Threadworms in humans

Answer 1

Threadworm actually refers to two different parasites and both are found in humans. The first is Enterobius vermicularis,which is more commonly referred to as a pinworm or seatworm in the U.S. - the British and Australians refer to it as a threadworm as a common name. This is the most common parasite (particularly in children) in the United States. This is highly contagious and you can get it from contact with eggs, which can be essentially anywhere, but is very common in children due to hygiene issues. This nematode infects the large intestine (predominantly) and causes intense anal itching, mostly at night when the females exit the anus to lay their eggs.

Threadworm, as a common name, also refers to Strongyloides stercoralis in the U.S. The British refer to this nematode as a pinworm instead of threadworm. This worm lives in the mucosa of the small intestine - hence, it 'threads' itself in the intestine. Strongyloides has 53 species and can be found in many mammals, including cats and dogs. This animal has a more complex life cycle (i.e. heterogonic) and can alternate between free-living and parasitic cycles. Since this worm penetrates the skin (you get this one from soil), you have multiple symptoms depending upon the part of the life cycle it is in. Itching at the site of penetration, chest burning, wheezing and coughing during the lung migration phase and then chronic diarrhea in the intestinal phase, among other symptoms.