Giardia infection (giardiasis)

Giardia infection (giardiasis) is an intestinal infection caused by a microscopic parasite that's found worldwide, especially in areas with poor sanitation and unsafe water. Giardia infection is marked by abdominal cramps, bloating, nausea and bouts of watery diarrhea.

Giardia infection is a waterborne infection and can be caused by parasites found in backcountry streams and lakes, as well as in municipal water supplies, swimming pools, whirlpool spas and wells. Giardia infection can also be transmitted through food and person-to-person contact.

Giardia infections usually clear up within a few weeks. But you may 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.

Symptoms Causes Risk factors Complications Prevention

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 or malaise
  • Abdominal cramps and bloating
  • Belching gas with a bad taste
  • Nausea
  • Weight loss

Signs and symptoms of giardia infection usually last two to four weeks, but in some people they last longer or recur.

When to see a doctor

Call your doctor if you have loose stools, abdominal bloating and nausea lasting more than a week, or if you become dehydrated. Be sure to tell your doctor if you're at risk of giardia infection — that is, you have a child in child care, you've recently traveled to an area in which you know giardia infection is present, or you've swallowed water from a lake or stream.

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