Reduced Leishmania (L.) infantum chagasi parasitic loads in humans exposed to Lutzomyia longipalpis bites in the Amazon region of Brazil

Márcia Dalastra Laurenti,Ibrahim Abbasi,Luis Fernando Chaves,Thaíse Yumie Tomokane,Fernando Tobias Silveira,Alon Warburg

doi:10.1017/pao.2017.2

Abstract

SUMMARY We performed a cross-sectional survey in humans to evaluate Lutzomyia longipalpis, i.e. sand fly vector, bite exposure association with Leishmania (Leishmania) infantum chagasi infection in Bujarú municipality, Northern Brazil, an endemic area for visceral leishmaniasis. In recruited individuals, which were stratified by sex and age, we measured L. (L.) i. chagasi parasitic loads with quantitative polymerase chain reaction (qPCR), exposure to sand fly bites with an anti-saliva immunoglobulin G enzyme-linked immunosorbent assay and performed immunological diagnostic tests, in order to evaluate the association between exposure to sand fly bites, and infection. The prevalence increased from 11% when using immunological diagnostic tests to 28% when using qPCR, being around that value for all age classes, but children below 5 years (40%) and people over 60 years (15%). The association between PCR-based L. (L.) i. chagasi prevalence and saliva exposure was convex, reflecting the fact that at both high and low saliva exposure the PCR-based L. (L.) i. chagasi prevalence decreases. This scenario indicates that low sand fly exposure is likely associated with low parasite transmission, while high anti-saliva prevalence, i.e. a large sand fly bite exposure could be associated with anti-Leishmania protective immune mechanisms driven by vector saliva and/or increased parasite exposure.

Highlights

Visceral leishmaniasis (VL) is a systemic protozoan infection caused by intracellular Leishmania parasites
Crucial to the spread of disease is the fact that Lu. longipalpis, the main sand fly vector of VL is highly adaptable to modified peri-urban and urban settings (Costa, 2008; Amora et al 2010; Saraiva et al 2011)
We measured L. (L.) i. chagasi parasitic loads, exposure to sand fly bites and performed classical diagnostic tests, in order to evaluate the association between exposure to sand fly bites, L. (L.) i. chagasi infection and clinicalimmunological profiles, in a population stratified by sex and age

Summary

SUMMARY

We performed a cross-sectional survey in humans to evaluate Lutzomyia longipalpis, i.e. sand fly vector, bite exposure association with Leishmania (Leishmania) infantum chagasi infection in Bujarú municipality, Northern Brazil, an endemic area for visceral leishmaniasis. Chagasi parasitic loads with quantitative polymerase chain reaction (qPCR), exposure to sand fly bites with an anti-saliva immunoglobulin G enzyme-linked immunosorbent assay and performed immunological diagnostic tests, in order to evaluate the association between exposure to sand fly bites, and infection. Chagasi prevalence and saliva exposure was convex, reflecting the fact that at both high and low saliva exposure the PCR-based L. This scenario indicates that low sand fly exposure is likely associated with low parasite transmission, while high anti-saliva prevalence, i.e. a large sand fly bite exposure could be associated with anti-Leishmania protective immune mechanisms driven by vector saliva and/or increased parasite exposure

INTRODUCTION

MATERIALS AND METHODS

RESULTS

DISCUSSION