Parasites are some of the most fascinating — and unsettling — organisms on the planet. While many go unnoticed, others have evolved bizarre and often disturbing ways of surviving, from hijacking their host's body to altering behavior in ways that seem almost sci-fi.
In this list, we take a closer look at seven of the world’s strangest and most unsettling parasites. Some are creepy, others are just plain weird — and a few might make your skin crawl.
Weirdest parasites in the world
Tongue-eating parasite
What’s grosser than gross? A parasite that eats your tongue – and then lives in your mouth, as your tongue. Meet the nightmarish Cymothoa exigua. Luckily for us, the parasite is not interested in human flesh
Beginning life as a swimming form called a manca, a young isopod attaches itself to an appropriate host, passing through its gills and latching onto its tongue. Then it’s dinnertime. The uninvited guest sinks its syringe-like mouthparts into the meaty organ and begins draining it of blood.
The tick-sized isopod may grow as big as a cockroach within a few months. By then, it has extracted so much blood that the tongue withers away.
Guinea worm
Adult guinea worms can measure 600 to 800 mm in length and 2 mm in diameter, and their lifecycle is like something from a horror film.
A person becomes infected when they drink water contaminated by guinea worm larvae, residing in the body of small Cyclops crustaceans (the intermediate host). The cyclops is then dissolved in the stomach, releasing the worm larvae which then migrate through the intestinal wall and escape into the body. About a year later, after mating with the host, the now fully grown female will travel down the body, through muscles, to find an exit site. The worm will emerge, usually from the feet, erupting from the skin in an intensely painful blister. Horrific!
We named it one of the deadliest parasites in the world
Green-banded broodsac
One of the most revolting and horrific parasites is the flatworm Leucochloridium paradoxum or the green-banded broodsac says Aoife Glass (just look at the video above!) This parasite completes the first two parts of its life cycle in snails, but needs to get into a bird to complete the cycle.
To do this, it spreads tentacles through the circulatory system of the unfortunate snail host. Some of these end in broodsacs, and these grow up and into the eyestalks of the snail. These broodsacs are thick, wriggly, and pulsate, mimicking a worm or caterpillar, making them eyecatching for any birds that might be about. Sometimes the broodsac will explode out of the snail, but if the snail is really lucky, the bird will pull it out leaving the snail alive - at least for a while.
Candiru
Now this is something you definitely won't want to think about too much. This small parasitic fish from the Amazon River can cause significant damage by entering the human urethra, although such incidents are rare and often thought of as myths - however just the thought of it makes us think it deserves a place on this list - along with a place on our weirdest fish and our deadly fish lists...
African eye worm
One of the most terrifying worms in the world is the African eye worm. This parasitic worm, which is usually 1–3 inches long, can live in a variety of places inside the human body, from the lungs and lymphatic system to the tissues just under the skin. It can even cross the surface of the eyeball, causing 'Loiasis'.
The sight of the worm moving across the eye is both disturbing and painful, however the Mayo Clinic says they "don't cause blindness and usually don’t damage your eyes".
Spread by the bites of deerflies in West and Central African rainforests, Loa Loacan live inside a human for up to 17 years.
Sea lamprey
The sea lamprey is a most peculiar fish. It has a slimy, eel-like body and an alien-like mouth, and is a parasite, latching onto other creatures to feed. The first thing you notice about a sea lamprey is its remarkable mouth. It’s a perfectly round, sucker-like disc, wider than its body and lined with concentric rings of pointy little teeth.
It expertly uses this appendage to attach itself to other fish and marine mammals, piercing their flesh with its file-like tongue to feed on their fluids, a habit that has given rise to colourful monikers such as ‘vampire eel’ and ‘eelsucker’
Zombie-ant fungus
This is like something out of the Sky drama The Last Of Us! Once infected, the ant is controlled by the fungus, which causes it to leave its nest, climb up the stem of a plant and secure itself in place with a death grip – usually about 25cm above the forest floor. Once there, the fruiting bodies grow out of the ant’s head and shower spores down onto the ground below – the aim is infect more ants.
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