Giardia duodenalis Infection

Infection of rabbits with G. duodenalis is often subclinical, but several cases of enteritis have been associated with this organism in rabbits. The taxonomy of Giardia spp. is still in flux, but G.

Hepatozoon cuniculi Infection

Hepatozoon cuniculi is of minor significance, but has been reported in domestic rabbits. The nomenclature is his­torically based on the host (rabbit), and was originally named Leucocytogregarina cuniculi. The relationship to other Hepatozoon species is unknown. Gametocytes were observed in peripheral blood leukocytes and schiz­onts in the spleen of domestic rabbits. Hepatozoon spp. utilize an intermediate arthropod host, which has not been defined for rabbits, but fleas are suspected.

Sarcocystis cuniculi Infection

There are over 130 named species of Sarcocystis, nomen­clature of which has been historically based upon associ­ation with various hosts. Thus, taxonomy is in complete flux, and it remains to be determined if S. cuniculi is a valid separate species. Typical Sarcocystis cysts have been observed as incidental findings in skeletal and cardiac muscle of domestic rabbits, and are very common in different species of wild rabbits (including Oryctolagus) and hares. Domestic rabbits may have a high prevalence of seroconversion to this organism, with no clinical dis­ease. Rabbit Sarcocystis is infective to cats and back to rabbits, indicating that the definitive host is the cat.

Toxoplasma gondii Infection: Toxoplasmosis

Toxoplasma gondii infection has been documented in rabbits in many parts of the world. Serologic surveys indicate that infection is common, but clinical disease is rare. Toxoplasmosis is associated with contamination of feed and water by cat feces. In 1 reported outbreak of the disease, anorexia, pyrexia, and neurological disorders were the presenting signs. At necropsy, multiple foci of necrosis were found with a granulomatous inflamma­tory response in the lung, liver, and spleen. Tachyzoites and tissue cysts with PAS-positive bradyzoites were observed within thin PAS-negative cyst walls. No lesions were found in other organs, including brain. Another report found 25.4-51.2 μm cysts within the brain, but not other organs of a clinically ill rabbit. Wild and domestic meat rabbits are considered to pose a major source of infection for humans. In contrast to Encepha- litozoon cuniculi, T. gondii tachyzoites and bradyzoites within cysts are Gram-negative.

Trypanosoma nabiasi Infection: Trypanosomiasis

Trypanosomiasis is indigenous to the wild European rabbit, and similar organisms are found in North Ameri­can Sylvilagus rabbits. Infection with T. nabiasi has been found in Australian wild Orytolagus rabbits. Although it may have been carried with the original 24 rabbits that were introduced to Australia in 1859, it is more likely to have been carried with the rabbit flea, which was pur­posely introduced into the wild in 1968 for myxomatosis control. This trypanosome has been reported in Euro­pean domestic rabbits, as well as outside of Europe. The vector is the rabbit flea, Spilopsyllus cuniculi, and trans­mission is via flea feces and ingestion of fleas during grooming. Upon infection, parasitemia increases rap­idly, peaks around 20 days, then declines, and duration of infection is 4-8 months, followed by recovery. The organism is rabbit species specific and essentially nonpathogenic.

Nonpathogenic (Commensal) Intestinal Protozoa

The rabbit intestine contains Chilomastix cuniculi, Mono- cercomonas cuniculi, Retortamonas cuniculi, and Entamoeba cuniculi, among others, which are all nonpathogenic.