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Abstract Introduction . Insecticide treated nets (ITNs) contributed significantly to the decline in malaria since 2000. Their protective efficacy depends not only on access, use, and net integrity, but also location of people within the home environment and mosquito biting profiles. Anopheline mosquito biting and human location data were integrated to identify potential gaps in protection and better understand malaria transmission dynamics in Busia County, western Kenya. Methodology . Direct observation of human activities and human landing catches (HLC) were performed hourly between 1700 to 0700 hrs. Household members were recorded as home or away; and, if at home, as indoors/outdoors, awake/asleep, and under a net or not. Aggregated data was analyzed by weighting hourly anopheline biting activity with human location. Standard indicators of human-vector interaction were calculated using a Microsoft Excel template. Results . There was no significant difference between indoor and outdoor biting for An. gambiae s.l. (RR = 0.82; 95% CI 0.65-1.03); significantly fewer An. funestus were captured outdoors than indoors (RR= 0.41; 95% CI 0.25-0.66). Biting peaked before dawn and extended into early morning hours when people began to awake and perform routine activities, between 0400-0700 hrs for An. gambiae and 0300-0700 hrs for An. funestus . The study population away from home peaked at 1700-1800 hrs (58%), gradually decreased and remained constant at 10% throughout the night, before rising again to 40% by 0600-0700 hrs. When accounting for resident location, nearly all bites within the peri-domestic space occurred indoors for unprotected people (98%). Using an ITN while sleeping was estimated to prevent 79% and 82% of bites for An. gambiae and An. funestus respectively. For an ITN user, most remaining exposure to bites occurred indoors in the hours before bed and early morning. Conclusion. While use of an ITN was estimated to prevent most vector bites in this context, results suggest gaps in protection, particularly in the early hours of the morning when biting peaks and many people are awake and active. Assessment of additional human exposure points, including outside of the peri-domestic setting, are needed to guide supplementary interventions for transmission reduction.
Odero et al. (Tue,) studied this question.