Update: Mosquito aquatic habitat modification and manipulation interventions to control malaria

Which permanent and temporary changes to the water environments of immature mosquitoes work better to reduce malaria in people?

Why is it important to reduce malaria in people?

Malaria has a very high impact on the health of the public, mostly in people in Africa and Asia. Strategies to reduce malaria have been studied for many years. Most strategies focus on reducing the number of immature mosquitoes (larvae and pupae) to prevent them from becoming adult mosquitoes, since it is the adult female mosquito that can spread malaria through biting people.

What are permanent and temporary changes to the environment of immature mosquitoes?

The water environments where immature mosquitoes live can be disturbed using permanent (modification) and temporary (manipulation) changes. Examples of permanent changes include construction of drainage canals, land levelling, and filling ditches. Examples of temporary changes include altering the flow of water in streams, draining canals, cutting grass, shading of water using plants. These interventions may be used on their own or together with other standard treatments, such as the regular application of insecticides to water bodies (larviciding).

What did we want to find out?

We wanted to find out which permanent and temporary changes to the environment of immature mosquitoes reduce malaria in people (clinical outcomes), and the quantity of immature and adult mosquitoes (entomological outcomes).

What did we do?

We searched for studies that looked at permanent and temporary changes to the environment of immature mosquitoes compared to no intervention or a different permanent or temporary change. We compared and summarized the results of the studies and rated our confidence in the evidence, based on factors such as study methods.

What did we find?

The review included 16 studies that used a range of different randomized and non‐randomized study designs. Eleven studies were conducted in Africa and five in Asia. Only a few studies reported clinical outcomes, with most focussing on the number of immature mosquitoes, or adult mosquitoes, or both (entomological outcomes). We found there was some evidence to support the use of permanent (modification) and temporary (manipulation) changes to the water environments to reduce the number of immature mosquitoes in specific settings. However, when looking at clinical outcomes, 1. the effect of habitat manipulation on malaria parasite prevalence and clinical malaria incidence was unclear; 2. malaria parasite prevalence may be reduced when using habitat manipulation with larviciding; 3. combining manipulation and modification with larviciding probably makes little or no difference to malaria parasite prevalence and haemoglobin levels.

What are the limitations of the evidence?

The review included a wide range of different changes to the water environment of immature mosquitoes, with some combining them with water treatments (larviciding), which meant that very few studies looked at the same intervention. Many of the included studies had issues regarding how well they were conducted.

How up to date is the evidence?

This review updates a 2013 Cochrane Review. The evidence is up to date to 30 November 2021.