During a malaria outbreak investigation in a district in Odisha, a field epidemiologist identifies a cluster of 47 cases of Plasmodium vivax malaria within a 2 km radius over 6 weeks. Entomological surveys reveal high densities of Anopheles culicifacies breeding in nearby rice paddies and open wells. The district has achieved >85% bed net coverage but <30% of nets are insecticide-treated nets (ITNs). What is the most appropriate next step in outbreak control?