SURATEX(R) - A SIMPLE LATEX AGGLUTINATION ANTIGEN TEST FOR DIAGNOSIS OF TRYPANOSOMA-EVANSI INFECTIONS (SURRA)

A simple and rapid, held-oriented latex agglutination test for the det ection of circulating invariant trypanosomal antigens in Trypanosoma e vansi infections (surra) is described. In an initial evaluation, the t est, Sura-tex(R), detected the antigens in 53 (88.3 %) of 60 serial bl ood samples collected over a period of 11 weeks from 3 experimentally infected rabbits. By comparison, the buffy coat technique and wet bloo d film examination diagnosed the infection in 22 (36.7 %) and 2 (3.3 % ) of the blood samples, respectively. In experimental infections in ca mels, Suratex diagnosed the infection in 10 of the 12 animals by day 7 post-infection, compared to 7 animals detected by the buffy coat tech niques. The 5 animals misdiagnosed by the buffy coat technique remaine d parasite negative throughout the study period of 127 days, yet they had persistent antigenaemia. Analysis of field sera from two camel her ds which were experiencing a T. evansi outbreak, confirmed the superio r sensitivity of Suratex(R). Whereas only 5 (15.6 %) animals in a herd of 32 were diagnosed by the buffy coat technique, 30 (94.0 %) tested positive for antigens. This high prevalence of T. evansi infections in the herd was confirmed by the high antibody titres detected in sera f rom all the 32 animals. The second herd, consisting of 60 camels, was investigated using both mouse inoculation and Suratex(R). Twenty- eigh t (46.7 %) of the animals were diagnosed to be infected with T. evansi by mouse inoculation, while Suratex showed all the 60 animals to be i nfected. Four of the 5 camels diagnosed using the BCT and all the 28 d etected by mouse inoculation (32/33; 97.0 %) were Suratex(R) positive, thus showing a high degree of correlation between parasitological res ults and those obtained by Suratex. All the control sera from 30 camel s from a T. evansi-free herd were negative.