Common Intestinal Parasites in Humans

More than seven hundred bacterial species reside the human intestinal tract, most of which are essential to good digestive function as well as overall health. However, there are some intestinal parasites, which are at best benign and at worst potentially lethal. The vast majority of those divide into two groups, which are single celled organisms, called protozoans, and parasitic worms.

They typically get into the gut due to the consumption of improperly cooked or poorly washed food, or contaminated water. Once there, they find the mucous lining on the intestinal tract a favorable growth environment and they reproduce. The result is often an infection, which, if left untreated, may result in harmful health consequences. That can vary wildly from uncomfortable stomach cramping with constipation or diarrhea to nausea or vomiting, colitis, or maybe even blindness.

E. vermicularis, for instance, (a common roundworm) can cause sleep disturbances and infects around two hundred million folks globally. The adult male worms are approximately 2-5 mm in size (about the length of a pencil lead) and the females 8-13 mm. Females can lay as many as fifteen thousand eggs. Luckily for us, the majority die within three days and infection is usually cured spontaneously by the immune system within four to six weeks.

Giardia, or G. lamblia, can cause nausea, vomiting as well as diarrhea. This pear shaped protozoan is very common, infesting well over two and a half million folks in the U.S. alone each year, according to the Centers for Disease Control. It can be spread by contact with fecal matter or, since it is water borne, by consuming contaminated water. It is even resistant to the chlorine in normal tap water. Incubation typically takes one to two weeks, after which symptoms start to appear.

Hookworms such as A. duodenale can cause anemia. Together with its cousin, N. americanus, this parasite is less common nowadays in developed countries than in the past, because of improved plumbing and much better sanitation. Nevertheless, it is prevalent enough to be the second most common helminthic (parasitic worm) infection in the U.S.

A primary reason is that, in contrast to many others, they are able to infect the host through the skin pores or hair follicles. They do not require a break in the skin or ingestion. Within five to six weeks, the parasite has attached itself to the intestine where it feeds. Symptoms might not appear for very long periods, but the hookworm acts like an anticoagulant, leading eventually to loss of blood and therefore anemia. In advanced stages it can develop mental retardation in children.

E. histolytica can cause intestinal ulcers, fever, or peritonitis. It is unfortunately extremely prevalent, producing as many as fifty million cases annually worldwide, of which one hundred thousand or so are fatal. After malaria, it is the second leading cause of death from protozoan infection. It acts to disrupt the mucous lining in the intestinal tract, leading to colitis, ulcers, and possible bloody diarrhea.

Fortunately, all of these can be guarded against with proper health procedures and the majority are easily treated, once diagnosed. Once infected, many anti-biotics are effective. Normally, prevention is always the best option. Food needs to be thoroughly washed and/or well cooked. Keeping the immune system healthy as well as practicing good colon health can reduce the chances of disease to begin with.

Page Updated: November 12, 2016
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