Diseases & Conditions

Giardiasis

Giardia infection is an intestinal infection marked by abdominal cramps, bloating, nausea and watery diarrhea. Giardia infection is caused by a parasite that is found worldwide, especially in areas with poor sanitation and unsafe water.

Giardia infection (giardiasis) is one of the most common waterborne diseases in the United States. The parasites are found in backcountry streams and lakes, but also in municipal water supplies, swimming pools and spas. Giardia infection can also be transmitted through food and person-to-person contact.

Infections usually clear up within six weeks. But you may have recurrent episodes or have intestinal problems long after the parasites are gone. Several drugs are generally effective against giardia parasites, but not everyone responds to them. Prevention is your best defense.

Some people with giardia infection never develop signs or symptoms but still carry the parasite and can spread it to others through their stool. For those who do get sick, signs and symptoms usually appear one to two weeks after exposure and may include:

• Watery, sometimes foul-smelling diarrhea that may alternate with soft, greasy stools
• Fatigue
• Abdominal cramps and bloating
• Nausea
• Weight loss — as much as 10 percent of your body weight

Signs and symptoms of giardia infection usually improve in two to six weeks, but in some people they become chronic, lasting for months or years.

Diarrhea that goes away within a week or less probably isn't giardiasis. Call your doctor if you have loose stools, abdominal bloating and nausea lasting two weeks or more, or you become dehydrated. It's easy to overlook giardiasis because the signs and symptoms resemble those of other gastrointestinal diseases. Be sure to tell your doctor if you have a child in child care, you've recently traveled to an endemic area, or you've swallowed water from a lake or stream.

To help diagnose giardiasis, your doctor is likely to test a sample of your stool. For accuracy, you may be asked to submit several samples collected over a period of days. The samples are then examined in a laboratory for the presence of the parasites. Stool tests may also be used to monitor the effectiveness of treatment you receive.

Children and adults who have giardia infection but no symptoms usually don't need treatment unless they're likely to spread the parasites. Many people who do have problems often get better on their own in a few weeks. When signs and symptoms are severe or the infection persists, doctors usually treat giardiasis with antibiotics such as metronidazole or tinidazole. The two drugs are equally effective, but tinidazole requires a shorter course of treatment. Both can cause side effects such as a metallic taste, nausea and vomiting, and you must avoid drinking alcohol while taking them. Pregnant women shouldn't use these drugs during the first trimester because they may lead to birth defects. Some doctors prefer not to treat women at all during pregnancy, or they may opt to use the less toxic — though less effective — drug paramomycin. Metronidazole may be considered in extreme cases where signs and symptoms are severe.