Asymptomatic domestic dogs are carriers of Leishmania infantum: possible reservoirs host for human visceral leishmaniasis in southern Iran

Abstract

In the past few years, the incidence of human visceral leishmaniasis (HVL) has increased in many districts of Fars Province, southwest of Iran, particularly, among communities of nomadic tribes. Recent epidemiological reports in Leishmania infantum endemic regions of Iran indicate that more than 50–70% of seropositive dogs are asymptomatic for Leishmania infection. Between 2004 and 2006, blood samples were collected from 110 domestic dogs from nomadic and rural areas. Each of these samples was tested for anti-Leishmania antibodies, in direct agglutination tests (DATs), and for L. infantum kinetoplast deoxyribonucleic acid (kDNA), in polymerase chain reaction (PCR)-based assays. Of the 110 dogs, 5.5% (6/110) were found seropositive and 23% (25/110) PCR-positive. Four of the six seropositive (67%) and 22 of the 25 PCR-positive (88%) were asymptomatic. The rate of infection in dogs from nomadic communities was higher (27%) than dogs from rural areas (18%). Since positivity in the PCR-based assay indicated the presence of L. infantum amastigotes in the peripheral blood of 23% of the subjects, it is clear that these asymptomatic dogs (88%) are quite common in the study areas and probably act as reservoirs in the transmission of Leishmania parasites, to humans and to other dogs, by sandflies. Moreover, our study showed that application of PCR to buffy coat samples gave a better estimate of the real rate of infection in asymptomatic dogs than DAT.