Assessing the Bio-Efficacy, Physical Integrity, and Care Practices of Yorkool® Pyrethroid-Based Long-Lasting Insecticidal Nets after one Year of use in Seme, Kisumu County

Abstract

The physical integrity and insecticide efficacy of long-lasting insecticide-treated nets (LLINs) are influenced by handling practices during use. This was an evaluation of Yorkool® pyrethroid-based LLINs after 12 months of use to determine the washing and drying practices, physical conditions, and bio-efficacy. This was a cross sectional household survey in an area where rectangular Yorkool® pyrethroid LLINs were distributed during the national mass net distribution campaign in 2021. Questionnaires were used for data collection, and bioassay tests were conducted on 30 randomly selected nets. A total of 262 household heads were interviewed, with their mean age being 46.9 years (SD 17.4 years), and the level of education was mainly primary (70.2%). Most households (71.8%) had 1 to 2 sleeping spaces. The households had 468 LLINs, with 95.1% having been washed at least once. About three-quarters (74.4%) of the LLINs had been washed using local bar soap, with 99.6 % having not been scrubbed on a hard surface during washing, and 72.1% were dried under a shade. Those evaluated for physical integrity and had at least one hole made up 77.8% of the nets and 57.2% were too torn and required replacement. Bio efficacy test recorded a mean KD of 92% after 1 hour, and a mean mortality of 86% after 24 hours. The nets that passed the WHO efficacy cut-off for mortality (≥ 80%) after 24 hours were 83.3%, and 70% passed the KD (≥ 95%) cut-off after 1 hour. In conclusion, while more than half of the Yorkool® LLINs needed replacement due to poor physical integrity after one year of use in the households, the bio-efficacy of the LLINs was relatively high with the mortality on vectors meeting the WHO threshold. Key words: Integrity, Efficacy, Bioassay, Washing, Drying, Knockdown