Honey I Passed a Worm!
An Overview of Parasites
Not everyone who returns from the tropics has the pleasure of passing a worm, but some do! It can be a little bit disconcerting to say the least, but don't let panic set in .. Grab that worm!
While there are a zillion different worms which infect humans, only four of them will make their exit via the rectum. Therefore it is fairly easy for someone with a bit of helminthic (worm) experience to figure out what species you have passed. After reading this section, you will also be able to make an educated guess. The four worms which I will describe differ in size, shape, length and means of acquisition.
Roundworms (Ascaris lumbricoides) are transmitted through infected food or water, and is usually acquired in the tropics, though there are some communities in North America where it is still transmitted. It is unlikely that the average traveller would encounter this charming worm, though those who are a bit off the beaten path might. The worm is usually a pinkish-white in colour, and is round, much like an earthworm. It can be up to 6 inches in length. Most infected people have no symptoms from a roundworm infection other than the sheer horror of seeing it crawl into the toilet bowl! Often, it is because they are unable to find a sexual partner that the lonely roundworm makes this terminal migration out of our bowels.
The Whipworm (Trichuris trichiura) is also round, much shorter (about 1-2 inches), and curved somewhat like a bull whip. It is also limited to the tropics, where it is acquired through the ingestion of contaminated food and water. Considering that these worms do not divide in their human host, and that most people don't pick up very many worms to start with, they are usually fairly inocuous.
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!
Tapeworms are a bit different. They are flat. Almost ribbony. They are often passed as short little segments of less than an inch, but if the whole worm were passed intact, it could be as long as 30 feet! There are three human tapeworms, the beef tapeworm (taenia saginata), the pork tapeworm (taenia solium) and the fish tapeworm (diphyllobothrium latum). They are contracted by eating raw or undercooked meats. This is sometimes the local custom, sometimes due to carelessness, and sometimes due to a need to sample the food as it is being prepared.
The symptoms of tapeworm infections are usually mild, and it is usually a short segment wriggling around the rectum that gives it away. However there can be other complications from these worms, so don't forget to cook your meat!
Most travellers who pick up some sort of intestinal worm in the tropics do not become terribly ill. This is in part because the worms do not divide in humans, so if we only get infected with one worm, we stay with just one worm. In addition, most worms require in incubation period outside of our body, like a few weeks spent in some warm, moist soil. Considering that we have toilets year round, and snow for part of the year, these infections are not usually transmitted in temperate climates. Pinworm infections are an exception to these rules!
Read more about parasites on Comeunity: Adoption Health (Parasites)
©Dr. Mark Wise is the director of The Travel Clinic (TM) in Thornhill, Ontario, Canada and the Medical Director of The Travel Wise (TM) Clinic in Scarborough, Ontario, Canada. He is a family physician with training from the London School of Tropical Medicine in Tropical Diseases.
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