Sustainable vector control and management of Chagas disease in the Gran Chaco, Argentina

Abstract

Chagas disease remains a serious obstacle to health and economic development in Latin America, especially for the rural poor. We report the long-term effects of interventions in rural villages in northern Argentina during 1984 -2006. Two community-wide campaigns of residual insecticide spraying immediately and strongly reduced domestic infestation and infection with Trypanosoma cruzi in Triatoma infestans bugs and dogs and more gradually reduced the seroprevalence of children <15 years of age. Because no effective surveillance and control actions followed the first campaign in 1985, transmission resurged in 2-3 years. Renewed interventions in 1992 followed by sustained, supervised, community-based vector control largely suppressed the reestablishment of domestic bug colonies and finally led to the interruption of local human T. cruzi transmission. Human incidence of infection was nearly an order of magnitude higher in peripheral rural areas under pulsed, unsupervised, community-based interventions, where human transmission became apparent in 2000. The sustained, supervised, community-based strategy nearly interrupted domestic transmission to dogs but did not eliminate T. infestans despite the absence of pyrethroid-insecticide resistance. T. infestans persisted in part because of the lack of major changes in housing construction and quality. Sustained community participation grew out of establishing a trusted relationship with the affected communities and the local schools. The process included health promotion and community mobilization, motivation, and supervision in close cooperation with locally nominated leaders. community participation ͉ deltamethrin ͉ pyrethroids ͉ Triatoma infestans ͉ Trypanosoma cruzi

Molecular epidemiology of domestic and sylvatic Trypanosoma cruzi infection in rural northwestern Argentina

“…infestans, 697 domestic dogs, 109 cats, 586 wild mammals and 612 humans were examined for T. cruzi infection between years 2000 and 2007 (Table 1) In humans, seropositivity to T. cruzi was 5.2% (n = 346) in 2006 and 5.3% (n = 266) in 2007 (Gürtler et al, 2007b). A xenodiagnosis-positive seropositive patient was found in 2006 (11.1%, n = 9) and another in 2007 (16.7%, n = 6).…”

“…The study area has been described elsewhere Gürtler et al, 2007b). Briefly, two areas were visited: i) the core area, including Amamá and four neighboring villages (137 houses), and ii) the periphery, including 186 houses grouped in 35 villages or settlements surrounding the core area.…”

“…Timed manual collections consisted of searching for triatomine bugs in all bedrooms (one person) and peridomestic areas (two persons) of all compounds using 0.2% tetramethrin (Icona, Buenos Aires, Argentina) for 30 min per compound (Gürtler et al, 2007b). Peridomestic structures included corrals for goats or sheep, cows or horses and pigs, chicken coops, trees where chickens roosted, storerooms, kitchens and other possible refuges for triatomines within the area of human activity.…”

“…Xenodiagnostic procedures were as described for domestic animals using 40 bugs for each patient. Serological test procedures and results have been reported elsewhere (Gürtler et al, 2007b). The mean age of study patients was 49 years (range, 21-79, n = 9) in 2006 and 44 years (range, 28-62, n = 6) in 2007.…”

“…As part of a longitudinal study aimed at modeling the transmission dynamics and control of T. cruzi in a well-defined rural area of northwestern Argentina, we have described the prevalence of T. cruzi infection in two neighboring areas with different histories of vector control and transmission intensity (Cardinal et al, , 2007Gürtler et al 2007b). In this study, we have assessed the occurrence and distribution of parasite lineages in domestic and sylvatic hosts and vectors to establish whether domestic and sylvatic cycles of transmission overlap or exist independently in these areas.…”