Latin American Symposium
Latin American Symposium
Malaria vector control in Colombia has long relied on the use of long-lasting insecticidal nets (LLIN) and indoor residual spraying (IRS). Thus, evaluating the efficacy of these tools is essential to decision making around national vector control strategies. Here we measure the durability of two vector control tools in use in Cauca Department. First, we assessed physical integrity, bio-efficacy, and survivorship of an alpha-cypermethrin-impregnated LLIN. Second, we determined coverage and residual efficacy of both a deltamethrin- and an alpha-cypermethrin-based IRS. Durability was evaluated at six and 12 months post-distribution in 40 LLINs randomly selected from across 20 clusters that had previously received one round of distribution in 2021. Residual efficacy of IRS was measured using WHO cone bioassays (with a susceptible strain of Anopheles albimanus) conducted seven days post-spraying in 40 households randomly selected from across 20 clusters that had previously received IRS in four different spray campaigns between 2021-23. For the LLINs, at six months post-distribution, 80% of the nets were in serviceable condition, however bio-efficacy was very low, with a mean knock-down of 3% and mean mortality of 5%. By 12 months post-distribution, 60% of the nets were in serviceable condition. Survivorship of nets was 97% at six months and 86% at twelve months. For the IRS, coverage decreased with each subsequent round (approximately every six months), from 85% to 76% to 70% to 64%. WHO cone bioassay results showed a mean mortality of 46% and 74% for deltamethrin and 76% for alpha-cypermethrin. Taken together, these data raise serious concerns about the entomological efficacy of both the LLINs and IRS used in the study area. To ensure that vector control interventions are performing as expected, and to enhance their community acceptance and use, we recommend rigorous quality control monitoring and pilot testing prior to widespread distribution and implementation.