Insecticide‐treated nets for preventing malaria
What is the aim of this review?
Insecticide‐treated nets (ITNs) are a core intervention for malaria control. A previous version of this Cochrane Review showed they are very effective at reducing malaria‐related death and illness. Since the review was published, many areas affected by malaria have reported mosquito populations that are resistant to the insecticides used in ITNs. The aim of this review update was to evaluate the available evidence and find out whether ITNs continue to be effective at controlling the disease. Cochrane researchers collected and analysed relevant studies and assessed the overall certainty of the evidence.
What was studied in the review?
This review update summarized trials published since the previous review that evaluated the impact of ITNs on malaria‐related deaths and illness, compared to both no nets and untreated nets. After searching for relevant trials up to 18 April 2018, we identified three new randomized controlled trials (studies in which participants are assigned to a treatment group using a random method). In total, we included 23 trials, enrolling more than 275,000 adults and children, to evaluate the effectiveness of ITNs for reducing the burden of malaria. The included studies provided evidence of the impact of ITNs on infection from two types of malaria parasites, Plasmodium falciparum and Plasmodium vivax.
What are the main results of the review?
Twelve trials (nine in Africa, one in Cambodia, one in Myanmar, and one in Pakistan) assessed the impact of ITNs in comparison to no nets. From these trials, we concluded that ITNs reduce the child mortality from all causes, corresponding to a saving of 5.6 lives each year for every 1000 children protected with ITNs (high‐certainty evidence). ITNs also reduce the number of P falciparumcases per person per year and the proportion of people infected with P falciparum parasites (high‐certainty evidence). ITNs probably reduce the number of P vivax cases per person per year and may reduce the proportion of people infected with P vivaxparasites (moderate‐certainty evidence).
Eleven trials (three in sub‐Saharan Africa, six in Latin America, and two in Thailand) assessed the impact of ITNs in comparison to untreated nets. From these trials, we concluded that ITNs probably reduce the child mortality from all causes, corresponding to a saving of 3.5 lives each year for every 1000 children protected with ITNs (moderate‐certainty evidence). ITNs also reduce the number of P falciparum cases per person per year (high‐certainty evidence), and probably reduce the proportion of people infected with P falciparum parasites (moderate‐certainty evidence). Whilst ITNs may also reduce the number of P vivax cases per person per year (low‐certainty evidence), it is unclear if the proportion of people infected with P vivax parasites is any lower in those using an ITN than those using an untreated net (very low certainty evidence).
In interpreting these results, we considered that there are a growing number of mosquito populations that have been shown to be able to survive exposure to the insecticides used in ITNs. However, it is currently unclear how quantitatively important this is, and this seems insufficient to downgrade the existing evidence of an effect of ITNs in preventing malaria‐related mortality and illness.
Key messages
ITNs, whether compared to no nets or to untreated nets, continue to be effective at reducing child mortality and malaria‐related illness in affected areas.