Evaluation of various diagnostic techniques for Trypanosoma evansi infections in naturally infected camels

One hundred and eight camels (Camelus dromedarius) from Trypanosoma evansi endemic areas of the Thar Desert of Rajasthan State, India, were evaluated by various diagnostic tests including parasitological tests (wet blood film-WBF, stained thick blood film), chemical test (mercuric chloride), biological test (mouse subinoculation-MSI), and immunodiagnostic tests based on antibody detection (double immunodiffusion test-DID, card agglutination test-CATT), antigen detection (double antibody sandwich enzyme linked immunosorbent assay-Ag-ELISA). Of the tested camels 49 were found infected using the WBF of which nine gave false negative results with the mercuric chloride test. The efficacy of MSI was 87.03 percent, while the mercuric chloride test was 60.18 percent efficient. The diagnostic efficacy of CATT (72.22 percent) was found to be much better than DID (28.70 percent). Ag-ELISA was 86.11 percent efficient in detecting trypanosomal antigens. A good correlation was found between the positive results obtained by wet blood film, CATT and Ag-ELISA. It was inferred that CATT can be used to study the seroprevalence of T. evansi with great ease, however, trypanosome antigen detection may give a more accurate idea of the prevalence of T. evansi in an endemic area.