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Joint Pathology Center Veterinary Pathology Services WEDNESDAY SLIDE CONFERENCE 2014-2015 Conference 18 11 February 2015 Guest Moderator: Timothy K. Cooper, DVM, PhD, DACVP Penn State Milton S. Hershey Medical Center College of Medicine CASE I: A (JPC 4048645). the floor was limed before applying new shavings. Only the rabbits being raised on the Signalment: 9-week-old mixed sex commercial floor were dying. The rabbits were initially treated meat rabbits, Oryctolagus cuniculus. with amprolium for two weeks because of bloody diarrhea but the rabbits developed a bloated History: Some members of this group of 9- appearance, and so were retreated with amprolium week-old rabbits were being raised on the barn for an additional two weeks. Two days following floor because of insufficient numbers of cages. the last treatment, three rabbits were submitted for The rabbits raised on the floor were bedded on postmortem examination. shavings. The bedding was changed weekly, and 1-1. Liver, rabbit: The liver was enlarged with numerous tortuous and 1-2. Liver, rabbit: Biliary ducts are tortuous and markedly ectatic, cystic biliary duct scattered throughout. (Photo courtesy of: Animal replacing large amounts of hepatic parenchyma. (HE 6X) Health Laboratory, University of Guelph, Guelph, Ontario, Canada. http://ahl.uoguelph.ca) 1 WSC 2014-2015 large numbers of a mixture of Eimeria spp. oocysts. Histopathologic Description: Liver: There is generalized marked dilation of bile d u c t s c a u s i n g compression of the surrounding hepatic p a r e n c h y m a . Hyperplastic biliary epithelium forms papillary projections into duct lumens. Most epithelial cells are filled with asexual and sexual developmental stages of coccidial organisms and cystic duct lumina contain numerous oocysts. Few to moderate numbers of plasma cells and lymphocytes i n f i l t r a t e w i t h i n increased periductal fibrous tissue and 1-3. Liver, rabbit: Dilated biliary ducts are lined by proliferating epithelium containing numerous life stages of within the connective Eimeria stiedae. (HE 38X) tissue stroma of the proliferative biliary Gross Pathology: The rabbits were in very poor epithelium. Other portal tracts have mild body condition with reduction in muscle mass and cholangiolar proliferation, mildly increased marked reduction in external and internal fat periportal fibrosis and few to moderate numbers stores. Similar internal changes were noted for of mixed mononuclear cells within and around each. There was increased clear fluid in the biliary epithelium. Occasional portal and hepatic abdominal cavity. Stomachs contained feed and veins contain low numbers of oocysts. Hepatocyte the small intestine, cecum and sacculated colon cords are markedly atrophied, and sinusoids are had normal contents. The distal colon and rectum moderately congested and contain increased contained normal fecal pellets. The liver was dark numbers of circulating neutrophils. red, enlarged with an irregular bosselated capsular surface and large numbers of variably sized, pale, Contributor’s Morphologic Diagnosis: 1. cystic, round to elongate corded nodules filled Marked proliferative and nonsuppurative with turbid pale green yellow fluid were scattered cholangitis with large numbers of intralesional throughout the hepatic parenchyma. The coccidial organisms. 2. Marked hepatic atrophy. 3. gallbladder was thickened and contained similar Ascites. cloudy fluid. Contributor’s Comment: While enteric Laboratory Results: Parasitology: Oocysts with coccidiosis continues to be one of the important measurements consistent with Eimeria stiedae potential causes of enteritis in commercial were identified in the biliary fluid collected from rabbitries in Ontario, hepatic coccidiosis is the cystic hepatic lesions. Fecal flotation revealed seldom identified in commercially raised rabbits submitted to our laboratory for diagnostic workup 2 WSC 2014-2015 1-4. Liver, rabbit: Developing schizonts containing numerous merozoites 1-5. Liver, rabbit: Gametes of Eimeria stiedae including macrogametes (arrows). (HE 400X) with brightly eosinophilic plastic bodies at the periphery (large arrows) and microgametes (small arrows). (HE 400X) of diarrhea. However, increasingly over the last Recommendations for the control of hepatic few years, smaller collections of rabbits raised for coccidiosis parallel the recommendations for meat or as pets are being housed on or provided control of intestinal coccidiosis, and sanitation is access to the ground. Owners of these small of great importance.2,7 Coccidial oocysts are rabbitries seek veterinary assistance for morbidity extremely resistant to environmental influences and mortality concerns and in turn, the diagnostic and no commonly available disinfectants will kill