Medically Reviewed by Debra Jaliman, MD on August 06, 2021

Acanthamoeba

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If you wear contact lenses, don’t wash them in tap water. You might pick up this bug, which can burrow into your eye and cause an infection called Acanthamoeba keratitis. Symptoms include redness, a feeling that something’s in your eye, and sensitivity to light. If it isn’t treated, you could lose your sight. It’s most common among contact lens wearers, but anyone can get the bug. It lives in bodies of water like lakes and oceans, and in soil and air.

Loa Loa

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This worm is a parasite that spreads through deer-fly bites. It burrows into your skin and causes itchy areas around your joints called Calabar swellings. It also leads to an infection called loiasis, or African eye worm. You may even see the worm as it crawls across the surface of your eye or under your skin. But you probably won’t get it unless you spend time in the rain forests of West and Central Africa.

Chigoe Fleas

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These bugs, known as sand fleas or jiggers, dig into your feet at the heel, sole, or toes. They cause a skin disease called tungiasis. You don’t feel it when they go in. But they grow up to 2,000 times bigger once inside your foot. This makes your skin itchy and irritated. Your foot may also swell and get ulcers. Some people get gangrene or tetanus. Chigoe fleas live in sandy, tropical places, and aren’t common in the United States.

Sparganum

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This tapeworm can grow up to a foot long in your intestines. It’s rare for people to get it in the U.S., but animals can have it. Most human cases are in Southeast Asia. Sparganum can live almost anywhere inside your body for up to 20 years. The infection doesn’t usually cause symptoms, unless it’s in your brain. Then you can have weakness, a headache, numbness, tingling, or a seizure.

Filarial Worms

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These squirmers are way too small to see without a microscope. You get them when an infected mosquito bites you. They live in your lymph system and cause a disease called lymphatic filariasis. It can lead to fever, swollen lymph nodes, and a buildup of fluid in your body. Most people never have any symptoms, though. The worms are most common in the tropics. They don’t affect people in the U.S.

Screwworm

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This pest isn’t a worm at all -- it’s a fly. Adults lay eggs on a cut or sore on your skin. When they hatch, the larvae feed on the wound and cause an infection. Livestock get it more often than humans. It’s most common in South American and Caribbean countries. 

Naegleria Fowleri

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This is called the “brain-eating amoeba” because it destroys brain tissue. It lives in warm lakes and rivers, and it can travel up your nose when you swim. Symptoms include headaches, fever, nausea, and vomiting. Later, it can cause stiff neck, seizures, and hallucinations. Most infected people die, but the disease is rare. Between 1962 and 2008 there were 111 reported cases in the U.S., mostly among young, healthy men.

Gnathostoma Spinigerum

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This spiky parasite travels through your stomach wall after it infects you. It’s most common in cats, but people can get it by eating undercooked freshwater fish. You can’t catch it from a person who has it. The larva infects your stomach and liver first, causing pain. Then it moves to your skin, which swells and itches. It can be deadly if it gets into your nervous system. It’s mostly found in Southeast Asia and is rare in the U.S.

Ticks

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These pests can dig into any part of your body, but they really like folds, creases, or hairy areas like your scalp. They can range from the size of a sesame seed to that of an apple seed or larger. They tend to hang out on tall grass and shrubs, and they hook onto you when you brush against them. Ticks cut into your skin so they can stick in a tube and suck out blood. The ones that carry Lyme disease and Rocky Mountain spotted fever and other conditions infect you as they feed

Kissing Bugs

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These critters get their name from where they like to bite -- around your mouth and eyes. They usually attack while you’re asleep. They often hang out in woodpiles or rats’ nests. They’re also drawn to the lights and carbon dioxide in your house. They feed on both pets and people. Their bite can cause an allergic reaction. They also spread Chagas disease, which can be life-threatening.

Scabies

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These mites dig tunnels under your skin and lay eggs in them. You can get them if you have close contact or sleep in the same bed with someone who has them. They’re too small to see, though. They prefer the skin between fingers, arm and leg folds, the penis, breasts, and shoulder blades. It can take up to a month for you to feel the itch. Your doctor will give you something to get rid of them.

Lice

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Three kinds of them live on people: body, head, and pubic lice. These sesame seed-sized bugs grab onto hair and feed on blood through your skin. Mostly they make you itch, but they can spread disease. You get them from direct contact with a person who has them. Pubic lice can be spread through sex. Lice are very common. Treat them with over-the-counter and prescription medications.

Chiggers

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When you think of critters that dig in, chiggers may be the first things that come to mind. But they don’t burrow. They attach to your outer layer of skin and feast on the cells. Once the bug is full, it lets go. This usually takes 3 days. In the meantime, the bites itch. A lot. Chiggers live in shady, grassy areas or on leaves close to the ground. They like areas under the tight parts of clothing, like waistbands or sock cuffs.

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