Synthetic sex-aggregation pheromone of Lutzomyia longipalpis, the South American sand fly vector of Leishmania infantum, attracts males and females over long-distance

Background In South America the sand flyLutzomyia longipalpisis the predominant vector ofLeishmania infantum, the parasite that causes canine and human visceral leishmaniasis. Co-location of synthetic male sex-aggregation pheromone with an insecticide provided protection against canine seroconversion, parasite infection, reduced tissue parasite loads, and female sand fly densities at households. Optimising the sex-aggregation pheromone + insecticide intervention requires information on the distance over which female and maleLu.longipalpiswould be attracted to the synthetic pheromone in the field. Methodology/Principal findings WildLu.longipalpiswere collected at two peridomestic study sites in Governador Valadares (Minas Gerais, Brazil). Sand flies were marked with coloured fluorescent powder using an improved protocol and then released into an existing domestic chicken shed at two independent sites, followed by recapture at synthetic-pheromone host-odour baited traps placed up to 30 metres distant from the release point. In total 1704 wild-caughtLu.longipalpiswere released into the two chicken sheds. Overall 4.3% of the marked flies were recaptured in the pheromone baited experimental chicken sheds compared to no marked flies recaptured in the control sheds. At the first site, 14 specimens (10.4% of the marked and released specimens) were recaptured at 10m, 36 (14.8%) at 20m, and 15 (3.4%) at 30m. At the second site, lower recapture rates were recorded; 8 marked specimens (1.3%) were recaptured at 5 and 10m and no marked specimens were recaptured at 15m. Approximately 7x more marked males than females were recaptured although males were only 2x as common as females in the released population. 52% of the markedLu.longipalpiswere collected during the first night of sampling, 32% on the second night, and 16% on the third night. Conclusions/Significance The study established that both male and female sand flies can be attracted to the synthetic sex-aggregation pheromone in the presence of host odour over distances up to at least 30m in the field depending on local environmental and meterological conditions. Author summary Visceral leishmaniasis (VL) is a disease caused by an insect transmitted protist parasite. In South America and Brazil in particular, it causes significant morbidity and mortality, with thousands of human cases and deaths reported every year. Domestic dogs are the most important source of human infection. Controlling the sand flies that transmit the parasite is one way to reduce the number of VL cases and recent research has shown the potential for a new pheromone-based approach to vector control. In a recent cluster-randomised control trial, co-location of a synthetic copy of the male sand fly sex-aggregation pheromone with pyrethroid insecticide reduced numbers of sand flies in households and provided protection for dogs against leishmaniasis infection incidence. The current study was carried out to determine the distance over which the synthetic sex-aggregation pheromone could attractLu.longipalpisin a peridomestic environment in a Brazilian city. Male and femaleLu.longipalpiswere attracted up to 30m in one night towards a source of the pheromone. This information will help to inform the optimisation of placement of sex pheromone/insecticide intervention in Brazil.