Lutzomyia longipalpis spatial distribution and association with environmental variables in an urban focus of visceral leishmaniasis, Misiones, Argentina

This study describes the spatial distribution pattern of Lu. longipalpis abundance in Posadas-Garupá, Argentina, where four cases of human Visceral Leishmaniasis had been recorded. A total of 2428 Lu. longipalpis were captured in 42% of the 305 sites sampled with CDC light traps, its abundance shows spatial autocorrelation ranging up to 590 m (semivariogram model), with six downtown ‘islands’ of vector highest abundance (≥60 individuals). A significant association between Lu. longipalpis and the presence of chickens was observed (odds ratio 3.26). The best stepwise multiple regression using Generalized Linear Models explained 31% of the deviance for Lu. longipalpis abundance, including as explanatory variables: (a) negatively: households with ‘lack of building material and with economic deprivation’, (b) positively: surface covered by trees and bushes at 50 meters of the house, and households without electrical lighting. In conclusion, Lu. longipalpis in a recent settled focus of visceral leishmaniasis was urbanized with a highly heterogeneous spatial distribution within the cities, with the vectors concentrated in limited ‘islands’ of high abundance, in the downtown relatively more affluent and dense populated areas, but also more heterogeneous with patches that had higher tree coverage and poor urban services. These results once validated will contribute to the control strategy design through risk maps, in order to prioritize areas for prevention and control, and setting the appropriate scale for intervention.