Parasites that infect humans are much more widespread than many people realize. These diseases affect not only poverty-stricken peoples in remote areas of the world, but they also can be important health problems for rich and poor throughout the world, including the United States.

As with other parasitic diseases, roundworm infections are more common in warm climates than in cooler, temperate areas. Many roundworm parasitic diseases result from human carelessness and a lack of appropriate personal hygiene and sanitation measures. Thus, the best solution to the problem rests in preventing these infections rather than in curing them. Roundworms, or nematodes, range in size from those plainly visible to the naked eye to those several hundredths-of-an-inch long and visible only under a microscope. Most roundworms or their eggs are found in the soil and can be picked up on the hands and transferred to the mouth or can enter through the skin. With the exception of the roundworm that causes trichinosis, mature roundworms eventually end up or live in human intestines and cause a variety of health problems.

Some of the most common parasitic roundworms in humans are:

• Enterobius vermicularis, the pinworm that causes enterobiasis
• Ascaris lumbricoides, the large intestinal roundworm that causes ascariasis
• Necator and Ancylostoma, two types of hookworms that cause ancylostomiasis
• Trichuris trichiura, the whipworm that causes trichuriasis
• Strongyloides stercoralis that causes strongyloidiasis
• Trichinella spiralis that causes trichinosis