Evaluation of OlysetTM insecticide-treated nets distributed seven years previously in Tanzania

Background: Insecticide-treated nets represent currently a key malaria control strategy, but low insecticide re-treatment rates remain problematic. OlysetTM nets are currently one of two longlasting insecticidal nets recommended by WHO. An assessment was carried out of the effect of OlysetTM nets after seven years of use in rural Tanzania. Methods: A survey of OlysetTM nets was conducted in two Tanzanian villages to examine their insecticide dosage, bioassay efficacy and desirability compared with ordinary polyester nets. Results: Of 103 randomly selected nets distributed in 1994 to 1995, 100 could be traced. Most nets were in a condition likely to offer protection against mosquito biting. Villagers appreciated mainly the durability of OlysetTM nets and insecticide persistence. People disliked the small size of these nets and the light blue colour and preferred a smaller mesh size, features that can easily be modified. At equal price, 51% said they would prefer to buy an OlysetTM net and 49% opted for an ordinary polyester net. The average permethrin content was 33%-41% of the initial insecticide dose of 20,000 mg/Kg. Bioassay results indicated high knock-down rates at 60 minutes, but the mosquito mortality after 24 hours was rather low (mean: 34%). No significant correlation was found between bioassay results and insecticide concentration in and on the net. Conclusions: OlysetTM nets are popular, durable and with a much longer insecticide persistence than ordinary polyester nets. Hence, OlysetTM nets are one of the best choices for ITN programmes in rural malaria-endemic areas. Background Tanzania, with its 34 million people, carries a heavy malaria disease burden with an estimated 16 million clinical episodes per year and 100,000 child deaths [1]. In order to address this enormous burden, the country recently launched a national insecticide-treated nets (ITNs) initiative with the aim of protecting 60% of all children and pregnant women by 2007 [1]. Globally, ITNs were shown to substantially reduce morbidity and mortality from malaria in numerous settings [2] and they are currently deployed on a large scale in many malaria-endemic countries. Published: 29 June 2004 Malaria Journal 2004, 3:19 doi:10.1186/1475-2875-3-19 Received: 04 March 2004 Accepted: 29 June 2004 This article is available from: http://www.malariajournal.com/content/3/1/19 © 2004 Tami et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. Malaria Journal 2004, 3:19 http://www.malariajournal.com/content/3/1/19