Parasite

Parasites are worm like creatures that are in medium mobs, the medium mobs are cows, sheep, pigs, llamas, dolphins, etc. They come out to attack you if you kill their host, they are a little taller than silverfish and 3x longer than a silverfish. They deal a half a heart and have 10 hp. They move fast and glide underwater. The way you tell if a mob has a parasite is if they start running/swimming around for no reason.