Repellency and other biological effects of natural substances against the sand fly, Phlebotomus papatasi

Authors: Temeyer, Kevin; Schlechte, Kristie; DANDENEAU, LARYSSA - Non ARS Employee; DAVIS, MEGAN - US Department Of Energy; Li, Andrew; COSTA-JUNIOR, LIVIO - Universidade Federal Do Maranhao; Perez De Leon, Adalberto - Beto

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/21/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Blood feeding insects may transmit diseases. Mosquitoes, sand flies and other arthropod vectors are well-known agents capable of transmitting malaria, leishmaniasis and many other diseases. Many of these vectors are endemic to tropical or subtropical underdeveloped regions of the world. In addition to posing substantial health threats to indigenous human populations, these arthropod vectors can severely impact military operations, requiring development of new and effective control strategies. Insecticides may be useful for control at military bases but are potentially hazardous and of limited utility for field operations. Efficacious attractants and repellents greatly facilitate pest control and protection of personnel through use of attractants in traps to reduce localized pest populations and repellents for personal protection and/or limited area-wide protection. Recent experiments have identified natural products that exhibit both repellent and insecticidal activity to sand flies (Phlebotomus papatasi Israeli). Some of the natural products with identified repellent or insecticidal activity are available as a commercially available material. Addition of mineral oil to the commercial product was observed to extend the period of apparent repellent efficacy, suggesting potential utility in elimination of cracks and crevices in stucco walls as effective hiding places in close proximity to human populations and providing potential utility for area-wide repellent treatments. Identification of lead chemicals with effective repellent activity provides an opportunity for further identification and development of novel repellents based on structure activity relationships (SAR).

Technical Abstract: Leishmaniasis is an insect-borne disease caused by several protozoan species in the genus Leishmania, vectored by sand fly species in the genera Phlebotomus, Lutzomyia or others, with different species affecting different geographic ranges. Phlebotomus papatasi (Scopoli) is a major vector of Leishmania major, the principal causative agent of human cutaneous leishmaniasis in the Middle East, southern Europe, northern Africa, and southern Asia. Lutzomyia longipalpis is a principal vector of Leishmania spp. in Central and South America. Up to 1.3 million people can be affected globally where leishmaniasis is endemic. Sand fly control relies on area-wide pesticide treatment and use of pesticide-treated bed nets and repellents. In addition to substantial effects on human populations in endemic areas, sand fly bites and leishmaniasis significantly impacted U.S. military operations in Iraq and Afghanistan. Although there have been scattered reports of sand fly pesticide resistance, there have been very few studies actually demonstrating resistance. One study from Sudan, Africa, reported high level resistance to organophosphate (OP) pesticide in bioassays, but mechanistic information was lacking. We identified, cloned, sequenced, and expressed the cDNA encoding acetylcholinesterase 1 of Phlebotomus papatasi. The enzyme had very high amino acid sequence identity to acetylcholinesterase 1 of Lutzomyia longipalpis, Anopheles gambiae, Aedes aegypti, Culex quinquefaciatus, and other mosquito vectors of human pathogens. In addition to biochemical characterization of the wild type (susceptible) recombinant enzyme (PpAChE1), we constructed, expressed and characterized recombinant PpAChE1 incorporating mutations known to produce OP-resistant acetylcholinesterase in mosquitoes. The mutations G119S, F290V, and F331W, each resulted in production of a recombinant PpAChE1 with reduced inhibition by organophosphate inhibitors. Novel synthetic carbamates were produced that exhibited improved inhibition properties for one or more of the various enzyme constructs, including improved mammalian safety profile or improved inhibition of OP-resistant forms of the enzyme, and molecular docking models of inhibitors successfully mimicked biochemical inhibition results. Further, we developed DNA-based molecular assays to survey P. papatasi flies for the presence of the G119S mutation or the codon (GGC) that can produce the G119S mutation by a single nucleotide transversion. Use of these assays demonstrated presence of the GGC codon, but not the G119S mutation, in our laboratory colony sand flies, as well as wild sand flies collected from Marigat in Kenya, Africa, which strongly suggested that natural sand fly populations may rapidly develop OP-resistance via the G119S mutation when subjected to selection pressure, such as the malaria control program. Anopheles mosquitoes in West Africa exhibit G119S-based resistance to OP pesticides. Several novel synthetic carbamates were identified in our studies that were effective inhibitors of recombinant PpAChE1(G119S) constructs, suggesting that these compounds may effectively prevent or remediate G119S-based pesticide resistance.