Giardia is a microscopic parasite that causes the diarrheal illness known as giardiasis. Giardia (also known as Giardia intestinalis, Giardia lamblia, or Giardia duodenalis) is found on surfaces or in soil, food, or water that has been contaminated with feces (poop) from infected humans or animals.
Giardia is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection. While the parasite can be spread in different ways, water (drinking water and recreational water) is the most common mode of transmission.
Giardiasis is a diarrheal disease caused by the microscopic parasite Giardia. A parasite is an organism that feeds off of another to survive. Once a person or animal (for example, cats, dogs, cattle, deer, and beavers) has been infected with Giardia, the parasite lives in the intestines and is passed in feces (poop). Once outside the body, Giardia can sometimes survive for weeks or months. Giardia can be found within every region of the U.S. and around the world.
Giardiasis can be spread by:
- Swallowing Giardia picked up from surfaces (such as bathroom handles, changing tables, diaper pails, or toys) that contain feces (poop) from an infected person or animal
- Drinking water or using ice made from water sources where Giardia may live (for example, untreated or improperly treated water from lakes, streams, or wells)
- Swallowing water while swimming or playing in water where Giardia may live, especially in lakes, rivers, springs, ponds, and streams
- Eating uncooked food that contains Giardia organisms
- Having contact with someone who is ill with giardiasis
- Traveling to countries where giardiasis is common
Anything that comes into contact with feces (poop) from infected humans or animals can become contaminated with the Giardia parasite. People become infected when they swallow the parasite. It is not possible to become infected through contact with blood.
Giardia infection can cause a variety of intestinal symptoms, which include:
- Gas or flatulence
- Greasy stool that can float
- Stomach or abdominal cramps
- Upset stomach or nausea
These symptoms may also lead to weight loss. Some people with Giardia infection have no symptoms at all.
Symptoms of giardiasis normally begin 1 to 3 weeks after becoming infected.
In otherwise healthy people, symptoms of giardiasis may last 2 to 6 weeks. Occasionally, symptoms last longer. Medications can help decrease the amount of time symptoms last.
Though giardiasis is commonly thought of as a camping or backpacking-related disease and is sometimes called “Beaver Fever,” anyone can get giardiasis. People more likely to become infected include:
- Children in childcare settings, especially diaper-aged children
- Close contacts of people with giardiasis (for example, people living in the same household) or people who care for those sick with giardiasis
- People who drink water or use ice made from places where Giardia may live (for example, untreated or improperly treated water from lakes, streams, or wells)
- Backpackers, hikers, and campers who drink unsafe water or who do not practice good hygiene (for example, proper handwashing)
- People who swallow water while swimming and playing in recreational water where Giardia may live, especially in lakes, rivers, springs, ponds, and streams
- International travelers
- People exposed to human feces (poop) through sexual contact
Contact your healthcare provider.
Your healthcare provider will ask you to submit stool (poop) samples to see if you are infected. Because testing for giardiasis can be difficult, you may be asked to submit several stool specimens collected over several days.
Many prescription drugs are available to treat giardiasis. Although the Giardia parasite can infect all people, infants and pregnant women may be more likely to experience dehydration from the diarrhea caused by giardiasis. To prevent dehydration, infants and pregnant women should drink a lot of fluids while ill. Dehydration can be life threatening for infants, so it is especially important that parents talk to their healthcare providers about treatment options for their infants.
Your child does not usually need treatment if he or she has no symptoms. However, there are a few exceptions. If your child does not have diarrhea, but does have other symptoms such as nausea or upset stomach, tiredness, weight loss, or a lack of hunger, you and your healthcare provider may need to think about treatment. The same is true if many family members are ill, or if a family member is pregnant and unable to take the most effective medications to treat Giardia. Contact your healthcare provider for specific treatment recommendations.
To prevent and control infection with the Giardia parasite, it is important to:
- Practice good hygiene
- Avoid water (drinking or recreational) that may be contaminated
- Avoid eating food that may be contaminated
- Prevent contact and contamination with feces (poop) during sex
The risk of humans acquiring Giardia infection from dogs or cats is small. The exact type of Giardia that infects humans is usually not the same type that infects dogs and cats.
Illness & Symptoms
Giardiasis is the most frequently diagnosed intestinal parasitic disease in the United States and among travelers with chronic diarrhea. Signs and symptoms may vary and can last for 1 to 2 weeks or longer. In some cases, people infected with Giardia have no symptoms.
Acute symptoms include:
- Greasy stools that tend to float
- Stomach or abdominal cramps
- Upset stomach or nausea/vomiting
- Dehydration (loss of fluids)
Other, less common symptoms include itchy skin, hives, and swelling of the eye and joints. Sometimes, the symptoms of giardiasis might seem to resolve, only to come back again after several days or weeks. Giardiasis can cause weight loss and failure to absorb fat, lactose, vitamin A and vitamin B12.
In children, severe giardiasis might delay physical and mental growth, slow development, and cause malnutrition.