Parasites are organisms that live inside humans or other organisms who act as hosts. They are dependent on their hosts because they are unable to produce food or energy for themselves. Parasites are harmful to humans because they consume needed food, eat away body tissues and cells, and eliminate toxic waste, which makes people sick.
Because of sanitary living conditions in America, parasites do not cause widespread life-threatening infections. In other parts of the world, however, parasitic infections are epidemic. They kill and disable millions of people every year. Parasitic infection cases in the United States are on the rise due to increased travel to and from underdeveloped countries. In addition, parasitic infections can cause severe infections in AIDS patients and other patients with weakened immune systems.
Because parasites can live inside the human body for years without making their presence known, they are more common than one might think. According to a recent study, approximately half of all Americans have at least one form of parasite. Their presence causes a variety of chronic diseases and conditions such as chronic fatigue, weakness, low energy levels, skin rashes, pain, constipation and frequent colds and influenza.
There are two types of parasites: large and small. Large parasites such as intestinal worms are easily seen with the naked eye. These are roundworms, flukes, and tapeworms. They usually lay their eggs on the intestinal walls. As they hatch, the young larvae feed on the food in the intestinal tract. Then they grow, reproduce, and start the cycle all over again. They sometimes dig through the digestive tract to get into the bloodstream, muscles, and other organs where they cause even more havoc. These types of parasites most often cause malnutrition and anemia because they tend to rob the body of essential nutrients it needs.
Small parasites—mostly protozoa and amoebae—are so tiny that they can only be seen with a microscope. These tiny parasites are even more dangerous to the body than the large ones. Although they usually stay in the intestines, they can migrate virtually anywhere in the body: into the bloodstream, muscles, and even vital organs such as the brain, the lungs, or the liver, where they do substantial damage.
Because parasites are everywhere, it is not difficult to become infected. People can become infested through:
eating raw or undercooked pork, beef or fish
eating contaminated raw fruits and vegetables
eating foods prepared by infected handlers
drinking contaminated water
contact with infected persons (including sexual contact, kissing, sharing drinks, shaking hands, or sharing toys)
inhaling dust that contains parasitic eggs or cysts
playing with or picking up pet litter contaminated with parasitic eggs or cysts
In 2002, the Centers for Disease Control (CDC) announced the first documented cases of transplant patients contracting a dangerous parasitic disease from infection with T. cruzi from organs harvested from a Central American donor. The infection caused Chagas disease, causing two of the three donor recipients to die. The CDC was studying additional precautions to screen for parasitic infections like T. cruzi, explaining that even blood donors were not currently screened for the parasite. However, the agency also stressed that tissue graft surgery was still a safe procedure.
Mai Tran, Teresa G. Odle, The Gale Group Inc., Gale, Detroit,