Genetic diversity of Trypanosoma cruzi infecting raccoons (Procyon lotor) in 2 metropolitan areas of southern Louisiana: implications for parasite transmission networks

Abstract

Trypanosoma cruzi, the aetiological agent of Chagas disease, exists as an anthropozoonosis in Louisiana. Raccoons are an important reservoir, as they demonstrate high prevalence and maintain high parasitaemia longer than other mammals. Given the complex nature of parasite transmission networks and importance of raccoons as reservoirs that move between sylvatic and domestic environments, detailing the genetic diversity of T. cruzi in raccoons is crucial to assess risk to human health. Using a next-generation sequencing approach targeting the mini-exon, parasite diversity was assessed in 2 metropolitan areas of Louisiana. Sequences were analysed along with those previously identified in other mammals and vectors to determine if any association exists between ecoregion and parasite diversity. Parasites were identified from discrete typing units (DTUs) TcI, TcII, TcIV, TcV and TcVI. DTUs TcII, TcV and TcVI are previously unreported in raccoons in the United States (US). TcI was the most abundant DTU, comprising nearly 80% of all sequences. All but 1 raccoon harboured multiple haplotypes, some demonstrating mixed infections of different DTUs. Furthermore, there is significant association between DTU distribution and level III ecoregion in Louisiana. Finally, while certain sequences were distributed across multiple tissues, others appeared to have tissue-specific tropism. Taken together, these findings indicate that ongoing surveillance of T. cruzi in the US should be undertaken across ecoregions to fully assess risk to human health. Given potential connections between parasite diversity and clinical outcomes, deep sequencing technologies are crucial and interventions targeting raccoons may prove useful in mitigating human health risk.

Intra-host Trypanosoma cruzi strain dynamics shape disease progression: the missing link in Chagas disease pathogenesis

“…Therefore, our objective was to assess T. cruzi parasite strain dynamics and disease progression in a cohort of naturally infected rhesus macaques, which closely mimic human infection ( 43 ). There is indeed extensive zoonotic circulation of T. cruzi in the southern USA ( 44 ), with occasional spill-over infections in captive macaques ( 45 ) with T. cruzi strains that are similar to those circulating in local Triatoma sanguisuga vectors and mammalian hosts in Louisiana ( 26 , 29 , 32 , 33 , 46 , 47 ). We measured parasite dynamics and clinical disease progression over a 2.5-year period in macaques that had been infected for 1–6 years to shed light for the first time on a unique interplay between multiple parasite strains and clinical profile during the chronic phase and provide a new framework for understanding Chagas disease progression.…”