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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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Related in: MedlinePlus

Map of the sites for mosquito collection. Red circles indicate houses used for mosquito collection.
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Figure 1: Map of the sites for mosquito collection. Red circles indicate houses used for mosquito collection.

Mentions: Indoor collection of adult mosquitoes was performed in houses in Nyandago, Nyaroya, Hao (E34°18′–E34°19′, S0°27′–S0°28′), and Nyamanga villages (E34°10′–E34°12′, S0°26′–S0°28′) in the Gembe area in Mbita District on the eastern side of Lake Victoria; Roo, Ragwe villages (E34°04′–E34°08′, S0°32′–S0°35′) in Suba District on the western side of Lake Victoria; and Mfangano Island (E34°03′–E34°04′, S0°27′–S0°28′) (Figure 1). Collections were performed from May 11th to July 6th, 2011, using a battery-powered aspirator (C-Cell Aspirator; BioQuip Products, CA, USA) between 7:00 and 9:00 AM by 3 people. After collection, blood-fed and gravid female mosquitoes were individually confined in a 20-mL glass vial containing ca. 2 mL of dechlorinated tap water. A strip of filter paper (approximately 3 × 4 cm) was placed inside each vial to collect eggs. F1 larvae from the separate egg batches were pooled into 1 batch of the same species after identification with PCR and reared with dechlorinated tap water until adult emergence. Larvae were fed a 1:1 mixture of powdered animal food (CE-2; Clea Inc., Tokyo, Japan) and dried yeast (Ebios®; Mitsubishi Tanabe Pharma, Tokyo, Japan).


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)

Map of the sites for mosquito collection. Red circles indicate houses used for mosquito collection.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Map of the sites for mosquito collection. Red circles indicate houses used for mosquito collection.
Mentions: Indoor collection of adult mosquitoes was performed in houses in Nyandago, Nyaroya, Hao (E34°18′–E34°19′, S0°27′–S0°28′), and Nyamanga villages (E34°10′–E34°12′, S0°26′–S0°28′) in the Gembe area in Mbita District on the eastern side of Lake Victoria; Roo, Ragwe villages (E34°04′–E34°08′, S0°32′–S0°35′) in Suba District on the western side of Lake Victoria; and Mfangano Island (E34°03′–E34°04′, S0°27′–S0°28′) (Figure 1). Collections were performed from May 11th to July 6th, 2011, using a battery-powered aspirator (C-Cell Aspirator; BioQuip Products, CA, USA) between 7:00 and 9:00 AM by 3 people. After collection, blood-fed and gravid female mosquitoes were individually confined in a 20-mL glass vial containing ca. 2 mL of dechlorinated tap water. A strip of filter paper (approximately 3 × 4 cm) was placed inside each vial to collect eggs. F1 larvae from the separate egg batches were pooled into 1 batch of the same species after identification with PCR and reared with dechlorinated tap water until adult emergence. Larvae were fed a 1:1 mixture of powdered animal food (CE-2; Clea Inc., Tokyo, Japan) and dried yeast (Ebios®; Mitsubishi Tanabe Pharma, Tokyo, Japan).

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