Hookworm infection

Hookworms 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
Hookworms infect the small intestine. They can be found worldwide, most often in tropical and subtropical regions where the soil is contaminated by human feces. These infections are caused by two species of parasites: Ancylostoma duodenale and Necator americanus. Infections in the United States are most often caused by N. americanus, which is found mostly in the southeastern states due to the favorable climate. Children are infected more often than adults because they tend to contact more contaminated soil (during play or when going barefoot, for example).

Transmission
The spread of hookworms is more common with inadequate hygiene and sanitation or when human feces are used for fertilizer. Hookworm infections do not spread from person to person. Instead, the infection spreads through tiny infective hookworm larvae (immature worms) that live in the soil. Larvae that penetrate the skin, the most common form of transmission, travel through the bloodstream to the lungs. From there, they move up the bronchial passages in the lungs, are swallowed, and travel to the small intestine. Then, they attach themselves to the intestinal wall, where they can live for up to five years. Swallowed larvae go directly to the small intestine. Feeding on the blood of the host, the larvae mature into half-inch long worms. The mature females produce more than 100,000 eggs a day, which pass out of the body in the feces. After five to 10 days in the soil, the eggs develop into hookworm larvae that are capable of causing infection in someone else. An infected person will begin passing hookworm eggs in his or her stool about four to six weeks after being infected by the larvae.

Signs/symptoms
If you contracted a hookworm infection through a break in your skin, the first symptom may be an itchy rash where the tiny worms entered your body. Rarely, the worms may cause mild symptoms such as a cough when they pass through your lungs. If there aren't many, mature hookworms living in the small intestine may go unnoticed. A heavy infection can cause abdominal pain, diarrhea and loss of appetite. Losing blood to the feeding worm can eventually lead to anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron), which may be characterized by pale skin, fatigue and weight loss.

Diagnosis
Diagnosis is based on the presence of hookworm eggs in a stool sample. The worms are rarely seen. Blood tests can confirm the presence of anemia.

Treatment
A hookworm infection may be treated with the drugs albendazole, mebendazole or pyrantel pamoate. The doctor may recommend a repeat stool sample test two weeks later. If you have anemia, an iron supplement may be prescribed. In areas where hookworm infections are common, light infections that cause no symptoms in otherwise healthy people are often left untreated due to the likelihood of reinfection.

Complications
For children, heavy hookworm infections with severe anemia can stunt mental and physical development. The infection may also lead to an enlarged heart and irregular heartbeat. Life-threatening infections, although rare, are more likely in small children.

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.