What is the aim of this review?
Adult female Anopheles mosquitoes transmit the Plasmodium parasites that cause malaria. The aim of this Cochrane Review was to evaluate whether introducing fish that eat mosquito larvae and pupae (early life stages of mosquitoes) into water sources near where people live will decrease the adult Anopheles mosquito population and thus the number of people infected with Plasmodium parasites.
We do not know if introducing fish that eat mosquito larvae and pupae has an impact on the number of people with malaria or on the adult Anopheles mosquito population.
What was studied in the review?
The review authors examined the available research that evaluated introducing fish that eat larvae (‘larvivorous’) to Anopheles mosquito larval habitats in areas where malaria was common. Fifteen small studies looked at the effects of larvivorous fish on Anopheles larvae and pupae in different larval habitats, including localized water bodies (such as wells, domestic water containers, fishponds, and pools; seven studies), riverbed pools below dams (two studies), rice field plots (four studies), and water canals (two studies). These studies were undertaken in Sri Lanka (two studies), India (three studies), Ethiopia (one study), Kenya (two studies), Sudan (one study), Grande Comore Island (one study), Korea (two studies), Indonesia (one study), and Tajikistan (two studies). This is an update of a 2013 Cochrane Review and includes some older unpublished studies from Tajikistan and a new trial from India.
What are the main results of the review?
In our main analysis, we found no studies that looked at the effects of larvivorous fish on adult Anopheles mosquito populations or on the number of people infected with Plasmodium parasites. In our analysis exploring the effect of fish introduction on the number of Anopheles larvae and pupae in water collections, these studies produced inconsistent results on immature mosquito density (12 studies, unpooled data, very low certainty evidence). Some studies that measured the number of water sources with Anopheles larvae and pupae reported a reduction in the number of sites with Anopheles larvae and pupae after introducing fish (five studies, unpooled data, low certainty evidence). None of the included studies examined the effects of introducing larvivorous fish on other native species present, but these studies were not designed to do this. All included studies were at high risk of bias.
Before much is invested in this intervention, we need better research to determine the effect of introducing larvivorous fish on the number of people infected with malaria, and on adult Anopheles populations. Researchers need to use robust controlled designs with an adequate number of sites. In addition, researchers should explore the potential harms from introducing these fish on native fish and other non-Anopheles species.
How up-to-date is this review?
The review authors searched for studies published up to 6 July 2017.