P 26 - Successful control of Triatoma dimidiata with residual application of a microencapsulated formulation of pirimiphos-methyl (Actellic 300cs) in southeast Mexico.

Triatoma dimidiata, the main vector of Trypanosoma cruzi throughout south Mexico and Central America, infest domiciles and peridomestic ecotopes of rural communities. This study reports the effect of the residual application of the organophosphate pirimiphos-methyl, in a microencapsulated formulation (Actellic 300cs®) for the control of intradomiciliary and peridomestic T. dimidiata in the rural community of Tekik de Regil in Yucatan, Southeast Mexico. A two-arm entomological randomized trial was carried out between March and October 2022. Timed Manual Collections (TMC) characterized house and peridomicile infestation by T. dimidiata prior (baseline) and monthly after spraying for up 6 months. A total of 122 premises surveyed at baseline (61 positive and 61 negatives to T. dimidiata) were randomly allocated 1:1 to treatment and control groups. Monthly post-spraying entomological surveys (May-Oct) with TMC were carried-out in a random sample of ten houses (5 positive & 5 negative) from each arm. Post-treatment domestic infestations were only detected in the control group (2/60 houses, 3.3%). Cumulative (across all post-spraying surveys) peridomestic infestation was significantly higher in the control arm (31.7%; 19/60) compared to the treatment arm (11.7%; 7/60) (X2=0.007, p< 0.01). The for a cumulative 6-month estimated efficacy of the intervention (% reduction in treatment versus control arm) was 65% (95% CI: 21%-86%). A single application of Actellic 300cs reduced T. dimidiata infestations by more than 60% for up to 6 months post treatment and is an alternative formulation for the control of triatomines in Mexico.