Feline babesiosis.

OBJECTIVE: To review and summarize current information regarding the etiology, clinical presentation, diagnosis, treatment, and prognosis of feline babesiosis, especially with regard to features distinct from canine babesiosis. ETIOLOGY: Babesiosis is caused by hemoprotozoa of the genus Babesia. Numerous species of Babesia exist worldwide. The babesial organism spends the majority of its life cycle within the erythrocyte of the definitive host, resulting in hemolysis, with or without systemic complications. DIAGNOSIS: Definitive diagnosis depends on direct visualization of the organism on blood smear or a positive polymerase chain reaction. Positive serologic tests indicate only exposure, with or without active infection. THERAPY: Antiprotozoal drugs and supportive care are the mainstays of therapy. Primaquine phosphate is considered the treatment of choice in cats. PROGNOSIS: Prognosis depends on the severity of disease, which in turn depends on both organism and host factors. Mortality rates of 15-20% are reported.