A very common parasite, roundworms live inside the small intestines of canines and felines. Young puppies and kittens can become infected before birth and via nursing. Eggs are passed inside the feces, develop within as little as one week, and remain infective in the soil for years.
Canines and felines become infected with roundworms by walking across contaminated soil then licking their paws or from contaminated feces, vegetation or infective larvae in small mammals or birds.
Roundworms also have the potential of harming people. Roundworms enter the body as eggs which soon develop into larvae. The larvae can migrate through major organs. In most human cases, no symptoms exist. However, the larvae can cause tissue damage which can affect the nerves and the eye, causing permanent eye damage, even blindness.