South Africa appears to be the only country where feline babesiosis is a significant clinical entity in domestic cats. Little is known about its epidemiology or the clinical challenges facing practitioners. A questionnaire posted to 1760 South African veterinarians was returned by 16 %, representing approximately 40 % of practices. Just over half reported seeing feline babesiosis, with most cases occurring in the coastal areas of the Western Cape, Eastern Cape and KwaZulu-Natal Provinces. Overall incidence is highest in summer, but seasonality is less pronounced in non-seasonal and winter rainfall areas. No age, breed or sex predisposition was identified. Weight loss, weakness, anaemia, fever and icterus are common clinical findings. Complications include hepatopathy, renal failure, pulmonary oedema, cerebral signs, immune-mediated haemolytic anaemia and concurrent infections. The antibabesial drug of choice is primaquine phosphate. Response to therapy is generally good, but recurrence and chronic infections were identified as problems. The average mortality rate was 15 %. Approximately 3000 cases are seen annually by the respondents, at an estimated cost of R750 000 to the owners. Feline babesiosis is a significant problem in South Africa, and further investigations of taxonomic status, concurrent infections, chemotherapy, complications and management of refractory cases are warranted

Fifty-six cats with naturally occurring Babesia felis infection were studied. No breed or sex predilection could be identified, but there was an apparent predilection for young adult cats less than 3 years of age. Macrocytic, hypochromic, regenerative anaemia was present in 57 % of the cats and in-saline agglutination tests were positive in 16 %. No characteristic changes were observed in total or differential leukocyte counts. Thrombocyte counts were variable and thrombocytopaenia was an inconsistent finding. Hepatic cytosol enzyme activity and total bilirubin concentrations were elevated in the majority of cats. Serum protein values were mostly normal, but increased values were occasionally observed and polyclonal gammopathies were observed in all cats with increased total globulin concentrations. No remarkable changes in renal parameters were observed. A variety of electrolyte abnormalities occurred in a number of cats, but no consistent pattern of change could be identified. A close correlation was evident between peripheral and central parasite counts. Concurrent infections with Haemobartonella felis, feline immunodeficiency virus and/or feline leukemia virus were identified in a number of cats.

Babesia felis, originally identified in wild cats in the Sudan, was subsequently found to cause clinical disease in domestic cats. Although babesiosis in domestic cats has been reported sporadically from various countries, as a significant disease it appears to be a distinctly South African phenomenon. Apart from an inland focus, feline babesiosis is reported regularly only from coastal regions. The infection is assumed to be tick-borne, but the vector has not been identified. Feline babesiosis tends to be an afebrile, chronic, low-grade disease. The most frequently reported complaints by owners are anorexia and lethargy. The main clinical findings are anemia, depression, and occasionally icterus. Concurrent infections (e.g., Mycoplasma haemofelis, FeLV, FIV) may contribute to the clinical picture. Laboratory findings commonly include regenerative anemia, elevation of alanine transaminase (but not alkaline phosphatase) and total bilirubin concentrations, and a variety of electrolyte disturbances. Secondary immune-mediated hemolytic anemia can be seen occasionally. Drugs effective against other Babesia species give variable and questionable results. The drug of choice is primaquine phosphate, which effects a clinical cure but does not sterilize the infection. Repeated or chronic therapy may be required.

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