The PCR-based detection of Leishmania major in Mus musculus and other rodents caught in southern Iran: a guide to sample selection.

In recent years, rural cutaneous leishmaniasis (CL) has become one of the most challenging public-health problems in several countries. Rodents play an important role as the ‘reservoir’ hosts of the parasite (Leishmania major) that causes the vast majority of the CL found in rural Iran. The present study deals with the role of rodents in the epidemiology of CL in Fars province, in the south of Iran, where the incidence of the disease has doubled over the last decade. Samples, of skin, foot pads, ears, livers and spleens, were collected from 89 rodents (three Meriones persicus, one Me. libycus, 64 Tatera indica and 21 Mus musculus), that had been caught in an endemic area, killed, and fixed in formalin [5% (w/v) formaldehyde]. When each sample was checked for L. major DNA by PCR, at least one sample from each of three (100%) of the Me. persicus, 35 (54·7%) of the T. indica and nine (42·9%) of the Mu. musculus was found to contain L. major DNA. Only 60% of the ear samples, 56% of the footpad samples, 38% of the liver samples and 38% of the spleen samples from the PCR-positive rodents were, however, found PCR-positive. Four of the rodents (two T. indica and two Mu. musculus) were each found to have PCR-positive ear and footpad samples but PCR-negative liver and spleen samples. Only four of the rodents (all T. indica) had PCR-positive spleen and/or liver samples but PCR-negative ear and footpad samples. It is therefore recommended that, for the PCR-based detection of L. major in Iranian rodents, priority is given to the collection and investigation of both ear and footpad samples. Zoonotic cutaneous leishmaniasis (CL) caused by Leishmania major is now endemic in 14 of the 29 provinces of Iran, with many rural foci in the north, east and south of the country (Yaghoobi–Ershadi et al., 2005). Several species of rodents have been identified as ‘reservoir’ hosts for the causative parasite in Iran, including Meriones libycus, Me. hurrianae, Nosokia indica, Rhombomys opimus, Tatera indica and Rattus norvegicus. (Seyedi–Rashti and Nadim, 1967; Nadim and Faghih, 1968; Seyedi–Rashti and Salehzadeh, 1990; Javadian et al., 1998; Motazedian et al., 2010). Unfortunately, because L. major may cause no or only minor skin lesions in such hosts, it is not always easy to detect the infections in wild rodents (WHO, 1990; Moemenbellah–Fard et al., 2003). Most infected rodents have been identified by the collection of skin scrapings from ears or feet and the culture of these samples (Edrissian et al., 1982). PCR has, however, already been found useful for the identification of possible reservoir hosts, without the need for culture and parasite isolation (Alexander et al., 1998; Oliveira et al., 2005; Brandao–Filho and Shaw, 2006). The main aim of the present study was to use a PCR-based assay and ear, footpad, liver and spleen samples to explore the prevalences of leishmanial infection among rodents that had been trapped in various parts of Fars province, in southern Iran.