Insecticide-treated bed nets and curtains reduce child mortality by 17% and severe malaria episodes by 44%.
Photos by: World Bank Yuri Kozyrev (R))
Why are insecticide-treated bed nets and curtains important?
Insecticide-treated bed nets and curtains (ITNs) are mosquito nets that are treated with insecticide, providing protection to populations at risk of malaria sleeping under them by repelling and killing mosquitoes that come into contact with them. ITN delivery programs are one of the four main strategies for reducing malaria mortality and morbidity, and the World Health Organization (WHO) recommends ITNs as the core intervention for malaria control. Many large scale ITN programs have now been implemented.
Do ITNs work?
- ITNs reduces child mortality by 17%.
- ITNs also reduces episodes of clinical uncomplicated malaria by almost 50%.
- Between 2010 and 2015, as the at-risk population sleeping under an ITN rose, malaria incidence decreased by 21% and malaria-related deaths have decrased by 29%.1
Equity: do ITNs work in the disadvantaged?
- A large proportion of the malaria disease burden is among disadvantaged populations. Therefore, ITNs can reduce child mortality among disadvantaged populations.
- In addition, non-intervention areas within close proximity to intervention areas also had reductions in child mortality – this may be important for equity since those who are unable to purchase an ITN may receive benefits from neighbours using ITNs.
Intervention Delivery
- The WHO recommends a miminum target impregnation dose for bed nets or curtains treated with a synthetic pyrethroid insecticide as follows:
- 200 mg/m2 permethrin or etofenprox, 30 mg/m2 cyfluthrin, 20 mg/m2 alpha‐cypermethrin, 10 mg/m2 deltamethrin/lambda‐cyhalothrin.
- The ITNs were treated with permethrin, lambdacyhalothrin, or deltamethrin (range from 10-1000 mg/m2).
Population and Setting
- 23 studies were included in this review. 6 of the 7 studies that reported on child mortality were conducted in sub-Saharan Africa in highly malaria-endemic regions.
- 21 of the 23 studies included in this review were conducted in low and middle income countries.
- The trials that were included in this review were conducted in sub-Saharan Africa (Burkina Faso, Cameroon, Gambia, Ghana, Ivory Coast, Kenya, Madagascar, Sierra Leone, and Tanzania), Latin America (Colombia, Ecuador, Nicaragua, Peru, and Venezuela), the Greater Mekong subregion (Cambodia, Myanmar, and Thailand), and Pakistan.
- The participants were children between 1 month and 5 years old.
Summary of Findings [SOF] Table:
Patient or population: Children 1 month to 5 years old
Settings: Communities in Sub-Saharan Africa, Latin America, the Greater Mekong subregion, Pakistan
Intervention: Insecticide treated bed nets and curtains
Comparison: No net or untreated bed nets and curtains
| Outcomes
| Anticipated absolute effects per year | Relative Effect
| No of Participants
| Quality of the evidence
| ||
| Risk without insecticide-treated bed nets and curtains (Control) | Risk difference with insecticide treated bed nets and curtains (95% CI) | |||||
| Child mortality (all cause) | Compared to no nets | RR 0.83 (0.77, 0.89) | 200,833 (5 studies) | High | ||
| 37.8 deaths per 1000 | 6.4 fewer deaths per 1000 (3.6 to 7.6 fewer) | |||||
| Compared to untreated nets | RR 0.67 (0.36 to 1.23) | 25,389 (2 studies) | moderate | |||
| 24.3 deaths per 1000 | 8 fewer deaths per 1000 (15.5 fewer to 5.6 more) | |||||
| P falciparum prevalencea | Compared to no nets | RR 0.83 (0.73 to 0.98) | 18.809 (6 studies) | high | ||
| 147 infections per 1000 | 25 fewer infections per 1000 (3 to 45 fewer) | |||||
| Compared to untreated nets | RR 0.91 (0.78 to 1.05) | 2,259 (3 studies) | moderate | |||
| 378 infections per 1000 | 34 fewer infections per 1000 (84 fewer to 19 more) | |||||
| P vivax prevalencea | Compared to no nets | RR 1.00 (0.75 to 1.34) | 10,967 (2 studies) | low | ||
| 130 infections per 1000 | 32 fewer infections to 45 more per 1000 | |||||
| Compared to untreated nets | RR 0.68 (0.25 to 1.85) | 350 (1 study) | very low | |||
| 39 infections per 1000 | 12 fewer infections per 1000 (29 fewer to 34 more) | |||||
| Severe malaria prevalence | Compared to no nets | RR 0.56 (0.38 to 0.82) | 31,173 (2 studies) | high | ||
| 15.1 episodes per 1000 | 6.6 fewer episodes per 1000 (2.7 to 9.4 fewer) | |||||
| Compared to untreated nets | ||||||
| *no trials reported this outcome | ||||||
| Anemia (mean packed cell volume (PCV), equivalent to the percentage hematocrit)b | Compared to no nets | Mean difference 1.29 (0.42 to 2.16) | 11,489 (5 studies) | high | ||
| 31.4 PCV | 1.3 percentage PCV higher (0.4 to 2.2 higher) | |||||
| Compared to untreated nets | Mean difference 0.48 (-0.54 to 1.50) | 1,909 (2 studies) | low | |||
| 32.8 PCV | 0.5 percentage PCV higher (0.5 lower to 1.5 higher) | |||||
