A review of phylogenetic relationship among Trypanosoma cruzi I and Triatoma sanguisuga: First TcIa report in New Orleans

Chagas disease is a chronic parasitic disease transmitted by triatomine insects (Reduviidae: Triatominae). The causative agent is the protozoan Trypanosoma cruzi, which is grouped in six discrete typing units (DTUs) TcI–TcVI and a seventh one named Tcbat. The DTU TcI is the most abundant and widely dispersed in the Americas. It is found throughout the range of triatomine vector distribution, and can be associated with sylvatic and domestic cycles. Previous studies based on intergenic sequences of the mini-exon gene have identified within TcI, five genotype groups presenting specific epidemiological properties.

This study focused on the specific molecular identification of T. cruzi isolated from the primary vector in Louisiana, Triatoma sanguisuga, based on miniexon gene intergenic region amplification. The intestinal contents from twelve T. sanguisuga collected during 2012-2013 from the site of Louisiana’s local human T. cruzi infection were analyzed by Direct Microscope Observation (DMO) to identify flagellate forms. Feces from vectors with positive observation for flagellates were cultured in RPMI-NNN complete medium, and checked every third day until parasite growth was observed. Eight samples of feces from vectors (8/12, 66.6%) were trypanosomatid-positive by DMO. Six strains were successfully isolated and genotyped as TcI. All TcI samples were further typed as haplotype TcIa. The phylogenetic analysis of the TcI NOLA strains showed a high level of similarity to other T. cruzi strain isolates from T. gerstaeckeri (an important vector in Texas), armadillos and opossums in the USA.

This first report of TcIa from New Orleans suggests that this genotype plays a role in the eco-epidemiological cycle of T. cruzi in the USA.