Assessment of canine visceral leishmaniasis diagnosis by means of a rapid test using recombinant antigen K39 in endemic regions of São Paulo state, Brazil

Canine visceral leishmaniasis (CVL) coexists with human visceral leishmaniasis (HVL) in Brazil. Dogs play an important role as reservoir of etiological agent, and for CVL dissemination. For diagnosing CVL, IFA and ELISA have been routinely employed. These assays have not been suitable for diagnosis studies owing to low sensitivity and/or specificity. The CVL diagnosis in different regions of São Paulo was assessed, comparing the performance of a immunochromatographic dipstick – based rapid test using K39 recombinant antigen (rK39RT) on whole blood and serum samples, and with IFI and ELISA on serum samples. The 1,333 samples dogs were tested including 1,199 samples from randomly selected dogs from eight municipalities with CVL transmission. The control group was comprised by samples from 134 animals living VL-free area or from dogs with other diseases. Of 1,199 samples, 31.3% were positive by rK39RT on sera, and 17.4% on whole blood. Anti-Leishmania antibodies were detected in 25.1% and 27.2% of samples on IFA and ELISA, respectively. rK39RT revealed a low performance on whole blood, however on dog serum higher number of positive samples were detected. All samples from 47 dogs with other diseases were negative on rK39RT. The rK39RT is a simple, rapid, inexpensive, specific and sensitive, and suitable as an alternative screening testing.