Fluralaner administered to dogs reduced house infestation and abundance of Triatoma infestans in the Argentine Chaco: a cluster-randomized trial

Insecticide resistance challenge vector control efforts worldwide. Alternative control tools, such as vector intoxication through their blood meals (xenointoxication), have attracted wide interest. Here, we conducted a cluster-randomized trial to assess the effectiveness of treating dogs with fluralaner to reduce house infestation and relative abundance of Triatoma infestans in a region with predominantly high pyrethroid resistance. The trial included 10 treated and 10 control clusters in Juan Jose Castelli (Chaco, Argentina), totaling 203 households. Dogs in treated clusters received an oral dose of fluralaner, whereas no treatment was offered to dogs in control clusters. House infestation and triatomine abundance was assessed at 0 and 10 month post-treatment (MPT) by timed-manual searches (TMS) using a flushing-out aerosol. COVID-19-related lockdown restrictions during 2020 determined that house infestation at 2 and 8 MPT was assessed through householder reports by telephone. An out-of-trial rescue treatment with fluralaner targeted control clusters and infested houses at 10 MPT. House infestation was re-assessed through TMS at 14 and 22 MPT. The trial treated 314 dogs, a 72% treatment coverage of all dogs registered at the treated arm. Cluster-level analysis adjusted for baseline infestation revealed that fluralaner treatment significantly reduced TMS-based estimates of house infestation by 47% at 10 MPT, while triatomine relative abundance significantly decreased by 70% relative to the control clusters, as shown by a random-effects negative binomial model with cluster identity as the random factor. Through householder-based triatomine surveillance, fluralaner treatment was associated with a negative trend in the odds of house infestation over 0–8 MPT. Dead triatomines were reported tenfold more frequently in baseline-infested houses from the treated clusters than at their control counterparts. No fluralaner-related adverse effect was reported by dog owners . In an out-of-trial rescue treatment of dogs initiated at 10 MPT, house infestation and triatomine abundance plummeted over 14–22 MPT at the treated houses, while infestation strongly increased among untreated dwellings. Fluralaner administered to dogs significantly reduced house infestation and triatomine relative abundance by moderate amounts relative to control dwellings. Future studies should evaluate the cost-effectiveness of multi-host treatment with fluralaner within an integrated vector control strategy bolstered by community engagement.