The correct answer is C, Enterobius vermicularis (pinworm).  Pinworm eggs contain an infective larva that hatches when the egg is ingested.  The female eggs and worms appear in the perianal area 3-7 weeks after infection.  The presence of worms and eggs may cause intense anal pruritus.  Scratching of the perianal region leads to contaminated fingers which can spread the eggs to utensils and food.  In this fashion, Enterobius can be transmitted between and among people without the soil phase or specific arthropod transmission vector.

Click here to open a new window with a schematic diagram of the life cycle of E. vermicularis.  Close the new window to return to this page.