ORIGINAL ARTICLE Asymptomatic domestic dogs are carriers of Leishmania infantum: possible reservoirs host for human visceral leishmaniasis in southern Iran Mahdi Fakhar & Mohammad Hossein Motazedian & Qasem Asgari & Mohsen Kalantari Received: 9 April 2010 / Accepted: 8 February 2011 / Published online: 22 February 2011 # Springer-Verlag London Limited 2011 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 epidemio- logical 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 agglu- tination tests (DATs), and for L. infantum kinetoplast deoxyribonucleic acid (kDNA), in polymerase chain reac- tion (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 amasti- gotes 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. Keywords Canine visceral leishmaniasis . Asymptomatic dogs . Leishmania infantum, Polymerase chain reaction . Direct agglutination test Introduction Visceral leishmaniasis (VL) or kala-azar is a systemic disease which is caused by Leishmania donovani complex. It is estimated that the annual incidence of human visceral leishmaniasis (HVL) cases worldwide is about 500,000 cases (World Health Organization 1998). Visceral leishmaniasis in the countries of the Mediterranean basin and the Middle East including Iran is caused by Leishmania infantum (Mohebali et al. 2005). In Iran, the main endemic foci for VL are Fars and Bushehr Provinces, in the southwest, the districts of Meshkin-shahr and Kaleybar in the northwest and Qom Province in the center of Iran (Asgari et al. 2006; Mohebali et al. 2001, 2005; Fakhar et al. 2004, 2006, 2008). Commonly, domestic dogs (Canis familiaris) are the most important domestic reservoir hosts for Mediterranean visceral leishmaniasis (MVL; Mazloumi Gavgani et al. 2002). L. infantum infection in dogs ranged from 10% to 37% in the Mediterranean basin (Fisa et al. 1999; Sideris et al. 1999; Mohebali et al. 2005). In Iran, canine visceral leishmaniasis (CVL) is endemic in northwest, southwest, and central parts, and the incidence varies between 4.5% M. Fakhar Department of Parasitology and Mycology, School of Medicine, Mazandaran University of Medical Sciences, Km 18, Khazar-Abad Road, P.O. Box 48175-1665, Sari, Iran M. Fakhar (*) Molecular and Cellular Biology Research Center, Mazandaran University of Medical Sciences, Km 18, Khazar-Abad Road, P.O. Box 48175-1665, Sari, Iran e-mail: mahdif53@yahoo.com M. H. Motazedian : Q. Asgari : M. Kalantari Department of Parasitology and Mycology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Comp Clin Pathol (2012) 21:801–807 DOI 10.1007/s00580-011-1179-6