Evaluation of KO-Tab 1-2-3: a wash-resistant 'dip-it-yourself' insecticide formulation for long-lasting treatment of mosquito nets.
BACKGROUND
Insecticide-treated nets (ITN) are an important method of preventing malaria. To remain effective, they need to be re-treated with pyrethroid insecticide at approximately yearly intervals. Systems for re-treating nets in Africa are limited, and the vast majority of nets in use have never been treated or were treated only once. Bayer Environmental Science (BES) has developed a long-lasting formulation 'KO-Tab 1-2-3' which can be applied to the net post-manufacture, under field conditions, and renders the insecticide wash-resistant.


METHODS
The performance of polyester nets treated with three kinds of BES long-lasting formulations, a conventional ITN (treated with standard KO-Tab) and PermaNet 2.0 were evaluated after washing samples of treated netting up to 30 times using standard WHO procedures. Performance was measured using 'three-minute exposure' and 'median time to knockdown' bioassay tests and by measuring the levels of deltamethrin using high-pressure liquid chromatography.


RESULTS
The conventional ITN was largely stripped of deltamethrin within 5-10 washes and insecticidal efficacy in bioassay declined to suboptimal levels. With PermaNet and KO-Tab 1-2-3 the loss of deltamethrin was much slower: insecticide content halved within 20 washes and there was no loss of biological efficacy in three-minute exposure bioassays in WHO cylinders even after 30 washes. After 30 washes there remained on the netting 16% (4.4 mg/m2) of the loading dose of KO-Tab 1-2-3 and 28% (18.8 mg/m2) of the loading dose of PermaNet.


CONCLUSIONS
KO-Tab 1-2-3 was confirmed to be a long-lasting insecticide formulation. This finding raises the prospect of conventional polyester nets being converted into long-lasting insecticidal nets through simple dipping in the community or at home. This single development, if widely adopted, could transform the malaria control landscape in Africa and have a major impact on malaria.
Yates
Alison
A
London School of Hygiene & Tropical Medicine, London, WC1E 7HT, UK. Alison.yates@lshtm.ac.uk
N'Guessan
Raphael
R
Kaur
Harparkash
H
Akogbéto
Martin
M
Rowland
Mark
M
D000818:Animals; D000852:Anopheles / Q000187:drug effects; D001512:Bedding and Linens; D007306:Insecticides / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D007846:Laundering; D008288:Malaria / Q000517:prevention & control; D009032:Mosquito Control / Q000379:methods*; D009570:Nitriles / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D011091:Polyesters; D011722:Pyrethrins / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology
D007306:Insecticides; D009570:Nitriles; D011091:Polyesters; D011722:Pyrethrins; C017180:decamethrin