U.S. National Library of MedicineNational Institutes of Health
Skip navigation
MedlinePlus Trusted Health Information for You MedlinePlus Trusted Health Information for You MedlinePlus Trusted Health Information for You
Contact Us FAQs Site Map About MedelinePlus
español

Printer-friendly version E-mail this page to a friend
Illustration of the digestive system organs

Parasites are living things that use other living things - like your body - for food and a place to live. You can get them from contaminated food or water, a bug bite, or sexual contact. Parasitic diseases can cause mild discomfort or be deadly.

Parasites range in size from tiny, one-celled organisms called protozoa to worms that can be seen with the naked eye. Some parasitic diseases happen in the United States. Contaminated water supplies can lead to Giardia infections. Cats can transmit toxoplasmosis, which is dangerous for pregnant women. Others, like malaria, are common in other parts of the world.

If you are traveling, it's important to drink only water you know is safe. Prevention is especially important. There are no vaccines for parasitic diseases. Some medicines are available to treat parasitic infections.

Start Here
Basics Learn More Multimedia & Cool Tools
  • No links available
Research Reference Shelf For You