Some healthy fish have bacteria in their brains
Microbes in animal brains are typically linked to disease
![An illustration of a rainbow trout is shown from the middle of the fish's body to the fish's head](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2024/09/091824_eg_fish-brain_feat.jpg?fit=1030%2C580&ssl=1)
Brains are usually thought of as a bacteria-free zone. But that’s not the case for certain fish, including rainbow trout (illustrated) and other species in the salmon family.
Duane Raver/USFWS