title: Persistence and wash-resistance of insecticidal efficacy of nettings treated with deltamethrin tablet formulation (K-O TAB) against malaria vectors.
abstract: Persistence, wash-resistance, and shelf life of mosquito nets treated with a water-dispersible tablet formulation of synthetic pyrethroid insecticide deltamethrin (K-O TAB) at 25 mg/m2 was evaluated against malaria vectors in India. During June 2001, treated and untreated polyester, nylon, and cotton nets were separately distributed in 3 villages and cone bioassays were performed on Anopheles culicifacies and An. stephensi 1 day after treatment and thereafter every month for 12 months. The mosquitoes were exposed for 3 min on the nettings (treated and unwashed, or treated and washed once or twice in 3 months, and untreated) and knock-down (1 h) and 24 h postexposure mortality were recorded. Unwashed polyester nets, and those washed once 1 month after treatment, gave 100% mortality in An. culicifacies for 6 months. A 2nd wash at 3 months after treatment marginally reduced the insecticidal action. Anopheles stephensi was fully susceptible up to 4 months when exposed to unwashed nets but washing considerably reduced insecticidal action (65-78% after 2 washes). Treated nylon and cotton nets were effective for 4 months on both vectors. Treated nets kept on shelf retained 100% efficacy for 10 months. Overall, the treated nets gave a considerably long persistence of insecticidal action even after a single wash. Treated polyester nets were found most effective. Compared with our earlier experiences of using liquid formulations, the tablet formulation is likely to have a better community acceptance in treating nets.
authors.affiliation: Malaria Research Centre, Field Station, Civil Hospital, Nadiad 387001, Gujarat, India.
authors.forename: Rajendra M
authors.initials: RM
authors.lastname: Bhatt
authors.forename: Rajpal S
authors.initials: RS
authors.lastname: Yadav
authors.forename: Tridibes
authors.initials: T
authors.lastname: Adak
authors.forename: Chazoor J
authors.initials: CJ
authors.lastname: Babu
mesh_terms: D000818:Animals; D000852:Anopheles; D001681:Biological Assay; D006801:Humans; D007194:India; D007303:Insect Vectors; D007306:Insecticides; D007846:Laundering; D008288:Malaria / Q000517:prevention & control*; D009032:Mosquito Control / Q000379:methods*; D009570:Nitriles; D011722:Pyrethrins; D013607:Tablets
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; D013607:Tablets; C017180:decamethrin