Common Intestinal Parasites

Over 700 bacterial species inhabit the human colon, many of which are essential to good digestion and overall health. There are some intestinal parasites, though, that are at best benign and at worst potentially lethal.

The majority of those divide into two groups: one-celled organisms (called protozoans) and parasitic worms. They generally enter the gut as a result of consuming inadequately cooked or poorly washed food, or contaminated water. Once there, they find the mucous lining on the intestine a conducive growth environment and they reproduce.

The result is frequently an infection that, left untreated, can lead to harmful health consequences. That can run the gamut from unpleasant abdominal cramps with constipation or diarrhea to nausea, colitis, or even blindness.

E. vermicularis, for example, (a common roundworm) can induce sleep disturbances and infects about 200 million people worldwide. The adult male worms are about 2-5 mm in size (about the length of a pencil lead) and the females 8-13 mm. Females can lay up to 15,000 eggs. Fortunately, most die within 3 days and infection is often cured spontaneously by the immune system within 4-6 weeks.

Giardia, or G. lamblia, can cause nausea, vomiting, and diarrhea. This pear-shaped protozoan is extremely common, infesting more than 2.5 million individuals in the U.S. alone annually, according to the CDC. It can be spread by contact with feces or, because it's water borne, by drinking contaminated water. It's even resistant to the chlorine in normal tap water. Incubation generally takes 1-2 weeks, after which symptoms begin to appear.

Hookworms like A. duodenale can cause anemia. Along with its cousin, N. americanus, this parasite is less common today in developed countries than in the past, thanks to improved plumbing and better sanitation. Still, it is prevalent enough to be the second most common helminthic (parasitic worm) infection in the U.S.

One of the reasons is that, unlike many others, they can infect the host through the pores or hair follicles; they don't require a break in the skin or ingestion. Within about six weeks, the parasite has attached itself to the intestine where it feeds. Symptoms may not appear for long periods, but the hookworm acts like an anticoagulant, leading ultimately to blood loss and hence anemia. In advanced stages it can produce mental retardation in children.

E. histolytica may cause intestinal ulcers, fever, or peritonitis. It's unfortunately very widespread, producing up to 50 million cases per year worldwide, of which 100,000 or so are fatal. After malaria, it's the most second leading cause of death from protozoan infection. It acts to disrupt the mucous lining in the intestine, resulting in colitis, ulcers, and possible bloody diarrhea.

Fortunately, all of these can be guarded against with proper health procedures and most are readily treated, once diagnosed. Once infected, many antibiotics are effective. Naturally, prevention is always the best option. Food should be thoroughly washed and/or well-cooked. Keeping the immune system healthy and practicing good colon health can minimize the odds of disease in the first place.