TRANSMISSION AND DIAGNOSIS OF EQUINE BABESIOSIS IN SOUTH-AFRICA

The transmission and prevalence of Babesia equi and B. caballi are bei ng studied. Rhipicephalus evertsi mimeticus an ixodid tick from Namibi a was identified as a new vector of B. equi, however, R. turanicus, pr eviously reported to be a vector, failed to transmit both B. equi and B. caballi in the laboratory. The accurate diagnosis of B. caballi is being investigated because the nature of its low level parasitaemia do es not allow easy detection in thin blood smears, routinely used for d iagnosis, by clinicians. Consequently its role as a pathogen remains o bscure. The importance of identifying infected horses, destined for ex port to Babesia-free countries, is also stressed Thick and thin blood smears, serology (IFAT) and DNA probes are currently employed to study disease prevalence. To date 293 healthy, adult, thoroughbred horses h ave been screened by all three methods. The percentage positives are a s follows: B. equi 4.4%, 70.6%, 13% and B. caballi 0.7%, 37%, 18.4% re spectively. The DNA probes were more sensitive than blood smear examin ation for diagnosing carrier infections but are probably not sensitive enough to identify all carrier infections. A poor correlation was fou nd between detection of the parasites' DNA and seropositivity. However , polymerase chain reaction could be used to amplify parasite DNA in a particular sample and this could result in more accurate diagnosis.