Comprehensive Survey of Domiciliary Triatomine Species Capable of Transmitting Chagas Disease in Southern Ecuador

Abstract

BackgroundChagas disease is endemic to the southern Andean region of Ecuador, an area with one of the highest poverty rates in the country. However, few studies have looked into the epidemiology, vectors and transmission risks in this region. In this study we describe the triatomine household infestation in Loja province, determine the rate of Trypanosoma cruzi infection in triatomines and study the risk factors associated with infestation.Methodology/Principal FindingsAn entomological survey found four triatomine species (Rhodnius ecuadoriensis, Triatoma carrioni, Panstrongylus chinai, and P. rufotuberculatus) infesting domiciles in 68% of the 92 rural communities examined. Nine percent of domiciles were infested, and nymphs were observed in 80% of the infested domiciles. Triatomines were found in all ecological regions below 2,200 masl. We found R. ecuadoriensis (275 to 1948 masl) and T. carrioni (831 to 2242 masl) mostly in bedrooms within the domicile, and they were abundant in chicken coops near the domicile. Established colonies of P. chinai (175 to 2003 masl) and P. rufotuberculatus (404 to 1613 masl) also were found in the domicile. Triatomine infestation was associated with surrogate poverty indicators, such as poor sanitary infrastructure (lack of latrine/toilet [w = 0.95], sewage to environment [w = 1.0]). Vegetation type was a determinant of infestation [w = 1.0] and vector control program insecticide spraying was a protective factor [w = 1.0]. Of the 754 triatomines analyzed, 11% were infected with Trypanosoma cruzi and 2% were infected with T. rangeli.Conclusions/SignificanceTo date, only limited vector control efforts have been implemented. Together with recent reports of widespread sylvatic triatomine infestation and frequent post-intervention reinfestation, these results show that an estimated 100,000 people living in rural areas of southern Ecuador are at high risk for T. cruzi infection. Therefore, there is a need for a systematic, sustained, and monitored vector control intervention that is coupled with improvement of socio-economic conditions.

Distribution of triatomine species in domestic and peridomestic environments in central coastal Ecuador

“…As previously described[8], if no bugs were found after the initial 20-min search, the searches were continued for an additional 10 min using of 6% pyrethrins solution (PRENTOX, Excite, Prentiss Inc., New York, USA) as a bug irritant. Collected triatomines were placed individually in labeled plastic containers and transported to either the field laboratory or the insectary at the Center for Research on Health in Latin America at Catholic University in Quito[4,24].…”

“…This species has the ability to invade domestic, peridomestic, and sylvatic habitats and show high infection rates with the parasite T . cruzi [7,8]. Sylvatic populations have been found in association with squirrel nests ( Sciurus nebouxii , previously known as Sciurus stramineus )[7,9,10, 31], the endemic palm Phytelephas aequatorialis [3] and other plant species [9].…”

“…However, sylvatic populations are absent for P . rufotuberculatus [8] or very restricted for P . howardi [9].…”

“…The presence of P . rufotuberculatus has been restricted to domestic environments from central coast to southern Ecuador (in Santo Domingo de los Tsáchilas, Manabí, El Oro, Los Ríos and Loja provinces) and is widely distributed in Central and South America [3,5,8,9]. Despite the emerging importance of these species in the coastal region of Ecuador, little is known about its distribution and biology.…”

Salivary gland transcripts of the kissing bug, Panstrongylus chinai , a vector of Chagas disease

“…Of these, the genus Panstrongylus is composed of 13 species, and Panstrongylus chinai is known as a vector species of Chagas disease in Ecuador, Peru, and Venezuela (Abad-Franch et al, 2001; Grijalva et al, 2005, 2015; Patterson et al, 2009). Different from some other blood feeders such as mosquitoes, kissing bugs including P. chinai take 20–30 min for blood-sucking (Beard, 2005); however, they take blood efficiently regardless of host hemostatic and immune responses, suggesting their unique strategy to counteract host responses.…”