Detection of Leishmania infantum Kinetoplast DNA in the Whole Blood of Asymptomatic Individuals by PCR-ELISA and Comparison with Other Infection Markers in Endemic Areas, Southern Iran

Visceral leishmaniasis (VL), caused by Leishmania infantum, is endemic in southern Iran. To detect asymptomatic individuals, we used kinetoplast DNA (kDNA) polymerase chain reaction (PCR)-ELISA methods on 388 blood samples of healthy persons in two endemic loci and compared the results with the leishmanin skin test (LST) and the immunofluorescent antibody test (IFAT). kDNA PCR, LST, and IFAT were positive in 95 (24.5%), 132 (34%), and 212 (54.6%) cases, respectively. Fifty-five (21.4%) individuals that were LST negative were PCR positive. All PCR-positive individuals had a titer of >or=1:20, whereas 45% of those that were IFAT positive were PCR positive. For a reliable index of prevalence rate of infection, LST alone is not sufficient and needs to be accompanied by PCR-ELISA. The high rate of kDNA-positive results may indicate the possibility of humans being a reservoir and source of transmission. In endemic areas, kDNA PCR-ELISA is not a reliable test for the diagnosis of active VL.