I. Baylisascaris procyonis
II. Dermatophytosis
III. Encephalitozoonosis
IV. Salmonellosis
V. Tularemia
Infection of rabbits with the raccoon ascarid, Baylisascaris procyonis, occurs by ingestion of bedding or hay contaminated with raccoon feces. Reports of this nematode as a rabbit pathogen are increasing. Clinically infected rabbits display torticollis, ataxia, tremors, and falling (loss of balance). At necropsy, multiple, white raised nodules in the epicardium, endocardium and serosal surface of the liver may be seen. Larval granulomas and multifocal necrosis in the cerebrum and cerebellum, and larval granulomas and tracks in the viscera are typical histologic lesions. Cross sections of larvae with cuticular alae are often visualized in brain sections. Diagnosis is made from clinical signs and the presence of larvae in histosections. Treatment has not been attempted. Efforts to prevent infection include use of clean bedding and hay.
A. Etiology: Trichophyton mentagrophytes is an opportunistic, ubiquitous fungal soil organism.
B. Incidence: There is high incidence of the carrier state, with low incidence of disease.
C. Clinical Signs: A crusty, pruritic, patchy alopecia on
the head which spreads to the paws and other parts of the body is typical
(see photo). Secondary bacterial infections are common. 
D. Diagnosis: Diagnosis is based on clinical signs, scraping and identification of spores on hair shaft or mycelia within hair shaft, and culture on Sabaraud or DTM agars.
E. Treatment: Topical treatment with a fungicide (Tresiderm, Iodine, Conofite cream) or griseofulvin (25 mg/kg in aqueous suspension or 0.375 gm powdered form/lb food for 14 days) has been successful. Topical 10% chlorox solution is also effective. Griseofulvin therapy should be used with caution in breeding herds, as the incidence of teratogenesis is associated with treatment.
F. Control: Disinfect cage and nest boxes with 10% bleach solution. There is a possibility of transmission of infection to people handling the rabbits, so gloves should be worn when treating the rabbits. Ventilation should be improved to decrease the relative humidity, and all filters, water pads, curtains/blinds or other materials used to control the air temperature should be replaced weekly to prevent collection of fungus spores.
Public Health Significance: People handling rabbits with T. mentagrophytes induced lesions have developed dermatophytosis.
A. Etiology: Encephalitozoon cuniculi (once called Nosema cuniculi) is a microsporidian parasite, 2.5 x 1.5 micrometers (oval) with thick wall.
B. Transmission: E. cuniculi is shed in the urine and has been experimentally transmitted by direct contact (ingestion, aerosol).
C. Clinical Signs: Usually there are no clinical signs (latent infection); however, in heavy infections there may be torticollis, convulsions, tremors, posterior paresis, and edema.
D. Pathology: In acute cases the kidneys are swollen.
Chronic lesions are more commonly seen and include multifocal, pinpoint,
white, pitted areas on the surface of the kidneys. Histological examination
of kidneys and brain will reveal a granulomatous interstitial reaction
with fibrosis in the kidney and focal granulomas in the brain (white arrow)
with perivascular plasma cell cuffs and nonsuppurative meningitis.
The organism may be found in renal tubular epithelial cells or in microglia
in the brain. Encephalitozoon stains poorly with hematoxylin and
eosin stains, but is Gram-positive (black arrow) and refractile when viewed
with polarized light.
E. Diagnosis: Diagnosis is provided by histopathologic demonstration of organisms and serologic detection of antibody via ELISA and indirect fluorescent antibody tests. Most research animal diagnostic laboratories offer an ELISA or FA test.
F. Treatment and Control: No treatment is effective. Control is difficult in colonies, especially breeding colonies. Housing rabbits on wire and placing the cages away from contact with walls and in single rows (no stacking) may prevent cage-to-cage urine contamination. Rabbits will seroconvert 30 days prior to shedding sporocysts in urine, so a strict program of culling seropositive rabbits can be instituted based on results of serologic screening every 2 weeks.
Public Health Significance: Encephalitozoon cuniculi has been diagnosed in immunosuppressed humans. The direct association between rabbit ownership and infection has not been documented.
A. Etiology: Salmonella enterica serovars are Gram-negative aerobic, nonlactose fermenting, H2S producing rods.
B. Transmission: Salmonellae are transmitted by ingestion through direct contact with contaminated feces, food or fomites. Incidence of infection is rare.
C. Clinical Signs: Acute disease is characterized by anorexia, fever, dehydration, diarrhea (hemorrhagic), death, and abortions. Rabbits that recover from acute disease are asymptomatic shedders.
D. Pathology: Lesions are consistent with those of septicemia and include congestion and hemorrhage of the viscera associated with septicemia, ulcerative colitis, and focal necrosis of liver.
E. Diagnosis: Definitive diagnosis is made by isolation of the bacteria through culture of blood, spleen, mesenteric lymph nodes and feces on selective media (brilliant green, selenite, citrate, or tetrathionate).
F. Treatment: Since antibiotic therapy does not eliminate bacterial carriage, it is advisable to eliminate the colony and restock.
G. Control: Good management practices will prevent infection. Disinfection, replacement with clean stock and prevention of wild bird or rodent contamination of bedding, water, or food should prevent future or continued problems.
Public Health Significance: Man can contract Salmonella from infected rabbits.
A. Etiology: Francisella tularensis is a Gram-negative, pleomorphic rod.
B. Transmission: Blood sucking arthropods (squirrel flea, deerfly, mosquitoes, lice, and woodticks) may serve as mechanical or biological vectors. Transmission may occur by direct contact, ingestion, or aerosol (rare). The incidence of infection in domestic rabbits is rare.
C. Clinical Signs: Depression, anorexia, ataxia, and death are the nonspecific signs associated with this disease.
D. Gross Pathology: Widespread visceral congestion, splenomegaly,
consolidated and congested lungs, and multiple pinpoint white foci on the
liver and spleen are characteristic lesions.
E. Diagnosis: Necropsy findings, and bacterial isolation are
recommended diagnostic measures.
F. Treatment: There is no treatment.
G. Control: Elimination or control of vectors and wild mammal populations will prevent exposure.
Public Health Significance: Man is susceptible to infection. Transmission can occur by ingestion of contaminated water, penetration of unbroken skin or contamination of cutaneous wounds, tick bites, or by aerosolization of the organism in dust, feces, or when skinning wild rabbits. Human tularemia is manifest by cutaneous lesions, septicemia, and/or meningitis.
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