Comparative insecticidal power of three pyrethroids on netting

Abstract

Abstract. Adult mosquitoes, Anopheles gambiae Giles and Culex quinquefasciatus Say (Diptera: Culicidae), were exposed for 3 min to replicate samples of polyester netting cut from replicate bednets treated with pyrethroid insecticide formulations at the recommended concentration (alphacypermethrin SC at 40 mg ai=m 2 ; cyfluthrin EW at 50 mg ai=m 2 ; deltamethrin WT at 25 mg ai=m 2 ), or treated with only a quarter of those dosages. After 4 months domestic use of the bednets in Malawi, chemical assays showed that pyrethroid deposits on the netting were somewhat less than the target concentrations. Comparing the pyrethroid bioassay results with Anopheles at both treatment concentrations, deltamethrin gave significantly higher mortality (99.7±100%) than the other compounds (alphacypermethrin 94±96%, cyfluthrin 80±89%). Culex bioassay mortality was lower (alphacypermethrin 56±74%; cyfluthrin 63±65%; deltamethrin 50±81%) and results with the three pyrethroid insecticides at their recommended doses did not differ significantly.Key words. Anopheles gambiae, Culex quinquefasciatus, alphacypermethrin, bednets, bioassays, cyfluthrin, deltamethrin, insecticide potency, mosquitoes, pyrethroids, Africa.For malaria control, various pyrethroid insecticide compounds and formulations are used for treatment of bednets and curtains (Chavasse & Yap, 1997). The World Health Organization Pesticides Evaluation Scheme (WHOPES) has endorsed particular products and dosages for their safety and efficacy when used for bednet impregnation (WHO, 1997(WHO, , 1998(WHO, , 1999(WHO, , 2001Zaim et al., 2000). Bioassay comparisons between bednets with different pyrethroid treatments (e.g. Curtis et al., 1996;Lengeler et al., 1996;Maxwell et al., 1999) have seldom been adequately replicated to give definitive answers as to which are most efficacious.Therefore, the present study was designed to ascertain which recommended pyrethroid treatment of bednets gave the best insecticidal bioassay results with Anopheles and Culex mosquitoes. The study was undertaken for the PSI= Malawi=ITN project 1 as part of the Blantyre Integrated Malaria Initiative using standard polyester bednets (A to Z Textiles Mills Ltd, Arusha, Tanzania).By standard dipping procedures (Chavasse et al., 1999), multiple bednets were impregnated with pyrethroid at the recommended dosage: 25 mg ai=m 2 deltamethrin from 25% wettable tablet (WT) formulation (KO-tab TM : Aventis, Frankfurt, Germany); 40 mg ai=m 2 alphacypermethrin from 6% suspension concentrate formulation (Fendona TM 6 SC: American Cyanamid, Princeton, NJ, U.S.A) or 50 mg ai=m 2 cyfluthrin from 5% emulsion in water (Solfac TM EW 50: Bayer, Leverkusen, Germany). Other sets of bednets were treated at one-quarter of the dosage recommended, to represent badly under-dosed nets or those overdue for re-treatment. The six sets of treated bednets (as listed in

Evidence for a useful life of more than three years for a polyester-based long-lasting insecticidal mosquito net in Western Uganda

“…This is, however, in keeping with results reported in the literature for alpha-cypermethrin. Adams et al [21] tested low doses of various insecticides in Malawi and demonstrated that even a dose of only 6.5 mg/m 2 alpha-cypermethrin resulted in a 93% mortality rate in Anopheles gambiae s.s . Similarly high bio-assay results were obtained by Graham et al in Pakistan [22] after 21 washes and a target dose of 15 mg/m 2 achieving a 49% mortality rate for Anopheles stephensi .…”

A randomized and controlled comparison of the wash-resistances and insecticidal efficacies of four types of deltamethrin-treated nets, over a 6-month period of domestic use with washing every 2 weeks, in a rural area of Iran

“…activity after just a few washes with soap or detergent Miller et al, 1991Miller et al, , 1995Pleass et al, 1993;Jawara et al, 1998;Vythilingam et al, 1999;Adams et al, 2002;Gonzalez, 2002;Kayedi, 2004;Graham et al, 2005). Although nets that have lost most of their insecticide after repeated washing can be successfully retreated, the observed frequencies of such re-treatment, when the nets are in routine use in the field, have generally been found to be very low (Aikins et al, 1994;Cheng et al, 1995;Elissa and Curtis, 1995;Jana-Kara et al, 1995;Curtis, 1996;Lengeler et al, 1996;Lines, 1996;Cham et al, 1997;Kroeger et al, 1997;Winch et al, 1997;Kachur et al, 1999;Miller et al, 1999;Clarke et al, 2001;Kalmolratanakul et al, 2001;Schellenberg et al, 2001;Maxwell et al, 2002;Curtis et al, 2003;Kayedi, 2004).…”

Phenotypic effects of concomitant insensitive acetylcholinesterase ( ace-1 R ) and knockdown resistance ( kdr R ) in Anopheles gambiae : a hindrance for insecticide resistance management for malaria vector control

“…kdr R resistance is caused by mutations in the sodium channel: leucine to phenylalanine substitution, originally observed in West Africa [31], and leucine to serine mutation in East Africa [32]. Recently, a new mutation in the sodium channel associated with kdr-west mutation conferring additional resistance to DDT and permethrin [33] was reported [34]. Experimental studies conducted in Southern Benin and in South Africa respectively with lambdacyhalothrin [33] on bednets and with deltamethrin [33] through indoor residual house spraying [35] suggested that PYRs resistance may have contributed to the failure of vector control endeavours in these areas [21,[35][36][37][38].…”