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. 2020 Jan 2;221(2):304-312.
doi: 10.1093/infdis/jiz453.

The Impact of Multiple Rounds of Indoor Residual Spraying on Malaria Incidence and Hemoglobin Levels in a High-Transmission Setting

Kate Zinszer  1   2 , Katia Charland  1 , Sarah Vahey  2 , Deepa Jahagirdar  3 , John C Rek  4 , Emmanuel Arinaitwe  4 , Joaniter Nankabirwa  4 , Kathryn Morrison  5 , Margaux L Sadoine  1   2 , Marc-Antoine Tutt-Guérette  1   2 , Sarah G Staedke  6 , Moses R Kamya  4   7 , Bryan Greenhouse  8 , Isabel Rodriguez-Barraquer  8 , Grant Dorsey  8
Affiliations

The Impact of Multiple Rounds of Indoor Residual Spraying on Malaria Incidence and Hemoglobin Levels in a High-Transmission Setting

Kate Zinszer et al. J Infect Dis. .

Abstract

Background: Indoor residual spraying (IRS) is widely used as a vector control measure, although there are conflicting findings of its effectiveness in reducing malaria incidence. The objective of this study was to estimate the effect of multiple IRS rounds on malaria incidence and hemoglobin levels in a cohort of children in rural southeastern Uganda.

Methods: The study was based upon a dynamic cohort of children aged 0.5-10 years enrolled from August 2011 to June 2017 in Nagongera Subcounty. Confirmed malaria infections and hemoglobin levels were recorded over time for each participant. After each of 4 rounds of IRS, malaria incidence, hemoglobin levels, and parasite density were evaluated and compared with pre-IRS levels. Analyses were carried out at the participant level while accounting for repeated measures and clustering by household.

Results: Incidence rate ratios comparing post-IRS to pre-IRS incidence rates for age groups 0-3, 3-5, and 5-11 were 0.108 (95% confidence interval [CI], .078-.149), 0.173 (95% CI, .136-.222), and 0.226 (95% CI, .187-.274), respectively. The mean hemoglobin levels significantly increased from 11.01 (pre-IRS) to 12.18 g/dL (post-IRS).

Conclusions: Our study supports the policy recommendation of IRS usage in a stable and perennial transmission area to rapidly reduce malaria transmission.

Keywords: Uganda; children; hemoglobin; indoor residual spraying; malaria.

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Figures

Figure 1.
Figure 1.
Cohort participants over time and incident episodes of malaria from August 2011 to June 2017. Each line represents a cohort participant and each incident malaria episode is demarcated. IRS, indoor residual spraying.
Figure 2.
Figure 2.
Weekly overall incidence rate across all cohort participants by week from August 2011 to June 2017. January 1, 2014 is indicated by a dotted line. Significant decreases in the trend were detected from weeks 6–9 after an indoor residual spraying (IRS) round began, whereas significant increases in the trend were detected from weeks 24–44 across the various spraying rounds.
Figure 3.
Figure 3.
Adjusted incidence rate ratio (IRR) comparing post-indoor residual spraying (IRS) incidence to pre-IRS weekly incidence stratified by age group. All age groups experienced significant reductions in malaria incidence with the youngest age group (0–3 year olds) having the largest reductions. These results are based on the restricted baseline period of January 1, 2014 onwards. CI, confidence interval.
Figure 4.
Figure 4.
Adjusted mean hemoglobin levels per indoor residual spraying (IRS) interval for incident and all cohort members. There were significant increases in hemoglobin levels in both groups, when comparing pre-IRS levels to IRS 4. These results are based on the restricted baseline period of January 1, 2014 onwards. CI, confidence interval.
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References

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