Ecological parameters of the (S)-9-methylgermacrene-B population of the Lutzomyia longipalpis complex in a visceral leishmaniasis area in São Paulo state, Brazil

Abstract

BackgroundVisceral leishmaniasis (VL) is an important public health challenge in Brazil because of the high number of human and canine cases reported annually. Leishmania infantum is the etiological agent of VL and Lutzomyia longipalpis is its main vector. However, evidence suggests that this taxon constitutes a species complex. In Sao Paulo state, there are two populations of Lu. longipalpis, each secreting distinct pheromones, (S)-9-methylgermacrene-B and Cembrene 1; both have been associated with different patterns of VL transmission. The aim of the present study was to investigate the temporal distribution and natural infection of the (S)-9-methylgermacrene-B population of the Lu. longipalpis complex in a highly VL endemic area of Sao Paulo state to obtain information that may contribute to the surveillance of this zoonosis and to the planning of preventive and control measures.MethodsThe study was carried out in Panorama municipality, Sao Paulo State. Captures were made during 24 months in seven domiciles. The relation between sand fly abundance and climatic variables, temperature and humidity, was analyzed and natural infection by Leishmania spp. in sand fly females was investigated by nested PCR.ResultsA total of 4120 sand flies, with predominance of Lu. longipalpis (97.2%) were captured. The highest averages of sand flies/night/trap occurred in the rainy season (November-March) and a positive, significant correlation between sand fly abundance and the temperature and humidity 20 days before the capture days was found. Leishmania infantum DNA was detected in three out of 250 pools of females analyzed, giving an estimated minimum infection rate of 1.2%.ConclusionThe identification of the climatic association between the high abundance of the vector in this highly endemic VL focus constitutes a fundamental point for evaluating future vector and dog control measures and this information increases the data of VL foci in Sao Paulo state that could contribute to the public health authorities in planning prevention and control measures. The identification of natural infection by Le. infantum in Lu. longipalpis specimens reinforces the importance of entomological surveillance activities in this municipality.

Leishmaniose visceral e sua relação com fatores climáticos e ambientais no Estado do Tocantins, Brasil, 2007 a 2014

“…Em relação a variável precipitação pluviométrica, os clusters com alta precipitação e alta taxa de incidência, e clusters com baixa precipitação e baixa taxa demonstram a correlação espacial positiva entre essas variáveis. A variável precipitação pluviométrica, que se correlaciona com a umidade, favorece o desenvolvimento e reprodução do vetor e consequente aumento da incidência de LV 30,31,32 . Como Tocantins apresenta características do bioma Amazônia e do cerrado, com o bioma Amazônia ocorrendo mais ao norte do estado, o regime de chuvas da floresta tropical exerce forte influência na pluviosidade e consequente umidade do estado, contribuindo para incidência da LV nessa região do estado.…”

A field study of the survival and dispersal pattern of Lutzomyia longipalpis in an endemic area of visceral leishmaniasis in Brazil

“…The estimated population size shows the high frequencies of Lu . longipalpis in this municipality in the rainy season as observed in a study with monthly captures in this focus [ 18 ] where females carrying eggs were also captured in the intradomicile. This information suggests that in this period the probability of contact between competent vector and infected and susceptible host increased.…”

“…Previous study in this locality had identified six sand fly species belonging to the Nyssomyia , Evandromyia , Brumptomyia and Lutzomyia genera, with the predominance of the (S)-9-methylgermacrene-B population of the Lu . longipalpis complex [ 18 ].…”

“…Though the Brazilian northeast region is the most affected, recently VL has emerged in several areas of the Southeast region, an event associated mainly with the dispersion of populations of the Lu . longipalpis sibling species [ 17 , 18 ]. Ecological differences in these populations could be associated with different epidemiological patterns of VL transmission as suggested by Casanova et al [ 17 ] in relation to Sao Paulo State.…”

Repellent efficacy of a new combination of fipronil and permethrin against Lutzomyia longipalpis

“…In the New World the main vector is Lutzomyia longipalpis , a species adapted to sylvatic and rural [ 6 ], urban and peri-urban environments [ 7 ]. This vector species occurs from Mexico to Argentina [ 8 ] and is progressively expanding its distributional range in Brazil, Paraguay, Argentina [ 3 ] and Uruguay [ 4 ], and consequently expanding the risk for human and canine VL cases in these areas [ 8 ].…”