The diversity of the Chagas parasite, Trypanosoma cruzi, infecting the main Central American vector, Triatoma dimidiata, from Mexico to Colombia

Abstract

Little is known about the strains of Trypanosoma cruzi circulating in Central America and specifically in the most important vector in this region, Triatoma dimidiata. Approximately six million people are infected with T. cruzi, the causative agent of Chagas disease, which has the greatest negative economic impact and is responsible for ~12,000 deaths annually in Latin America. By international consensus, strains of T. cruzi are divided into six monophyletic clades called discrete typing units (DTUs TcI-VI) and a seventh DTU first identified in bats called TcBat. TcI shows the greatest geographic range and diversity. Identifying strains present and diversity within these strains is important as different strains and their genotypes may cause different pathologies and may circulate in different localities and transmission cycles, thus impacting control efforts, treatment and vaccine development. To determine parasite strains present in T. dimidiata across its geographic range from Mexico to Colombia, we isolated abdominal DNA from T. dimidiata and determined which specimens were infected with T. cruzi by PCR. Strains from infected insects were determined by comparing the sequence of the 18S rDNA and the spliced-leader intergenic region to typed strains in GenBank. Two DTUs were found: 94% of infected T. dimidiata contained TcI and 6% contained TcIV. TcI exhibited high genetic diversity. Geographic structure of TcI haplotypes was evident by Principal Component and Median-Joining Network analyses as well as a significant result in the Mantel test, indicating isolation by distance. There was little evidence of association with TcI haplotypes and host/vector or ecotope. This study provides new information about the strains circulating in the most important Chagas vector in Central America and reveals considerable variability within TcI as well as geographic structuring at this large geographic scale. The lack of association with particular vectors/hosts or ecotopes suggests the parasites are moving among vectors/hosts and ecotopes therefore a comprehensive approach, such as the Ecohealth approach that makes houses refractory to the vectors will be needed to successfully halt transmission of Chagas disease.

Canine trypanosomiasis in an endemic Costa Rican community: Demonstration of the active infection cycle

“…The same genetic variant of the T. cruzi parasite, the TcI lineage, was observed in both vectors and dogs in Getsemaní community, which agrees with previous studies that reports this lineage to be the most common in Central America (Zuriaga et al, 2012;Dorn et al, 2017). The finding of TcI in sympatric vectors and in dogs needs further studies in order to identify genotypic differences using more appropriate gene markers and assays with better sensitivity that could contribute to elucidate population dynamics (Izeta-Alberdi et al, 2016).…”

Biological and Genetic Heterogeneity in Trypanosoma dionisii Isolates from Hematophagous and Insectivorous Bats

“…The interest in identifying differences among isolates of the same species of trypanosome began with the discovery of T. c. cruzi and its life cycle by Carlos Chagas [ 29 ]. To date, most of these studies have concentrated on the T. c. cruzi and T. rangeli species, as high morphological, biological, biochemical, and molecular variability has been observed in these species [ 30 , 31 ]. Studies regarding differences among T. dionisii isolates are scarce, and most recent publications have focused solely on the molecular identification of this parasite in both hosts and vectors from Brazil and some other countries [ 7 , 8 , 10 , 11 , 12 , 18 ].…”

Histopathological findings of infections caused by canine distemper virus, Trypanosoma cruzi, and other parasites in two free-ranging White-nosed Coatis Nasua narica (Carnivora: Procyonidae) from Costa Rica

“…The exact mechanisms underlying CDV infections and circulation of the virus among susceptible wild mesocarnivores, however, are relatively unknown, that is, several authors suggested that this could be related to CDV genotypes with different virulence and cell tropism (Origgi et al 2012;Rentería-Solís et al 2014;Kubiski et al 2016). As for the discrete typing unit (DTU), TcI is the most common in Central America, and has been reported in coatis in Mexico, but unfortunately the DTU in these animals was not determined (Herrera 2010;Rocha et al 2013;Martínez-Hernández et al 2016;Dorn et al 2017). More studies are necessary to elucidate if coatis may be competent reservoirs of T. cruzi and a source of infection for the triatomine bugs in the region (Roellig et al 2009;Curtis-Robles et al 2016).…”