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.

Fig. 1.

Prevalence of domestic infestation (observed and predicted by a logistic model), mean domestic density of T. infestans, and the timing of appearance of new cases of T. cruzi infection after two community-wide campaigns including residual insecticide spraying, Amamá and neighboring villages, 1984–2006. (A) Domestic infestation and bug density and timing of appearance of new cases and insecticide sprays. (B) Infection with T. cruzi in domestic T. infestans, dogs, and children <15 years of age.

Fig. 2.

Prevalence of infestation by T. infestans, total bug collection, and insecticide spray coverage carried out by professional spray workers (1993–1995) or householders (1996–2004) in Amamá and four neighboring villages during sustained surveillance with selective control actions. (A) Domestic sites. (B) Peridomestic sites.

Fig. 3.

Age-specific prevalence of T. cruzi infection in Amamá and four neighboring villages, 1984–2006, before initial interventions in 1985 and during sustained surveillance with selective control actions 1992–2006. (A) Prevalence of T. cruzi infection in dogs. (B) Seropositivity in humans <25 years of age. The prevalence of infection at birth (age 0) was assumed to be zero for both humans and dogs.