Giardiasis or beaver fever: Symptoms, causes, and risk factors

Giardiasis, or beaver fever, is a parasitic infection of the digestive system. Symptoms include severe abdominal discomfort and diarrhea, but some people have no symptoms.

The parasite that causes it is a microscopic, single-celled organism called Giardia lamblia.

According to the Centers for Disease Control and Prevention (CDC), giardiasis is the most common intestinal parasitic disease in the United States.

In 2012, people reported 15,223 cases of the disease in the U.S.

Giardiasis occurs all over the world, but it is more common in areas with poor sanitation. In developing countries, it can affect 20 to 30 percent of the population at any one time. In some places, it affects 100 percent of the population.


Abdominal discomfort and a fever
Abdominal discomfort and a fever are common symptoms of giardiasis.

Not everyone with giardiasis has symptoms, but they can still spread the disease.

Symptoms can appear between 1 and 3 weeks after infection.

They may include:

a slight fever

watery or soft stools and constipation

foul-smelling diarrhea and gas


abdominal bloating, pain and cramps

belching and halitosis, or foul-smelling breath


heartburn and indigestion

loss of appetite and weight loss


a general feeling of being unwell

Stools usually eventually become greasy but do not contain blood.

Diarrhea can lead to dehydration. If water loss is severe, it can become serious, especially for infants. It is important to consume plenty of fluids, preferably water.

Symptoms normally improve within 2–6 weeks, but this may take longer. Medications can help speed up recovery.


There are two types of Giardia.

The active form is present in the gut of an infect person or animal.

The inactive cyst form can remain dormant in the environment for several months.

Parasites can leave their host’s body when a person or animal has a bowel movement.

Outside, they form a hard, protective shell and become a Giardia cyst. A cyst can survive for several months in the environment.

A gust of wind can pick up the cysts from infected manure on farmland and blow it in any direction.

The infection usually spreads when people drink water that has come into contact with infected feces, especially in countries with poor sanitation.

giardia is a parasite
Giardiasis happens when a parasite causes intestinal problems, especially when traveling.

A doctor will take a stool sample and send it to a lab to check for Giardia cysts.

Sometimes, they will ask for several samples, because a person does not expel cysts every time they use the bathroom.

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