Fasciola Species Introgression: Just a Fluke or Something More?

The threats posed by a range of viral and bacterial zoonotic diseases inevitably receive renewed attention in the wake of global pandemic events due to their overt and devastating impacts on human health and the economy. Parasitic zoonoses, however, many of which affect millions of people each day, are frequently ignored. In the case of fasciolosis, caused by infection with Fasciola hepatica or Fasciola gigantica, this oversight has allowed for the expansion of areas of parasite sympatry and thus increased the incidence of hybridization and possible introgression between the two species. Here we highlight how an increased demand for animal-derived protein, combined with a lack of appropriate tools for detection of these events, is changing the status quo of these zoonotic parasites.
Highlights Increased demand for animal-derived protein from Fasciola hepatica-endemic countries has led to a growing number of reports of hybridization between F. hepatica and Fasciola gigantica in Southeast Asia. Hybridization and eventual introgression have been reported in a range of protozoan, helminth, and arthropod parasites and act as important drivers of evolutionary change and adaptation. Introgression between Fasciola spp. remains unproven but has potentially serious human and animal health consequences as seen in other parasites. New tools for the characterization of hybridization and introgression events between Fasciola spp. are needed.