Encephalitozoonosis, caused by Encephalitozoon cuniculi, a microsporidian intracellular protozoan, is common in rabbits. Infection is persistent, but may be latent, never causing signs of illness. However, it may cause transient neurologic signs or severe signs of meningoencephalitis, nephritis or intraocular inflammation. Many rabbits acquire infection from their dams or other rabbits in the rabbitry. Transmission is by excretion of spores in the urine during acute infection with ingestion by susceptible rabbits. The organisms spread to various organs and as antibodies develop, they become encapsulated, limiting tissue damage and spore excretion. A healthy immune system prevents the organisms from multiplying but the spores remain viable. Immunosuppression may result in overt disease many years after the initial infection. Currently, there are no definitive clinical means of diagnosing encephalitozoonosis. However, since the infection is persistent, antibodies continue to be produced.
Pasteurellosis, caused by the bacterium Pasteurella multocida, is common in rabbits. The most frequent manifestation of disease is upper respiratory tract disease involving the conjunctiva, nasolacrimal ducts, nares, nasal sinuses and nasopharynx. Clinical signs include sneezing, matted forepaws, nasal discharge and upper respiratory rales. The best way of detecting the organism in accessible sites is by culture. A swab (type IV Calgiswab) of the nares, along the nasal septum, should be streaked onto a blood agar plate for isolation of the organism. Some strains of P. multocida require incubation for 48 hours at 37 C or in 5% CO2 for primary isolation. Infections of the lower respiratory tract, middle ears or reproductive tract are usually inaccessible for culture. For these infections, serologic testing is a useful diagnostic tool, as infection results in production of antibodies.
Syphilis in rabbits is caused by Treponema cuniculi, a spirochete bacterium. Infection results in ulcers and crusty exudates at mucocutaneous junctions of the vulva, prepuce, anus, nose, lips and eyelids. Lesions may resolve and the infection can become subclinical. The agent is transmitted venereally or by contact, and may be passed to young rabbits by the dam. T. cuniculi is endemic in many rabbitries. It is not transmissible to humans. T. cuniculi can be eliminated from rabbitries and individual rabbits with treatment. In clinical cases, an etiologic diagnosis can be made by dark field microscopy of exudate from lesions. Serologic detection of antibodies indicates infection with T. cuniculi.
Tyzzer's disease, caused by Clostridium piliforme, may exist as a subclinical infection or result in severe enteritis. Weanling rabbits are mainly affected with diarrhea and high mortality. If the bacteria gain access to the bloodstream, the liver and heart are also affected. Since bacteria are passed in the feces, the organisms may spread easily in rabbitries, and become endemic. The incidence of disease in infected pet rabbits is unknown. Control of infection depends on reduction of stress and good sanitation.Testing for antibodies to C. piliforme reveals whether adult rabbits have been infected and may develop secondary disease or be carriers.