Multiscale environmental determinants of Leishmania vectors in urban and rural context

QUINTANA, M.G.; SANTINI, M.S.; CAVIA, R.; MARTÍNEZ, M.; LIOTTA, D.J.; FERNÁNDEZ, M.S.; PÉREZ, A.A.; DIRENI MANCINI, J.M.; MOYA, S.L.; GIULIANI, M.G.; SALOMÓN, O.D.

PARASITES AND VECTORS

BIOMED CENTRAL LTD

Lugar: Londres; Año: 2020

1756-3305

In South America, Cutaneous Leishmaniasis (CL) and Visceral Leishmaniasis (VL) are emerging, expanding in the border area of Argentina, Brazil and Paraguay. The study area includes the city of Puerto Iguazú and the village of Puerto Libertad and two close rural areas, in the Argentinean Northeast Region. The area reported outbreaks of CL since the ´90s, with Nyssomyia whitmani as the main vector associated to unmodified environments and its ecotones. Regarding to 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 and dispersion of VL and CL in the Argentina-Brazil-Paraguay border region. We divided the urban and periurban environments of both cities into a grid of 400 m2, with 55 and 15 samples sites respectively. In the two rural areas we set 12 and 13 sample sites including farms and the surrounding natural forest. In each site, one REDILA-BL trap was set for three consecutive nights, and a total of 68 meso and microscale environmental characteristics were surveyed simultaneously. Also, landscape environmental characteristics around each sampled site were evaluated using the percentage of different land cover classes estimated at buffer areas of 25, 50, 100 and 250 meters of radius. Likewise land cover classes were defined also ad-hoc based on the previous studies: trees and shrubs, herbaceous, crops, bare soil, impervious or constructed surfaces and water bodies. The association between vector abundance with microsclae, mesoscale and landscape scale environmental characteristics, was evaluated using Generalized Linear Model with zero-inflated negative binomial distribution. We analyzed females for detection of Leishmania sp. DNA, PCR products were purified and sequenced for identity analysis with BLASTm. The analysis for Lu. longipalpis indicate 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 are present, and when blood sources such as chickens or dogs at microscale level are present. For Ny. whitmani, no variable was found associated with the absences, while its abundance was positive with higher tree cover percentage; at mesoscale level, abundance was higher when associated with the variable garbage collection service present, the number of people housed and at microscale with the presence of poultry. Leshmania infantum DNA was detected in 2/49 (4%) Lu. longipalpis. The 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 Ny whitmani increase the risk of LV and LC. The high micro heterogeneity at urban settings provides a broad gradient of resting-breeding sites and clustered meal-sources, thus allowing the presence of "hot spots". The selection of the better variables for each scale will allow to design appropriate control strategies according to each species.