Evaluation of Interceptor long-lasting insecticidal nets in eight communities in Liberia

Background: By 2008, the WHO Pesticide Evaluation Scheme (WHOPES) recommended five long-lasting insecticidal nets (LLINs) for the prevention of malaria: Olyset (R), PermaNet 2.0 (R), Netprotect (R), Duranet (R) and Interceptor (R). Field information is available for both Olyset (R) and PermaNet (R), with limited data on the newer LLINs. To address this gap, a field evaluation was carried out to determine the acceptability and durability of Interceptor (R) LLINs. Methods: A one-year prospective field study was conducted in eight rural returnee villages in Liberia. Households were randomized to receive Interceptor (R) LLINs or conventionally treated nets (CTNs). Primary outcomes were levels of residual alpha-cypermethrin measured by HPLC and participant utilization/acceptability of the ITNs. Results: A total of 398 nets were analysed for residual alpha-cypermethrin. The median baseline concentrations of insecticide were 175.5 mg/m2 for the Interceptor (R) LLIN and 21.8 mg/m2 for the CTN. Chemical residue loss after a one year follow-up period was 22% and 93% respectively. Retention and utilization of nets remained high (94%) after one year, irrespective of type, while parasitaemia prevalence decreased from 29.7% at baseline to 13.6% during the follow up survey (p = < 0.001). Interview and survey data show perceived effectiveness of ITNs was just as important as other physical attributes in influencing net utilization. Conclusion: Interceptor (R) LLINs are effective and desirable in rural communities in Liberia. Consideration for end user preferences should be incorporated into product development of all LLINs in the future, in order to achieve optimum retention and utilization.