Encephalitozoon cuniculi infects a wide range of animals, including rabbits. The organism invades and infects the CNS, resulting in signs of vestibular disease. Positive antibody titers or CSF analysis can indicate infection; diagnosis can be confirmed by PCR-based spore identification in urine or by histopathology. In this study, investigators compared 2 different treatment protocols over 8 years. Between 2000 and 2003, 50 rabbits with confirmed or highly suspected infection were treated for 10 days with oxytetracycline (20 mg/kg SC q24h) with (n = 27) or without (n = 23) dexamethasone (0.2 mg/kg SC q24h). Between 2004 and 2008, 45 rabbits were treated for 10 days with oxytetracycline and fenbendazole (20 mg/kg PO q24h) with (n = 20) or without (n = 25) dexamethasone. All rabbits were hospitalized and provided supportive care; pre- and posttreatment neurological examinations were performed. Antibody titers were positive in 93.7% of the rabbits and PCR was positive in 48.7% of 37 rabbits. Forty-six rabbits either died or were euthanized during hospitalization; E cuniculi was found in 40/40 rabbits postmortem. Among rabbits treated with fenbendazole was a statistically significant improvement in neurological scores, and rabbits were 1.6 times more likely to survive until at least day 10. Treatment with dexamethasone did not show effect on neurological signs or short- or long-term survival.

Diagnosis of encephalitozoonosis in rabbits is frequently presumptive, and treatment can be protracted and unrewarding. This study reaffirmed the previous finding that benzimidazoles appear to provide optimum treatment results. In practice, I have seen similar positive responses to benzimidazoles, although I exercise caution in monitoring patients because of risk for bone marrow suppression. Since neither oxytetracycline nor dexamethasone were found to change neurologic status or survival rates, these medications should be avoided in treatment unless there is a specific reason for inclusion (ie, suspected secondary bacterial infection).—Sarah Churgin, DVM

Clinical evaluation of therapeutic success in rabbits with suspected encephalitozoonosis. Sieg J, Hein J, Jass A, et al. VET PARASITOL 187:328-332, 2012.