Insights from LLIN Post-Distribution Monitoring Surveys in the Dominican Republic's Malaria Transmission Foci: Implications for Quantification and Distribution Strategies

Background: Long-lasting insecticidal nets (LLINs) have been distributed in the Dominican Republic since 2008, and they remain the main vector control intervention used to pursue malaria elimination in the country. However, LLIN performance remains unclear due to a lack of monitoring over the past decade. Methods: We conducted a cross-sectional household survey to monitor LLIN coverage, access, use, physical integrity, washing and drying practices and the time people go to bed and wake up in the two main malaria foci of the country: Azua (4-6 months post distribution) and San Juan (one year post distribution). Results: The percentage of sleeping spaces that could be covered with an LLIN given the LLINs present in the household was 64% in Azua and 63% in San Juan, and with any net they were 75% in Azua and 80% in San Juan. Reported LLIN retention was 88.4% in Azua and 80.9% in San Juan. The percentage of people that had access to sleeping under an LLIN was 58.8% in Azua and 65.4% in San Juan. LLIN use was 32.3% in Azua and 50.5% in San Juan. Among people with full LLIN access, use was 48.8% in Azua and 75% in San Juan. Most LLINs remained in serviceable physical condition (96.4%, 88.9%) but those with holes were not repaired. Most LLINs were washed with aggressive products (65%, 86%), at a frequency that suggests they will be washed more than twenty times in three years (52%, 73%), and dried under the sun (75%, 90%). Conclusion: Poor washing and drying practices are prevalent in both areas, low LLIN use was observed in Azua and some LLIN coverage gaps were measured in both foci. Urgent behavioral change strategies are needed to improve LLIN care in both foci and increase LLIN use in Azua, alongside revisions to LLIN quantification methods to ensure full coverage of all sleeping spaces in use during distribution. Heterogeneities in LLINs use across foci suggest that LLIN need to be monitored in each distinct distribution area to identify individual gaps and promptly address them.