The things you make me do
It’s strange but true. A microscopic single celled organism can change the behavior of animals that it infects. From a snail that climbs instead of hiding below, to rabies, to a disease that causes rodents to lose their fear of cats; behavior can be changed by a sickness to make it more likely that the disease will spread.
Here are some articles on toxoplasmosis, which can cause rats and mice to become unafraid of, and even become attracted to, cats.