The Consequences of Declining Population Access to Insecticide Treated Nets (ITNs) on Net Use Patterns and Physical Degradation of Nets after 22 Months of Ownership

Abstract BackgroundAs the number of insecticide-treated nets (ITNs) in households (access) declines when nets wear out some household-members are prioritised to use the remaining ITNs. This study assessed how nets are allocated within households to individuals of different age categories as ITNs are lost or damaged and as new ITNs are obtained. The study also explored how ITN allocation affects ITN durability. MethodsA cross-sectional household survey and ITN durability study was conducted among 2,875 households across Tanzania to determine the proportion of nets that remain protective (serviceable) twenty-two months after net distribution aiming for universal coverage. Allocation of study nets within houses and re-allocation of ITNs when new Universal Replacement Campaign (URC) nets arrived in study households in Musoma District was also assessed.ResultsOnly 57.0% [95% CI: 53.9-60.1%] of households had enough ITNs for every household member (assuming one net covers every 2 members). In households with enough nets, 77.5% of members slept under ITNs. In households without enough nets, pregnant women (54.6%), children<5 (45.8%) and adults (42.1%) were prioritised, with fewer school-age children 5-14 (35.9%), youths 15-24 (28.1%) and seniors>65 (32.6%) sleeping under ITNs. Crowding ( 3 people slept under nets) was twice as common among people residing in houses without enough nets for all age groups apart from children<5. Nets were less likely to be serviceable if 3 people slept under them (OR=0.50 [95%CI 0.40-0.63]); if nets were used by school-age children (OR=0.72 [95%CI 0.56-0.93]) and if the net product was Olyset®. One month after the URC, only 23.6% [95%CI 16.7-30.6%] had access to an URC ITN in Musoma district. Householders in Musoma district continued the use of old ITNs even with the arrival of new URC nets.ConclusionUsers determined the useful life of ITNs and prioritized pregnant women and children<5 to serviceable ITNs. When household net access declines, users adjust by crowding under remaining nets, which further reduces ITN lifespan. School-age children that commonly harbour gametocytes that mediate malaria transmission are compelled to sleep under unserviceable nets, crowd under nets or remain uncovered. However, they were accommodated by the arrival of new nets. More frequent ITN delivery through the school-net program in combination with mass distribution campaigns is essential to maximise ITN effectiveness.