Trypanosoma cruzi strain TcI is associated with chronic Chagas disease in the Brazilian Amazon

Abstract

BackgroundChagas disease in the Amazon region is considered an emerging anthropozoonosis with a predominance of the discrete typing units (DTUs) TcI and TcIV. These DTUs are responsible for cases of acute disease associated with oral transmission. Chronic disease cases have been detected through serological surveys. However, the mode of transmission could not be determined, or any association of chronic disease with a specific T. cruzi DTU’s. The aim of this study was to characterize Trypanosoma cruzi in patients with chronic Chagas disease in the State of Amazonas, Brazil.MethodsBlood culture and xenodiagnosis were performed in 36 patients with positive serology for Chagas disease who participated in a serological survey performed in urban and rural areas of Manaus, Amazonas. DNA samples were extracted from the feces of triatomines used for xenodiagnosis, and the nontranscribed spacer of the mini-exon gene and the mitochondrial gene cytochrome oxidase subunit II (COII) were amplified by PCR and sequenced.ResultsBlood culture and xenodiagnosis were negative in 100% of samples; however, molecular techniques revealed that in 13 out of 36 (36%) fecal samples from xenodiagnosis, T. cruzi was characterized as the DTU TcI, and different haplotypes were identified within the same DTU.ConclusionThe DTU TcI, which is mainly associated with acute cases of Chagas disease in the Amazon region, is also responsible for chronic infection in patients from a region in the State of Amazonas.

Chagas disease in the State of Amazonas: history, epidemiological evolution, risks of endemicity and future perspectives

“…Chronic CD morbidity was lower in the State of Amazonas than in the classical endemic areas, with the disease occurring mainly in the indeterminate form (17) (38) (39) . In general, there were no differences in the proportion of radiological changes between positive and negative groups, suggesting low morbidity in the chronic phase of CD in the State of Amazonas, which was likely related to low parasitemia and/or reduced pathogenicity of the sylvatic T. cruzi strain in this region (31) .…”

“…Studies in Amazonas have demonstrated the presence of DTUs TcI, TcIII and TcIV in the parasite sylvatic transmission cycle (33) (34) (35) (38) . TcIV predominates among orally transmitted acute human cases (34) , and TcI predominates among the isolated and chronic cases (35) (38) , suggesting their association with different transmission profiles.…”

Trypanosoma cruzi I genotype among isolates from patients with chronic Chagas disease followed at the Evandro Chagas National Institute of Infectious Diseases (FIOCRUZ, Brazil)

“…More recently, Sangenis et al 42 identified TcI mixed with TcVI in an asymptomatic patient from the Rio de Janeiro State. Otherwise, in the Amazon region (Northern Brazil), TcI is the prevailing DTU found in humans as the agent of acute infections 6,7,21 , but this genotype was also identified in fourteen chronic patients with the indeterminate form of Chagas disease 22,40 .…”

“…Subsequently, a new genotype closely related to TcI was described in Brazilian bats 16 and named Tcbat or TcVII, although without consensus regarding its DTU assignment 8,17,18 . In Brazil, TcI (formerly Z1) is widely distributed among mammalian hosts within the wild cycle, mainly the common opossum, Didelphis marsupialis, but it can also be found in human acute infections and more rarely in chronic patients 6,7,[19][20][21][22][23] . Otherwise, TcII (formerly Z2) and TcVI (formerly ZB or Paraguayan Z2) are mainly restricted to hosts within the domiciliary habitats, including humans 7,8 .…”

Nucleoside triphosphate diphosphohydrolase1 (TcNTPDase-1) gene expression is increased due to heat shock and in infective forms of Trypanosoma cruzi

“…The different disease spectrums and the course of chronic infection may be consequences of complex interactions between genetic variability of T. cruzi subpopulations (classified into TcI to TcVI) [3], host immunogenetics and eco-epidemiological characteristics [3][4][5]. Current chemotherapy is based on the drugs nifurtimox and benznidazole, which present a lack of effectiveness on the chronic phase of the disease [6].…”