ASSESSING THE BIO-EFFICACY OF THE YORKOOL ® , A PYRETHROID- BASED LONG LASTING INSECTICIDAL NET OVER A ONE-YEAR PERIOD OF USE AND DETERMINING NET WASHING AND DRYING PRACTICES IN SEME, KISUMU COUNTY.

Abstract

Malaria remains a major public health problem globally, despite significant success in malaria control programs in the past. Long lasting insecticidal nets (LLINs) are the major vector control method used to prevent malaria transmission. These nets work by preventing mosquitos from feeding on blood and killing mosquitos, providing personal and communal protection, respectively. The use of long-lasting insecticidal nets is one of the key vector control strategies recommended by the World Health Organization for malaria management due to their cost-effectiveness and its wide availability. Long lasting insecticidal nets (LLINs) are nets which have been treated with insecticides at the point of manufacturing and thus do not require any reimpregnation. The nets are designed to maintain the insecticidal efficacy up to 3 years of use. However, some studies have shown that there is reduction of efficacy in the LLINs as early as 12 months under field condition and thus the need to evaluate the nets after one-year use. The aim of this study was to evaluate the insecticidal activity of Yorkool® LLINs after 12 months of use and the community net washing and drying practices in Seme, Kisumu County. The LLINs distributed during the 2021 mass net distribution were sampled from the 16 villages and assessed for bio efficacy after 12 months of use. The bio efficacy of Yorkool® LLINs was evaluated against Kisumu strain Anopheles gambiae using cone bioassay tests in a cross-sectional survey design. Community household net washing and drying practices was assessed through structured questionnaires. The targeted population were households in Seme sub county, Kisumu County that received rectangular Yorkool® LLINs during mass net distribution in 2021 from the Ministry of health. The sample size for bioassay testing was 30 LLINs as per the WHO guidelines. Households were sampled using systematic random sampling method, where the household heads were consented to participate in the study. Long lasting insecticidal nets (LLINs) were recovered from some of the study households and taken to the laboratory for bioassays. Households where nets were retrieved for bioassay tests were replaced with new Yorkool® nets. Data was analyzed using STATA version 15.1. The nets’ efficacy was determined in terms of mosquito knockdown and mosquito mortality. The WHO efficacy criteria used were ≥ 95% knockdown and/or ≥ 80% mortality rate in cone bioassays. A total of 262 household heads participated in the study. The mean age of the household heads was 46.9 years (SD 17.4 years) and ranged from 18 to 92 years. Level of education was mainly primary (70.2%) and 44.3% used electricity as the main source of lighting. The median sleeping spaces in the households were 2 and ranged from 1 to 8 spaces. Bio-efficacy test recorded a mean KD of 92% after 1 hour, and mean mortality of 86% after 24 hours. The nets that passed the WHO efficacy cut off for mortality were 83.3% (≥80%) after 24 hours with another 70% passing the cut off for KD((≥95%KD) after 1hour.A total of 468 nets were counted across all households studied and 95.1% had been washed at least once. About three-quarters (74.4%) of the nets had been washed using local bar soap, with a majority (99.6%) of the nets not scrubbed on hard surface during washing. Majority of the nets (72.1%) were dried under a shade. In conclusion, the findings from this study provided deep insight on Yorkool® nets insecticidal activity after one year of use under field conditions in Seme community. This study demonstrated that most of distributed nets are still protective and retained substantial levels of active ingredients. The bio-efficacy of the nets was relatively high with the mortality on vectors meeting the WHO threshold. Seme community practiced good adherence to appropriate net handling approaches in terms of washing and drying. Findings of this study was used to inform National Malaria Control Program (NMCP) and Long-lasting insecticidal nets distribution strategies to improve on malaria vector control in the region.