Spatial Repellents for the Prevention of Malaria in Kenya

Spatial repellents (SRs) have been widely used for the prevention of mosquito bites but their protective efficacy (PE) in reducing mosquito-borne diseases has never been evaluated in Africa. To address this knowledge gap, western Kenya was selected as a site to estimate the impact of a transfluthrin-based spatial repellent on malaria-related outcomes in Busia County, where baseline malaria transmission ranges from 2.5 to 4.1 new infections per person per year.

A total of 5,984 children between 6 months and <10 years of age will be enrolled in three separate cohorts (baseline, cohort 1 and cohort 2). A total of 2,040 children from among 60 clusters will be enrolled for a four-month baseline prior to placement of the SR intervention. After baseline, a total of 1,972 participants from among 58 clusters, will be enrolled into cohort 1 and followed for one year. Cohort 2, consisting of a total of 1,972 children, will be enrolled from among 58 clusters to provide a total of two years of follow up. Children who have been selected for inclusion in the baseline cohort will be eligible for selection to cohort 1 or 2 but not both.

Cohort 1 and Cohort 2 during intervention will be split into two groups, one to estimate the direct effect of the SR (total of 1,624 children, 812 per follow up year) and a second to estimate the degree of diversion (or mass effect) of mosquitoes and malaria transmission from persons protected by the SR to persons who are unprotected (total of 2,320 children, 1,160 per follow up year). All cohorts will be followed once every two weeks with finger prick blood samples taken once every 4 weeks to test for malaria or whenever a participant reports a recent (within 48 hours) history of fever.

The incidence of malaria in the baseline cohort will be used to validate underlying assumptions prior to intervention. The incidence of malaria in each cohort followed with intervention will be estimated and compared to determine the benefit of using an SR in an area with high, year-round transmission of malaria. Monthly collections of mosquitoes using CDC light traps will be conducted to determine if there are entomological correlates of SR efficacy that may be useful for the evaluation of new SR products. Quarterly human landing catches will be done to assess the behavioral effects of the SR. The primary hypothesis on PE against the first-time malaria infection will be estimated by comparing the hazard rates of first-time malaria infection between SR and placebo upon the completion of the study in the ITT population.

Inclusion criteria

• Children aged 6 months to <10 years
• Hb > 5mg/dl
• Sleeps in cluster >90% of nights during any given month
• No plans for extended travel (>1month) outside of home during study
• Not participating in another clinical trial investigating a vaccine, drug, medical device, or a medical procedure during the Trial
• Provision of informed consent form signed by the parent(s) or guardian
• Children not on regular malaria prophylaxis° such as Proguanil
• Willingness to take AL and no history of hypersensitivity to AL

Exclusion criteria

• Children < 6 months or ≥ 10 years
• Hb ≤ 5 mg/dL, or Hb < 6mg/dL with signs of clinical decompensation
• Sleeps in cluster <90% of nights during any given month
• Plans for extended travel (>1month) outside of home during study
• Participating or planned participation in another clinical trial investigating a vaccine, drug, medical device, or a medical procedure during the trial
• No provision of informed consent form signed by the parent(s) or guardian
• Children on regular malaria prophylaxis° such as Proguanil
• Unwillingness or refusal to take AL and history of AL hypersensitivity

• Other malaria prophylaxis medicines: Mefloquine, Atavaquone/Proguanil (Malarone), Doxycycline, Tafenoquine, Sulfadoxine-Pyrimethamine (Fansidar), Amodiaquine and Co-trimoxazole (Septrin)