First Report of Colonies of Sylvatic Triatoma infestans (Hemiptera: Reduviidae) in the Paraguayan Chaco, Using a Trained Dog

Abstract

In the Gran Chaco region, control of Triatoma infestans has been limited by persistent domestic infestations despite the efforts of the Vector Control Services. In Paraguay, this region is the highest endemic area in the country, showing high levels of indoor and outdoor infestation. Although sylvatic T. infestans have been found in the Bolivian and Argentine Chaco, similar searches for sylvatic populations of this species in Paraguay had been unsuccessful over the last 20 years. Here we present a new approach to detecting sylvatic Triatominae, using a trained dog, which has successfully confirmed sylvatic populations of T. infestans and other triatomine species in Paraguay. A total of 22 specimens corresponding to dark morph forms of T. infestans were collected, and 14 were confirmed as T. infestans by the mitochondrial cytochrome B gene analysis. Through this analysis, one of which were previously reported and a second that was a new haplotype. Triatomines were captured from amongst vegetation such as dry branches and hollows trees of different species such Aspidosperma quebracho-blanco, Bulnesia sarmientoi and Stetsonia coryne. The colonies found have been small and without apparent infection with Trypanosoma cruzi. During the study, Triatoma sordida and Triatoma guasayana have also been found in ecotopes close to those of T. infestans.

Author Summary

Confirmation of sylvatic colonies of Triatoma infestans has a significant connotation for Paraguay. Prior to our findings, we believed this vector —unlike in other regions of the Gran Chaco—was living exclusively in domestic and peridomestic habitats. We never considered the possibility of sylvatic species re-infesting domiciliary dwellings. After this discovery, the frame of transmission dynamics of Trypanosoma cruzi in the Paraguayan Chaco proposes new research perspectives. This also opens the door to promote knowledge regarding potential genetic flows between different T. infestans populations, reservoirs associated with their colonies, as well as their impact over control actions. Fieldwork for wild species identification is difficult and often unsuccessful, we used several techniques and tools, proven by others such as light traps, and mouse-baited sticky traps however, the triatomine collection in our study area was scarce or null. Incorporating a trained dog – NERO – to our work team has been a highly successful and productive initiative. The surprising ability NERO has shown will enable us to provide specific data regarding the still unknown wild ecotopes of T. infestans, as well as the potential use of trained dogs as a community surveillance tool of triatomine species considered particularly important for public health.