Asymptomatic human carriers ofLeishmania infantum: possible reservoirs for Mediterranean visceral leishmaniasis in southern Iran

Abstract

Over the last decade, the incidence of visceral leishmaniasis (VL) has increased in many districts of the province of Fars, in southern Iran. Recent epidemiological reports indicate that asymptomatic human infections with Leishmania infantum (the causative agent of VL throughout the Mediterranean basin) occur more frequently in Iran than was previously believed. Between 2004 and 2006, blood samples were collected from 802 apparently healthy subjects from communities, in the north-west and south-east of Fars province, where VL cases had been recorded. Each of these samples was tested for anti-Leishmania antibodies, in direct agglutination tests (DAT), and for L. infantum kinetoplast DNA, in PCR-based assays. Of the 426 subjects from north-western Fars, eight (1.9%) were found seropositive and 68 (16.0%) PCR-positive. The corresponding values for the 376 subjects from south-eastern Fars were lower, with five (1.3%) seropositive and 32 (8.5%) PCR-positive. Of the 100 PCR-positive subjects, 18 (18.0%) each lived in a household in which there had been a case of VL, and six (6.0%) had had VL themselves (in each case, more than a year before the blood sampling for the present study). Although 21 of the PCR-positives have now been followed-up for at least 18 months, none has developed symptomatic VL. Since positivity in the PCR-based assay probably indicated the presence of L. infantum amastigotes in the peripheral blood of 12.5% of the subjects, it is clear that asymptomatic human carriers of L. infantum are quite common in the study areas and probably act as reservoirs in the transmission of the parasite, to humans and to dogs, by sandflies.

Emergence of a new focus of visceral leishmaniasis due to Leishmania infantum in Golestan Province, north-eastern of Iran

“…Our DAT results showed that 50 % (3/6), 93.7 % (15/16) of human and dogs were asymptomatic, respectively. Recent epidemiological reports from Iran (Fakhar et al 2008;Alborzi et al 2008) have shown that asymptomatic HVL infection with L. infantum occurs more frequently than was previously believed. Fakhar et al (2008) suggested that those with asymptomatic infection can act as reservoirs for HVL in southern Iran.…”

“…Overall, 1.33 and 32 % of the human and dogs investigated in the present study were found seropositive in a DAT based assay respectively. DAT is a simple, cost-effective and field-applicable method that is often suggested for the field diagnosis of VL in endemic regions and frequently used for that reason in Iran (Mohebali et al 2001(Mohebali et al , 2011Edrissian et al 1999;Fakhar et al 2006Fakhar et al , 2008. The sensitivity and specificity of this method varies in different studies between 90-100 % and 72-100 %, respectively (Sundar and Rai 2002;Fakhar et al 2012a).…”

“…It was re-suspended in 100 ll sterile distillated water and stored at 4°C until it could be tested in a modified genous-specific PCR for a sequence from the kinetoplast DNA (k DNA) of Leishmania. The primers used, RV 1 (5 0 -CTT TTC TGG TCC CGC GGG TAG G-3 0 ) and RV 2 (5 0 -CCA CCT GCG CTA TTT TAC ACC A-3 0 ) amplify a 145-bp sequence from the Leishmania kDNA minicircles, according to the methods as described by Fakhar et al (2008).…”

“…Each sample found PCRpositive for leishmanial DNA was then investigated using the PCR described by Fakhar et al (2008), which is based on the species-specific primers LINR4 and LIN17 to confirm that the DNA detected was that of L. infantum. Data analyses were performed with SPSS (version 13.5; SPSS Inc, Chicago, IL, USA), with a probability (P) value of \0.05 were considered as statistically significant.…”

The PCR-based detection and identification of the parasites causing human cutaneous leishmaniasis in the Iranian city of Ahvaz

“…Currently, the most commonly used methods involve iso-enzyme electrophoresis, monoclonal antibodies, specific DNA probes or PCR with or without RAPD analysis (Jaffe and McMahon-Pratt, 1983;Rioux et al, 1990). Several PCR-based assays have been developed to detect and identify leishmanial parasites (Barker, 1989;De Bruijin and Barker, 1992;Piarroux et al, 1994;Osman et al, 1997;Noyes et al, 1998;Fakhar et al, 2008). The results of the present study were encouragingly clear-cut; every test sample produced a single amplicon (that matched, in size, the single amplicon produced from the reference strains of L. major or L. tropica) and the absence of amplicons from the negativecontrol samples indicated the absence of contamination that could have given falsepositive results.…”