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.
Highlights
Visceral leishmaniasis (VL) is an important public health challenge in Brazil because of the high number of human and canine cases reported annually
From 1999 to 2013, there were recorded in Brazil 53,067 new cases of visceral leishmaniasis (VL), with an annual mean of 3500 new cases
Of the 520 existing American sand flies described [4], Lutzomyia longipalpis is the Neotropical species most widely studied because of its epidemiological importance as the main vector of Leishmania infantum, agent of VL [5,6,7]. This species occur from Mexico to Argentina, with the exception of Ecuador, Peru and Chile, and is widely distributed in Brazil where has shown in recent years that it is well adapted to urban areas [8]
Summary
Visceral leishmaniasis (VL) is an important public health challenge in Brazil because of the high number of human and canine cases reported annually. Of the 520 existing American sand flies described [4], Lutzomyia longipalpis is the Neotropical species most widely studied because of its epidemiological importance as the main vector of Leishmania infantum, agent of VL [5,6,7]. This species occur from Mexico to Argentina, with the exception of Ecuador, Peru and Chile, and is widely distributed in Brazil where has shown in recent years that it is well adapted to urban areas [8]. This fact has further contributed to its rapid expansion [6,7,8,9] and constitutes a challenge
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