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Background Indoor residual spraying (IRS), the coating of interior walls of houses with insecticides, is common in malaria-endemic areas. While important in malaria control, IRS potentially exposes residents to harmful insecticides. The World Health Organization recommends steps to minimize exposure; however, no programme has focused on educating populations. Methods A dramatic presentation and song were developed by study personnel and performed by lay performers in order to spread awareness of the importance of IRS and to minimize insecticide exposure. Performances were staged at 16 sprayed villages in the Vhembe District of Limpopo, South Africa, at which 592 attendees completed short questionnaires before and after the performance about behaviors that might limit insecticide exposure. Overall indices of the attendees’ change in knowledge of precautions to take prior to and after spraying to prevent insecticide exposure were analyzed using hierarchical mixed models to assess the effect of the performance on change in participants’ knowledge. Results Approximately half of attendees lived in homes that had been sprayed for malaria and 62% were female. Over 90% thought it better to allow IRS prior to the presentation, but knowledge of proper precautions to prevent exposure was low. The proportion answering correctly about proper distance from home during spraying increased from 49.4% pre-performance to 62.0% post-performance (RR = 1.26, 95% CI = 1.13, 1.41), and the proportion reporting correctly about home re-entry interval after spraying increased from 58.5 to 91.1% (RR = 1.54, 95% CI 1.35, 1.77). Attendees improved in their knowledge about precautions to take prior to and after spraying from mean of 57.9% correct to a mean of 69.7% (β = 12.1%, 95% CI 10.9, 13.4). Specifically, increased knowledge in closing cupboards, removing food and bedding from the home, covering immoveable items with plastic, and leading animals away from the home prior to spraying were observed, as was increased knowledge in sweeping the floors, proper disposal of dead insects, and discarding dirty washrags after spraying. Conclusions A dramatic presentation and song were able to increase the attendees’ knowledge of precautions to take prior to and after spraying in order to limit their insecticide exposure resulting from IRS. This approach to community education is promising and deserves additional study.

Despite its epidemiological importance, the impact of insecticide resistance on vector-parasite interactions and malaria transmission is poorly understood. Here, we explored the impact of Plasmodium infection on the level of insecticide resistance to dichlorodiphenyltrichloroethane (DDT) in field-caught Anopheles gambiae sensu stricto homozygous for the kdr mutation. Results showed that kdr homozygous mosquitoes that fed on infectious blood were more susceptible to DDT than mosquitoes that fed on noninfectious blood during both ookinete development (day 1 after the blood meal) and oocyst maturation (day 7 after the blood meal) but not during sporozoite invasion of the salivary glands. Plasmodium falciparum infection seemed to impose a fitness cost on mosquitoes by reducing the ability of kdr homozygous A. gambiae sensu stricto to survive exposure to DDT. These results suggest an interaction between Plasmodium infection and the insecticide susceptibility of mosquitoes carrying insecticide-resistant alleles. We discuss this finding in relation to vector control efficacy.

Currently, there is a strong trend towards increasing insecticide-based vector control coverage in malaria endemic countries. The ecological consequence of insecticide applications has been mainly studied regarding the selection of resistance mechanisms; however, little is known about their impact on vector competence in mosquitoes responsible for malaria transmission. As they have limited toxicity to mosquitoes owing to the selection of resistance mechanisms, insecticides may also interact with pathogens developing in mosquitoes. In this study, we explored the impact of insecticide exposure on Plasmodium falciparum development in insecticide-resistant colonies of Anopheles gambiae s.s. , homozygous for the ace-1 G119S mutation (Acerkis) or the kdr L1014F mutation (Kdrkis). Exposure to bendiocarb insecticide reduced the prevalence and intensity of P. falciparum oocysts developing in the infected midgut of the Acerkis strain, whereas exposure to dichlorodiphenyltrichloroethane reduced only the prevalence of P. falciparum infection in the Kdrkis strain. Thus, insecticide resistance leads to a selective pressure of insecticides on Plasmodium parasites, providing, to our knowledge, the first evidence of genotype by environment interactions on vector competence in a natural Anopheles–Plasmodium combination . Insecticide applications would affect the transmission of malaria in spite of resistance and would reduce to some degree the impact of insecticide resistance on malaria control interventions.