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. 2022 Nov 1;226(9):1657-1666.
doi: 10.1093/infdis/jiac361.

Irrigation-Induced Environmental Changes Sustain Malaria Transmission and Compromise Intervention Effectiveness

Guofa Zhou  1 , Elizabeth Hemming-Schroeder  1   2 , Brook Jeang  1 , Xiaoming Wang  1 , Daibin Zhong  1 , Ming-Chieh Lee  1 , Yiji Li  1   3 , Lauren Bradley  1 , Sabrina R Gobran  1 , Randy E David  1 , Benyl M Ondeto  4 , Pauline Orondo  5 , Harrysone Atieli  6   7 , John I Githure  7 , Andrew K Githeko  8 , James Kazura  9 , Guiyun Yan  1
Affiliations

Irrigation-Induced Environmental Changes Sustain Malaria Transmission and Compromise Intervention Effectiveness

Guofa Zhou et al. J Infect Dis. .

Abstract

Background: Irrigated agriculture enhances food security, but it potentially promotes mosquito-borne disease transmission and affects vector intervention effectiveness. This study was conducted in the irrigated and nonirrigated areas of rural Homa Bay and Kisumu Counties, Kenya.

Methods: We performed cross-sectional and longitudinal surveys to determine Plasmodium infection prevalence, clinical malaria incidence, molecular force of infection (molFOI), and multiplicity of infection. We examined the impact of irrigation on the effectiveness of the new interventions.

Results: We found that irrigation was associated with >2-fold higher Plasmodium infection prevalence and 3-fold higher clinical malaria incidence compared to the nonirrigated area. Residents in the irrigated area experienced persistent, low-density parasite infections and higher molFOI. Addition of indoor residual spraying was effective in reducing malaria burden, but the reduction was more pronounced in the nonirrigated area than in the irrigated area.

Conclusions: Our findings collectively suggest that irrigation may sustain and enhance Plasmodium transmission and affects intervention effectiveness.

Keywords: Plasmodium infection prevalence; indoor residual spraying; irrigation; malaria; molecular force of infection.

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Conflict of interest statement

Potential conflicts of interest. All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest.

Figures

Figure 1.
Figure 1.
(A and B) Seasonal changes in Plasmodium infection prevalence in different irrigation areas in Homa Bay (10 clusters each in irrigated and nonirrigated areas) detected by microscopy (A) and 18S rDNA polymerase chain reaction (PCR) (B).
Figure 2.
Figure 2.
Active case surveillance in Homa Bay: (A) biweekly dynamics of clinical malaria incidence (cases/1000 people/month) in the irrigated and nonirrigated areas, with shaded areas representing 95% confidence intervals; and (B) distribution of average clinical incidence in each study cluster. Each dot represents 1 cluster.
Figure 3.
Figure 3.
(A) Monthly dynamics of indoor-resting malaria vector density in Homa Bay and in Kisumu. (B) Monthly changes in Plasmodium infection prevalence of school-age children in different irrigation areas of Homa Bay and Kisumu detected by microscopy. Blood sampling was not done in most months from March 2020 to July 2021. Four clusters were selected in each irrigation zone of Homa Bay and 3 clusters in Kisumu for both surveys. The yellow arrows indicate the months when IRS was carried out in Homa Bay; no indoor residual spraying (IRS) was carried out in Kisumu.
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