An experimental hut study evaluating the impact of pyrethroid-only and PBO nets alone and in combination with pirimiphos-methyl-based IRS in Ethiopia

• Published in: Malaria Journal
• Main Authors: Delenasaw Yewhalaw, Meshesha Balkew, Endalew Zemene, Sheleme Chibsa, Peter Mumba, Cecilia Flatley, Aklilu Seyoum, Melissa Yoshimizu, Sarah Zohdy, Dereje Dengela, Seth Irish
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2022
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-022-04263-x; https://doaj.org/article/329a6fd7284f494a8b81253f1f8a79e9

Abstract Background Pyrethroid resistance observed in populations of malaria vectors is widespread in Ethiopia and could potentially compromise the effectiveness of insecticide-based malaria vector control interventions. In this study, the impact of combining indoor residual spraying (IRS) and insecticide-treated nets (ITNs) on mosquito behaviour and mortality was evaluated using experimental huts. Methods A Latin Square Design was employed using six experimental huts to collect entomological data. Human volunteers slept in huts with different types of nets (pyrethroid-only net, PBO net, and untreated net) either with or without IRS (Actellic 300CS). The hut with no IRS and an untreated net served as a negative control. The study was conducted for a total of 54 nights. Both alive and dead mosquitoes were collected from inside nets, in the central rooms and verandah the following morning. Data were analysed using Stata/SE 14.0 software package (College Station, TX, USA). Results The personal protection rate of huts with PermaNet® 2.0 alone and PermaNet® 3.0 alone was 33.3% and 50%, respectively. The mean killing effect of huts with PermaNet® 2.0 alone and PermaNet® 3.0 alone was 2% and 49%, respectively. Huts with PermaNet® 2.0 alone and PermaNet® 3.0 alone demonstrated significantly higher excito-repellency than the control hut. However, mosquito mortality in the hut with IRS + untreated net, hut with IRS + PermaNet® 2.0 and hut with IRS + PermaNet® 3.0 were not significantly different from each other (p > 0.05). Additionally, pre-exposure of both the susceptible Anopheles arabiensis laboratory strain and wild Anopheles gambiae sensu lato to PBO in the cone bioassay tests of Actellic 300CS sprayed surfaces did not reduce mosquito mortality when compared to mortality without pre-exposure to PBO. Conclusion Mosquito mortality rates from the huts with IRS alone were similar to mosquito mortality rates from the huts with the combination of vector control intervention tools (IRS + ITNs) and mosquito mortality ...