THE USE OF ENZYME-LINKED IMMUNOSORBENT ASSAYS TO INVESTIGATE THE PREVALENCE OF TRYPANOSOMA-EQUIPERDUM IN ETHIOPIAN HORSES

A field study involving 309 horses was undertaken in the provinces of Arsi and Bale in the Ethiopian highlands to investigate the prevalence of Trypanosoma equiperdum infections using enzyme linked immunosorben t assays (ELISAs) for the detection of both trypanosomal antigen and a ntibody. Adult horses of both sexes were examined for clinical signs o f T. equiperdum infection and serum samples were collected for the ass ays. One hundred and one horses showed the presence of trypanosomal an tibodies in their serum and 70 animals showed typical clinical signs o f dourine. Nineteen horses showed the presence of trypanosomal antigen . Eight horses were positive for both T. equiperdum antibody and antig en. Blood and genital washes from seven antigenaemic horses were inocu lated into mice and rabbits in an attempt to isolate trypanosomes but none became infected. Statistical analysis of the results of the antib ody assays indicated that there were significant differences in the di stribution of serologically positive horses in the different clinical groupings, with seroprevalence increasing with the severity of the obs erved clinical signs (P < 0.001). There was also a positive correlatio n between the presence of circulating trypanosomal antigen and clinica l evidence of infection, Although it was not possible to obtain direct parasitological evidence of infection, the results of the serological assays, together with the clinical signs of disease observed in many of the horses, provide strong circumstantial evidence that T. equiperd um occurs in Arsi and Bale provinces of Ethiopia. Furthermore, in view of the large number of horses in Ethiopia and the unrestricted moveme nt of animals throughout the country it is likely that dourine may be more widespread in Ethiopia than is currently realised. The assays use d show potential for diagnosis of dourine, but to be widely applied in field situations for the diagnosis and control of dourine in Africa t hey require further validation of their specificity and sensitivity. ( C) 1997 Elsevier Science B.V.