Evaluation of an indirect fluorescent antibody test, enzyme-linked immunosorbent assay and quantification of immunoglobulins in the diagnosis of bovine trypanosomiasis.

An indirect fluorescent antibody test (IFAT), a microscale version of the enzyme-linked immunosorbent assay (microELISA) and determination of IgM levels in serum were assessed for their comparative diagnostic value in the detection of bovine trypanosomiasis. Serum samples from drug-treated N'dama cattle and untreated N'dama and Zebu cattle from Liberia were examined for the presence fo antibodies to trypanosomes. In the untreated Zebu cattle, infections with T. vivax predominated and the prevalence of infection was higher than that found in untreated N'damas in which infections with T. congolense predominated. The proportion of animals which showed serological evidence of trypanosomiasis in the untreated Zebus was slightly higher than that found in the untreated N'damas. The prevalence of infection was low in N'dama cattle which had been treated with diminazene aceturate and homidium chloride but 50% of the animals showed serological evidence of trypanosomiasis. More serologically positive animals were detected by microELISA than IFAT, but both tests were equally sensitive in detecting antibodies in cattle in which trypanosomes were demonstrated by examination of peripheral blood. With both IFAT and microELISA it was necessary to carry out tests using antigens prepared from T. brucei, T. vivax and T. congolense in order to detect all serologically positive animals. Increases in serum IgM occurred in both N'dama and Zebu cattle but the levels were raised in only approximately half of the known infected animals. Overall, more animals gave positive reactions with IFAT and microELISA than showed raised IgM levels.