Control of Triatoma infestans in an area with pyrethroid resistant populations”

CARDINAL MV; GASPE MS; LAIÑO, M.A.; ALVEDRO A; ENRIQUEZ GF,; MACCHIAVERNA NP; GÜRTLER RE

La Plata

Congreso; II Latin American Society for Vector Ecology Congress (LA SOVE 2022); 2022

Several, geographically wide-spread pyrethroid-resistant Triatoma infestans populations have been detected in the Argentine Chaco posing a severe obstacle to the ongoing elimination efforts. We conducted a placebo-controlled before-and-after efficacy trial in 28 infested sites in Castelli (Argentine Chaco) over 22 months. All 72 dogs initially present received either an oral dose of fluralaner (treated group) or placebo (control group) at month 0 posttreatment (MPT). Preliminary results justified treating all 38 control-house dogs with fluralaner 1 month later, and 71 of 78 existing dogs at 7 MPT. Site-level infestation and triatomine abundance were evaluated using timed manual searches with a dislodging aerosol. Vector infection was mainly determined by kDNA-PCR and blood meal sources by ELISA. In the fluralaner-treated group, infestation dropped significantly from 100% at baseline to 18-19% over 6–22 MPT whereas mean abundance fell highly significantly from 5.5 to 0.6 triatomines per unit effort. In the placebo group infestation dropped similarly post-treatment. The overall prevalence of T. cruzi infection steadily decreased from 13.8% at 0–1 MPT (baseline) to 6.4–2.3% thereafter while in domiciles, kitchens and storerooms it dropped from 17.4% to 4.7–3.3%. Most infected triatomines occurred in domiciles and were human-fed. Infected-bug abundance plummeted after fluralaner treatment and remained marginal or nil thereafter. The human blood index of triatomines collected in domiciles, kitchens and storerooms highly significantly fell from 42.9% at baseline to 5.3–9.1% over 6–10 MPT, to increase to 36.8% at 22 MPT. Dog blood meals occurred before fluralaner administration only. The cat blood index increased from 9.9% at baseline to 57.9–72.7% over 6–10 MPT and dropped to 5.3% at 22 MPT, whereas chicken blood meals rose from 39.6% to 63.2–88.6%. Fluralaner severely impacted infestation and transmission-related indices over nearly two years, causing evident effects at 1 MPT, and deserves larger efficacy trials.