HOST PARASITES: THE CASE OF TRYPANOSOMA CRUZI IN DOMESTIC AND SYLVATIC MAMMALS IN THE GRAN CHACO

GURTLER RE, CARDINAL MV, CEBALLOS LA, OROZCO MM, KITRON U

Iguazu, Argentina

Congreso; 59th Annual International Conference of the Wildlife Disease Association; 2010

The diversity of host species in widely different habitats that can be infected by the protozoan Trypanosoma cruzi (Kinetoplastida) is outstanding. This pathogen, the etiologic agent of Chagas disease affecting 10-20 million people in the Americas, may be subdivided into at least 6 group or “Discrete Typing Units” (DTU) and circulates in complex transmission cycles involving >70 species of triatomine bugs (vectors) and >150 species of sylvatic and peridomestic mammals (mainly opossums, armadillos, rodents, primates, dogs and cats) acting as reservoir hosts from northern Patagonia to Virginia (US). Chagas disease exemplifies a neglected disease of poverty associated with poor rural housing, unsustainable resource management, low socio-economic status and political exclusion. Despite declining trends, vector-borne transmission persists in the Gran Chaco –a 1.3 million km2 ecoregion extending over Argentina, Paraguay and Bolivia. During the 20th century the Gran Chaco suffered extensive deforestation, slash-and-burn agriculture and cattle-ranching leading to overgrazing, unproductive scrub and a subsistence economy in which rural poverty and Chagas disease have gone hand in hand. Long-term prospective studies showed that domestic dogs play a crucial role as a reservoir and risk factor for domestic transmission, and can also serve as sentinel animals following insecticide spraying campaigns. Using molecular epidemiology tools and spatial statistics, we investigated the structure and links between domestic and sylvatic transmission cycles. We found a dramatic decrease in the prevalence and incidence of T. cruzi infection in Didelphis albiventris opossums and Conepatus chinga skunks over nearly two decades in the dry Chaco. Each wildlife host harbored different DTUs. In more recent surveys in the wet Chaco, Dasypus novemcinctus armadillos and opossums were found to be the main sylvatic hosts of different DTUs. We conclude that independent sylvatic transmission cycles of T. cruzi coexist within well-defined areas in the same region, and have limited overlap with concurrent domestic and peridomestic cycles in the Argentine Chaco.