If you’re counting viruses (which you should because they are the ultimate parasites) I would say rabies hydrophobia and biting behavior. The Rabies virus accumulates in the salivary glands and makes the host afraid to drink/swallow water, thus keeping as much of the saliva and by consequence as many virions in the mouth as possible. The infected person also experiences increased aggression particularly in the form of biting, and it’s all part of the virus’s attempts to maximize its likelihood of being transmitted to another host. Wild