Detecting American tegumentary leishmaniasis in dogs using ELISA tests

Abstract

American tegumentary leishmaniasis (ATL) shows a reduced humoral response in dogs and levels of specific antibodies may therefore not be detected by indirect immunofluorescence. Although the sensitivity of enzyme-linked immunosorbent assay (ELISA) is higher than that of indirect immunofluorescence, the best antigen for the diagnosis of ATL in dogs has not been defined. The detection of IgG subclasses represents an alternative to increase the efficiency of the serological diagnosis. In Rio de Janeiro, sporotrichosis is the main differential diagnosis of ATL in dogs, and a sensitive, specific and little invasive method that permits the discrimination of the two diseases is desired. In the present study, 69 serum samples, 34 obtained from dogs with ATL and 35 from dogs with sporotrichosis, all of them with a confirmed etiological diagnosis, were tested. The samples were analyzed by ELISA using Leishmania (Viannia) braziliensis and L. (L.) chagasi antigens for the detection of anti-Leishmania IgG, IgG1 and IgG2. The use of L. (V.) braziliensis antigens for the detection of IgG and IgG2 yielded the best results. Using L. (L.) chagasi antigen, the sensitivity and specificity for the detection of IgG were 82.4% and 100%, respectively, whereas both sensitivity and specificity were 97.1% with the L. (V.) braziliensis antigen. No improvement in the performance of the test was observed when IgG2 was analyzed separately. The IgG1 assays presented low accuracy, irrespective of the antigen used: sensitivity and specificity of 58.8% and 60% for L. (V.) braziliensis and of 64.7% and 77.1% for L. (L.) chagasi, respectively. The present results suggest that IgG ELISA using the L. (V.) braziliensis shows the best performance for the diagnosis of ATL, permitting the discrimination between cases of ATL and sporotrichosis in dogs.