House Reinfestation With Triatoma infestans (Hemiptera: Reduviidae) After Community-Wide Spraying With Insecticides in the Argentine Chaco: A Multifactorial Process

Abstract

We investigated the dynamics and underlying causes of house (re)infestation with Triatoma infestans (Klug 1834) after a community-wide residual spraying with pyrethroids in a well-defined rural section of Pampa del Indio municipality (northeastern Argentina) over a 4-yr period. House infestation was assessed by timed manual searches, during insecticide applications, and by opportunistic householders' bug collections. All reinfested houses were selectively re-sprayed with insecticides. The resident population comprised Qom (66.6%) and Creole (33.4%) households, whose sociodemographic profiles differed substantially. The prevalence of house infestation dropped, less than expected, from 20.5% at baseline to 5.0% at 14 months postspraying (MPS), and then fluctuated between 0.8 and 4.2% over 21-51 MPS. Postspraying house infestation was positively and highly significantly associated with prespraying infestation. Most of the foci detected over 14-21 MPS were considered persistent (residual), some of which were moderately resistant to pyrethroids and were suppressed with malathion. Infestation patterns over 27-51 MPS suggested bug invasion from internal or external foci, but the sources of most findings were unaccounted for. Local spatial analysis identified two hotspots of postspraying house infestation. Using multimodel inference with model averaging, we corroborated that baseline domestic infestation was closely related to refuge availability, housing quality, and occurrence of peridomestic infestation. The diminished effectiveness of single pyrethroid treatments, partly attributable to moderate resistance compounded with rather insensitive vector detection methods and poor housing conditions, contributed to vector persistence. Improved control strategies combined with broad social participation are needed for the sustainable elimination of vector-borne human Chagas disease from the Gran Chaco.

Inequalities in the social determinants of health and Chagas disease transmission risk in indigenous and creole households in the Argentine Chaco

“…The higher social vulnerability of Qom compared to creole households is consistent with the higher infestation rates of Qom domiciles in Area III and elsewhere in Pampa del Indio [27–29]. In these multimodel-based analyses the effects of ethnic background ceased to be significant when other ecological and socio-economic variables more closely related to house infestation or vector abundance were allowed for [28].…”

“…The risk of preintervention house infestation increased with increasing refuge availability (closely related to building materials) and overcrowding, and decreased with increasing educational level and use of domestic insecticides [27]. Vector abundance was also positively associated with the household number of domestic animals and people [27–29], as in other areas infested with various triatomine species [58–61].…”

“…Particularly in Pampa del Indio, house infestation rates with the main vector of Chagas disease, Triatoma infestans , were higher in Qom than in creole households [27–29] and dogs and cats from Qom households exhibited a higher T. cruzi- infection prevalence than those owned by creoles [30]. These differences coincided with more precarious living conditions in Qom households associated with house infestation: lower housing quality, higher household size and overcrowding, lower educational level and fewer livestock or poultry [27–29, 31]. However, the effects of socio-economic inequalities on the risk of vector-borne transmission were not assessed in an integrated manner, particularly within ethnic groups.…”

New human isolates of Trypanosoma cruzi confirm the predominance of hybrid lineages in domestic transmission cycle of the Argentinean Chaco

“…This study is part of an ongoing research and disease control program implemented since 2007 in the Municipality of Pampa del Indio, Chaco, Argentina, which aims to achieve the sustainable elimination of T. infestans from rural dwellings and the interruption of vector-borne transmission. All rural villages within this area have been under sustained vector surveillance and control, and house infestation was kept under 3% district-wide (Gaspe et al, 2015;Gurevitz et al, 2013;Provecho et al, 2017). Several surveys genotyped T. cruzi parasites from Pampa del Indio sylvatic and domestic hosts, and vectors.…”

Fast recovery of house infestation with Triatoma brasiliensis after residual insecticide spraying in a semiarid region of Northeastern Brazil

“…The house dwellers report that adult insects frequently fly into the households, which does not exclude the possibility of passive dispersal, as the peridomicile ecotopes are near the households. Considering the long period (319 days) for development of the evolutionary cycle of T. brasiliensis [42], the fact that insects at different stadium of development were found in the peridomicile, in all sampled periods, is indicative of insects that remained even after chemical control, in addition to those coming from the wild environment [10,18,23,24,[43][44][45][46][47][48].…”