What is giardiasis?

Giardiasis is an infection caused by a parasite called Giardia. It causes diarrhea. It is passed on through oral contact with infected feces. You can get the parasite by eating food or drinking water that contains infected feces. When you travel, make sure not to drink water that may be unsafe.

Giardiasis a common intestinal parasite. It is most prevalent in countries with poor sanitary conditions, poor water quality control, and overcrowding. However, it is also a common cause of parasitic infection in the U.S. Hikers and campers who drink water from streams and other potentially contaminated sources are often infected.

What causes giardiasis?

The parasite that causes giardiasis lives in two stages:

  • Trophozoites (the active form inside the body)
  • Cysts (the resting stage that enables the parasite to survive outside the body)

Infection begins when the cysts are taken in through contaminated food or water. Stomach acid activates the cysts and the trophozoites are released. They attach to the lining of the small intestine and reproduce. Cysts form in the lower intestines and are then passed in the feces.

The parasite may be passed from person-to-person by contact with infected feces, or through consuming contaminated food or water.

What are symptoms of giardiasis?

Symptoms of giardiasis may include:

  • Explosive, watery, foul-smelling stools
  • Greasy stools that tend to float
  • Bloating
  • Nausea
  • Loss of appetite
  • Abdominal (belly) pain
  • Excessive gas
  • Fatigue

The time between infection and the start of symptoms is usually from 1 to 2 weeks. Some infected people have very mild symptoms or no symptoms at all. The symptoms of giardiasis are a lot like those of other gastrointestinal diseases. See a healthcare provider for diagnosis.

How is giardiasis diagnosed?

Diagnosis of giardiasis is made by testing stool samples in a lab. Several stool samples may be needed at different times. If you think you may have this illness, contact your healthcare provider for advice.

How is giardiasis treated?

Giardiasis may be treated with prescription medicines. Specific treatment for giardiasis will be determined by your healthcare provider based on:

  • How old you are
  • Your overall health and medical history
  • How sick you are
  • How well you can handle specific medicines, procedures, or therapies
  • How long the condition is expected to last
  • Your opinion or preference
Several medicines can be used to treat the infection. Effective treatments include metronidazole, tinidazole, and nitazoxanide.

What are the complications of giardiasis?

If the infection is not treated and persists, you may not be able to absorb nutrients. It can also cause unintended weight loss.

Can giardiasis be prevented?

You can prevent giardiasis by practicing good personal hygiene. Proper hygiene when caring for those who may be infected with the parasite is also important. When visiting in an area where giardiasis may exist:

  • Drink only boiled water or bottled water or drinks.
  • Avoid ice and beverages made from tap water.
  • Do not eat locally grown uncooked or unpeeled fruits and vegetables.

When should I call my healthcare provider?

Call your healthcare provider if:

  • Your symptoms get worse or you have new symptoms
  • You lose your appetite and start to lose weight
  • You become dehydrated from prolonged diarrhea

Key points about giardiasis

  • Giardiasis is an infection caused by a parasite called Giardia. It causes diarrhea.
    Symptoms include explosive, watery, greasy, foul-smelling stools, bloating, nausea, pain, gas, fatigue, and loss of appetite.
  • Several medicines are available that cure the infection.
  • Prevention includes good personal hygiene, and avoiding drinking water, fruits, and vegetables that may be contaminated with the parasite.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.
  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
  • Ask if your condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if you do not take the medicine or have the test or procedure.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.

Request an Appointment

Find a Doctor
Find a Doctor