According to the Cleveland Clinic, this parasite is most commonly found in tropical areas like the southern United States. The whipworm is a species of roundworm shaped like a whip. Whipworm eggs are passed by the feces. Dogs catch whipworms by ingesting contaminated soil, food or feces. Infection rates in humans are high, especially in children. Infection occurs by ingestion of eggs or worms in soil or on contaminated food. Like most worms, the whipworm responds to drugs and is easily killed. Even if left untreated, most infestations are not severe. The best prevention comes from regularly deworming pets and washing hands after contacting soil.