Full length articleThe Jordanian Mid Jordan Valley is a classic focus of Leishmania major as revealed by RFLP of 56 isolates and 173 ITS-1-PCR-positive clinical samples
Graphical Abstract
Introduction
The Jordanian Mid Jordan Valley (JMidJV, Fig 1) is endemic for cutaneous leishmaniasis (Arbaji et al, 1993, Khoury et al, 1996) and the disease is underreported (Mosleh et al., 2008a). The actual annual incidence of the disease is, however, known to be quite high (Khoury et al, 1996, Mosleh et al, 2008a, Oumeish, 1991). Khoury et al. (1996), for example, reported 987 cases from the Jordanian side of the Jordan Valley between 1983 and 1992. In the same region, the highest incidence, of more than 313/100 000 cases per year, was reported in 2004/2005 (Mosleh et al., 2008a). The desert rodent (Psammomys obesus) was confirmed as the main reservoir host (Saliba et al., 1994) and Phlebotomus papatasi as the vector of the disease caused by L. major (Janini et al., 1995b). In Jordan, the disease is diagnosed clinically, and when parasitological investigation is performed, it is restricted, in most of the cases, to the smears of lesion scrapings stained with Giemsa.
Species identification of the causative agent is vital to determine the best ways of control measures and treatment regimens (Schönian et al., 2003). A well-established PCR method, targeting the internal transcribed spacer 1 (ITS1) region between the SSU and 5.8S rRNA genes, is useful for the direct diagnosis of different forms of leishmaniasis. The method is highly specific and sensitive, able to detect approximately 0.2 parasites per sample (Schönian et al., 2003) and identify all medically relevant Leishmania species which are distinguished by DNA sequencing or restriction fragment length polymorphism (RFLP) of the PCR product (Dávila, Momen, 2000, Schönian et al, 2000, Schönian et al, 2001, Schönian et al, 2003).
Few studies have investigated the identity of the causative species of cutaneous leishmaniasis (CL) in the endemic JMidJV (Mosleh et al, 2008b, Mosleh et al, 2009, Nimri et al, 2002, Saliba et al, 1988, Saliba et al, 2004). These studies either performed on a limited number of cases, not designed to cover all of the foci in the region, or do not precisely record the origin of the reported Leishmania species. The present study is a wide scale investigation of the identity and the geographical distribution of Leishmania along the JMidJV. It also investigates the usefulness of ITS1 PCR in diagnosis of Leishmania in lesion scrapings of Jordanian patients.
Section snippets
Study area
The JMidJV is divided into two districts (Fig. 1) with a total population of around 87 000 (Department of Statistics, Jordan). The majority of the population is distributed in 24 towns and villages, which are mainly located in the eastern part of the two districts. The strip of the valley that is located along the eastern bank of the Jordan River (‘X's’ in Fig. 1) is a poorly inhabited military zone. There are 28 governmental health centers distributed in the villages and towns of the two
PCR results and geographical distribution of CL patients
DNA extracts from the lesion scrapings of the suspected CL patients (n = 185, one lesion/patient), the cultured promastigotes of the clinical isolates (n = 56), and the reference strains were investigated by PCR. All the (56) clinical isolates and 173 out of the 185 lesion scrapings gave an amplicon similar to that shown in Fig. 3a.
PCR results of the 185 patients, categorized into groups 1–5, are shown in Table 1. PCR detected leishmanial DNA in at least 90% of the patients in all of the five
Discussion
ITS1 PCR followed by RFLP was used to identify Leishmania species found in the JMidJV. This technique worked well regardless of the type of the clinical sample investigated. The investigation on a considerable number of cultured promastigotes and lesion scrapings spotted on filter papers revealed that only one species, L. major, is the causative species of the endemic CL in the JMidJV. Earlier studies performed in the study area using the isoenzyme characterization (Nimri et al, 2002, Saliba et
Acknowledgments
We thank the Director of South Shuneh Hospital, Dr. Saed Kharabsheh and Major Mohammad Shgeerat and Major Ahmad Khateeb of the Jordanian Army who facilitated access to the patients during the course of this work. The senior author (I.M.M.) was supported by the Deanship of Scientific Research, University of Jordan, and the Deutsche Forschungsgemeinschaft (DFG), Germany.
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