Sounds like something from a bad science fiction movie on the SciFi channel. The parasitic hairworm, Spinochordodes tellini, develops inside grasshoppers or crickets, but is an aquatic worm in its adult stage. How to get from the grasshopper gut to body water, you ask? Brainwash the grasshopper into committing suicide. The hairworm produces proteins that interfere with the grasshopper's nervous system. These proteins mimic certain molecules of the grasshopper. The researchers found that grasshoppers carrying the worm expressed different proteins in the brain than uninfected grasshoppers and that some of these proteins were linked to neurotransmitter activities.
Crazy and creepy.