Parasitic Infections Health Article

Definition

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.

Description

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:

• insect bites
• walking barefoot
• 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.

Causes & symptoms

Risk factors for getting parasitic infections include:

• an immune system weakened by disease or long-term exposure to toxic chemicals or environmental pollution
• prolonged antibiotic use
• alcohol and/or drug abuse
• smoking
• emotional and/or physical stress
• diet high in fat and sugar and low in fiber
• food allergies
• malabsorption syndrome
• obesity

Causes

There are more than 100 types of human parasites. The following describe some of the most common species in America.

ARTHROPODS (INSECTS). In the United States, because of high sanitary standards and a temperate climate, parasitic insects do not flourish. Common bugs such as ticks, mites, fleas, lice, and bedbugs may cause intense itching in affected areas. They are a nuisance but not a major health risk. One exception is the deer tick, which is associated with the debilitating Lyme disease. Other parasites, spread by mosquitoes, cause more serious diseases like western and eastern equine encephalitis, malaria, Dengue fever, and yellow fever.

INTESTINAL PARASITES. Some of the most common intestinal parasites include:

• Pinworms. This is the most common parasitic infection in the United States. The worm resides in the colon, yet it lays eggs outside the body, usually near the anus, a process that causes severe itching. The disease can be transmitted from one individual to another through dirty hands, clothing, bedclothes, and toys.
• Tapeworms. The two most common tapeworms are Taenia solium (pork tapeworm) and Taenia saginata (beef tapeworm). Taenia solium infestation is caused by eating undercooked pork while Taenia saginata (pork tapeworm) infestation is associated with consuming raw beef. Adult tapeworms may become quite big, some as long as 20 feet (6.1 m). Pork tapeworm is the more harmful. It often causes anemia and weight loss. More seriously, when adult pork tapeworm eggs, excreted in human feces, are ingested by other people (which can happen with poor hygiene and sanitation), the parasitic life cycle that occurs in pigs and cattle takes place in the human host. Once in the human digestive system, the tapeworm eggs, called proglottids, develop into an embryonic form of the parasite called onchospheres that burrow through the intestinal wall and into the bloodstream. From there they migrate into the muscles, eyes, and the brain, a condition called cysticercosis. Cysts in the brain often cause epileptic seizures.
• Protozoa (one-celled organisms) such as Giardia lamblia, Entamoeba histolytica, or Cryptosporidium. These organisms are some of the most common and infectious parasites in the world. They can be transmitted through contaminated food and water. They can also be spread from one person to another. Protozoa may spread throughout the body, causing abscesses in the lungs, liver, heart, and brain. Cramps, watery diarrhea, abdominal pain, and serious weight loss are common symptoms of Giardia infection. Entamoeba histolytica can cause dysentery, a severe form of intestinal infection, as well as liver and lung damage. Cryptosporidia can cause severe diarrhea in AIDS or cancer patients who have weakened immune systems.

CNS PARASITIC INFECTIONS. Toxoplasma gondii is the most common parasite that invades the central nervous system (CNS). Humans become infected with this organism by eating raw or undercooked meat or by handling infected cat litter, which can contain eggs. Pregnant women who are infected may miscarry or deliver stillborn babies. Infected babies are born with congenital toxoplasmosis, and have symptoms that include eye inflammation, blindness, jaundice, seizures, abnormally small or large heads, and mental retardation. In people with weakened immune systems, such as AIDS patients, toxoplasmosis can affect the whole body, causing inflammation, convulsions, trembling, headache, confusion, paralysis in half of the body, or coma.