A parasitic infection, worms may live in the intestines, blood, lymphatic system, bile ducts or organs. In many cases there are little or no symptoms, but some can cause chronic illness. There are two main classes - roundworms and platyhelminths, with subdivisions commonly known as tapeworms and flukes.
It may be caused by eating undercooked, infected meats, coming into contact with infected soil or water, or accidental ingestion of worm eggs from the soil. Most infections are easily solved with anthelmintic drugs.