Molecular epidemiology of human oral Chagas disease outbreaks in Colombia

Abstract

Background: Trypanosoma cruzi, the causative agent of Chagas disease, displays significant genetic variability revealed by six Discrete Typing Units (TcI-TcVI). In this pathology, oral transmission represents an emerging epidemiological scenario where different outbreaks associated to food/beverages consumption have been reported in Argentina, Bolivia, Brazil, Ecuador and Venezuela. In Colombia, six human oral outbreaks have been reported corroborating the importance of this transmission route. Molecular epidemiology of oral outbreaks is barely known observing the incrimination of TcI, TcII, TcIV and TcV genotypes.

Methodology and principal findings: High-throughput molecular characterization was conducted performing MLMT (Multilocus Microsatellite Typing) and mtMLST (mitochondrial Multilocus Sequence Typing) strategies on 50 clones from ten isolates. Results allowed observing the occurrence of TcI, TcIV and mixed infection of distinct TcI genotypes. Thus, a majority of specific mitochondrial haplotypes and allelic multilocus genotypes associated to the sylvatic cycle of transmission were detected in the dataset with the foreseen presence of mitochondrial haplotypes and allelic multilocus genotypes associated to the domestic cycle of transmission.

Conclusions: These findings suggest the incrimination of sylvatic genotypes in the oral outbreaks occurred in Colombia. We observed patterns of super-infection and/or co-infection with a tailored association with the severe forms of myocarditis in the acute phase of the disease. The transmission dynamics of this infection route based on molecular epidemiology evidence was unraveled and the clinical and biological implications are discussed.

Figure 1. Geographical distribution and location of the municipalities in Colombia where oral transmission outbreaks have been reported.

Figure 2. Network haplotype and un-rooted DAS tree of T. cruzi biological closes isolated from the six cases of oral Chagas disease transmission.

A. Median-Joining haplotype network based on MLSTmt of 49 TcI clones isolated from oral outbreaks in Colombia shows the presence of 32 different haplotypes and the discrimination of domestic and sylvatic mitochondrial haplotypes according to the median vectors. Red star indicate the reference sequence of TcI domestic mithocondrial haplotype (EM) and previously typed as TcIa using SL-IR region. Green star indicate the reference sequence of TcI sylvatic mitochondrial haplotype and previously typed as TcId using SL-IR region. There is congruence between MLSTmt and SL-IR genotypes that convey in domestic haplotypes for TcIa/TcIb and sylvatic haplotypes for TcId. The black spots are considered ‘mv’ that can be biologically interpreted as possibly extant unsampled sequences or extinct ancestral sequences. B. Neighbor-Joining genetic distance tree based on MLMT of 49 TcI clones isolated from the oral outbreaks in Colombia shows the clustering of the allelic profiles within each outbreak. A significant number of allelic multilocus genotypes can be considered within each cluster. The topology of the un-rooted tree demonstrates the allelic relatedness among the clones isolated within the same oral outbreak with the presence of some outliers.