Pinworm is a nematode parasite that lives in the human rectum, and causes itching in the anal area. What best explains the itching symptom?

Question

A.  Any kind of parasite will naturally irritate the skin.
B.  The itching induces the person to scratch, helping to spread the parasite to another person.
C.  The itching is a side-effect when the immune system has successfully attacked the nematode.
D.  The itching is because of the mismatch between humans and the parasite’s natural host.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content
· What do you already know about nematode diseases?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  The itching induces the person to scratch, helping to spread the parasite to another person.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses nematode diseases.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.

Gather Content
· What do you already know about nematode diseases?
        o About 50 species of nematodes, including ones in the United States, parasitize humans.
        o Hookworms suck blood through the intestinal wall, causing anemia.
        o Eating undercooked meat can cause trichinosis, an infection of the worm Trichinella, which can sometimes be fatal.
        o The intestinal roundworm Ascaris lumbricoides infects approximately one of six people worldwide, but is rare in areas with modern plumbing.
        o Filariasis is caused by several species of nematodes that infect at least 250 million people worldwide. Wuchereria bancrofti can cause elephantiasis, in which the lower extremities may swell to disfiguring proportions. The larvae are typically transmitted by a mosquito.
        o Pinworms, Enterobius vermicularis, infect 11% of the people in the United States, mainly children. Adult pinworms live in the human rectum where they usually cause nothing more serious than itching of the anus; large numbers, however, can lead to prolapse of the rectum. The worms can easily be killed by drugs.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o A common need for every parasite is the necessity for offspring to travel to a new host. This is achieved in a variety of ways. Some use an intermediate host, like the mosquito.
        o In the pinworm, however, the itching symptom induces the host to scratch, carrying eggs on the hands and allowing them to possibly infect a new host.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that causing itching benefits the parasite by helping it to spread?