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Insecticidal and repellent activities of pyrethroids to the three major pyrethroid-resistant malaria vectors in western Kenya.

Kawada H, Ohashi K, Dida GO, Sonye G, Njenga SM, Mwandawiro C, Minakawa N - Parasit Vectors (2014)

Bottom Line: The frequency of takeoffs from the pyrethroid-treated surface and the flying times without contacting the surface increased significantly in pyrethroid-susceptible An. gambiae s.s. and An. arabiensis colonies and wild An. arabiensis and An. funestus s.s. colonies, while there was no significant increase in the frequency of takeoffs or flying time in the An. gambiae s.s. wild colony.It might be that resistant mosquitoes governed by knockdown resistance (kdr) loose repellency to pyrethroids, whereas those lacking kdr maintain high repellency irrespective of their possessing metabolic resistance factors to pyrethroids.Further genetic evaluation is required for the demonstration of the above hypothesis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Vector Ecology & Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan. vergiss@nagasaki-u.ac.jp.

ABSTRACT

Background: The dramatic success of insecticide treated nets (ITNs) and long-lasting insecticidal nets (LLINs) in African countries has been countered by the rapid development of pyrethroid resistance in vector mosquitoes over the past decade. One advantage of the use of pyrethroids in ITNs is their excito-repellency. Use of the excito-repellency of pyrethroids might be biorational, since such repellency will not induce or delay the development of any physiological resistance. However, little is known about the relationship between the mode of insecticide resistance and excito-repellency in pyrethroid-resistant mosquitoes.

Methods: Differences in the reactions of 3 major malaria vectors in western Kenya to pyrethroids were compared in laboratory tests. Adult susceptibility tests were performed using World Health Organization (WHO) test tube kits for F1 progenies of field-collected An. gambiae s.s., An. arabiensis, and An. funestus s.s., and laboratory colonies of An. gambiae s.s. and An. arabiensis. The contact repellency to pyrethroids or permethrin-impregnated LLINs (Olyset® Nets) was evaluated with a simple choice test modified by WHO test tubes and with the test modified by the WHO cone bioassay test.

Results: Field-collected An. gambiae s.s., An. arabiensis, and An. funestus s.s. showed high resistance to both permethrin and deltamethrin. The allelic frequency of the point mutation in the voltage-gated sodium channel (L1014S) in An. gambiae s.s. was 99.3-100%, while no point mutations were detected in the other 2 species. The frequency of takeoffs from the pyrethroid-treated surface and the flying times without contacting the surface increased significantly in pyrethroid-susceptible An. gambiae s.s. and An. arabiensis colonies and wild An. arabiensis and An. funestus s.s. colonies, while there was no significant increase in the frequency of takeoffs or flying time in the An. gambiae s.s. wild colony.

Conclusion: A different repellent reaction was observed in the field-collected An. gambiae s.s. than in An. arabiensis and An. funestus s.s. It might be that resistant mosquitoes governed by knockdown resistance (kdr) loose repellency to pyrethroids, whereas those lacking kdr maintain high repellency irrespective of their possessing metabolic resistance factors to pyrethroids. Further genetic evaluation is required for the demonstration of the above hypothesis.

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Number of takeoffs of female An. gambiae s.s., An. arabiensis, and An. funestus s.s. during a 3-min exposure to an Olyset® Net, 0.75% permethrin paper, or untreated net material by modified WHO cone bioassay. Figures indicate the significance levels by a Kruskal-Wallis test. Bars indicate SEs.
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Figure 4: Number of takeoffs of female An. gambiae s.s., An. arabiensis, and An. funestus s.s. during a 3-min exposure to an Olyset® Net, 0.75% permethrin paper, or untreated net material by modified WHO cone bioassay. Figures indicate the significance levels by a Kruskal-Wallis test. Bars indicate SEs.

Mentions: The contact repellency of permethrin 0.75% paper and an Olyset® Net against laboratory colonies (ICIPE colonies) and field-collected F1 colonies (wild colonies) of An. gambiae s.s. and An. arabiensis, and a wild colony of An. funestus s.s. by a modified WHO cone assay is shown in Figures 4 and5. The number of takeoffs in the control test was 1.1 ± 0.3 (ICIPE colony) and 1.5 ± 0.5 (wild colony) in An. gambiae s.s., 0.5 ± 0.2 (ICIPE colony) and 0.5 ± 0.2 (wild colony) in An. arabiensis, and 0.6 ± 0.4 (wild colony) in An. funestus s.s. Significant differences in the number of takeoffs were observed in the An. gambiae s.s. ICIPE colony (Kruskal-Wallis test, df = 2, χ2 = 24.0, p < 0.0001), An. arabiensis ICIPE colony (Kruskal-Wallis test, df = 2, χ2 = 38.3, p < 0.0001), An. arabiensis wild colony (Kruskal-Wallis test, df = 2, χ2 = 20.6, p < 0.0001), and An. funestus s.s. wild colony (Kruskal-Wallis test, df = 2, χ2 = 8.3, p = 0.016), indicating that the number of takeoffs in these colonies significantly increased after exposure to permethrin 0.75% paper and an Olyset® Net. In contrast, there was no significant difference in the number of takeoffs in the An. gambiae s.s. wild colony (Kruskal-Wallis test, df = 2, χ2 = 0.70, p = 0.698) (Figure 4).


