Distribution of Lutzomyia longipalpis Chemotype Populations in São Paulo State, Brazil

Abstract

BackgroundAmerican visceral leishmaniasis (AVL) is an emerging disease in the state of São Paulo, Brazil. Its geographical expansion and the increase in the number of human cases has been linked to dispersion of Lutzomyia longipalpis into urban areas. To produce more accurate risk maps we investigated the geographic distribution and routes of expansion of the disease as well as chemotype populations of the vector.Methodology/Principal FindingsA database, containing the annual records of municipalities which had notified human and canine AVL cases as well as the presence of the vector, was compiled. The chemotypes of L. longipalpis populations from municipalities in different regions of São Paulo State were determined by Coupled Gas Chromatography – Mass Spectrometry. From 1997 to June 2014, L. longipalpis has been reported in 166 municipalities, 148 of them in the Western region. A total of 106 municipalities were identified with transmission and 99 were located in the Western region, where all 2,204 autochthonous human cases occurred. Both the vector and the occurrence of human cases have expanded in a South-easterly direction, from the Western to central region, and from there, a further expansion to the North and the South. The (S)-9-methylgermacrene-B population of L. longipalpis is widely distributed in the Western region and the cembrene-1 population is restricted to the Eastern region.Conclusion/SignificanceThe maps in the present study show that there are two distinct epidemiological patterns of AVL in São Paulo State and that the expansion of human and canine AVL cases through the Western region has followed the same dispersion route of only one of the two species of the L. longipalpis complex, (S)-9-methylgermacrene-B. Entomological vigilance based on the routes of dispersion and identification of the chemotype population could be used to identify at-risk areas and consequently define the priorities for control measures.

The Lutzomyia longipalpis complex: a brief natural history of aggregation-sex pheromone communication

“…Over the past 30 years, a new scenario has emerged as L. longipalpis has extended its natural range and adapted to domiciliary habitats in urban areas throughout Brazil, resulting in an increase in the incidence of both canine and human visceral leishmaniasis [26, 29]. Given its epidemiological significance a thorough understanding of the ecology and life history of the Lutzomyia species complex is critical.…”

“…The most parsimonious explanation is that it provides an efficient means by which closely related sympatric subspecies can limit hybridization [52, 59]. Only a small number of hybrids exist in sympatric populations in nature [29, 46]. Field [54] and laboratory [36–38] data indicate that Brazilian populations of L. longipalpis respond to the male pheromone in a sibling species-specific manner.…”

“…How geographical barriers [121] and, more recently, anthropogenic environmental changes and activities have contributed to the evolution of sibling species remains a future challenge [26]. Molecular analyses and geological history [59, 121] will aid our understanding of populations distributions but these need to be coupled with studies of variation in traits involved in mating such as copulation songs [64, 65, 68] and chemical communication [29, 46, 47]. These latter factors have undoubtedly played (and continue to play) a significant role in maintaining reproductive isolation among the different sibling species [48, 55, 60].…”

“…Finally, it is unclear whether there are any general epidemiological implications associated with the observed variation in chemotype such as that hypothesized by Casanova [29]. An obvious disadvantage to rapid adaptation of the components of the sex pheromone is that this makes it far trickier to detect and/or control using synthetic chemical baits, unless the different chemotypes are key signature pheromones that operate within the species complex.…”

Mudanças climáticas e saúde urbana

“…longipalpis, a partir de Mato Grosso do Sul, em direção à capital de São Paulo (Casanova et al, 2015), seguindo a Rodovia Marechal Rondon, que atravessa área quente e seca do estado. Apesar da conexão dessa rodovia com o eixo rodoviário que adentra a Grande São Paulo, até a atualidade não foi constatada a presença dessa população domiciliada nessa área, onde altitudes mais elevadas e temperaturas mais amenas talvez estejam funcionando como uma barreira à sua dispersão.…”