Impact of community-based vector control on house infestation and Trypanosoma cruzi infection in Triatoma infestans, dogs and cats in the Argentine Chaco

Abstract

The relative impact of two community-based vector control strategies on house infestation by Triatoma infestans and Trypanosoma cruzi infection in bugs, domestic dogs and cats was assessed in two neighboring rural areas comprising 40 small villages and 323 houses in one of the regions most endemic for Chagas disease in northern Argentina. The prevalence and abundance of domestic infestation were 1.5-and 6.5-fold higher, respectively, in the area under pulsed, non-supervised control actions operating under the guidelines of the National Vector Control Program (NCVP) than in the area under sustained, supervised surveillance carried out jointly by the UBA research team and NCVP. The prevalence of infestation and infection varied widely among village groups within each area. In the pulsed control area, the prevalence of infection in bugs, dogs and cats was two-to three-fold higher than in the area under sustained surveillance, most of the infected animals qualified as autochthonous cases, and evidence of recent transmission was observed. Infection was highly aggregated at the household level and fell close to the 80/20 rule. Using multiple logistic regression analysis clustered by household, infection in dogs was associated positively and significantly with variables reflecting local exposure to infected T. infestans, thus demonstrating weak performance of the vector surveillance system. For high-risk areas in the Gran Chaco region, interruption of vectormediated domestic transmission of T. cruzi requires residual insecticide spraying that is more intense, of a higher quality and sustained in time, combined with community participation and environmental management measures.

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

“…The household distribution of T. cruzi lineages showed that bugs, dogs and cats from a given house compound shared the same parasite lineage in most cases. Based on molecular evidence, this result lends further support to the importance of dogs and cats as domestic reservoir hosts of T. cruzi given their high infectivity and frequent contact with domestic bugs (Cardinal et al, 2007;Gürtler et al, 2007a, b). Households harboring infected dogs or cats were observed and predicted to be at greater risk of transmission (Cohen and Gürtler, 2001;Gürtler et al, 2005), but molecular evidence of the links between bugs and host species at the household level were lacking.…”

“…The core area has been under sustained, community-based surveillance supervised jointly by the University of Buenos Aires (UBA) research team and the National Vector Control Program (NVCP) since 1992. The peripheral area, operating under the guidelines of the "Plan Ramón Carrillo" program between 1993 and 1999 and variations of it thereafter, experienced pulsed (mostly in 1993-1996 and in 2000-2001), non-supervised, communitybased insecticide applications promoted by NVCP (Cardinal et al, , 2007. The infestation and history of control of Tr.…”

“…04223 at University of Illinois at UrbanaChampaign. A house-to-house census of all dogs was undertaken in all houses of the core area in May 2000 and again in November 2002; the latter also included cats (Cardinal et al, , 2007. In the peripheral area, the census of dogs and cats was undertaken in three surveys (November 2002, March andJuly 2003) totaling 103 houses from 17 villages and two isolated settlements.…”

“…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.…”

“…We also examined the distribution of T. cruzi lineages among bugs, dogs and cats at a household level. Based on previous evidence (Cardinal et al, , 2007Gürtler et al, 2005Gürtler et al, , 2007a, we hypothesized that domestic Tr. infestans and reservoir hosts from the same house compound would share the same parasite lineages.…”