Risk of bias (ROBINS‐I)
Outcome assessed: primary outcome: parasite prevalence
Bias	Review authors' judgement	Signalling questions and responses	Support for judgement
Bias due to confounding	Moderate	1.1 Potential for confounding? Yes 1.4 Appropriate analysis to control for baseline confounding? Probably yes 1.5 Controlled for confounding domains measured validly and reliably? Probably yes 1.6 Control for postintervention variables? Yes 1.7 Appropriate analysis to control for baseline and time varying confounders? No	Adjusted for important confounders relating to rainfall, bed net use, age adjusted for. Controlled for postintervention variables relating to use of larviciding. But potential for other important confounders not adjusted for.
Bias in selection of participants into the study	Low	2.1 Selection of participants based on their characteristics? No 2.4 Start of follow‐up and intervention coincide? Yes	Selection made independent of characteristics and timings coincided.
Bias in classification of interventions	Low	3.1 Intervention groups clearly defined? Yes 3.2 Information to define intervention groups recorded at start of intervention? Yes 3.3 Classification of intervention status affected by knowledge of outcome or risk of outcome? Probably no	Intervention groups clearly defined, information used to classify groups was recorded at start of intervention, and classification of intervention probably unaffected by knowledge or risk of outcome.
Bias due to deviations from intended interventions	Low	4.1 Deviations from intended intervention? No	No evidence of deviations from intended intervention.
Bias due to missing data	Low	5.1 Outcome data available for all, or nearly all, participants? Probably yes 5.2 Participants excluded due to missing data on intervention status? Probably no 5.3 Participants excluded due to missing data on other variables? Probably no	Outcome data probably available for all participants, with none excluded due to missing intervention status or missing data on other variables.
Bias in measurement of outcomes	Moderate	6.1 Outcome measures have been influenced by knowledge of intervention? No 6.2 Outcome assessor aware of intervention received? Yes 6.3 Methods of outcome assessment comparable across groups? Yes 6.4 Systematic errors in measurement of outcome related to intervention? No	Method of measuring the outcome was appropriate, and did not differ between groups. Outcome assessor aware of intervention implemented. Assessment of outcome unlikely to be influenced by knowledge of intervention implemented.
Bias in selection of the reported result	Low	Reported effect estimate likely to be selected on 7.1 Multiple outcome measurements? No 7.2 Multiple analyses? No 7.3 Different subgroups? No	Numerical outcome unlikely to be selected based on results or multiple outcome measurements, analyses of the data, or multiple subgroups.
Overall bias	Moderate	—	Low risk of bias for most domains except for due to confounding and measurement of outcomes, which were moderate.