Tapeworm infection

Tapeworms are a type of intestinal worm, which is a 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
Intestinal tapeworm infections can be caused by several different types of worms, which are found worldwide. In the United States, they're caused most often by the dwarf tapeworm, Hymenolepis nana. Other intestinal tapeworms include beef tapeworm (Taenia saginata), pork tapeworm (Taenia solium), fish tapeworm (Diphyllobothrium latum), rodent tapeworm (also Hymenolepis nana) and dog tapeworm (Dipylidium caninum or echinococcosis granulosus). As their names imply, tapeworms require another animal to complete their life cycle. The only exception to this is the dwarf tapeworm, which can survive solely in a human.

Transmission
Tapeworm eggs are ingested by animals. They become infective in the muscle tissue. You may become infected by eating infected meat or fish that's raw or undercooked. Depending on the type of worm, it developed into an adult in the intestines within two to 12 weeks. An adult tapeworm consists of a head that attaches to the intestinal wall and successive square, flat segments that contain eggs. Several segments detach each day and pass out in the feces. The eggs can survive in the environment for a period of several months to years. If they're ingested by an animal, the cycle begins again.
Unlike other types of tapeworms, dwarf tapeworm and pork tapeworm infections can also spread from person to person when there is inadequate hygiene or poor sanitation. Dwarf tapeworm eggs are already infective when they're passed in the feces. If ingested, the eggs will develop into adults when they reach the person's intestines.

Tapeworms vary in length depending on the type of worm. They may range from 2 to more than 10 meters long with up to 2,000 segments. Each segment contains up to 100,000 eggs. Left untreated, some tapeworms can survive in humans for more than 30 years.


Signs/symptoms
A tapeworm infection may have only mild symptoms or none at all, depending on the type of tapeworm causing the infection. When symptoms are present, they may include abdominal pain, nausea, diarrhea, appetite loss, weight loss and weakness. There may also be rectal itching with the passage of the segments. The fish tapeworm prevents the body from absorbing vitamin B12 from food, which may result in anemia, pale skin, weakness, fatigue and shortness of breath.

Diagnosis
Diagnosis is based on the presence of eggs in a stool sample. The tapeworm segments are sometimes visible in the stool. Blood tests can confirm the presence of anemia caused by the fish tapeworm. Other tests are needed to diagnose pork tapeworm infections, such as tests to detect antibodies (compounds that help neutralize or destroy foreign substances in the blood) associated with the pork tapeworm in your blood and cerebrospinal fluid. The presence of the pork tapeworm in other organs may be detected through computed tomography (CT scan; a computer-generated, cross-sectional picture of internal body parts) or magnetic resonance imaging (MRI, an imaging technique based on computer analysis of the body's response to a magnetic field).

Treatment
Intestinal tapeworms may be treated with the medications praziquantel, niclosamide, albendazole or mebendazole. Repeat stool sample tests may be needed to verify the treatment's effectiveness. Injections of vitamin B12 may be given if you've developed anemia due to the fish tapeworm.

Complications
Rare complications of intestinal tapeworms may include poor nutrition, intestinal blockage, inflammation of the bile duct (the tube that leads from the liver to the intestines) and appendicitis. The pork or dog tapeworm can have the most serious complications. This tapeworm's larvae can migrate and develop into cysts on the liver, lungs or in various organs other than the intestines (a condition known as cysticercosis), which can lead to serious organ damage. This is most dangerous if the brain and spinal cord are involved. Seizures, behavior changes, memory loss, visual impairment, hallucinations, emotional disturbances, stroke, paralysis and coma can occur. Sometimes, the infection is fatal.

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.