EVALUATION OF A SIMPLE PCR TECHNIQUE FOR THE DIAGNOSIS OF TRYPANOSOMA-VIVAX INFECTION IN THE SERUM OF CATTLE IN COMPARISON TO PARASITOLOGICAL TECHNIQUES AND ANTIGEN-ENZYME-LINKED IMMUNO SORBENT ASSAY

Polymerase chain reaction (PCR) with specific oligonucleotides for the amplification of Trypanosoma vivax DNA has been developed by Masiga e t al. (1992) to detect the presence of T. vivax DNA in biting flies. T he aim of this experiment was to evaluate the efficacy of this techniq ue when applied directly on cattle serum, without DNA purification, to detect infection. The sensitivity of this PCR technique was compared with parasitological techniques, namely haematocrit centrifuge techniq ue (HCT) and buffy coat method (BCM). and with the antigen-enzyme-link ed immunosorbent assay (Ag-ELISA) for T. vivax developed by Nantulya a nd Lindqvist (1989). Blood and serum samples were collected from four calves experimentally infected with a stock of T. vivax from French Gu yana (IL4007). During the first 51 days of infection, a total of 164 s amples were collected and processed using the four tests. Mean percent ages of positive results were 68% with HCT, 59% with BCM, 4% with Ag-E LISA and 64% with PCR. Parasitological and PCR techniques yielded appr oximately the same sensitivities. PCR was able to detect active infect ion in serum samples when parasitaemia was over 10(3) trypanosomes/ml. With this isolate of T. vivax the Ag-ELISA was not found to be sensit ive enough to be used as a diagnostic tool. The sensitivity of this PC R technique is not greater than parasitological techniques but it allo ws delayed processing of the samples and gives a highly species-specif ic diagnosis. This simple PCR technique should be evaluated for field diagnosis because it makes retrospective epidemiological survey using serum banks possible. Moreover, it can be substituted to parasitologic al techniques when immediate examination is not feasible. (C) 1997 Els evier Science B.V.