Severity of Old World Cutaneous Leishmaniasis Is Influenced by Previous Exposure to Sandfly Bites in Saudi Arabia

<div><p>Background</p><p>The sandfly <i>Phlebotomus papatasi</i> is the vector of <i>Leishmania major</i>, the main causative agent of Old World cutaneous leishmaniasis (CL) in Saudi Arabia. Sandflies inject saliva while feeding and the salivary protein PpSP32 was previously shown to be a biomarker for bite exposure. Here we used recombinant PpSP32 to evaluate human exposure to <i>Ph. papatasi</i> bites, and study the association between antibody response to saliva and CL in endemic areas in Saudi Arabia.</p><p>Methodology/Principal Findings</p><p>In this observational study, anti-PpSP32 antibodies, as indicators of exposure to sandfly bites, were measured in sera from healthy individuals and patients from endemic regions in Saudi Arabia with active and cured CL. <i>Ph. papatasi</i> was identified as the primary CL vector in the study area. Anti-PpSP32 antibody levels were significantly higher in CL patients presenting active infections from all geographical regions compared to CL cured and healthy individuals. Furthermore, higher anti-PpSP32 antibody levels correlated with the prevalence and type of CL lesions (nodular vs. papular) observed in patients, especially non-local construction workers.</p><p>Conclusions</p><p>Our findings suggest a possible correlation between the type of immunity generated by the exposure to sandfly bites and disease outcome.</p>