| Popis: |
Background: Optimising insecticide use and managing insecticide resistance are important to sustain gains against malaria using long-lasting insecticidal nets (LLINs). Restricting insecticides to where mosquitoes are most likely to make multiple contacts could reduce insecticide needed to treat nets. Previous studies have shown that nets partially treated with a pyrethroid insecticide in experimental huts with human sleepers gave equivalent mortality to a fully treated net. This remains to be demonstrated in LLINs with dual active ingredients developed to control pyrethroid resistant vectors. Here, the efficacy of Interceptor®G2 (IG2; a dual active LLIN containing alpha-cypermethrin and chlorfenapyr) netting in different roof and side combinations with untreated netting was compared against wild free-flying Anopheles arabiensis in terms of mortality, blood-feeding inhibition, exophily and deterrence using the following treatment arms: untreated nets, roof-treated IG2 (IG2 on roof and untreated sides), side-treated IG2 (IG2 on sides and untreated roof) and IG2 (standard fully treated net).Methods: The study was conducted in cow baited experimental huts, Moshi Tanzania, using a 4-arm Latin square design. Test nets had 30 holes cut in panels to simulate a typical net after 2-3 years use. Analysis used grouped logistic regression with random effects to analyse proportions and negative binomial regression to analyse count data.Results: The roof-treated IG2, side-treated IG2 and IG2 nets significantly increased the likelihood of mortality by 51-fold, 138-fold and 223-fold (PP=0.009) compared to the roof-treated IG2 net. While mortality was not significantly different between IG2 and side-treated IG2 (P>0.05) nets, there was a trend of more area covered the higher the mortality. There was no significant difference in the likelihood of blood feeding or exiting between untreated net arm and the treatment arms. Conclusion: The results show that although the roof-treated IG2 net induced greater mortality compared to untreated nets, its efficacy was reduced compared to IG2 nets. Further investigations are required to explore how attractant used (human or animal), hut type, mosquito species, and properties of active ingredient can influence the effectiveness of restricted treatment on Dual-AI nets. |
