It is gross to think about, but did you know that some worms can live in your liver? Liver fluke, a type of flatworm, can infect your liver and make you very sick. These parasites grow in freshwater snails before they invade a mammalian host. Liver flukes infect millions of wild animals, farm animals, and humans worldwide. Here, we studied an invasive snail species and their liver fluke parasites in Lake Kariba in Africa – the largest manmade lake in the world. We found large numbers of snails from North America that are new to the lake. The majority of these snails were infected with a native liver fluke parasite. We also found another non-native invasive species, the water hyacinth, a floating water plant. The snail population was higher in areas where the hyacinth population was also high. Our study shows that artificial lakes are vulnerable to a chain of biological invasions. And this may promote the spread of native parasites.