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

Abstract

Genetic diversity of Trypanosoma cruzi populations and parasite transmission dynamics have been well documented throughout the Americas, but few studies have been conducted in the Gran Chaco ecoregion, one of the most highly endemic areas for Chagas disease, caused by T. cruzi. In this study we assessed the distribution of T. cruzi lineages (identified by PCR strategies) in Triatoma infestans, domestic dogs, cats, humans and sylvatic mammals from two neighboring rural areas with different histories of transmission and vector control in northern Argentina. Lineage II predominated among the 99 isolates characterized and lineage I among the six isolates obtained from sylvatic mammals. Trypanosoma cruzi lineage IIe predominated in domestic habitats; it was found in 87% of 54 isolates from Tr. infestans, in 82% of 33 isolates from dogs, and in the four cats found infected. Domestic and sylvatic cycles overlapped in the study area in the late 1980s, when intense domestic transmission occurred, and still overlap marginally. The introduction of T. cruzi from sylvatic into domestic habitats is likely to occur very rarely in the current epidemiological context. The household distribution of T. cruzi lineages showed that Tr. infestans, dogs and cats from a given house compound shared the same parasite lineage in most cases. Based on molecular evidence, this result lends further support to the importance of dogs and cats as domestic reservoir hosts of T. cruzi. We believe that in Argentina, this is the first time that lineage IIc has been isolated from naturally-infected domestic dogs and Tr. infestans.

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

“…All of these factors are potential entry points of TcIII into domestic transmission cycles. 7,20,24 Two of 44 T. cruzi-infected domestic dogs from our study area had TcIII, 46 and evidence of TcIII in domestic Triatoma infestans and dogs was obtained elsewhere in the Chaco 24,47 and in the Amazon. 9,43 Local wild mammals had no evidence of the parasite DTUs (TcV and TcVI) that infected local domestic dogs, cats, or Triatoma infestans.…”

“…Our empirical results therefore support the theory that arboreal transmission cycles that include opossums are usually associated with TcI, whereas terrestrial transmission cycles with armadillos as hosts include TcIII. 7,9,24,42 This separation is not complete because other DTUs have occasionally been found in opossums and armadillos. 4,7,23,43 The most likely local vectors of TcI and TcIII, as yet not identified conclusively, are Triatoma sordida and Panstrongylus geniculatus, respectively.…”

“…24 Parasite growth was monitored weekly during four months until reaching 3 + Molecular diagnosis and genotyping. Parasite DNA was extracted from blood samples mixed with GEB and boiled for 15 minutes by using the DNeasy Blood & Tissue Kit (QIAGEN, Valencia, CA) according to manufacturer's instructions.…”

“…The hindgut contents were diluted in 50 mL of deionized sterile water, boiled for 15 minutes, and the DNA was extracted with DNAzol (Invitrogen, Carlsbad, CA). 24 Infections with T. cruzi were identified by PCR amplification of the 330-basepair fragment from the kDNA minicircles of T. cruzi (kDNA-PCR) using primers and cycling conditions described. 29 Aliquots of 12 μL of PCR products were visualized under ultraviolet light after electrophoresis in 3% agarose gels containing GelRed (Biotium, Inc., Hayward, CA).…”

“…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.…”