Treatment of dogs with fluralaner reduced pyrethroid-resistant Triatoma infestans abundance, Trypanosoma cruzi infection and human-triatomine contact in the Argentine Chaco.BACKGROUND
 Triatomine elimination efforts and the interruption of domestic transmission of Trypanosoma cruzi are hampered by pyrethroid resistance.  Fluralaner, a long-lasting ectoparasiticide administered to dogs, substantially reduced site infestation and abundance of pyrethroid-resistant Triatoma infestans Klug (Heteroptera: Reduviidae) in an ongoing 10-month trial in Castelli (Chaco Province, Argentina).  We assessed the effects of fluralaner on vector infection with T. cruzi and blood meal sources stratified by ecotope and quantified its medium-term effects on site infestation and triatomine abundance.


 We conducted a placebo-controlled, before-and-after efficacy trial of fluralaner in 28 infested sites over a 22-month period.  All dogs received either an oral dose of fluralaner (treated group) or placebo (control group) at 0 month post-treatment [MPT].  Placebo-treated dogs were rescue-treated with fluralaner at 1 MPT, as were all eligible dogs at 7 MPT.  Site-level infestation and abundance were periodically assessed by timed manual searches with a dislodging aerosol.  Vector infection was mainly determined by kDNA-PCR and blood meal sources were determined by enzyme-linked immunosorbent assay.


 In fluralaner-treated households, site infestation dropped from 100% at 0 MPT to 18-19% over the period 6-22 MPT while mean abundance plummeted from 5.5 to 0.6 triatomines per unit effort.  In control households, 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% and subsequently 2.3% thereafter, while in domiciles, kitchens and storerooms it dropped from 17.4% to 4.7% and subsequently 3.3% thereafter.  Most infected triatomines occurred in domiciles and had fed on humans.  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 the period 6-10 MPT, increasing 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 the period 6-10 MPT and dropped to 5.3% at 22 MPT, whereas chicken blood meals rose from 39.6% to 63.2-88.6%.


 CONCLUSION
 Fluralaner severely impacted infestation- and transmission-related indices over nearly 2 years, causing evident effects at 1 MPT, and deserves larger efficacy trials.
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