An adult pinworm. Note that the posterior end (on the right) is drawn to a fine point. You can also see the cephalic alae at the anterior end.
Pinworms (Enterobius vermicularis) are not at all tropical, but thrive in temperate climates, and they are the only one of our helminthic infections that can be immediately passed from person to person. The pinworm is the smallest of our four worms, measuring only ½ inch. They are also round and white. Adult pinworms inhabit the large intestine, and at nighttime, the fertilized female ventures towards the rectum to deposit her eggs. Why she does this at night is a Nobel Prize waiting to be won! These eggs are quite sticky, and irritating, so that most children, and adults, will eventually scratch the area, and more than likely then put their fingers in their mouth, or onto someone else’s hands. In this way, the infection can be easily passed on to others, or perpetuated within oneself. The usual symptoms are itching around the rectal area, at night, though sleeplessness, abdominal pains or vaginal symptoms may also occur. The tiny worms may be seen at night, especially if you shine your flashlight on the itchy area at midnight!
An adult pinworm. Note that the posterior end (on the right) is drawn to a fine point. You can also see the cephalic alae at the anterior end.