It seems like science fiction, or some bizarre insect zombie movie, but...
Scientists have been researching the parasitic relationship between grasshoppers and the nematomorph hairworm (Spinochordodes tellinii). The hairworm lives and breeds in fresh water, but spends a part of its life eating the insides of live grasshoppers and then brainwashing the grasshopper into committing suicide by hopping into a pool of water and drowning. The hairworms, several times the length of the grasshopper at the time of the unfortunate incident, then emerge and continue their lifecycle in water. A team of researchers at the French National Center for Scientific Research is studying just how the hairworm manages to take over the body of the grasshopper.
This is just one example of a parasite seemingly taking over its host to produce specific results. In Costa Rica, there is a wasp whose larva lives inside the body of an orb-weaving spider. The evening before the larva kills the spider, the larva somehow manages to reprogram the web building activity of the spider so that it creates a durable platform for the larva to pupate on, instead of its usual temporary web. Studies show that if the larva is removed from the spider before the larva kills the spider, the spider will return to its usual web building activities within a couple of days.
And, if you think about it, the rabies virus makes animals so rabid that they want to bite others — which transmits the virus.