substantial concern for the turkey and game bird industries. Metronidazole, carnidazole nifursol, and furazolidone are recommended for treatment.
Species Affected Chickens, 4'5'28 turkeys, 4.5,11,16,19,40,41,47,50-52,54 peafowl,41 quail, 4'5'28'5~ chukar partridges, 4'5'28 guinea fowl,4'5"35'42 ruffled grouse, 4'5'28 palawan peacock pheasant, 51 assorted "zoo birds", 5l and ratites. 3,40,47
Pleuromonas Name: Pleuromonas jaculans. Identification The body is slightly ameboid. Two flagella are present and are located on opposite poles of the organism. The anterior flagella is short and may be rolled into a ring-like structure. The posterior flagella is at least two to three times the length of the body and is relatively large in diameter. The cysts are spherical. 56
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Disease Signs Assumed to be enteritis depending on host immune status, host species tolerance, and total numbers of parasites. Primary source of infection is listed as stagnant water. Anatomical Location: Ceca. Species Affected: Chicken.
Monocercomonas Name: Monocercomonas gallinarium. 4'5 (Synonyms): trichomastix and eutrichomastix. May be a degenerate form of Tritrichomonas eberthi. Identification Unicellular body is pirilorm with a bluntly rounded anterior end. The four flagella are found on the leading edge with three flagella pointed forward and the fourth trailing backwards. No undulating membrane is present. No cysts are formed.
Disease Signs Possibly associated with enteritis, but pathogenicity is assigned to the species associated with this organism. Total numbers and host resistance are probably similarly relevant to disease presence, as in other flagellate infections. Anatomical Location: Ceca. Species Affected: Reported in chickens.
Hexamita Name: Hexamita meleagridis. Now renamed Spironucleus meleagridis. Other species include S columbae (also known as Hexamita columbae, Octomitus columbae) in pigeons. 4'5'16 S intestinalis in ducks. 4 Identification This flagellate is piriform in shape with a less r o u n d e d anterior end than most other flagellates in avians, is smaller than Giardia at 9 • 3 ~Lm, has no suction disc, and swims in a smooth, linear fashion. 4'5'1~'2s It has eight prominent flagella, four anterior, one project-
ing down each side and two trailing from the posterior. No cysts are formed and reproduction is by longitudinal binary fission.4
Disease Signs Spironucleosis is referred to classically as infectious catarrhal enteritis when f o u n d in poults. Weight loss, chronic diarrhea, poor feather coat, lethargy, and death are described for both fowl and other groups of avians, including psittacines. 4"5'1t'16 Affected individuals remain fairly bright and maintain an appetite and vocalization until shortly before death, unlike many other protozoal enteric diseases. The incubation is reported to be 4 to 7 days and the disease is largely found in juvenile birds. 35
Anatomical Location Duodenum and small intestine, with same incidence noted in the cecum and bursa.
Diagnosis Saline smears of loose stools taken directly from warm droppings may demonstrate the active trophs. 57 The small size, large number of flagella, and linear locomotion are important differences from Giardia and trichornonas. S columbae can be readily demonstrated on asymptomatic pigeon fecal mounts from infected birds. Necropsy efforts should include scrapings from the small intestine, particularly the jejun u m and d u o d e n u m . The small bowel will characteristically show poor muscle tone of the gut loops plus thin, foamy contents. 4'5'28 The disease incidence of this parasite is extremely low in comparison with most other flagellates.49 Only 10 cases were reported in domestic birds in the United States in 1986 versus a 2-million annual loss to the turkey industry alone from Histomoniasis. 2s An increasing awareness of this organism and its presence in Europe and Australia may change the clinical appreciation for this parasite and its impact on aviculture.
Treatment Most drugs are ineffective against S meleagridis. Those drugs approved for meat and egg-producing fowl include chlortetracycline,
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furazolidone, and butynorate with no degree of efficacy reported. 2s Prevention is the same standard sanitation, disinfection, species separation, and good husbandry practices recommended for all livestock and avicultural operations. The use of wire floors and elimination of stagnant water is the most efficient means of eliminating transmission. 4,5,28
Species Affected Domestic turkeys,4'5'16'28 Rio Grande Turkey, 51 pheasant, 4,5,28 quail, 4,5,28 partridge,4.5, m,zs,S7,58 budgies,16 cockatiels,iX Splendid Grass Parakeets,11 lories,11 and King Parrots. 44
Cochlosoma Name: Cochlosoma anatis. Cochlosoma sp (unnamed species). Identification Members of this genus have an oval body (6-12 • 4-7 ~m) with a broad anterior pole and a narrowly rounded posterior. Six flagella of unequal length arise from the front end, two of them trailing. A large sucking organ is present on the anterioventral surface covering one third to one half of the body length. A slender, fibrillar axostyle is present also. The movement is described as being erratic and jerky with horizontal rotation, but no spiraling action like Giardia. 4'5'29 Cysts are reported for C anatis with an oval shape by one author. 5 Longitudinal binary fission is reported as being the mode of reproduction by a more current source. 4
Disease Signs Dehydration, yellow to green malodorous droppings, maldigestion, fading of fledglings, and mortality is reported in passerines. 27'45 Catarrhal enteritis has been documented in turkeys with C anatis. Necropsy shows lesions similar to spironucleosis. 4'5
Anatomical Location Small intestine, large intestine, ceca and cloaca.4,5,29,45
Diagnosis Saline smears from fresh feces or scrapings of gut mucosa on necropsy.
