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- Title
Laboratory wash resistance of long-lasting insecticidal nets.
- Authors
Gimnig, John E.; Lindblade, Kim A.; Mount, Dwight L.; Atieli, Francis K.; Crawford, Sara; Wolkon, Adam; Hawley, William A.; Dotson, Ellen M.
- Abstract
Long-lasting insecticidal nets (LLINs) may eliminate the need for retreatment of mosquito nets used for the control of malaria and other vector-borne diseases. The efficacy of LLINs after repeated washing under laboratory conditions has been used to predict long-lasting efficacy under field conditions. We evaluated under laboratory conditions the wash resistance of two LLINs (PermaNet® 1.0, Vestergaard-Frandsen, Denmark; Olyset®, Sumitomo Chemical Co., Japan), two candidate LLINs (Dawa®, Siamdutch Mosquito Netting Co., Thailand; Insector, Athanor, France) and a net treated with a process designed to increase its wash resistance and compared them with conventionally treated nets (deltamethrin, 25 mg/m2). Nets of all six types were washed using a standard protocol and tested weekly using WHO cone bioassays with Anopheles gambiae (Kisumu strain). The PermaNet® 1.0 was the most wash resistant with >50% mosquito mortality in WHO cone bioassays after as many as 20 washes. The Dawa® net also retained some activity after repeated washing but exhibited wide variation in insecticide retention and biological activity. The remaining nets lost >90% of their biological activity after six washes as measured by 24-h mortality of A. gambiae in WHO cone tests. After 20 washes, all nets lost >50% of their initial insecticide concentrations except for the Olyset® net. After 20 washes, nets were heated for 4 h at 60 °C to determine whether biological activity could be restored by heat-assisted regeneration. Only the Olyset® net was regenerated by heating, with average mosquito mortality and knockdown in WHO cone tests rising to >90% after heating for 4 h at 60 °C. However, regeneration of the biological activity of Olyset® nets that had been washed three times did not occur at 30 °C or 35 °C after 12 weeks. The wash resistance of these LLINs corresponded well to their retention of biological activity observed in a field trial, suggesting that wash resistance may be a good predictor of the longevity of insecticidal activity of LLINs under field conditions.
- Subjects
JAPAN; THAILAND; INSECTICIDAL plants; PESTICIDAL plants; MALARIA; MORTALITY
- Publication
Tropical Medicine & International Health, 2005, Vol 10, Issue 10, p1022
- ISSN
1360-2276
- Publication type
Article
- DOI
10.1111/j.1365-3156.2005.01481.x