Hepatic lesions in a rabbit (Oryctolagus cuniculus)
Antonio Meléndez-Lazo1 DVM MSc PhD DipECVCP MRCVS
Laura Vilalta Solé1,2 DVM DipECZM (Small mammals)
1. 1. LABOKLIN
2. 2. Hospital de la Universidad Católica de Valencia (Spain)
SIGNALMENT AND HISTORY
A 2.5-months-old, intact female Angora rabbit (Oryctolagus cuniculus), weighing 540g presented for inability to gain weight. The rabbit was bought a month ago in a pet shop.
PHYSICAL EXAMINATION
Physical examination revealed no abnormal findings, except for a marked cachexia (BCS 1/5). The rabbit was active, eating and pacing normal faeces during consultation.
INVESTIGATION
Haematology and biochemistry
Haematological and biochemical examination revealed no abnormalities.
Imaging tests (plain radiographs and abdominal ultrasonography)
Plain radiographs (Figure 1) and abdominal ultrasonography (Figure 2) were performed.
Cytology
Fine needle biopsy (FNB) of the hepatic lesions was performed (Figure 3).
Faecal examination
Faecal examination was performed (Figure 4).
What is your interpretation of the imaging tests?
What is your interpretation of the cytology?
What is your interpretation of the faecal analysis?
What is your interpretation of the imaging tests?
Plain radiographs revealed moderate loss of peritoneal detail and hepatomegaly. Differential diagnosis of loss of peritoneal detail includes peritoneal effusion, cachexia, age (young animals), generalized peritonitis and/or poor peritoneal detail that normally presents the rabbits’ abdominal organs.
Abdominal ultrasound confirmed the moderate hepatomegaly, and multiple, generalized distributed hyperechoic nodular lesions with well-defined margins were observed closed to biliary ducts. The biliary ducts were moderated dilated, and mild anechoic peritoneal effusion was observed. No other alterations were detected. Differential diagnosis includes hepatitis/colangiohepatitis (probably of infectious origin: coccidiosis) or granulomas.
What is your interpretation of the cytology?
The FNB smears were of high cellularity, with excellent cell preservation. Hepatobiliary parenchymal cells and coccidian organism in various stages of development were observed.
The coccidian oocysts, ovoid to ellipsoidal in shape and large (approximately 30-39 by 18-22 µm) in size, were found between hepatocytes and bile duct epithelial cells (Figure 3 A).
Undifferentiated stages of coccidian development were present in a moderate number and they were located within the apical part of the bile duct epithelial cells or extracellularly. These structures were round, blue, with large prominent, eccentric nuclei and in some cases with intracytoplasmatic vacuoles (Figure 3 C).
Macrogametocytes (female gamonts) were found within the bile duct epithelial cells, these were oval and 30x20 µm in size. Inside of these a large amount of round, blue cytoplasmatic granules (wall-forming bodies) were observed (Figure 3 B).
Microgametes were present in low number, individually distributed or in small groups in the background. These structures were elongated, comma-shaped, purple 10x1µm in size and biflagellate (figure 3 D).
Cohesive clusters of densely cellular of moderately hyperplastic bile duct epithelial cells were present. These cells were cuboidal to columnar in shape with blue cytoplasm. Cohesive clusters of hepatocytes were also seen.
The cytologic findings were consistent with Eimeria stiedae infection (hepatic coccidiosis) associated with bile duct hyperplasia.
What is your interpretation of the faecal analysis?
High numerous of coccidian oocyst in different stage of sporulation could be detected Figure 4 A-B). In Eimeria species, each sporulated oocyst contains 4 sporocysts, each of which contains 2 sporozoites, and have a residuum (Figure 4C).
DIAGNOSIS: Hepatic coccidiosis (Eimeria stiedae infection)
TREATMENT AND FOLLOW-UP
Toltrazuril, 20 mg/kg PO SID was administered 2 consecutive days. Repeat the same treatment 5 days later was recommended.
Follow-up examination could not be performed but the owners reported a good response to the treatment
SUMMARY
Coccidiosis is a common, debilitating, sometimes fatal parasitic diseases, caused by one or more of sixteen species of the apicomplexan genus Eimeria. Eimeria stiedae is the most pathogenic species due to its effects on the bile ducts epithelial cells and the liver, leading to hepatomegaly, dullness, reduced food consumption, diarrhoea or constipation, ascites, icterus, abdominal distension and possibly death. Young animals are most susceptible, and adults become carriers of the disease and are a source of infection. Other Eimeria species are intestinal, and have also been associated with clinical disease, especially diarrhoea and sudden death, as well as subclinical effects such as poor weight gain and gastrointestinal disturbances.
Rabbits are infected by ingestion of sporulated oocysts. The ooscyst is ovoid to ellipsoidal and contains 4 sporocysts and each one contains 2 sporozoites. Sporozoites penetrate the mucosa of the small intestine and pass via the mesenteric lymph nodes and hepatic portal system to the liver. In the liver, they enter the epithelial cells of the bile duct and occasionally the liver parenchymal cells. Different number of asexual reproductions are produced preceding gametogony. The liver is greatly enlarged, and the bile ducts are dilated 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. The liver parenchyma is destroyed by pressure from expanding biliary ducts and is gradually replaced by fibrous connective tissue. Oocyst pass out through the bile and appear in the faeces 18 days after infection, sporulation occurs in 3 days.
E. stiedae infection can be diagnosed by identifying oocyst in the faeces, based on size, shape, and structure, or by FNB of the hepatic lesions. Oocysts must be differentiated from those of the intestinal coccidia, which also may be present in rabbits in large numbers. Serum AST, ALT and GGT activities and, globulin and total protein levels increase while albumin levels usually decrease in hepatic coccidiosis, depending on hepatocellular damage or cholestasis
Toltrazuril, a broad spectrum anticoccidial drug against different Eimeria species, is used for the treatment of coccidiosis in rabbits. The drug is effective against all intracellular developmental stages including those of schizogony and gametogony.