a. “Prevalence” referring to the proportion of people infected by parasites that cause malaria b. A decreased PCV meaning red blood cell loss RR = relative rate; CI = confidence interval | ||||||
| Adverse Events: Not described in this review Other outcomes identified in the review were uncomplicated clinical episodes, and the incidence and cumulative evidence (within a given time frame) of each P falciparum, P vivax, and any Plasmodium species. A decrease in the rate of clinical episodes was identified in one of the included studies. The proportion of people experiencing a clinical episode of P falciparum was reported in five of the included studies, and a decrease was identified in two. The proportion of people experiencing a clinical episode of P vivax was reported in five of the included studies, and a decrease was identified in two. The proportion of people experiencing a clinical episode of any Plasmodium species was reported in four of the included studies, and a decrease was identified in one. [Full data can be found in the summary of findings table in the original review] | ||||||
| About quality of evidence (GRADE) | ||||||
| ||||||
Relevance of the review for disadvantaged communities
Insecticide-treated bed nets and curtains reduce child mortality by 17%.
| Finding | Interpretation |
| Equity – Which of the PROGRESS groups examined | |
| The included studies assessed the effects of ITNs on preventing mortality among children between 1 month and five years old. 6 out of 7 studies that reported child mortality were conducted in communities with stable malaria (high transmission rates) in Sub-Saharan Africa. Gender ratios were not reported. | ITNs are an effective prevention intervention for malaria among disadvantaged populations and result in lower child mortality rates. |
| Equity Applicability | |
| All of the included studies were Randomized Controlled Trials (RCTs) so the coverage and use rates may be higher than those expected in a community setting. | Most of the information in this review relates to ideal conditions and reports on the efficacy of ITNs rather than impact. In community settings, the effectiveness of ITNs may be lower and will depend on ITN coverage rates. Given the reduction in child mortality, ITNs should be promoted for malaria control. |
| Cost-equity | |
| The review did not report on the cost-effectiveness of ITNs in preventing malaria, however a separate cost analysis has been done that indicates that long-lasting ITNs are a cost-effective malaria prevention intervention.2 The WHO recommends mass free net distribution through campaigns and continuous distribution through channels such as the Expanded Program on Immunization as a cost-effective way to achieve high and equitable coverage.3 | While ITNs are cost effective, policy makers need to consider the cost of ITNs and whether they will be for free or subsidized. The cost of ITN distribution needs to be considered as well as any plans to follow up to measure ownership and usage. ITNs require retreatment with insecticides which requires additional resources. Distribution of longer-lasting ITNs may reduce the cost, but the cost of retreatment should be included in any ITN distribution program. |
| Monitoring & Evaluation for PROGRESS Groups | |
| ITN programs require monitoring to ensure that bednets are being distributed and used and to monitor child mortality rates. ITN programs require monitoring to ensure that bednets are being distributed and used, and to monitor child mortality rates. Additionally, there has been an increase in mosquito populations that have been shown to be able to survive exposure to the insectides used in ITNs (insecticide-resistant malaria vectors); while there is no strong evidence of resistance reducing ITN effectiveness, future research should continue to concentrate on monitoring the spread of insecticide resistance and continued effectiveness of ITNs.
| ITN programs should be monitored to determine the difference in impact on child survival according to coverage rates. In addition, efforts should be made to ensure that the most disadvantaged groups of the population have access to ITNs and ITN repair & re-treatment programs. The effectiveness of ITNs on mosquito mortality in areas of known insecticide-resistant mosquito populations should be monitored as well. |
1. Global technical strategy for malaria, 2016-2030. (2015). Geneva, Switzerland: WHO Press, World Health Organization.
2. Pulkki-Brännström, A. M., Wolff, C., Brännström, N., & Skordis-Worrall, J. (2012). Cost and cost effectiveness of long-lasting insecticide-treated bed nets - a model-based analysis. Cost effectiveness and resource allocation : C/E, 10, 5. https://doi.org/10.1186/1478-7547-10-5
3. Guidelines for Malaria Vector Control. Geneva: World Health Organization; 2019. 4, Recommendations on core interventions. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538119/
This summary update was prepared by Janina Ramos.
Comments on this summary? Please contact Jennifer Petkovic.