Authors
A Bacigalupo1; P Arroyo2; RA Gacitúa-Gajardo2; D Gajardo-Canto2; R Muñoz-Ramos2; JA Segura3; MJ Caniullán4; C Adones5; A Parra-Garcés6; PE Cattan2; KR Elmer1; MS Llewellyn1; 1 Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, UK, UK; 2 Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Chile; 3 Seremi de Salud Región Metropolitana, Unidad de Zoonosis y Control de Vectores, Chile; 4 Seremi de Salud Región de Atacama, Unidad de Zoonosis y Control de Vectores, Chile; 5 Seremi de Salud Región de Coquimbo, Unidad de Zoonosis y Control de Vectores, Chile; 6 Ministerio de Salud, Oficina de Zoonosis y Control de Vectores, Chile Discussion
Chagas disease is a neglected illness caused by the protozoan parasite Trypanosoma cruzi. Nearly six million people are infected and about 10,000 die annually as a consequence of this chronic disease. Transmission includes several routes, including vectorial, which involves hematophagous insects of the Subfamily Triatominae (Hemiptera: Reduviidae) that are primarily distributed in the Americas. Some triatomines have adapted to living inside human dwellings, and these species represent a higher infection risk, due to their contact rate with the inhabitants. Triatoma infestans is one of the species highly adapted to live in houses and is distributed in Peru, Bolivia, Brazil, Paraguay, Uruguay, Argentina and Chile. In Chile, T. infestans domestic colonies have been eliminated by residual insecticide spraying, but adults continue to invade houses. The interruption of intra-domiciliary transmission is currently based on governmental spraying of the house for three consecutive years after a specimen of this species is reported. Triatomines of the genus Mepraia are considered mainly sylvatic; however, they are frequently found in peridomestic areas, and can also invade houses. Due to repeated findings of T. infestans in Chilean dwellings, our goal was to detect sylvatic foci of this species in six endemic areas, to compare them with the specimens found inside houses.
We set ~60 georeferenced yeast-baited traps per night during 5 nights in each of the six sylvatic sites during the Southern hemisphere summer of 2020-2021, spanning a ~600 km latitudinal range that included arid, semiarid and Mediterranean climate. Triatomines were collected, classified, and placed in labelled flasks, protected from extreme environmental conditions. We captured 260 T. infestans and over 4,000 individuals of the non-target species, M. spinolai. The altitude of T. infestans trapping points ranged from 370 to 1476 m.a.s.l (738.2±189.1). Only one male adult T. infestans was captured manually at night. The nymphal instars I-II were most frequently found (72.8%), followed by III-IV (17.5%), and instar V (9.3%). The highest abundance of T. infestans was detected in the southernmost study site (n=132), where it was the only species recorded, while M. spinolai was widespread in several of the studied sites. Both species were found in terrestrial bromeliads and rock piles, whilst M. spinolai was also found in rocky outcrops, and this is the first report of T. infestans among rubble and vines’ wood piles in Chile.
With this study, we expand the knowledge of Chilean sylvatic foci for both vector species and show that wild triatomine populations remain a threat in endemic areas, even in countries with high levels of domiciliary vector control. The ecotope preferences of these species should be informed in future prevention campaigns displayed at endemic areas, targeted to inhabitants, workers and industries, to avoid risky behaviour that could expose people to vectors.
To continue this work, we are performing DNA extraction, followed by sequencing, to analyse T. infestans population genomics, comparing these wild specimens with those found inside houses. Funding: ANID/Programa Becas/Doctorado Becas Chile 2019 72200391; ANID/FONDECYT Regular 1180940. 
