Knockdown Effects of Pyrethroid and Neonicotinoid-Treated Nets on Rhodnius prolixus

Kissing bugs (Rhodnius prolixus) are vectors of Trypanosoma cruzi, posing risks to military personnel and working dogs in endemic regions. This study quantified time-dependent knockdown of R. prolixus on commercial 300-series (80% blockage) netting treated with dinotefuran (neonicotinoid) or esfenvalerate (pyrethroid) under controlled laboratory conditions. Laboratory-reared adult R. prolixus were exposed to 8.2 × 8.2 cm net clippings in modified WHO cone bioassays. Four insects per replicate were exposed for 3, 6, 9, 12, or 15 minutes (five replicates per exposure × treatment; N = 300, including untreated controls). Knockdown was assessed at 1-hour post-exposure. Data were analyzed with two-way ANOVA with post-hoc pairwise comparisons (emmeans), three-parameter log-logistic models to estimate KD₅₀, and probit regression to calculate time-to-response metrics (KT₅₀/KT₉₀) with confidence intervals and model diagnostics. Knockdown increased with exposure time for both insecticides, with negligible effect in controls. Dinotefuran acted significantly faster, achieving ≥85% knockdown by 6 minutes, whereas esfenvalerate required approximately 12 minutes to reach similar levels; both reached 100% knockdown by 15 minutes. ANOVA indicated significant main effects of insecticide and exposure time, as well as a significant interaction (P ≤ 0.018), reflecting differing temporal dynamics. Pairwise comparisons identified a significant advantage for dinotefuran at 9 minutes (P = 0.001). Log-logistic modeling yielded KD₅₀ ≈ 4.0 min for dinotefuran versus ≈ 211 min for esfenvalerate, although estimates were imprecise. Probit regression corroborated the faster action of dinotefuran (KT₅₀ ≈ 0.18 min; KT₉₀ ≈ 6.1 min) compared with esfenvalerate (KT₅₀ ≈ 1.9 min; KT₉₀ ≈ 12.9 min), with good model fit. Although both dinotefuran and esfenvalerate treated nets have a knockdown effect on R. prolixus, Dinotefuran-treated netting produced substantially faster knockdown of R. prolixus than esfenvalerate-treated netting, consistent with their distinct neurophysiological modes of action. These findings support the use of neonicotinoid-treated netting as a rapid-acting barrier in military operational environments where brief insect contact occurs or pyrethroid efficacy may be compromised.