Long-Lasting Insecticide-Treated Bed Nets

Long-lasting insecticide-treated bed nets (LLINs) are an effective way to curb malaria transmission in an endemic population. The World Health Organization (WHO) currently recommends free distribution of LLINs, which are factory-treated to remain effective for a minimum of three years and 20 washes (WHO 2007). WHO encourages full coverage for all people at risk of malaria in areas targeted for malaria prevention with LLINs, especially children under 5 and pregnant women (WHO 2015). In malaria-endemic areas, all at-risk population groups should be covered with LLINs, especially children under 5 and pregnant women (WHO 2016).

LLINs can be provided through a combination of mass free distributions and continuous distribution through multiple channels, with mass campaigns repeated at an interval of no more than three years and with continuous distribution channels functioning before, during, and after any mass campaign (WHO 2013). Campaigns are often not carried out on a national level, but rather are targeted to high-risk areas, or those with increasing epidemics, and are often closely linked to external funding. Appropriate social and behavior change communication messaging on the proper use and maintenance of LLINs is crucial; you should ensure it is always part of malaria prevention interventions.

Insecticide resistance is a growing concern that threatens the success of malaria vector control in the future. More than 60 countries with endemic malaria transmission have reported resistance to one or multiple insecticides; the poor, ad-hoc monitoring in most affected countries makes it more difficult to address the problem (Roll Back Malaria and WHO 2012). Consider including locally relevant information on insecticide resistance in your landscape analysis.

Measurement and data sources

Population-based surveys typically report household ownership and the use of bed nets during a certain period of time preceding the survey. Surveys report bed net ownership as the percentage of households with at least one bed net or at least one bed net for every two persons who stayed in the household the night before the survey. Surveys report bed net use as the percentage of the population that slept under a bed net the night before the survey.

Surveys that collect information related to coverage of LLINs include—

• Demographic and Health Surveys
• Malaria Indicator Surveys
• Multiple Indicator Cluster Surveys
• National Micronutrient Surveys
• Knowledge, Practice, and Coverage Surveys
• other research or evaluation activities.

Health monitoring information systems may also record information about the distribution of LLINs or other bed nets to pregnant women or young children, especially if the country includes this service as part of the antenatal care platform or well-child visits.

Methodological issues

• While WHO recommends that governments procure and distribute only LLINs, many other types of bed nets are still in use throughout the world; therefore, indicators of bed net ownership and usage often report results in categories of any bed net or LLIN. While the LLIN indicators provide the best picture of optimal protection against malaria, consider the discrepancies in coverage between the other types of bed nets.
• Always consider seasonality when interpreting malaria-related data, especially population-based surveys. Generally, survey reports indicate when the survey was conducted to ensure that data are interpreted appropriately. Malaria transmission rates—and, therefore, the implementation of prevention activities—at the time of data collection will affect comparability of these estimates over time and across studies. For instance, Demographic and Health Surveys often avoid the rainy season, given the difficulties inherent with data collection at this time, while Malaria Indicator Surveys are deliberately scheduled at this time to capture indicators during a season of high malaria transmission.
• Most population-based surveys ask about the use of a bed net the night before data collection and, subsequently, use that information as a proxy for consistent use throughout the year. Therefore, actual, regular use of LLINs or other bed nets is likely to be lower than reported in surveys.
• The hot, humid seasons often coincide with high malaria transmission. Bed nets, in general, reduce airflow and can be uncomfortable for the user, especially during the hot, humid months of the year, so usage may be particularly low during these months (von Seidlein et al. 2012).
• Distribution data do not reflect proper use by individuals, especially if the data do not track indicators of social and behavior change strategies. When administrative data is used to estimate coverage, WHO recommends using a correction factor of 1.6 users per ITN is used to estimate population access to ITNs, rather than assuming each ITN covers two users (WHO 2014)².