Comparative evaluation of two sampling methods for Lutzomyia longipalpis in urban areas and identification of visceral leishmaniasis risk zones in Castilho, São Paulo, Brazil

Abstract

Visceral leishmaniasis (VL) is a major public health problem in Brazil, particularly in urban areas where the sand fly Lutzomyia longipalpis is the main vector of the disease. Behavioral studies of this species in urban areas are important for directing control measures. This study aimed to evaluate the behavior of the vector in response to two collection methods for Lu. longipalpis, and a simplified risk assessment tool was also evaluated in order to identify properties at high risk of the presence of the vector, based on the ecology of this sand fly species in urban areas. The study was conducted in Castilho, state of São Paulo, Brazil. Residences in the urban area of ​​the municipality were assessed for their peridomicile conditions. Captures were performed on properties that presented high scores, using manual collection with electric aspirators, and CDC light traps were exposed in places where the vector could breed. Parameters such as sand fly density, engorgement rate, and natural infection were evaluated. Sand flies were identified by taxonomic keys and molecular techniques (nested PCR, RFLP and sequencing) were used to detect and identify Leishmania species, as well as blood meal sources. Of the 535 households with high scores, captures were successful in 83.7 %. The highest number of female Lu. longipalpis was collected using CDC light traps, but manual captures yielded a higher proportion of engorged females. However, Lu. longipalpis collected in the CDC light trap showed higher positivity for Leishmania (Leishmania) infantum (1.9 %). The results highlight the importance of targeted entomological surveillance in urban areas endemic for VL. The risk assessment tool and the comparison of collection methods provide valuable information to optimize resource allocation and increase the effectiveness of VL control programs.