Parasitic worm: A worm classified as a parasite. (A parasite is a disease-causing organism that lives on or in a human or another animal and derives its nourishment from its host.) Lice are examples of parasites that live on humans; bacteria and viruses are examples of parasites that live either on humans or in humans; parasitic worms (also called helminths) live in humans.
Helminth eggs contaminate food, water, air, feces, pets and wild animals, and objects such as toilet seats and door handles. The eggs enter the body of a human through the mouth, the nose and the anus. Once inside the body, helminth eggs usually lodge in the intestine, hatch, grow and multiply. They can sometimes infest other body sites.
Diagnosis of helminth diseases in humans usually requires a medical history and physical examination, a laboratory analysis of stools, and sometimes other tests.
Treatment in most cases involves the use of highly effective anti-worm drugs known as vermifuges that kill the worms.
Prevention of helminth diseases usually requires frequent washing of hands, frequent cleaning of bathrooms and kitchens, and thorough cooking of the foods they infest -- mainly beef, pork, sausage and bear meat. Water supplies should be chlorinated, if possible.
Common helminths and the problems they cause include the following:
- Roundworm: Roundworms hatch and live in the intestines. The eggs usually enter the body through contaminated water or food or on fingers placed in the mouth after the hands have touched a contaminated object. Symptoms of their presence include fatigue, weight loss, irritability, poor appetite, abdominal pain and diarrhea. Treatment with medication results in a cure in about a week. Without treatment, anemia and malnutrition can develop.
- Pinworm: Also called seatworms and threadworms, pinworms hatch and live primarily in the intestines. The eggs usually enter the body through the anus, through the nose or mouth via inhaled air, or through the mouth on fingers that have touched a contaminated object. Symptoms of their presence include anal itching and sometimes pale skin and stomach discomfort. If pinworms enter the vagina in females, discharge and itching may develop. Pinworms do not cause serious complications. Treatment with medication results in a cure within days.
- Trichina spiralis: This worm lives in the intestines and causes a serious illness known as trichinosis. The eggs usually enter the body via raw or undercooked pork, sausage or bear meat. In the intestines, the eggs hatch, mature, and migrate to other parts of the body through the bloodstream and the lymphatic system. Early symptoms include vomiting, diarrhea, and abdominal cramps. In time, a high fever, puffiness of the face and muscle pain develop. Eventually the worms can penetrate the muscles, the heart and the brain and can cause death. Treatment with an anti-worm drug such as thiabendazole, as well as bed rest and a physician's care, can cure trichinosis. Recovery may take several months. Diagnosis of trichinosis sometimes requires analysis of a tissue sample (biopsy) taken from muscle.
- Tapeworm: Tapeworms live in the intestines. The eggs usually enter the body via raw or uncooked beef. Symptoms of their presence are usually absent. However, some patients experience abdominal pain, fatigue, weight loss, and diarrhea. Treatment with medication results in a cure within days.
- Fluke: Flukes live in different locations in the body, including the intestines, bladder, rectum, liver, spleen, lungs and veins. Flukes first mature inside freshwater snails. After leaving the snails, they can enter the body of humans by penetrating the skin of persons swimming, bathing or washing in water where flukes are active. Infected persons can re-contaminate the water by urinating or defecating in it. Most infected persons experience no symptoms. However, some infected persons may experience rash, itching, muscle aches, coughing, chills and fever. Flukes pass out of the body, but persons can become infected again and again. In time, the repeated infections can damage the liver, bladder, intestines and lungs. In rare cases, flukes can invade the spinal cord or brain and cause seizures and paralysis. Fluke-caused illnesses are classified as schistosomiasis (also called bilharziasis) and are mainly confined to Africa parts of South America and the Caribbean, and parts of the Middle East, China and the Philippines.
The word "helminth" is derived from the Greek "helmins" (worm). Helminthology is the study of parasitic worms.