Insects, spiders, snakes. There are so many creepy-crawlers that freak people out, and just the thought of them induces a feeling of itchiness that’s really not there. But while thinking about these, many of us forget that there are more disturbing animals to consider: parasites that live inside us.

While insects like flies and mosquitoes may leave you with a disgusted feeling after coming close — usually through their incessant buzzing — it’s the parasites they carry that pose the real threat. In the video below, from YouTube channel AllTime10s, we’re introduced to 10 of the most horrifying parasites that feed off our innards. Trypanosoma brucei, the cause of African trypanosomiasis, which is characterized by “sleeping sickness” and neurologic deterioration, is transmitted via tsetse fly. Ascaris lumbricoides is a worm that lives in the small intestine, where it produces up to 200,000 eggs per day. The 35 centimeter long worm can live in the intestine for up to two years without causing any symptoms in its host.

Although all of the parasites featured in the video are truly gross, and live in millions, perhaps billions, of humans around the world, the video fails to mention one of the most prevalent parasites known to humankind: malaria-causing plasmodium. In 2012, malaria affected an estimated 207 million people while causing 627,000 deaths, according to the World Health Organization. On top of that, the UN health agency puts as many as 3.4 billion people at risk of infection. The parasite is transmitted through mosquitoes, and causes severe fevers and body aches, and in rarer cases, anemia, low blood pressure, kidney failure, and hypoglycemia.