Polyclonal antibody-based antigen-detection immunoassay for diagnosis of Trypanosoma evansi in buffaloes and horses.

An enzyme-linked immunosorbent assay (ELISA) was employed for the detection of Trypanosoma evansi antigens in serum samples of field cases of buffaloes and horses in northern India. In 323 naturally infected/suspected buffaloes, circulating antigenaemia was detected in 180 (55.72%), whereas parasitaemia by wet blood smear examination was found in 62 (19.19%) only. The antigen-ELISA was positive in 47 of the 62 parasitologically proven cases and in 86 of the 116 cases with anti-trypanosome antibodies detected by ELISA. Of the 80 horses examined antigen-ELISA was positive in 45 (56.75%) sera. The antigen-detection assay was positive in 14 of the 19 parasitaemic cases whereas the antibody-detection assay was positive in 18 of the 30 parasitaemic cases. In the present study, antigen-ELISA was found to be more sensitive and specific compared with antibody-ELISA and wet blood examination, and could prove a useful tool for epidemiological studies of latent trypanosomosis in livestock.