Evaluating a novel multi-species vector control tool for humanitarian crises: the efficacy of attractive targeted sugar baits among forcibly displaced populations in Northern Nigeria.

Background: Armed conflicts, natural disasters and forced population displacement have escalated dramatically since the 1990s. By mid-2024, the total number of people driven from their homes, often surviving in very harsh conditions for years, reached 122.6 million globally. In emergencies characterised by flimsy shelters, food insecurity, inadequate sanitation, poor access to health services and increased exposure to blood-feeding insects, diseases such as malaria, dengue and leishmaniasis cause high levels of morbidity and mortality. Conventional vector control interventions are inadequate in these settings due to operational and biological limitations. Novel vector control tools which are lightweight, easy to use and effective against multiple vector species are urgently needed to protect displaced populations. 

Methods: We conducted a 6-month, 2-arm community field trial in two internally displaced people camps in Maiduguri, Nigeria, to evaluate the entomological efficacy of attractive targeted sugar baits (ATSB). Monthly entomological monitoring measured changes in adult and immature vector density. Intervention acceptability was assessed using focus group discussions and a cross-sectional survey. To investigate environmental drivers of vector abundance, which might influence field outcomes, a hybrid approach of unsupervised and supervised machine learning regression models was developed using composite demographic, bioclimatic and ecological remote sensing data. 

Results: ATSB demonstrated a significant impact on indoor female Anopheles gambiae s.l. density (IRR: 0.140 [95% CI: 0.093–0.212]; p < 0.0001) and indoor blood-fed An. gambiae s.l. density (IRR: 0.0193 [95% credible interval: 0.0111–0.0356]). ATSB also significantly reduced indoor blood-fed Aedes aegypti (IRR: 0.0746 [95% credible intervals: 0.00884–0.502]). More than 97% of camp residents showed high levels of acceptance for ATSB, including willingness to pay. The strongest environmental predictors of An. gambiae s.l. occurrence were composite indices of vegetation water content, soil moisture, moist canopy, landcover diversity, urbanisation and normalised and enhanced vegetation index which together contributed to 73.5% of the final model. 

Conclusions: Field trial findings strongly support the use of ATSB to control sympatric malaria and dengue vector populations in humanitarian crises. Remote sensing analysis identified key drivers of An. gambiae s.l. occurrence providing a high-resolution environmental profile where ATSB achieved an entomological impact against multiple vector species.