Quantifying individual variability in exposure risk to mosquito bites in the Cascades region, Burkina Faso
Background
The Cascades Region, Burkina Faso, has a high malaria burden despite reported high insecticide-treated mosquito net (ITN) use. Human and vector activities outside the hours when indoor interventions offer direct protection from infectious bites potentially increase exposure risk to bites from malaria-transmitting Anopheles mosquitoes. This work investigated the degree of variation in human behaviour both between individuals and through time (season) to quantify how it impacts exposure to malaria vectors.
Methods
Patterns in human overnight activity (18:00-06:00) to quantify time spent using an ITN across 7 successive nights in two rural communities, Niakore (N = 24 participants) and Toma (71 participants), were observed in the dry and rainy seasons, between 2017-2018. Hourly human landing Anopheles mosquito catches were conducted in Niakore specifically, and Cascades Region generally, between 2016-2017. Data were statistically combined to estimate seasonal variation in time spent outdoors and Anopheles bites received per person per night (bpppn).
Results
Substantial variability in exposure to outdoor Anopheles bites was detected within and between communities across seasons. In October, when Anopheles densities are highest, an individual’s risk of Anopheles bites ranged from 2.2 to 52.2 bites per person per night (bpppn) within the same week with variable risk dependent on hours spent indoors. Comparably higher outdoor human activity was observed in April and July but, due to lower Anopheles densities estimated, bpppn were 0.2 – 4.7 and 0.5 – 32.0, respectively. Males and people aged over 21 years were predicted to receive more bites in both sentinel villages.
Conclusion
This work presents one of the first clear descriptions of the degree of heterogeneity in time spent outdoors between people and across the year. Appreciation of sociodemographic, cultural and entomological activities will help refine approaches to vector control.
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This is a list of supplementary files associated with this preprint. Click to download.
Supplementary Material 1 S1.1 Interview questions asked of participants S1.2 Guidelines of topics addressed in informal focus group discussions S1.3 Template followed for structured observations S1.4 Summary of methods used to estimate biting risk per person per night • Fig. S1 • Fig. S2 • Fig. S3
Supplementary Data file 1 • Raw data for GLM 1: Predicting the time spent indoors per person per night • Raw data for GLM 2: Predicting the bites received per person per night • Raw mosquito data: indoors • Raw mosquito data: outdoors • Output for GLMM 1, model statistics and predictions • Output for GLMM 2, model statistics and predictions
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Quantifying individual variability in exposure risk to mosquito bites in the Cascades region, Burkina Faso
Posted 23 Dec, 2020
On 05 Dec, 2020
On 05 Dec, 2020
On 05 Dec, 2020
On 27 Nov, 2020
Received 30 Oct, 2020
Invitations sent on 30 Oct, 2020
On 30 Oct, 2020
On 23 Oct, 2020
On 22 Oct, 2020
On 22 Oct, 2020
Invitations sent on 11 Oct, 2020
On 11 Oct, 2020
Received 11 Oct, 2020
On 07 Oct, 2020
On 06 Oct, 2020
On 06 Oct, 2020
On 13 Sep, 2020
Received 15 Aug, 2020
Received 03 Apr, 2020
On 24 Mar, 2020
On 12 Mar, 2020
Invitations sent on 10 Mar, 2020
On 28 Feb, 2020
On 27 Feb, 2020
On 27 Feb, 2020
On 27 Feb, 2020
Background
The Cascades Region, Burkina Faso, has a high malaria burden despite reported high insecticide-treated mosquito net (ITN) use. Human and vector activities outside the hours when indoor interventions offer direct protection from infectious bites potentially increase exposure risk to bites from malaria-transmitting Anopheles mosquitoes. This work investigated the degree of variation in human behaviour both between individuals and through time (season) to quantify how it impacts exposure to malaria vectors.
Methods
Patterns in human overnight activity (18:00-06:00) to quantify time spent using an ITN across 7 successive nights in two rural communities, Niakore (N = 24 participants) and Toma (71 participants), were observed in the dry and rainy seasons, between 2017-2018. Hourly human landing Anopheles mosquito catches were conducted in Niakore specifically, and Cascades Region generally, between 2016-2017. Data were statistically combined to estimate seasonal variation in time spent outdoors and Anopheles bites received per person per night (bpppn).
Results
Substantial variability in exposure to outdoor Anopheles bites was detected within and between communities across seasons. In October, when Anopheles densities are highest, an individual’s risk of Anopheles bites ranged from 2.2 to 52.2 bites per person per night (bpppn) within the same week with variable risk dependent on hours spent indoors. Comparably higher outdoor human activity was observed in April and July but, due to lower Anopheles densities estimated, bpppn were 0.2 – 4.7 and 0.5 – 32.0, respectively. Males and people aged over 21 years were predicted to receive more bites in both sentinel villages.
Conclusion
This work presents one of the first clear descriptions of the degree of heterogeneity in time spent outdoors between people and across the year. Appreciation of sociodemographic, cultural and entomological activities will help refine approaches to vector control.
Figure 1
Figure 2
Figure 3