Treatment Dimetridazole and ronidazole are reported to be of value in the literature. 29'45 It is postulated that metronidazole would be an acceptable substitute in the face of the lack of availability of the first two drugs at this time. Carnidazole and metronidazole have been recommended by one authority based on good resolution of signs in psittacines.1
Species Affected Domestic ducks, 4"5 wild ducks, 4'5 turkeys, 5 and Australian Finches. 29'45 Also reported to be present in wild psittacines in Australia. 59 It is reported to be apathogenic in Bengalese and Japanese Finches who may act as the vector source for other finches when acting as surrogate parents. Factors common to other protozoal infections, such as immune status, age, sanitation, and stress, probably influence host susceptibility.
Chilomastix Name: Chilomastix gaUinarum. Chilomastix sp (unnamed species). Identification The body is asymmetrically piriform (6 to 24 • 3 to 10 ~m) and plastic with a substantial cytostomal groove at the anterior end. There are three anteriorly directed flagella and a short fourth flagellum, which undulates in the cytostomal cleft along the body wall. Cysts are formed and are lemon shaped. The fibrils of the trophozoite persist in the cystic form. Cysts are rare in fecal smears compared with other cyst-producing protozoa.
Disease Signs This organism is considered to be slightly pathogenic and found with regularity in the ceca of normal chickens and turkeys on routine examination. 4 Enteritis of a nonspecific character is assumed to be associated with those individuals sustaining the s t a n d a r d
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stresses of poor diet mismanagement or immunoinsufficiency.
Anatomical Location Ceca and large intestine.
Diagnosis Direct fecal saline smear on warm droppings and mucosal scrapings of the large 'intestine.
Species Affected Ratites appear to have the only significant incidence of confirmed diagnosis of B coli at this time. 1-3'46'48 It is assumed that the overgrowth of this organism is primarily an indicator of other preexisting disease and should serve as an activator for a more detailed investigation of health status and m a n a g e m e n t practices.
Tetrahymena
Treatment None is listed in the literature reviewed.
Names: T. pyriforms. 4
Species Affected
Identification
Chicken, 4'41 t u r k e y , 4'5'41 ducks, 4'5 and geese. 4
A smaller ciliate (40 to 60 • 15 to 30 ~m) than B coli with a piriform body and uniformly distributed cilia.
Ciliated Protozoan Parasites: Balantidium Name: Balantidium coli. (Synonyms) B sui, B wenrichi. Identification The body is oval and extremely large in comparison with the previously described flagellates (30 to 150 • 25 to 120 pxm). A sausage or bean-shaped macronucleus and the associated micronucleus are evident. Many vacuoles containing food, bacteria, and red blood cells are present. The rows of cilia are obvious along the lateral margins, and the method of locomotion is a smooth gliding via the rhythmic motion of the rows of cilia.
Disease Signs Rare, but reported as dysentery and diarrhea, or present in cases of enteritis. 1"3'46 It is ordinarily a commensal in the hind gut, especially the cecum, where it digests starch and bacteria.l~
Disease Signs Nonspecific. Found only in birds with vitamin A deficiency.
Anatomical Locations Digestive tract, infraorbital sinuses and conjunctiva.
Diagnosis Direct smears of affected tissues.
Treatment Vitamin A and antibiotics, as indicated.
Species Affected Only documented in chickens to date. This is a free-living organism and is frequently used in protozoal research. It is a facultative parasite of man and thereby assumed to be potentially in contact with captive avians. More investigation into the many species of captive kept exotic avian species is warranted.
Anatomical Location
Amebic Protozoal Parasites (Table 2)
Large intestine.
Very few of this large group (subphylum Sarcodina) are pathogenic for animals. The few documented reports are of significance because they serve as important differentials and as significant indicators for mismanagement in captive operations for aviculturists.
Treatment None prescribed. Treatment for predisposing factors and other disease processes present is the recommended therapeutic approach.
