Monitoring long-lasting insecticidal net (LLIN) durability to validate net serviceable life assumptions, in Rwanda

Abstract

BackgroundTo validate assumptions about the length of the distribution–replacement cycle for long-lasting insecticidal nets (LLINs) in Rwanda, the Malaria and other Parasitic Diseases Division, Rwanda Ministry of Health, used World Health Organization methods to independently confirm the three-year LLIN serviceable life span recommendation of WHO.MethodsApproximately 3,000 coded LLINs, distributed as part of a national campaign, were monitored in six sites, by means of six–monthly visits to selected houses. Two indicators, survivorship/attrition, a measure of the number of nets remaining, and fabric integrity, the proportion of remaining nets in either ‘good’, ‘serviceable’ or ‘needs replacement’ condition, based on holes in the net material, were tracked. To validate the assumption that the intervention would remain effective for three years, LLIN coverage, calculated using either survivorship, or integrity, by removing nets in the ‘needs replacement’ category from the survivorship total, was compared with the predicted proportion of nets remaining, derived from a net loss model, that assumes an LLIN serviceable life of three years.ResultsAfter two years, there was close agreement between estimated LLIN survivorship at all sites, 75% (range 64-84%), and the predicted proportion of nets remaining, 75%. However, when integrity was considered, observed survivorship at all sites, declined to 42% (range 10-54%).ConclusionsMore than half, 58%, of the LLINs fell into the ‘needs replacement’ category after two years. While these nets were counted for survivorship, they were judged to be of little-to-no benefit to a user. Therefore, when integrity was taken into account, survivorship was significantly lower than predicted, suggesting that net serviceable life was actually closer to two, rather than three years, and, by extension, that the impact of the intervention during year three of the LLIN distribution-replacement cycle could be well below that seen in years one and two.

Access to and use of long-lasting insecticidal nets and factors associated with non-use among communities in malaria-endemic areas of Al Hudaydah governorate in the Tihama region, west of Yemen

“…Furthermore, there is no monitoring on the durability or loss of the net for replacement which might lead to the reduction in the coverage level [26, 28–30]. The use to access ratio in this study was 0.37.…”

Susceptibility of Anopheles gambiae to insecticides used for malaria vector control in Rwanda

“…However, the gains made are fragile due to the decrease of efficacy of interventions, partially as a result of insecticide resistance development that has spread throughout Africa [4, 23, 24]. Rwanda achieved universal coverage with LLINs in 2011, but the major challenge is to maintain this coverage and use with effective mosquito nets, especially after it was recently reported for Rwanda that LLIN effectiveness lasts less than 3 years due to the rapid loss of insecticidal activity and physical deterioration in the field [25]. LLIN deterioration problems were also shown in recent findings from Senegal where damaged nets provided less protection from malaria compared to intact ones [26].…”

Insecticide Resistance in East Africa — History, Distribution and Drawbacks on Malaria Vectors and Disease Control

“…In East Africa, several intervention strategies are set to reduce morbidity and mortality from malaria. Effective measures of malaria control have been achieved mainly through the use and high coverage of IRS and scaling up of LLINs in Tanzania [24,25], Kenya [26], Uganda [27], Ethiopia [28] and Rwanda [29]. Community involvement has been another strategy in malaria prevention in different parts of East Africa [10,27,28].…”