The midgut transcriptome of Phlebotomus (Larroussius) perniciosus, a vector of Leishmania infantum: comparison of sugar fed and blood fed sand flies

<p>Abstract</p> <p>Background</p> <p>Parasite-vector interactions are fundamental in the transmission of vector-borne diseases such as leishmaniasis. <it>Leishmania </it>development in the vector sand fly is confined to the digestive tract, where sand fly midgut molecules interact with the parasites. In this work we sequenced and analyzed two midgut-specific cDNA libraries from sugar fed and blood fed female <it>Phlebotomus perniciosus </it>and compared the transcript expression profiles.</p> <p>Results</p> <p>A total of 4111 high quality sequences were obtained from the two libraries and assembled into 370 contigs and 1085 singletons. Molecules with putative roles in blood meal digestion, peritrophic matrix formation, immunity and response to oxidative stress were identified, including proteins that were not previously reported in sand flies. These molecules were evaluated relative to other published sand fly transcripts. Comparative analysis of the two libraries revealed transcripts differentially expressed in response to blood feeding. Molecules up regulated by blood feeding include a putative peritrophin (<it>PperPer1</it>), two chymotrypsin-like proteins (<it>PperChym1 </it>and <it>PperChym2</it>), a putative trypsin (<it>PperTryp3</it>) and four putative microvillar proteins (<it>PperMVP1</it>, <it>2</it>, <it>4 </it>and <it>5</it>). Additionally, several transcripts were more abundant in the sugar fed midgut, such as two putative trypsins (<it>PperTryp1 </it>and <it>PperTryp2</it>), a chymotrypsin (<it>PperChym3</it>) and a microvillar protein (<it>PperMVP3</it>). We performed a detailed temporal expression profile analysis of the putative trypsin transcripts using qPCR and confirmed the expression of blood-induced and blood-repressed trypsins. Trypsin expression was measured in <it>Leishmania infantum</it>-infected and uninfected sand flies, which identified the <it>L. infantum</it>-induced down regulation of <it>PperTryp3 </it>at 24 hours post-blood meal.</p> <p>Conclusion</p> <p>This midgut tissue-specific transcriptome provides insight into the molecules expressed in the midgut of <it>P. perniciosus</it>, an important vector of visceral leishmaniasis in the Old World. Through the comparative analysis of the libraries we identified molecules differentially expressed during blood meal digestion. Additionally, this study provides a detailed comparison to transcripts of other sand flies. Moreover, our analysis of putative trypsins demonstrated that <it>L. infantum </it>infection can reduce the transcript abundance of trypsin <it>PperTryp3 </it>in the midgut of <it>P. perniciosus</it>.</p

Synthetic sex pheromone in a long-lasting lure attracts the visceral leishmaniasis vector, lutzomyia longipalpis, for up to 12 weeks in Brazil

Current control methodologies have not prevented the spread of visceral leishmaniasis (VL) across Brazil. Here, we describe the development of a new tool for controlling the sand fly vector of the disease: a long-lasting lure, which releases a synthetic male sex pheromone, attractive to both sexes of Lutzomyia longipalpis. This device could be used to improve the effectiveness of residual insecticide spraying as a means of sand fly control, attracting L. longipalpis to insecticide-treated animal houses, where they could be killed in potentially large numbers over a number of weeks. Different lure designs releasing the synthetic pheromone (±)-9-methylgermacrene-B (CAS 183158-38-5) were field-tested in Araçatuba, São Paulo (SP). Experiments compared numbers of sand flies caught overnight in experimental chicken sheds with pheromone lures, to numbers caught in control sheds without pheromone. Prototype lures, designed to last one night, were first used to confirm the attractiveness of the pheromone in SP, and shown to attract significantly more flies to test sheds than controls. Longer-lasting lures were tested when new, and at fortnightly intervals. Lures loaded with 1 mg of pheromone did not attract sand flies for more than two weeks. However, lures loaded with 10 mg of pheromone, with a releasing surface of 15 cm2 or 7.5 cm2, attracted female L. longipalpis for up to ten weeks, and males for up to twelve weeks. Approximately five times more sand flies were caught with 7.5 cm2 10 mg lures when first used than occurred naturally in non-experimental chicken resting sites. These results demonstrate that these lures are suitably long-lasting and attractive for use in sand fly control programmes in SP. To our knowledge, this is the first sex pheromone-based technology targeting an insect vector of a neglected human disease. Further studies should explore the general applicability of this approach for combating other insect-borne diseases