Insecticidal and repellent activities of pyrethroids to the three major pyrethroid-resistant malaria vectors in western Kenya.

Kawada H, Ohashi K, Dida GO, Sonye G, Njenga SM, Mwandawiro C, Minakawa N - Parasit Vectors (2014)

Number of takeoffs of female An. gambiae s.s., An. arabiensis, and An. funestus s.s. during a 3-min exposure to an Olyset® Net, 0.75% permethrin paper, or untreated net material by modified WHO cone bioassay. Figures indicate the significance levels by a Kruskal-Wallis test. Bars indicate SEs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4017225&req=5

Figure 4: Number of takeoffs of female An. gambiae s.s., An. arabiensis, and An. funestus s.s. during a 3-min exposure to an Olyset® Net, 0.75% permethrin paper, or untreated net material by modified WHO cone bioassay. Figures indicate the significance levels by a Kruskal-Wallis test. Bars indicate SEs.
Mentions: The contact repellency of permethrin 0.75% paper and an Olyset® Net against laboratory colonies (ICIPE colonies) and field-collected F1 colonies (wild colonies) of An. gambiae s.s. and An. arabiensis, and a wild colony of An. funestus s.s. by a modified WHO cone assay is shown in Figures 4 and5. The number of takeoffs in the control test was 1.1 ± 0.3 (ICIPE colony) and 1.5 ± 0.5 (wild colony) in An. gambiae s.s., 0.5 ± 0.2 (ICIPE colony) and 0.5 ± 0.2 (wild colony) in An. arabiensis, and 0.6 ± 0.4 (wild colony) in An. funestus s.s. Significant differences in the number of takeoffs were observed in the An. gambiae s.s. ICIPE colony (Kruskal-Wallis test, df = 2, χ2 = 24.0, p < 0.0001), An. arabiensis ICIPE colony (Kruskal-Wallis test, df = 2, χ2 = 38.3, p < 0.0001), An. arabiensis wild colony (Kruskal-Wallis test, df = 2, χ2 = 20.6, p < 0.0001), and An. funestus s.s. wild colony (Kruskal-Wallis test, df = 2, χ2 = 8.3, p = 0.016), indicating that the number of takeoffs in these colonies significantly increased after exposure to permethrin 0.75% paper and an Olyset® Net. In contrast, there was no significant difference in the number of takeoffs in the An. gambiae s.s. wild colony (Kruskal-Wallis test, df = 2, χ2 = 0.70, p = 0.698) (Figure 4).

Bottom Line: The frequency of takeoffs from the pyrethroid-treated surface and the flying times without contacting the surface increased significantly in pyrethroid-susceptible An. gambiae s.s. and An. arabiensis colonies and wild An. arabiensis and An. funestus s.s. colonies, while there was no significant increase in the frequency of takeoffs or flying time in the An. gambiae s.s. wild colony.It might be that resistant mosquitoes governed by knockdown resistance (kdr) loose repellency to pyrethroids, whereas those lacking kdr maintain high repellency irrespective of their possessing metabolic resistance factors to pyrethroids.Further genetic evaluation is required for the demonstration of the above hypothesis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Vector Ecology & Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan. vergiss@nagasaki-u.ac.jp.

ABSTRACT

Background: The dramatic success of insecticide treated nets (ITNs) and long-lasting insecticidal nets (LLINs) in African countries has been countered by the rapid development of pyrethroid resistance in vector mosquitoes over the past decade. One advantage of the use of pyrethroids in ITNs is their excito-repellency. Use of the excito-repellency of pyrethroids might be biorational, since such repellency will not induce or delay the development of any physiological resistance. However, little is known about the relationship between the mode of insecticide resistance and excito-repellency in pyrethroid-resistant mosquitoes.

Methods: Differences in the reactions of 3 major malaria vectors in western Kenya to pyrethroids were compared in laboratory tests. Adult susceptibility tests were performed using World Health Organization (WHO) test tube kits for F1 progenies of field-collected An. gambiae s.s., An. arabiensis, and An. funestus s.s., and laboratory colonies of An. gambiae s.s. and An. arabiensis. The contact repellency to pyrethroids or permethrin-impregnated LLINs (Olyset® Nets) was evaluated with a simple choice test modified by WHO test tubes and with the test modified by the WHO cone bioassay test.

Results: Field-collected An. gambiae s.s., An. arabiensis, and An. funestus s.s. showed high resistance to both permethrin and deltamethrin. The allelic frequency of the point mutation in the voltage-gated sodium channel (L1014S) in An. gambiae s.s. was 99.3-100%, while no point mutations were detected in the other 2 species. The frequency of takeoffs from the pyrethroid-treated surface and the flying times without contacting the surface increased significantly in pyrethroid-susceptible An. gambiae s.s. and An. arabiensis colonies and wild An. arabiensis and An. funestus s.s. colonies, while there was no significant increase in the frequency of takeoffs or flying time in the An. gambiae s.s. wild colony.

Conclusion: A different repellent reaction was observed in the field-collected An. gambiae s.s. than in An. arabiensis and An. funestus s.s. It might be that resistant mosquitoes governed by knockdown resistance (kdr) loose repellency to pyrethroids, whereas those lacking kdr maintain high repellency irrespective of their possessing metabolic resistance factors to pyrethroids. Further genetic evaluation is required for the demonstration of the above hypothesis.

Show MeSH
Related in: MedlinePlus