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.
Highlights
IntroductionIn Brazil, the expansion of the geographic range of Lutzomyia longipalpis (Lutz & Neiva), the principal vector of Leishmania (Leishmania) infantum chagasi (Cunha & Chagas), and its adaptation to domiciliary habitats in the urban areas throughout Brazil has resulted in an increase in the incidence of both canine and human visceral leishmaniasis (VL) in the last 25 years [2,3,4,5,6]
Recording the geographic distribution and identifying the possible routes of expansion of both arthropod-borne diseases and their associated vectors is essential information for surveillance as well as the execution and elaboration of control strategies [1].In Brazil, the expansion of the geographic range of Lutzomyia longipalpis (Lutz & Neiva), the principal vector of Leishmania (Leishmania) infantum chagasi (Cunha & Chagas), and its adaptation to domiciliary habitats in the urban areas throughout Brazil has resulted in an increase in the incidence of both canine and human visceral leishmaniasis (VL) in the last 25 years [2,3,4,5,6]
The principal vector of American visceral leishmaniasis disease in the Americas, is a group of closely related species that can be separated according to the type of pheromone produced by male individuals
Summary
In Brazil, the expansion of the geographic range of Lutzomyia longipalpis (Lutz & Neiva), the principal vector of Leishmania (Leishmania) infantum chagasi (Cunha & Chagas), and its adaptation to domiciliary habitats in the urban areas throughout Brazil has resulted in an increase in the incidence of both canine and human visceral leishmaniasis (VL) in the last 25 years [2,3,4,5,6]. The appearance of L. longipalpis in urban areas of other municipalities has been linked to an increase in both canine and human visceral leishmaniasis within the State [11, 12]. 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
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