Intestinal worms are one of the most common causes of chronic infections worldwide. In the August 2003 issue of the "British Medical Journal," Dr. Shally Awasthi wrote that it is estimated that more than a quarter of the world's population are infected with one or more of the most prevalent parasites. These include roundworms, hookworms and whipworms.
Ascaris lumbricoides
Ascaris lumbricoides is a roundworm that causes the disease ascariasis. According to the Merck Manual, this is the most common intestinal worm infection worldwide, affecting over 1.3 billion people. Most infections occur in countries with poor sanitary practices, although the United States has an estimated 4 million cases. The National Institute of Allergy and Infectious Diseases, or NIAID, states that ascariasis occurs most often in children between 3 and 8 years old.
Ancylostoma duodenale and Necator americanus
Ancylostoma duodenale and Necator americanus both cause hookworm disease, which the Centers for Disease Control and Prevention, or CDC, reports as the second most common worm infection in humans. The Merck Manual estimates a worldwide hookworm disease prevalence of 1 billion, with most cases found in developing areas. Hookworms are an important cause of iron-deficiency anemia in these places.
Hookworms differ from other worms because they cause infection not through human ingestion of worm eggs or larva, but by penetrating human skin. People who walk barefoot on contaminated soil have increased risk of infection.
Trichuris trichiura
Trichuris trichiura causes trichuriasis, or whipworm disease. According to the CDC, this is the third most common roundworm disease of humans, with an estimated 800 million cases worldwide. Like many worm infections, trichuriasis presents most often in developing areas, but occurs in the southern United States as well.
Enterobius vermicularis
Enterobius vermicularis, also called human pinworm, causes enterobiasis or pinworm disease. The CDC reports it as the most common parasitic worm infection in the United States, with an estimated 40 million cases. In the March 2004 issue of the "American Family Physician," Dr. Corry Kucik states that pinworms affect an estimated 209 million people worldwide. Dr Kucik also wrote that more than 30 percent of the children in the world carry these worms.
According to the NIAID, enterobiasis occurs even in areas with good sanitary practices, with infections spread mainly by children. As such, it can often occur in schools, daycare centers and camps.
Hymenolepis nana
Hymenolepis nana, also known as the dwarf tapeworm, causes hymenolepiasis, which the CDC reports as the most commonly diagnosed tapeworm infection in the United States and worldwide. This often affects children and institutionalized people.
Fasciolopsis buski
Fasciolopsis buski, the largest human intestinal fluke worm, causes fasciolopsiasis. Ingestion of aquatic plants increases the risk of infection.
References
- "British Medical Journal"; Clinical Review-Helminthic Infections; Shally Awasthi, et al.; 2003
- Merck Manual: Nematodes (Roundworms)
- National Institute of Allergy and Infectious Diseases: Parasitic Roundworm Diseases
- CDC Division of Parasitic Diseases: Parasites and Health-Parasites of the Intestinal Tract
- "American Family Physician"; Common Intestinal Parasites; Corry Jeb Kucik, et al.; 2004
