Spatial dispersal of Lutzomyia longipalpis in an urban area under deltamethrin collars intervention

In the Americas, visceral leishmaniasis (VL) is caused by infection with Leishmania infantum, which has the domestic dog as its main reservoir in urban areas and is transmitted through the bite of infected female Lutzomyia longipalpis. VL has been expanding geographically in Brazil, and prevention and control actions are essential to reduce the impact on populations affected by these neglected diseases. Since 2021, Brazil has implemented the use of deltamethrin-impregnated collars (DM) for the prevention and control of VL in priority municipalities, based on evidence of the effectiveness of this measure in preventing vector-reservoir contact. However, considering the repellent effect of this device, it is necessary to evaluate the potential impact of mass dog collaring on ecological parameters of the vector. Therefore, this study aimed to describe the dispersal pattern of Lu. longipalpis in an area under intervention with DM collars. To achieve this, three mark-release-recapture (MRR) experiments were conducted after DM collar intervention to assess the spatial distribution of Lu. longipalpis in the municipality of Montes Claros, Minas Gerais, Brazil. Captures were carried out between November 2022 and September 2023. A dispersal perimeter was estimated by selecting random points from the household chosen for sand fly capture. Collections were performed through active searches in animal shelters within the household, and after release, automatic light traps were distributed within a perimeter of up to 500 m. 752 specimens were marked and released, and during recapture attempts 2883 specimens of Lu. longipalpis were collected, with an average recapture rate of 9%. The highest recapture percentages were observed on the third (21.8%) and fourth (43%) days of recapture attempts. Regarding spatial distribution, the highest frequency of recapture occurred within 100 m from the release point (78.2%) with a mean traveled distance of 63 m. Although insects were recaptured at seven different points, the greatest number was observed at the release point itself. Our results demonstrate a low spatial dispersal, similar to those reported in previous studies in non-intervention areas. These findings may be consistent with the influence of local ecological conditions, including the availability of alternative blood sources, and contribute to a better understanding of the ecological factors that should be considered when implementing and evaluating vector control interventions.