The sylvatic transmission cycle of Trypanosoma cruzi in a rural area in the humid Chaco of Argentina

Abstract

Little is known about the sylvatic transmission cycle of Trypanosoma cruzi in the Gran Chaco ecoregion. We conducted surveys to identify the main sylvatic hosts of T. cruzi, parasite discrete typing units and vector species involved in Pampa del Indio, a rural area in the humid Argentinean Chaco. A total of 44 mammals from 14 species was captured and examined for infection by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR). Ten (22.7%) mammals were positive by xenodiagnosis or kDNA-PCR. Four of 11 (36%) Didelphis albiventris (white-eared opossums) and six of nine (67%) Dasypus novemcinctus (nine-banded armadillos) were positive by xenodiagnosis and or kDNA-PCR. Rodents, other armadillo species, felids, crab-eating raccoons, hares and rabbits were not infected. Positive animals were highly infectious to the bugs that fed upon them as determined by xenodiagnosis. All positive opossums were infected with T. cruzi I and all positive nine-banded armadillos with T. cruzi III. Extensive searches in sylvatic habitats using 718 Noireau trap-nights only yielded Triatoma sordida whereas no bug was collected in 26 light-trap nights. Four armadillos or opossums fitted with a spool-and-line device were successfully tracked to their refuges; only one Panstrongylus geniculatus was found in an armadillo burrow. No sylvatic triatomine was infected with T. cruzi by microscopical examination or kDNA-PCR. Our results indicate that two independent sylvatic transmission cycles of T. cruzi occur in the humid Chaco. The putative vectors of both cycles need to be identified conclusively.

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

“…20 Small patches of native dry forest occur near houses; they usually are subjected to intense human pressure through intentional fires, hunting, logging, and deforestation for agriculture and goat, sheep, or cattle ranching. Before a residual insecticide spraying of all houses in the area in November 2007, the prevalence of house infestation with Triatoma infestans (46%) and infection with T. cruzi in domestic bugs (22%), dogs (26%), and cats (29%) indicated the occurrence of active domestic transmission (Cardinal MV and others, unpublished data 20 Six local collaborators with hunting skills and extensive knowledge of the area assisted us in the captures. The study area was divided into 10 square areas (quadrats).…”

“…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. 7,9,[16][17][18][19][20]24 Identification of the triatomine species acting as sylvatic vectors is lagging. 7,8,20,25 Assessing the impacts of ongoing environmental changes requires more information on the structure of transmission cycles over time.…”

“…7,9,[16][17][18][19][20]24 Identification of the triatomine species acting as sylvatic vectors is lagging. 7,8,20,25 Assessing the impacts of ongoing environmental changes requires more information on the structure of transmission cycles over time. A small-scale, baseline survey conducted in the interphase between the dry and humid Chaco identified white-eared opossums (Didelphis albiventris) and nine-banded armadillos (Da.…”

“…novemcinctus) as the only sylvatic hosts of T. cruzi, and they were infected with TcI and TcIII, respectively. 20 As part of a multi-site research project on the eco-epidemiology and control of Chagas disease in the Gran Chaco, we conducted a longitudinal study to investigate further the structure and spatiotemporal dynamics of sylvatic transmission cycles of T. cruzi in disturbed habitats, by expanding the range of species examined through targeting bats, tree-dwelling rodents, and small marsupials; assessing reservoir host competence, and identifying parasite DTUs in a wider range of hosts.…”

“…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.…”