Combining geospatial analysis and exploratory study of triatomine ecology to evaluate the risk of Chagas disease in a rural locality

Abstract

The use of geo-spatial analysis to anticipate transmission risk for Chagas disease was tested in a rural area of northeast Brazil in an approach that combined geo-referencing and exploratory study of triatomine infestation, including related elements such as the environment and hosts. A total of 617 triatomine specimens, mainly Triatoma brasiliensis, were captured, exhibiting an overall T. cruzi positivity of 44.4%. Layer analysis indicated that the greatest transmission risk to man was associated with woodpiles. The buffer area generated contained uninhabited dwellings teeming with bats and positive bugs. Other locations outside the buffer, near uninhabited dwellings housing cattle, contained colonies of triatomines harboring T. cruzi. The results indicate that local residents' activities themselves favor the development of risk areas for Chagas disease.

Ecohealth Interventions Limit Triatomine Reinfestation following Insecticide Spraying in La Brea, Guatemala

“…Various potential pathways of vector transport from sylvatic or peridomestic environments into the home have been suggested, including by domestic (e.g., chickens and dogs) or synanthropic (e.g., mice) animals or by the village residents themselves through gathering of firewood or accidentally in daily travels to and from nearby infested areas. 8,25,26 The increased use of electrical lighting in rural communities also raises the possibility that the vector may be drawn not only to the village but also to homes when the lights are in use. 9,27,28 Vector survival in peridomestic environments may also be lower than in domestic habitats.…”

An entomoepidemiological investigation of Chagas disease in the state of Ceará, Northeast Region of Brazil

“…For example, Rhodnius is more commonly associated with palm trees, Panstrongylus with animal burrows and tree cavities and Triatoma with rocky outcrops, caves and rodent burrows 23 . However, in and around houses, triatomines may prefer other types of shelter and peridomicile areas offer a number of options of hosts and shelter, besides possessing the ideal microclimate for successful population development 24 . However, some artificial ecotopes may be more attractive to some species than others and studies carried out in neighboring municipalities showed higher triatomine infestation in animal shelters such as goat/sheep corrals and chicken coops 17,25 .…”

A Common Caatinga Cactus, Pilosocereus gounellei, is an Important Ecotope of Wild Triatoma brasiliensis Populations in the Jaguaribe Valley of Northeastern Brazil

“…The common observation that rodents and T. brasiliensis also co-occur in timber/wood piles in peridomestic environments suggests that bugs and rodents are well adapted to this key ecotope. 15 Our hypothesis might also help explain why the risk of infestation with T. brasiliensis was shown to be higher in dwellings whose owners have more frequent contact with preserved Caatinga environments (odds ratio = 2.43, 95% confidence interval = 1.18-5.04; n = 131 dwellings). 23 Active dispersal of adult T. brasiliensis from either cacti or rocky outcrops can also directly contribute to dwelling infestation and re-infestation in some areas.…”

“…21,22 This model estimated mean bug density at approximately 4.3 (SE = 0.78) for an overall total abundance of about 187.9 T. brasiliensis in the 44 cacti we sampled, with an upper limit of the 95% confidence interval of 255.2. Previous surveys [12][13][14][15] have detected Trypanosoma cruzi infection in 17.4% (95% exact confidence interval 16.1-18.8%) of 2,982 T. brasiliensis specimens collected in the study region. Based on model estimates of bug-detection sensitivity (which, for the methods we used was low: mean = 0.15, SE = 0.02), on catch effort, and on the observed patterns of bug presence, our analyses suggest that most of the P. gounellei we sampled might have been infested: model-estimated infestation probability was 98.6% (95% confidence interval = 96.5-100%).…”

“…2,9-12 However, re-infestation of artificial structures is also commonplace in sedimentary lowlands where no such rocky outcrops exist; in addition, T. brasiliensis often occurs in wood piles near houses, [13][14][15] particularly when these are also occupied by rodents (Valença-Barbosa C, unpublished data). These observations led us to hypothesize that T. brasiliensis s.s. should be able to exploit alternative (i.e., non-rocky) ecotopes in the wild, possibly in association with rodents.…”