Are domestic and sylvatic Trypanosoma cruzi transmission cycles overlapped in the humid Argentinean Chaco?

CARDINAL M.V., OROZCO M.M., ENRIQUEZ G.F., MAFFEY L., SARTOR P.A., MACCHIAVERNA N.P., SCHIJMAN A.G., KITRON U., GÜRTLER R.E.

Porto de Galinhas

Congreso; 2nd International Congress on Pathogens at the Human-Animal Interface (ICOPHAI): One Health for Sustainable Development.; 2013

Trypanosoma cruzi transmission cycles include a wide diversity of mammal hosts, triatomine bug species and parasite genotypes (called Discrete Typing Units, DTUs) encompassing both domestic and sylvatic environments. Along the Americas, domestic and sylvatic transmission cycles show different degrees of overlapping. Could the introduction of sylvatic T. cruzi parasites pose a threat to domestic transmission control efforts? To study the structure of T. cruzi transmission cycles we assessed the distribution of parasite DTUs (identified by PCR strategies) in (peri)domestic Triatoma infestans and Triatoma sordida, domestic dogs and cats, humans and sylvatic mammals in the humid (Eastern) Argentinean Chaco. TcVI predominated in 61% of 69 (peri)domestic T. infestans and in 56% of 9 T. sordida, and was identified in 84% of 44 dogs and in 83% of 12 cats. TcV was the secondary DTU identified in the (peri)domestic environment. In humans, preliminary results found TcI infections and incomplete DTU identifications (due to very low parasitemia) indicating either TcII or TcV or TcVI infections. Among infected sylvatic mammals, all (n=12) Didelphis albiventris (white-eared opossums) were infected with TcI, whereas all armadillos (12 Dasypus novemcinctus, 1 Chaetophractus vellerosus, and 1 Tolypeutes matacus) were infected with TcIII, implying two distinct sylvatic cycles. These DTUs were absent in (peri)domestic T. infestans but three TcI-infected T. sordida were found in peridomestic ecotopes and two TcIII-infected dogs were recorded, suggesting a probable link with local sylvatic transmission. The household distribution of T. cruzi DTUs showed that bugs, dogs and cats from a given house compound shared the same parasite genotype in most cases. This result lends further support to the importance of dogs and cats as domestic reservoir hosts of T. cruzi. The introduction of T. cruzi from sylvatic into domestic habitats would occur very rarely in the current epidemiological context of rural communities in the Humid Chaco area as found previously in communities under sustained vector surveillance in the Dry Argentinean Chaco. However, ongoing large-scale changes in land use and habitat fragmentation throughout in the Argentinean Chaco may impact in sylvatic transmission cycles, host and parasite distributions may be modified and the risk of transmission could be increased in new suitable habitats.