Hidden digenean diversity in two African protected areas: metabarcoding as a tool for parasite identification

African protected areas support exceptional wildlife diversity, yet their parasite diversity remains poorly characterised. Documenting parasite biodiversity is increasingly urgent as global change alters species distributions and threatens to cause mass parasite extinctions. Digenean trematodes are thought to be particularly sensitive to environmental stressors due to their complex life cycles, involving gastropod intermediate hosts and a wide range of secondary and definitive hosts. This study used a metabarcoding approach targeting the nuclear 28S rDNA region with the aim of characterising trematode communities within freshwater snail hosts from two southern African protected areas: Kruger National Park, (KNP), South Africa and Bwabwata National Park (BNP), Namibia. Additionally, patterns of alpha diversity and trematode co-infection across snail species were assessed within both parks. Metabarcoding revealed high trematode diversity and co-infection rates in snail hosts, detecting species of veterinary (Schistosoma mattheei, Fasciola gigantica) and conservation (Riberioa cf. ondatrae) importance, across different snail species in both parks. The invasive snail Tarebia granifera in KNP showed significantly higher trematode richness compared to all other snail species, with all sampled individuals showing co-infection. Metabarcoding is a promising tool for assessing parasite diversity and within host communities, although there is an urgent need for improved trematode molecular reference databases. This work has important implications for biodiversity management, veterinary health and public health surveillance in African wildlife protected areas.