Variations in prevalence of infection by Trypanosoma cruzi in sylvatic mammals of rural northwestern Argentina.

CEBALLOS L.A.; VAZQUEZ-PROKOPEC G.M.; CARDINAL M.V.; OROZCO M. M.; CORTINAS R.; KITRON U.; GÜRTLER R.E.

Washington, EEUU.

Simposio; 54th Annual Meeting of the American Society of Tropical Medicine and Hygiene; 2005

Trypanosoma cruzi, the etiological agent of Chagas’ disease, has been detected in more than 100 mammal species in the Americas, with opossums, armadillos, and rodents the most important reservoir hosts. To study the sylvatic cycle in the Gran Chaco region, variations in prevalence of T. cruzi infection in sylvatic mammals according to age, season and vector control activities were studied in the forest around three rural communities, Amamá, Trinidad and Mercedes in northwestern Argentina. Between November 2002 and November 2004, a total of 521 sylvatic mammals from 13 species were collected during 10,703 trap days. From 505 mammals tested by xenodiagnosis, only 3/38 (7.9%) opossums (Didelphis albiventris) and 1/92 (1.1%) skunks (Conepatus chinga) were infected by T. cruzi. Infection in opossums increased with age (0% in juveniles and 17% in adults), and varied with season (10% in spring, 5% in winter and 0% in summer and autumn). When comparing with data collected in the study area in 1991-1992, just before intensive spraying in 1992 and entomologic surveillance since then, a significant reduction in overall T. cruzi infection rates was observed for opossums (36 % to 8 %) but not for skunks (4.1% to 1.1%). However, opossums followed by skunks still remain the main sylvatic reservoir species of T. cruzi. The sharp reduction of T. cruzi infection in opossums may be a result of the sustained vector surveillance during 1993-2002, that reduced the contact rate between opossums and infected domestic and peridomestic bugs, reflecting the significant contribution of an active domestic/peridomestic transmission of T. cruzi on sylvatic mammal’s infection. A reduction in density of opossums associated with deforestation and reduced habitat may also have contributed to reduced sylvatic transmission.