Roundworm infection (ascariasis)

Ascariasis is an intestinal worm infection. Intestinal worms are a type of parasite -- an organism that survives by feeding on other organisms or hosts. Parasites can inhabit the human body or live in soil, water, food or insects. Some parasites exist naturally in the human body, but are usually controlled by the immune system.


Causes/associated factors
Infection with the intestinal worm Ascaris lumbricoides causes ascariasis, the most common worldwide worm infection. A. lumbricoides is a large roundworm that's most prevalent in tropical and subtropical regions of the world where soil is contaminated by human feces. The infection is less common in the United States. When it does appear, it's most often in the southeastern states due to the favorable climate. This infection is more common in children than adults.

Transmission
The spread of ascariasis is more common with inadequate hygiene and sanitation or when human feces are used for fertilizer. Ascariasis does not spread from person to person. Instead, infection occurs after ingestion of the ascaris eggs, which may be found in contaminated soil or on contaminated produce that has not been washed. The eggs hatch in the stomach and the larvae (immature worms) travel through the bloodstream to the lungs. From there, they move up the bronchial passages in the lungs and are eventually swallowed. When the larvae reach the small intestine, they mature and can live for up to two years. The mature female ascaris produces up to 240,000 eggs a day, which pass out of the body in the feces. These eggs become capable of causing the infection in someone else after two to three weeks. An infected person will begin passing the eggs in his or her stool about two to three months after ingesting the eggs.

Signs/symptoms
Sometimes, ascariasis causes no symptoms, especially if there are only a few worms. Symptoms are more likely when there are many worms. When the tiny worms pass through the lungs, you may develop a fever, cough, blood-tinged sputum or breathing difficulty. When the adult worms are in the intestines, you may have abdominal pain or bloating, diarrhea, vomiting or even intestinal blockage. Adult worms are round like a pencil and can be up to 12 inches long. The worms are sometimes found in the stool or vomited or coughed up. In children, a heavy infection may aggravate poor nutrition.

Diagnosis
Diagnosis is based on the presence of ascaris eggs in a stool sample. The adult worms are sometimes observed in an infected personeated with the drugs albendazole, mebendazole or pyrantel pamoate. The doctor may recommend a repeat stool sample test three weeks later.

Complications
Heavy intestinal infections can cause intestinal blockage. Rarely, a worm may penetrate the intestinal wall and cause peritonitis (inflam- mation of the membrane lining the abdominal cavity) or obstruct the bile duct, causing jaundice (yellowing of the skin and whites of the eyes). Complications may require surgical intervention.

Pregnancy-specific information
A variety of medications may be prescribed for various intestinal worm infections, but certain standard medications should not be taken if you're pregnant. Thoroughly discuss your health history with your doctor and review the risks and benefits of any treatment. If you don't have significant symptoms, your doctor may recommend postponing treatment until after delivery.
If you are or may be pregnant, you may want to avoid traveling to areas with poor sanitation, where you're more likely to develop parasitic infection(s). If you do travel to these areas, be sure to follow the preventive measures outlined below.


Senior-specific information
Growing older is not a risk factor for this condition.

Prevention
To prevent intestinal worms of any type, follow these general guidelines:
Practice sanitary hygiene habits, especially when disposing of human waste. Never wipe feces on the ground, and dispose of diapers properly.

Wear shoes in areas where the soil or sand may be contaminated with feces or parasites. Don't sit directly on the ground or handle the soil or sand with your bare hands.

Wash your hands thoroughly with soap and water or an antibacterial handwashing solution before handling food or water and after using the toilet or changing diapers.

Wash, peel or cook raw fruits and vegetables before eating.

Cook meat thoroughly, to at least 160°F. It should no longer be pink in the center. Measure the internal temperature to assure doneness. Keep in mind that curing, smoking, drying or microwaving meat may not kill all worms.

Slabs of pork less than 6 inches thick can be frozen at 5°F (-15°C) for 20 days to kill any worms. Freezing may not be effective for wild game.

If you're traveling abroad, it's wise to avoid uncooked fruits and vegetables, unless you've peeled them yourself; raw or undercooked meat, poultry, fish and eggs; foods prepared in advance that haven't been kept cold or very hot; and foods purchased from street vendors. If you have any doubts about a food's safety, follow this simple rule: Boil it, cook it, peel it or forget it.

If you're unsure of the safety of drinking water (such as in areas where the water isn't chlorinated or hygiene and sanitation are poor), ensure water safety by boiling your water vigorously for one minute, filtering it or treating it with iodine or chlorine. Drink only this water, beverages made from it, canned or bottled carbonated beverages (including water and soft drinks), beer or wine. Wash uncooked fruits or vegatables using treated or filtered water. Avoid using ice cubes and drinking from unclean glasses and wet or dirty cans or bottles. (It's best to drink straight from the can or bottle after wiping it clean and dry.) Don't brush your teeth in tap water, and avoid swallowing water while swimming or bathing.