Insecticidal decay effects of long-lasting insecticide nets and indoor residual spraying on Anopheles gambiae and Anopheles arabiensis in Western Kenya

• Published in: Parasites & vectors 2015-11, Vol.8 (587), p.588-588, Article 588
• Main Authors: Wanjala, Christine L, Zhou, Guofa, Mbugi, Jernard, Simbauni, Jemimah, Afrane, Yaw A, Ototo, Ednah, Gesuge, Maxwell, Atieli, Harrysone, Githeko, Andrew K, Yan, Guiyun
• Format: Article
• Language: English
• Subjects: Animals; Anopheles; Anopheles - drug effects; Anopheles - growth & development; Biological Assay; Chromatography, Gas; Control; Indoor residual spraying; Infection control; Insecticidal decay; Insecticide resistance; Insecticide-Treated Bednets; Insecticides; Insecticides - pharmacology; Kenya; Long-lasting insecticide nets; Malaria; Methods; Mosquito Control - methods; Nets; Netting; Nitriles - pharmacology; Permethrin - pharmacology; Pyrethrins - pharmacology; Time Factors
• ISSN: 1756-3305; 1756-3305
• DOI: 10.1186/s13071-015-1194-6

Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are the first-line tools for malaria prevention and control in Africa. Vector resistance to insecticides has been extensively studied, however the insecticidal effects of the nets and sprayed walls on pyrethroid resistant mosquitoes has not been studied thoroughly. We evaluated the bioefficacy of LLINs of different ages and lambda-cyhalothrin (ICON 10cs) on the sprayed mud walls for a period of time on malaria vector survivorship. WHO tube bioassay was performed using diagnostic doses of lambda-cyhalothrin (0.05%), permethrin (0.75%) and deltamethrin (0.05%). Cone bioassays were conducted on netting materials from 0 to 3 years old long-lasting insecticide-impregnated nets. Wall bioassays were performed monthly on mud slabs sprayed with lambdacyhalothrin over a period of seven months. All bioassays used An. gambiae mosquitoes collected from the field and the laboratory susceptible reference Kisumu strain. Concentration of the insecticides on the netting materials was examined using the gas chromatography method. Mosquitoes were identified to species level using PCR and genotyped for the kdr gene mutation frequencies. WHO bioassays results showed that populations from five sites were highly resistant to the pyrethroids (mortalities ranged from 52.5 to 75.3%), and two sites were moderately resistant to these insecticides (80.4 - 87.2%). Homozygote kdr mutations of L1014S ranged from 73 to 88% in An. gambiae s.s. dominant populations whereas L1014S mutation frequencies were relatively low (7-31%) in An. arabiensis dominant populations. There was a significant decrease (P