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Common Intestinal Parasites

Roundworms, invertebrate organisms that range in size from 0.04 inches to longer than 3 feet, cause some of the most common parasite infections in humans. Poor sanitation and inappropriate hygiene practices contribute greatly to the spread of infection. Roundworm infections are more prevalent in warm or tropical climates, although people in any climate may be infected. The symptoms of parasite infections vary depending upon the type of worm.

  1. Ascaris

    • The ascaris roundworm causes a common human parasitic infection called ascariasis. According to the University of Maryland Medical Center, approximately 1 billion people around the world suffer from this disease. It infects people when they accidentally swallow ascaris eggs. The eggs hatch into larvae in the small intestine. They travel through the lungs and then into the throat, according to the Centers for Disease Control and Prevention, where the host swallows them back into the intestine. They develop into adult worms within the intestinal system, laying eggs that pass from the body through the feces. Infected people may see worms or blood in their stool. Other symptoms of infection include coughing and shortness of breath, stomach upset or pain, lack of energy and weight loss.

    Hookworms

    • Ancylostomiasis, or hookworm infections, affect about 25 percent of the world's population, according to the University of Maryland Medical Center. The CDC explains that infected people pass hookworm eggs out of the body through the stool and into the soil. The eggs, which develop into larvae, wait in the soil for an appropriate host. Infection occurs when a person steps on the larvae in his bare feet. The parasites burrow through the skin and enter the bloodstream. The bloodstream carries the larvae to the lungs and windpipe; the host swallows the parasites down into the intestine. The larvae, which mature into half-inch worms, attach themselves to the intestinal wall and live off the host's blood. Infected people suffer from an itchy rash at the point of entry, as well as stomach pain, appetite and weight loss, cough, wheezing and other breathing problems.

    Pinworms

    • Slender white roundworms called Enterobius vermicularis cause pinworm infections. According to My Cleveland Clinic, pinworms are the most common type of roundworm parasite in temperate climates. They infect up to one-third of children in some parts of the United States. Pinworms, which are often found in day-care centers and schools, enter the body when the eggs are ingested. The eggs stick to food, faucet handles, doorknobs and counters. Children become infected when they touch a contaminated object and then place their fingers in their mouths. Pinworms live in the colon and rectum. Female worms exit the body through the anus to lay eggs on the surrounding skin. Infected children experience intense itching that interferes with regular sleep.

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