Assessment of the insecticide effectiveness of OlysetnetandPermanet2.0was performed respectively for 36and 24month follow-up under fielduse conditions in N'gatty and Allaba,in lagoon environment of Côte d’Ivoire. After identifying users of LLINs in households,580O lysetnet and 100Permanet2.0were distributed to N'gatty and Allaba. Their effectiveness as been regularly assessed by a questionnaire sent to users ,by bio assays contacting females forceda sensitive reference strain of tests An.Gambiae"Kisumu" with netting materials and the determination of residual amount of insecticide by high pressure liquid chromatography (HPLC) in samples of nets in use. According tousers, loss of effectiveness of LLINs was experienced after2-3months of use. Bio assays conducted before the distribution of LLINs have confirmed their efficacy on the sensitive strain mosquito. Mortality rates at 6 monthswere37.8%with Olyset and 38.4% with Permanet2.0. After six months, the doses of permethrin and delta methrin were respectively 666.25mg/ m² or 57%of the initial dose(1168.75 mg /m²)innetOlysetand15.30mg/ m² or 35% of the original dose (43.40 mg /m²)inPermanet2.0. The concept of LLINs, as defined by WHO, seems to know the limits when they are used and subjected to washing practices in the field conditions in Côte d'Ivoire. The sewashing methods which clearly differ from the standard WHO method of washing nets, accelerate the degradation of the insecticide and shorten their effectiveness over time.
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