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

Mikel A. González,Orin Courtenay,Rafael Maciel-de-Freitas,Cristian F. Souza,James G. C. Hamilton,Reginaldo P. Brazil,Melissa Bell,Fabiano Oliveira

doi:10.1371/journal.pntd.0008798

Mikel A. González, Orin Courtenay + Show 6 more

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https://doi.org/10.1371/journal.pntd.0008798

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Abstract

BackgroundIn South America the sand fly Lutzomyia longipalpis is the predominant vector of Leishmania 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 male Lu. longipalpis would be attracted to the synthetic pheromone in the field.Methodology/Principal findingsWild Lu. longipalpis were 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-caught Lu. longipalpis were 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 marked Lu. longipalpis were collected during the first night of sampling, 32% on the second night, and 16% on the third night.Conclusions/SignificanceThe 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.

Highlights

Pheromones in Diptera are diverse and complex molecules and over the past two decades, elucidation of their composition and structure has concentrated predominantly on agricultural pest species [1]
In this study we showed that some fluorescent powders have a significant impact on sand fly survival, it is possible that the powder that we selected to use may have had other more subtle effects on the sand fly behaviour and this may have altered the response to the pheromone
This paper provides the evidence that both sexes are attracted from long distance and suggests that synthetic pheromone lures co-located with insecticide could be spaced 60m apart, which represents approximately a single trap per household in typical visceral leishmaniasis (VL) endemic communities in Brazil, with the objective to manipulate female vector blood-feeding and probability of transmission of Le. infantum

Summary

Introduction

Pheromones in Diptera are diverse and complex molecules and over the past two decades, elucidation of their composition and structure has concentrated predominantly on agricultural pest species [1]. Throughout Latin America, the Phlebotomine sand fly Lutzomyia longipalpis s.l. is the main vector of Leishmania infantum (Kinetoplastida: Trypanosomatidae), a Protist parasite that causes visceral leishmaniasis (VL) in humans and canids [5]. This disease is a significant cause of morbidity and mortality in both humans and dogs in Brazil [6] and despite the substantial efforts made by the Brazilian Ministry of Health and State Authorities, the burden of VL in Brazil more than doubled between 1990 and 2016 [7]. Optimising the sex-aggregation pheromone + insecticide intervention requires information on the distance over which female and male Lu. longipalpis would be attracted to the synthetic pheromone in the field

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