Application of a direct agglutination test for detection of specific anti-Leishmania antibodies in the canine reservoir.

A direct agglutination test (DAT) for detection of visceral leishmaniasis in humans has been developed. In this study, it was evaluated for applicability to detection of infections in dogs, a reservoir species. The reliability of the test was improved by treating the test sera with 0.2 M 2-mercaptoethanol and incubating them at 37 degrees C. Sensitivity was 100% and specificity was 98.9% when the test was used on serum samples from 220 dogs, including 26 with parasitologically confirmed canine leishmaniasis, 12 with suspected but unconfirmed leishmaniasis, and 182 with other conditions. The DAT detected specific antibodies in 10 dogs with canine leishmaniasis diagnosed by case history, clinical signs of leishmaniasis, and seropositivity in an immunofluorescence test using either promastigotes or amastigotes, as well as in 2 dogs suspected of having leishmaniasis. The performance of an antigen prepared from a homologous isolate of Leishmania infantum in the DAT was compared with that of an antigen from a laboratory-adapted strain of L. donovani (sensu lato). The homologous antigen compared favorably with the standard antigen, and the results provided further evidence of the potential of the DAT for detection of Leishmania infection in the canine reservoir host. The results of this study, together with those of our previous studies in human visceral leishmaniasis, demonstrate that the DAT is highly suitable for wide-scale epidemiological and ecological field work. This technique could also facilitate diagnosis of leishmaniasis in dogs in veterinary health services.