123
Pathogenic Flagellated Enteric Protozoa
Table 2. Amebic Protozoal Parasites Names
Host
1. Pathogenic Entamoeba anatis (E histolytic group) 4 2. Nonpathogenic Entamoeba gallinarum (E coli group) 4'~ Acanthamoeba polyphaga Hartmanella vermiformis Valkampfia enterica Endolimax gregariniformis
Duck Duck, chicken, turkey, guinea fowl, goose Pigeon, turkey Turkey Turkey Chicken, turkey, guinea fowl, pheasant, goose, duck, heron, owl, various wild avians
p a t h o g e n i c enteric p r o t o z o a l parasites affecting avian species. It b e c o m e s readily e v i d e n t that m o s t o f these o r g a n i s m s are o p p o r t u n i s t s o r s e c o n d a r y i n v a d e r s o f c o m p r o m i s e d o r imm a t u r e birds u n d e r c o n d i t i o n s o f less t h a n optimal m a n a g e m e n t a n d h u s b a n d r y . P e r h a p s the m o s t significant c o n c l u s i o n that the a t t e n d ing avian v e t e r i n a r i a n m i g h t d r a w is t h a t t h e t r u e scope o f the c u r r e n t h e a l t h p r o b l e m is multifactorial a n d p r e s e n t s an o p p o r t u n i t y to e d u c a t e the client. P r e v e n t i o n is usually b o t h a long-standing effort and reward once the s h o r t - t e r m n e e d s h a v e b e e n rectified with the a p p r o p r i a t e diagnostics a n d medication.6 ~
Identification T h e t r o p h o z o i t e is plastic, m o v e s by m e a n s o f p s e u d o p o d s , a n d has n o cilia o r flagella f o r t h e s p e c i e s r e l e v a n t to a v i a n s . C y s t s a r e f o r m e d . T h e r e a d e r is r e f e r r e d to the references n o t e d f o r a m o r e extensive d e s c r i p t i o n o f each f o r m . T h e basic issue o f n o t e h e r e is r e c o g n i t i o n o f these o r g a n i s m s a n d their potential f o r p a t h o genicity, especially in a b e r r a n t hosts, which are p o o r l y d o c u m e n t e d to date. 28'4t'48 W h e t h e r these parasites b e c a m e a n y g r e a t e r m a t t e r o f c o n c e r n will be b a s e d o n f u t u r e studies. W a r m fecal o r g u t c o n t e n t s m e a r s with saline, p h a s e c o n t r a s t m i c r o s c o p y , a n d / o r stained slides are o f t e n necessary to identify these variable-sized and relatively translucent parasites. 28 Tissue sections o n h i s t o p a t h o l o g y are also diagnostic. 52
References 1. 2. 3. 4. 5,
6. 7. 8. 9. 10.
11.
Anatomical Location P a t h o g e n i c f o r m s - - I n t e s t i n a l tract. A p a t h o g e n i c f o r m s - - I n t e s t i n a l tract, trachea.
12.
13.
Treatment M e t r o n i d a z o l e a n d v a r i o u s antibiotics to eliminate c o n c o m i t a n t e n t e r i c bacteria. 4'52
14.
Species Affected
15.
Ducks, ostriches, ratites. I'3,4A8
Conclusion T h e t h r u s t o f this p r e s e n t a t i o n has b e e n to p r e s e n t the diversity a n d c o m p l e x i t y o f motile,
16.
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18. Barnes H J: Parasites, in Harrison G, Harrison L (eds): Clinical Avian Medicine and Surgery. Philadelphia, PA, Saunders, 1986, pp 472-485 19. McCluggage D: Parasitology in caged birds, in Proceedings of Association Avian Veterinarians. Seattle, WA, 1989, pp 97-100 20. Gerlach H: Defense mechanism of the avian host, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Applications. Fortworth, FL, Wingers, 1994, pp 114-120 21. McDonald S: Personal communication, 1989 22. Ritchie G, Harrison G: Formulary, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Applications. Fortworth, FL, Wingers, 1994, pp 457-477 23. Joyner K: Personal communication, 1991 24. Dorrestein G, Marein H: Aviculture and veterinary problems in lovebirds, in Proceedings of Assoc of Avian Vet. Honolulu, HI, 1987, pp 243-261 25. Worell A: Management and medicine of toucans, in Proceedings of Association of Avian Veterinarians. Houston, TX, 1988, pp 253-262 26. Mac Whirter P: Passeriformes, in Harrison G, Harrison L, Ritchie B (eds): Avian Medicine: Principles and Application. Lake Worth, FL, Wingers, 1994, pp 1172-1199 27. Wade J: Ratite pediatric medicine and surgery, in Proceedings of the Association of Avian Veterinarians. New Orleans, LA, 1992, pp 340-353
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