Attraction of Lutzomyia longipalpis to synthetic sex-aggregation pheromone: Effect of release rate and proximity of adjacent pheromone sources.

Melissa J Bell,Reginaldo P Brazil,Luigi Sedda,James G C Hamilton,Erin Dilger,Cristian F De Souza,Orin Courtenay,Mikel A Gonzalez,Mary Ann Mcdowell

doi:10.1371/journal.pntd.0007007

Melissa J Bell, Reginaldo P Brazil + Show 7 more

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https://doi.org/10.1371/journal.pntd.0007007

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Abstract

In South America, the Protist parasite that causes visceral leishmaniasis, a potentially fatal human disease, is transmitted by blood-feeding female Lutzomyia longipalpis sand flies. A synthetic copy of the male produced sex-aggregation pheromone offers new opportunities for vector control applications. We have previously shown that the pheromone placed in plastic sachets (lures) can attract both females and males to insecticide treated sites for up to 3 months. To use the pheromone lure in a control program we need to understand how the application of lures in the field can be optimised. In this study we investigated the effect of increasing the number of lures and their proximity to each other on their ability to attract Lu. longipalpis. Also for the first time we applied a Bayesian log-linear model rather than a classic simple (deterministic) log-linear model to fully exploit the field-collected data. We found that sand fly response to pheromone is significantly related to the quantity of pheromone and is not influenced by the proximity of other pheromone sources. Thus sand flies are attracted to the pheromone source at a non-linear rate determined by the amount of pheromone being released. This rate is independent of the proximity of other pheromone releasing traps and indicates the role of the pheromone in aggregation formation. These results have important implications for optimisation of the pheromone as a vector control tool and indicate that multiple lures placed in relatively close proximity to each other (5 m apart) are unlikely to interfere with one another.

Highlights

The sand fly Lutzomyia longipalpis (Diptera: Psychododae) is the major vector of Leishmania infantum, a Protist parasite and the causative agent of Zoonotic Visceral Leishmaniasis (ZVL) in Latin America
90% of the cases of ZVL that occur in the Americas are recorded in Brazil where the greatest number of cases were found in the North East of the country [1]
In Minas Gerais State, Brazil, ZVL transmission is intense and over the last few decades has expanded from rural regions into cities [3, 4]

Summary

Introduction

The sand fly Lutzomyia longipalpis (Diptera: Psychododae) is the major vector of Leishmania infantum, a Protist parasite and the causative agent of Zoonotic Visceral Leishmaniasis (ZVL) in Latin America. 90% of the cases of ZVL that occur in the Americas are recorded in Brazil where the greatest number of cases were found in the North East of the country [1]. In Minas Gerais State, Brazil, ZVL transmission is intense and over the last few decades has expanded from rural regions into cities [3, 4]. The causes of ZVL urbanisation are unclear but it is likely to be related to the movement of people and their animals from rural to urban settings as well as the ability of the vector to adapt to an urban environment [1, 6]

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