Galactosomum

Galactosomum is a genus of flukes within the family Heterophyidae, which is part of the order Opisthorchiida. There are currently twenty-one recognised species within the genus. They mainly infect aquatic birds, but often infest fish as larvae. Three species are known to use marine mammals as hosts.

Inaccurately known as a species in popular culture, due to its mention in Resident Evil 4 as an example of a parasite which controls, or alters, the behavior of the host. This is based on some species of Galactosomum that cause infected fish to swim closer to the surface. Gastropods hosting select species suffer from sensory impairment due to infestation. This makes these prey animals more likely to be consumed by aquatic birds, providing a host for the parasite to reach the mature stage of its life cycle.