A COMPARISON OF THE ANTIGEN-DETECTION ELISA AND PARASITE DETECTION FOR DIAGNOSIS OF TRYPANOSOMA-EVANSI INFECTIONS IN CAMELS

Two herds of 60 camels each, living in Trypanosoma evansi endemic area s, were selected and studied for a period of 18 months. Animals in one herd were treated prophylactically with quinapyramine prosalt (May an d Baker, Dagenham, UK), while those in the other herd were treated ind ividually with quinapyramine dimethylsulphate (May and Baker, Dagenham , UK) when proven parasitaemic. The herd on prophylaxis was sampled fo r antigen and patent infection monthly. The other herd was sampled wee kly for patent infection and fortnightly for antigen. The results obta ined could be divided into four categories. The first category compris ed cases (52 out of 61 ) in which the presence of trypanosome antigens could be correlated with parasitological diagnosis. In 80% of these a nimals the antigens disappeared from the circulation within a period o f 30 days following chemotherapy. The second category comprised those animals with parasitologically proven infections but which did not hav e antigens in their sera. This was observed in nine camels, seven of w hich were from the herd that was being examined weekly for the presenc e of trypanosomes. These were considered to be animals in early infect ion, as the subsequent sera were also negative for anti-trypanosome an tibodies and immune complexes. The third category comprised camels whi ch were antigen-positive but aparasitaemic. Sera from these animals we re also positive for anti-trypanosome antibodies, indicating that anti gen-positivity was a true reflection of trypanosome infections in thes e animals. The last category comprised pre-weaned camel calves which a ppeared to have some form of protection against trypanosomosis, as evi denced by the absence of trypanosomes, antigens and antibodies through out the early period of their lives. Only occasional antigenaemia was found in a few calves. It is concluded that trypanosome antigen detect ion may give a more accurate idea of the prevalence of T. evansi infec tions than does whole parasite detection.