Efficacy of PermaNet^®2.0 and PermaNet^®3.0 against insecticide-resistant <it>Anopheles gambiae </it>in experimental huts in Côte d'Ivoire

• Main Authors: Koffi Alphonsine A, Koudou Benjamin G, Malone David, Hemingway Janet
• Format: Article
• Language: English
• Published: BMC 2011-06-01
• Series: Malaria Journal
• Online Access: http://www.malariajournal.com/content/10/1/172

<p>Abstract</p> <p>Background</p> <p>Pyrethroid resistance in vectors could limit the efficacy of long-lasting insecticidal nets (LLINs) because all LLINs are currently treated with pyrethroids. The goal of this study was to evaluate the efficacy and wash resistance of PermaNet^®3.0 compared to PermaNet^®2.0 in an area of high pyrethroid in Côte d'Ivoire. PermaNet^®3.0 is impregnated with deltamethrin at 85 mg/m²on the sides of the net and with deltamethrin and piperonyl butoxide on the roof. PermaNet^®2.0 is impregnated with deltamethrin at 55 mg/m²across the entire net.</p> <p>Methods</p> <p>The study was conducted in the station of Yaokoffikro, in central Côte d'Ivoire. The efficacy of intact unwashed and washed LLINs was compared over a 12-week period with a conventionally-treated net (CTN) washed to just before exhaustion. WHO cone bioassays were performed on sub-sections of the nets, using wild-resistant <it>An. gambiae </it>and Kisumu strains. Mosquitoes were collected five days per week and were identified to genus and species level and classified as dead or alive, then unfed or blood-fed.</p> <p>Results</p> <p>Mortality rates of over 80% from cone bioassays with wild-caught pyrethroid-resistant <it>An. gambiae </it>s.s were recorded only with unwashed PermaNet^®3.0. Over 12 weeks, a total of 7,291 mosquitoes were collected. There were significantly more <it>An. gambiae </it>s.s. and <it>Culex </it>spp. caught in control huts than with other treatments (P < 0.001). The proportion of mosquitoes exiting the huts was significantly lower with the control than for the treatment arms (P < 0.001). Mortality rates with resistant <it>An. gambiae </it>s.s and <it>Culex </it>spp, were lower for the control than for other treatments (P < 0.001), which did not differ (P > 0.05) except for unwashed PermaNet^®3.0 (P < 0.001), which gave significantly higher mortality (P < 0.001).</p> <p>Conclusions</p> <p>This study showed that unwashed PermaNet^®3.0 caused significantly higher mortality against pyrethroid resistant <it>An. gambiae s.s </it>and <it>Culex </it>spp than PermaNet^®2.0 and the CTN. The increased efficacy with unwashed PermaNet^®3.0 over PermaNet^®2.0 and the CTN was also demonstrated by higher KD and mortality rates (KD > 95% and mortality rate > 80%) in cone bioassays performed with wild pyrethroid-resistant <it>An. gambiae s.s </it>from Yaokoffikro.</p>