Question

The most common worm in children is:
a. Ascaris lumbricoides
b. Enterobius vermicularis
c. Ancylostoma duodenale
d. Trichinella spiralis

Answer 1

Hint: There are a variety of parasitic worms found in the human body such as flatworms and roundworms. Parasitic worms need not necessarily be parasites on humans, different parasites have different hosts. These can be ectoparasites, those which live on the host or endoparasites, those which live inside the host. The risk of getting infected is higher in places where food and water might be contaminated and sanitization is poor.

Complete answer:
Ascaris lumbricoides: Ascaris, the common roundworm is a helminth which is pathogenic to humans. It is an intestinal parasite which causes ascariasis. This is generally observed in adults with symptoms such as internal bleeding, muscular pain, fever, anemia and blockage of intestinal passage. One can acquire infection through contaminated food and water.
Option (a) is incorrect.
Enterobius vermicularis: The nematode (roundworm) E. vermicularis is widely known as the human pinworm due to the female’s long, pointed tail. It hatches in the small intestine of humans. The adults migrate to the large intestine and the females move to the perianal area. Small children contaminate their hands/fingernails and with their habit of sucking their fingers, they get infected. This causes pain, rashes and skin irritation around anus.
Option (b) is correct.
Ancylostoma duodenale: This hookworm is an endoparasite of the human small intestine. The adults are found attached to the wall of the small intestine and feed on blood. Their larvae can penetrate the skin of humans and the infection is mainly transmitted by walking barefoot over contaminated soil or through ingestion of larvae. Itching and localized rash are common symptoms.
Option (c) is incorrect.
Trichinella spiralis: These are also endoparasites of the small intestine. They live the majority of their adult life in the intestines of humans. The life cycle begins in pigs where it produces larvae that invade pig’s muscles, which later causes infection, when the contaminated pork meat is eaten undercooked or raw.
Option (d) is incorrect.

Hence the correct answer is option (b).

Note:
The parasites may have 2 or more hosts. The host may be primary/definitive, secondary/ intermediate depending upon the stage of parasite inside the host. Primary host is the one in which the host performs the sexual reproduction and the secondary is the one where the sexually immature parasites develop. For some parasites humans are primary and for some humans may be the intermediate host.