laboratory has received increased numbers of them. Removal of organic material from cages, phone calls and pathology submissions from feed pans and around waterers where oocysts can veterinary practitioners related to the diagnosis of reside can help reduce the challenge.7 Rabbits can hepatic coccidiosis in these rabbits. develop long-lasting immunity to Eimeria stiedae as long as they are not exposed to an excessively Infection with Eimeria stiedae is usually high dose initially and are immunocompetent.2 subclinical and historically, hepatic coccidiosis has been associated with significant With the advent of increased interest in raising condemnations of livers from meat-type rabbits at small groups of rabbits and allowing them access processing but not with elevated mortality during to the ground, hepatic coccidiosis may re-emerge grow-out.7 However, if young, naïve rabbits are as a clinical disease. exposed to high enough levels of sporulated oocysts, clinical disease including anorexia, poor JPC Diagnosis: Liver: Cholangitis, proliferative, weight gain, weight loss, development of a multifocal to coalescing, chronic, severe, with distended abdomens, diarrhea and elevated intra-epithelial coccidia. mortality can occur.2,7 In this particular situation, only the rabbits being reared on the floor were Conference Comment: There are over a clinically affected and although the rabbits thousand species of Eimeria, the vast majority of which are known to primarily infect the epithelial submitted for postmortem did not have diarrhea, 1 histologically, they also had significant numbers cells lining the gastrointestinal tract. Hepatic of coccidial organisms within the intestinal coccidiosis is commonly reported in rabbits, mucosa and results of flotations conducted on known to occur in ferrets (see WSC 2009-2010, feces from all rabbits indicated large numbers of Conference 12, Case 2), and reported in some mixed Eimeria spp. oocysts. Despite weekly avian species which acquire extra-intestinal coccidiosis to include the liver and kidneys, albeit cleaning and rebedding, the environment was 2,4 heavily contaminated with coccidial oocysts and infrequently. Each species has a host specific these rabbits were being continually challenged direct life cycle which originates with the with both intestinal and hepatic coccidia. unsporulated oocyst shed in the feces. 3 WSC 2014-2015 1-6. Liver, rabbit: The lumen is filled with coccidial oocysts. (HE 400X) The oocyst initially contains a single cell called a additional schizonts.4 This process repeats over a sporont, and through a process known as variable number of generations depending on the sporulation or sporogony, the sporont develops individual species. For reasons still unknown, into four sporocysts, each with two sporozoites. eventually some merozoites will infect epithelial This appearance of the sporulated oocyst (4 cells and begin the sexual phase of the life cycle sporocysts and 8 sporozoites) is a distinguishing called gametogony.3 The majority become feature of Eimeria spp. from other coccidian females (macrogametocytes), while some become apicomplexans.1 The sporulated oocyst is now males (microgametocytes) which form numerous infectious, and sporozoites will be released when biflagellate microgametes within epithelial cells.4 ingested by the host.1 The sporozoites invade Each microgamete can fertilize a macrogamete to epithelial cells and round up to become form a zygote known as the oocyst, which are trophozoites which are the growing forms.3 then shed in the feces.4 Among the phases of this Trophozoites undergo asexual nuclear division, elaborate life cycle, conference participants called both schizogony and merogony, to form a identified oocysts, schizonts containing schizont/meront.1,3,4 These two terms are used merozoites, micro- and macrogametocytes, and synonymously in most references of this stage, micro- and macrogametes in abundance in this with the term schizogony referring to multiple case. nuclear divisions (as occurs in Eimeria spp. while merogony equates with nonspecific asexual In hepatic coccidiosis, this life cycle still begins division. Each schizont develops within it within gastrointestinal epithelial cells, particularly numerous merozoites, which following rupture of in the duodenum. Following exposure, the host epithelial cell, are released to infect sporozoites have been documented in the regional additional cells and subsequently develop into lymph nodes within 12 hours, in bone marrow 4 WSC 2014-2015 within 24 hours, and in the liver within 48 hours. 5. Morgan KJ, Alley MR, Pomroy WE, Gartrell 6,7 Thus, spread by both hematogenous and BD, Castro I, Howe L. Extra-intestinal coccidiosis lymphatic routes have been proposed. in the kiwi (Apteryx

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