Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

Tiago Feitosa Mota,Lairton Souza Borja,Edelberto Santos Dias,Djalma Alves De Melo,Manuela Da Silva Solcà,Patrícia Sampaio Tavares Veras,Yuri De Jesus Silva,Bruna Martins Macedo Leite,Orlando Marcos Farias De Sousa,Deborah Bittencourt Mothé Fraga,Claudia Ida Brodskyn,Waleed Saleh Al-Salem

doi:10.1371/journal.pntd.0007626

Abstract

Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum and in Brazil is transmitted mainly by the bite of Lutzomuyia longipalpis sand flies. Data about the presence, distribution, natural infection rate, seasonal and monthly dynamics of the vector population are important for optimizing the measures to control VL in endemic areas. This study aimed to identify sand fly fauna in an endemic area for VL to detect the prevalence of L. infantum infection in the Lu. longipalpis population and to elucidate the influence of bioclimatic factors on the monthly fluctuations of this vector. HP light traps were monthly set in the intradomicile and peridomicile of residences located in the central and beachfront areas of Camaçari, a VL endemic area. The sand fly collection was conducted in two periods: i) period 1—between December 2011 and November 2012 and ii) period 2—August 2014 and July 2015. Sand fly species were identified and detection of L. infantum infection by qPCR was performed in pools of female Lu. longipalpis. For the first time, the parasite load of positive pools was correlated with the number of Lu. longipalpis captured per month in both periods. Correlation analyses between the monthly fluctuation of the sand fly population and bioclimatic indices of the municipality in both collection periods were also performed. In both evaluated periods, more than 98% of the collected sand flies were Lu. longipalpis, confirming the predominance of this species in the region. It was captured mostly in the beachfront area in all months evaluated (99%). For the period 1, Leishmania DNA was detected in 81% of tested pools representing a minimal infection rate of 9.6%. In the period 2, 40% of the pools were positive with a minimal infection rate of 10.2%. Infected sand flies were only detected in the beachfront area in both periods. The parasite load was low and did not vary in the evaluated months despite the number of collected sand flies. No correlation was observed for climatic factors in both areas of Camaçari. These findings emphasize the high risk of Leishmania transmission in Camaçari regardless of the season and that other factors, aside from bioclimatic elements, are influencing the sand fly population monthly fluctuation.

Highlights

Visceral leishmaniasis (VL) is an infectious disease considered to be neglected by the World Health Organization, mainly affecting poor regions in developing countries [1]
Visceral leishmaniasis (VL) is a parasitic disease transmited by a sand fly vector
VL is an important public health issue in Brazil occurring in all its regions with increasing incidences in big urban centers

Summary

Introduction

Visceral leishmaniasis (VL) is an infectious disease considered to be neglected by the World Health Organization, mainly affecting poor regions in developing countries [1]. In the State of Bahia, several studies were previously conducted, aiming to identify the phlebotomine sand fly species present in municipalities endemic for VL, such as Jacobina, Jequieand Camacari [12, 13, 14]. These studies are old, lacking in the literature updated data on the sand fly species present in Bahia. Studies to evaluate the natural infection rate of Lu. longipalpis with L. infantum and to elucidate the seasonal and monthly population dynamics are necessary Such studies should be performed employing entomological monitoring and evaluation of climatic factors’ influence on the sand fly population.

Objectives

Methods

Results

Discussion

Conclusion