Long-term reduction of Trypanosoma cruzi infection in sylvatic mammals following deforestation and sustained vector surveillance in northwestern Argentina

Abstract

Long-term variations in the dynamics and intensity of sylvatic transmission of Trypanosoma cruzi were investigated around eight rural villages in the semiarid Argentine Chaco in 2002-2004 and compared to data collected locally in 1984-1991. Of 501 wild mammals from 13 identified species examined by xenodiagnosis, only 3 (7.9%) of 38 Didelphis albiventris opossums and 1 (1.1%) of 91 Conepatus chinga skunks were infected by T. cruzi. The period prevalence in opossums was fourfold lower in 2002-2004 than in 1984-1991 (32-36%). The infection prevalence of skunks also decreased five-fold from 4. 1-5.6% in 1984-1991 to 1.1% in 2002-2004. Infection in opossums increased with age and from summer to spring in both study periods. The force of infection per 100 opossum-months after weaning declined more than six-fold from 8. . The striking decline of T. cruzi infection in opossums and skunks occurred in parallel to community-wide insecticide spraying followed by selective sprays leading to very low densities of infected Triatoma infestans in domestic and peridomestic habitats since 1992; to massive deforestation around one of the villages or selective extraction of older trees, and apparent reductions in opossum abundance jointly with increases in foxes and skunks. These factors may underlie the dramatic decrease of T. cruzi infection in wild reservoir hosts.

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

“…The predominance of lineage I among isolates from sylvatic habitats is probably due to the role of opossums as the major local sylvatic reservoir host of T. cruzi (Schweigmann et al 1999) and to the absence of T. cruzi infection among armadillos. Opossums have consistently been found infected almost exclusively with lineage I throughout the Chaco region and the Americas (Barnabé et al, 2000;Ceballos et al, 2006;Diosque et al, 2003;Wisnivesky-Colli et al, 1992;Yeo et al, 2005). Armadillos, especially Dasypus novemcinctus, are sylvatic hosts of T. cruzi II in the Paraguayan Chaco (Yeo et al, 2005) but they are very rare in the study area.…”

“…Natural infection by T. cruzi has been found in several local species of sylvatic mammals (Carcavallo and Martínez, 1968;Ceballos et al, 2006;Diosque et al, 2003;Yeo et al, 2005), whereas the putative sylvatic vectors have only been identified in Bolivia (Noireau et al, 2000). In the Gran Chaco, the bug Triatoma infestans is the main or single domiciliary vector; dogs, humans and chickens are usually the main blood meal sources of domestic bugs, and dogs and cats are considered the most important domestic reservoir hosts of T. cruzi (Minter, 1976;Gürtler et al, 1997Gürtler et al, , 2007a.…”

“…Overall, T. cruzi II (TC II) was more prevalent in the domestic environment, and sylvatic mammals were found infected with both TC I and TC II (De Luca d'Oro et al, 1993). TC IIe was first reported in Argentina by Diosque et al (2003) and TC IIc by Ceballos et al (2006).…”

New Sylvatic Hosts of Trypanosoma cruzi and Their Reservoir Competence in the Humid Chaco of Argentina: A Longitudinal Study

“…22 Ongoing large-scale changes in land use and habitat fragmentation throughout Latin America may impact sylvatic transmission cycles in unforeseen ways, either reducing or increasing parasite prevalence. 19,23 Little is known about the structure and spatiotemporal dynamics of sylvatic transmission cycles of T. cruzi in the Gran Chaco. Few areas have been investigated in recent decades, usually through cross-sectional or convenience surveys; sampling efforts have focused on a limited number of species and environments, and identification of parasite DTUs from wild hosts has been sparse.…”

“…12 In this region, the most frequently identified sylvatic hosts of T. cruzi are didelphid marsupials and various species of armadillos, followed by carnivores (including skunks, ferrets, foxes, and coatis) and a few species of small rodents. 7,9,[13][14][15][16][17][18][19][20] In general, host and parasite distributions may be modified by the combined effects of alterations in climate, landscape and biodiversity, which may create new habitats suitable for the development of parasites and vectors and increase the risk of transmission of pathogens. 21 The sylvatic distribution of triatomine bugs and transmission of T. cruzi appear to be closely associated with vegetation cover and landscape use.…”