Abstract
BackgroundIn South America, cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) are emerging diseases, expanding in the border area of Argentina, Brazil and Paraguay. Outbreaks of CL were reported since the 1990s, with Nyssomyia whitmani as the main vector in this region. Regarding VL, urban reports started in 2010 with Lutzomyia longipalpis as the main vector. The aim of this study was to evaluate environmental determinants related to the main vectors of leishmaniasis, to contribute to the prevention and control response to the emergence of VL and CL in the Argentina-Brazil-Paraguay border region.MethodsThe cross-sectional survey includes two cities and two close rural areas in the Argentinean Northeast Region, between November 2014 and January 2015, with a total of 95 sampling sites. REDILA-BL traps were set for three consecutive nights, and a total of 68 meso- and microscale environmental and landscape characteristics were surveyed. The association between vector abundance with different variables was evaluated using a generalized linear model with zero-inflated negative binomial distribution. We analyzed females for detection of Leishmania DNA.ResultsThe analysis for Lu. longipalpis indicates an excess of absences when the mean NDWI around the sites were higher. The abundance of Lu. longipalpis at mesoscale level was higher when more urban services were present, and when blood sources such as chickens or dogs at the microscale level were present. For Ny. whitmani, no variable was found to be associated with the absences, while its abundance increased in association with the following variables: percentage of tree cover, presence of garbage collection service, hosted people and, at microscale, the presence of poultry. Leshmania infantum DNA was detected in 2/49 (4%) Lu. longipalpis.ConclusionsThe abundance of both species is influenced by variables at different scales, their influence probably has a hierarchy and they are acting on different aspects of the biology of these vectors. The urban spatial segregation of Lu. longipalpis and the peri-urban and rural segregation of N. whitmani increase the risk of VL and CL. The selection of the better variables for each scale will allow the design of appropriate control strategies depending on species.
Highlights
In South America, cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) are emerging diseases, expanding in the border area of Argentina, Brazil and Paraguay
Phlebotomine surveillance was intensified in border areas since 2000 and Lu. longipalpis was found in Argentina at Clorinda (Formosa Province) in 2004 [8]
We reinforce the results about the spatial segregation of urban Lu. longipalpis and periurban-rural Ny. whitmani, and the VL and CL risk, but with a potential trend of Lu. longipalpis to spread to the rural areas and of Ny. whitmani to the urban areas [12, 13, 15, 17, 45, 74,75,76,77]
Summary
In South America, cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) are emerging diseases, expanding in the border area of Argentina, Brazil and Paraguay. The aim of this study was to evaluate environmental determinants related to the main vectors of leishmaniasis, to contribute to the prevention and control response to the emergence of VL and CL in the Argentina-Brazil-Paraguay border region. In Argentina, CL is mainly rural and endemic at least since the beginning of the 20th century, while VL is urban with recent epidemic events reported since 2006 [3]. Autochthonous CL cases (with c.200 cases reported per year) are recorded from nine provinces, with scattered outbreaks, and the transmission currently occurs in rural domestic environments. Leishmania braziliensis is the main parasite species isolated from cases related to outbreaks, domestic mammals and vectors [4]. Social and commercial pet-related networks allowed the dispersion of canine VL thorough the country [9]
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