The creepiest thing about a parasite in the animal world is that the creature can get so close to the host, they may never notice its presence. To be a good parasite, stealth is highly valued, or else you could be detected and lose your steady funnel of lunch. Let's hope these parasites don't make the jump into humans and start making us into zombies too.
1
Sacculina: This creature is a barnacle with a penchant for castrating both male and female crabs. It will also alter the mind of a male crab and force him to protect the sacculina's offspring like a female crab would do for her young.
2
Hairworms: These parasites like to infect crickets but must return to the water to reproduce. They tend to burrow deep into the brain, forcing crickets to walk to bodies of water and essentially commit suicide by diving in.
3
Insect iridovirus: This is a type of sexually transmitted virus that only effects a specific species of cricket. It eventually kills the bugs, but first it alters their brain to really want to have more sex, causing the infection to spread further into the cricket population.
4
Euhaplorchis californiensis: This parasitic worm burrows into the skulls of killifish and forces them to dance, jerking in such a way that it makes them easy prey for birds. The parasite's eggs are then transmitted through the bird's feces back into the water.
5
Toxoplasma gondii: A symptom of infection by these parasites is that it alters the sexual behavior of smaller warm-blooded animals. However, recent studies show it might also affect humans. Studies found that the virus causes introversion in men and extroversion in women. It's been estimated that a third of the world's population has been exposed to it.
6
Green-banded broodsac flatworm: Once this flatworm infects a snail, it controls its brain and causes the snail to climb to the highest leaves on the trees. It then pushes its larvae into the eyes of the snail, making it more visible to birds who can spread larvae further across the forest.
7
Zombie fungus: The brains of ants are soon infected after walking across this fungus. The parasite forces the ant to find a sufficient enough place on another plant to release the fungus's spores. Wherever the ant dies, more fungus will sprout from its head like a living monument to the horrifying process.
8
Hymenoepimecis argyraphaga: This is a Costa Rican wasp that lays its eggs in the belly of a spider. An injection causes an imbalance in the spider's brain, forcing it to spin a web for the specific purpose of building a cocoon to hold the wasp's larvae.
9
Zombie fungus: The brains of ants are soon infected after walking across this fungus. The parasite forces the ant to find a sufficient enough place on another plant to release the fungus's spores. Wherever the ant dies, more fungus will sprout from its head like a living monument to the horrifying process.
