THE USE OF AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR TROPICAL THEILERIOSIS RESEARCH IN MOROCCO

An enzyme-linked immunosorbent assay (ELISA) using sonicated purified Theileria annulata piroplasms was compared with an indirect immunofluo rescent antibody test (IFAT) during a vaccination trial in cattle to t est different doses and passage numbers of an attenuated T. annulata-i nfected lymphoblastoid cell-line, and also with Giemsa-stained blood s mears during an epidemiological field study of tropical theileriosis i n Morocco. The sensitivities of both the ELISA (0.56) and the IFAT usi ng T. annulata piroplasm antigen (0.56) were lower than the IFAT using schizont antigen (0.94) for detecting serum antibodies from 18 cattle immunised 38 days previously with cell-line. The ELISA was, however, the most sensitive test after 180 days (0.50 compared with 0.06 for th e piroplasm IFAT and 0.39 for the schizont IFAT), and each test detect ed antibodies in all sera after challenge with live T. annulata sporoz oites. There were minor differences in the ability of blood smear exam inations and the ELISA to detect infected and uninfected cattle in the field study at the start and end of the disease season. Initially, th e sensitivity and specificity of blood smears were both 0.96 and for t he ELISA were 0.83 and 0.86, whereas at the end of the season sensitiv ity and specificity of blood smears were 0.96 and 0.86 and for the ELI SA were 0.95 and 0.94. The specificity of the ELISA was affected by th e presence of calves with colostral antibodies, and if these were disr egarded the specificities before and after the season were 0.94 and 1. 00.