FINAL DIAGNOSIS - Hepatic coccidiosis
This case involved a meat rabbit farm with some
1500 animals. A female rabbit, approximately 7-11 weeks
of age, was presented alive to the Animal Disease Diagnostic
Laboratory at PurdueUniversity
for euthanasia and necropsy. The reported history was that
the animals are asymptomatic for approximately 5-6 weeks
at which time they begin to develop diarrhea. At this time,
the owners also report sudden deaths in many rabbits.
Gross Necropsy Findings:
The rabbit was thin (weighing 2 pounds, 4 ounces) with
reduced fat stores and muscle development. The hair coat
was rough and fecal material was adhered to hair at the
perineum. Small intestinal loops were swollen and gray.
Gray-green, semi-solid digesta filled the small intestines.
Formed fecal pellets were in the colon. A direct examination
of the fecal material revealed numerous oval, colorless,
thin-walled oocysts, each with a single, round sporont (morphologically
consistent with coccidian oocysts).
Hepatic lobules had extensive biliary hyperplasia with
numerous intralesional coccidia. Bile ducts were markedly
dilated and lined by hyperplastic columnar epithelial cells
thrown into multiple papillary fronds. Numerous protozoal
developmental stages (including undifferentiated gamonts,
micro- and macrogametocytes and developing oocysts) ranging
in size from 25-50 microns in diameter were within lining
epithelial cells. Ductal lumens were filled with numerous,
thin-walled, approximately 50 microns in length, ovoid oocysts
(based on location and morphologic characteristics, these
organisms were consistent with Eimeria stiedae).
The hyperplastic bile ducts were surrounded by large amounts
of fibrous connective tissue with lymphohistiocytic inflammatory
Liver; Marked chronic proliferative cholangitis with
intraepithelial coccidial organisms and hepatic atrophy
Eimeria species are coccidian parasites of the phylum
Apicomplexa. They are parasites of the epithelial cells
of the gut mucosa and those lining certain ducts. The life
cycle of each species is host specific and direct. Eimeria
species can be a serious problem in lagomorphs (especially
in the young), where as many as 14 species of coccidian
parasites have been described, all but one being found in
the small intestine, cecum or colon. E. stiedae
is an inhabitant of the epithelial cells of the bile
ducts and is the cause of severe liver damage in rabbits.
The rabbit is infected by ingestion of sporulated oocysts.
Sporozoites penetrate the mucosa of the small intestine
and pass via the hepatic portal system to the liver and
the mesenteric lymph nodes. In the liver, they enter the
epithelial cells of the bile duct and occasionally the liver
parenchymal cells, where they become schizonts. The schizonts
produce merozoites, but the number of asexual generations
is unknown. Oocysts pass through the bile and appear in
the feces 18 days after ingestion; sporulation occurs in
3 days. Light infections are often inapparent. Heavy infections
are characterized by anorexia, a distended abdomen and weight
loss and, occasionally, diarrhea and icterus. The liver
is greatly enlarged, the bile ducts are dilated and appear
on the surface of the liver as white nodules of variable
size and contain creamy fluid packed with oocysts. Microscopically,
there is destruction and regeneration of the bile ducts
epithelium with extensive hyperplasia of the ductular epithelium.
Developmental forms of the parasite are seen in the bile
duct epithelial cells and
oocysts appear in the lumen. Biliary outflow may be obstructed
by oocysts, resulting in a distended bile duct. The liver
parenchyma may be destroyed by the pressure from the expanding
biliary ducts and gradually replaced by fibrous connective
tissue. A diagnosis of E. stiedae infection
can be made by the demonstration of very large numbers of
oocysts in the feces, but since intestinal coccidian are
frequently present in rabbits and may be present in large
numbers without any serious clinical signs, the most significant
diagnosis is made by examination of the liver. Control
of infection requires strict attention to sanitation and
husbandry. Avoidance of stress, frequent disinfection of
cages, hutches, transport carriers, and litter pans with
10% ammonia solution may reduce or prevent clinical disease.
The most effective chemotherapeutic agents used to treat
hepatic and intestinal coccidiosis are the sulfonamides.
Their major role may be to control the organism until natural
- by Jan Lacey, DVM,
ADDL Graduate Student