Gardiasis

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 (beaver fever)

Last Reviewed: September 2016

What is giardiasis?

Giardiasis is an intestinal (bowel) illness caused by a microscopic parasite called Giardia lamblia. It is a common illness that causes diarrhea (loose stool/poop). Over 2,000 cases occur in New York State each year.

Who gets giardiasis?

Giardiasis occurs more often in children and staff in daycare centers, foreign travelers, and people who drink improperly treated surface water. Men who have sex with men may also be at increased risk of getting giardiasis.

How is this parasite spread?

Giardia can infect people and wild and domestic animals. It is passed in the feces (poop) of an infected person or animal and may contaminate water or food. The beaver has gained attention as a potential source of Giardia contamination of lakes, reservoirs, and streams, but human fecal wastes are also play an important role in spreading the parasite. People become infected by accidently swallowing Giardia and can carry the parasite in their bodies from a few weeks to a few months. Spread of the parasite directly from one person to another may occur in daycare centers or other settings where handwashing practices are poor or through anal sex.

What are the symptoms of giardiasis and how soon do they appear?

People exposed to Giardia may experience mild or severe diarrhea (loose stool/poop), gas, stomach cramps, nausea (a feeling of upset in the stomach), or dehydration (loss of water in the body causing weakness of dizziness). Some people experience no symptoms at all. Fever is rarely present. Occasionally, some people will have chronic diarrhea over several weeks or months, with significant weight loss. The symptoms may appear from 3 to 25 days after exposure but usually within 10 days.

How is giardiasis diagnosed?

Giardiasis is diagnosed by testing samples of your stool (poop). Sometimes, several stool samples must be obtained because the number of Giardia being passed in the stool, which varies from day to day, may be too low to detect from any single sample.

What is the treatment for giardiasis?

Doctors commonly treat giardiasis by prescribing antibiotics such as metronidazole, tinidazole, or nitazoxanide. However, some individuals may recover on their own in a few weeks without medication.

What can be done to prevent the spread of giardiasis?

Three important preventive measures are:

Carefully wash hands thoroughly with soap and water after toilet visits and handling soiled diapers.
Carefully dispose of sewage wastes so as not to contaminate surface water or groundwater.
Avoid consuming untreated water from springs, streams, or lakes.

Should an infected person be excluded from work or school?

People with active diarrhea (loose stool/poop) who are unable to control their bowel movements (infants and young children for example) may need to be excluded from settings such as daycare or group activities where they may present a risk to others. After they have been treated and have recovered, they may be permitted to return. Food handlers may not work while ill with Giardia. In addition, some local health departments may require follow-up stool (poop) testing to confirm that the person is no longer contagious. Individuals who are not in high-risk settings may return to their routine activities when they have recovered, if they carefully wash their hands with soap and water after each toilet visit.

NYS. Health Dept.

Giardia Frequetnly Asked Questions

What is Giardiasis?

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.

How do you get giardiasis and how is it spread?

Giardiasis can be spread by:

Swallowing Giardia picked up from surfaces (such as bathroom handles, changing tables, diaper pails, or toys) that contain stool 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.

What are the symptoms of giardiasis?

Giardia infection can cause a variety of intestinal symptoms, which include:

Diarrhea
Gas or flatulence
Greasy stool that can float
Stomach or abdominal cramps
Upset stomach or nausea
Dehydration

These symptoms may also lead to weight loss. Some people with Giardia infection have no symptoms at all.

Epidemiology & Risk Factors

General Epidemiology

Giardiasis is a diarrheal illness caused by the parasite Giardia intestinalis (also known as Giardia lamblia or Giardia duodenalis). A parasite is an organism that feeds off of another to survive.

Giardiasis is a global disease. It infects nearly 2% of adults and 6% to 8% of children in developed countries worldwide. Nearly 33% of people in developing countries have had giardiasis. In the United States, Giardia infection is the most common intestinal parasitic disease affecting humans.

People become infected with Giardia by swallowing Giardia cysts (hard shells containing Giardia) found in contaminated food or water. Cysts are instantly infectious once they leave the host through feces (poop). An infected person might shed 1-10 billion cysts daily in their feces (poop) and this might last for several months. However, swallowing as few as 10 cysts might cause someone to become ill^[. Giardia may be passed person-to-person or even animal-to-person. Also, oral-anal contact during sex has been known to cause infection. Symptoms of giardiasis normally begin 1 to 3 weeks after a person has been infected.

Giardia infection rates have been known to go up in late summer^. Between 2006-2008 in the United States, known cases of giardiasis were twice as high between June-October as they were between January-March.

Anyone may become infected with Giardia. However, those at greatest risk are:

Travelers to countries where giardiasis is common
People in child care settings
Those who are in close contact with someone who has the disease
People who swallow contaminated drinking water
Backpackers or campers who drink untreated water from lakes or rivers
People who have contact with animals who have the disease
Men who have sex with men

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

Molecular Characterization

Giardia intestinalis (aka: G. duodenalis, G. lamblia) can be subdivided based on molecular analysis into what are known as different genetic assemblages (A,B,C,D,E,F, and G). Some of these assemblages can be classified even further into subtypes like for example A-I, A-II, A-III, A-IV. Each assemblage is capable of infecting certain species, and some assemblages are more commonly seen than others

Molecular Characterization
Assemblages	Some Species Commonly Infected
A-I	Humans and animals (cats, dogs, livestock, deer, muskrats, beavers, voles, guinea pigs, ferrets)
A-II	Humans (more common than A-I)
A-III and A-IV	Exclusively animals
B	Humans and animals (livestock, chinchillas, beavers, marmosets, rodents)
C and D	Dogs, coyotes
E	Alpacas, cattle, goats, pigs, sheep
F	Cats

How long after infection do symptoms appear?

Symptoms of giardiasis normally begin 1 to 3 weeks after becoming infected.

How long will symptoms last?

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.

Who is most at risk of getting giardiasis?

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 child care settings, especially diaper-aged children are at risk for Giardia exposure.

Children in child care settings, especially diaper-aged children
Close contacts (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

What should I do if I think I may have giardiasis?

Contact your health care provider.

How is a giardiasis diagnosed?

Your health care 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.

What is the treatment for giardiasis?

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 health care providers about treatment options for their infants.

My child does not have diarrhea, but was recently diagnosed as having Giardia infection. My health care provider says treatment is not necessary. Is this correct?

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 health care 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 health care provider for specific treatment recommendations.

If my water comes from a well, should I have my well water tested?

What can I do to Prevent and Control giardiasis?

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

Can I get giardiasis from my pet?

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.

Giardia and Pets

Giardia intestinalis (aka: G.duodenalis, G.lamblia) is a common, microscopic (intestinal) parasite that commonly affects humans, dogs, and cats.

Common signs and symptoms of Giardia infection (in both humans and pets) are diarrhea, gas, abdominal discomfort, nausea, and vomiting. However, it is possible to be infected and have no signs or symptoms of illness.

Please visit our other web pages for a more detailed description of Giardia, including its life cycle, prevention tips, and treatment information for humans.

Can I get Giardia infection from my pet?

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.

Biology

Life Cycle:

Go to : http://www.cdc.gov/parasites/images/giardia/giardia_lifecycle.gif

Causal Agent:

Giardia intestinalis is a protozoan flagellate (Diplomonadida). This protozoan was initially named Cercomonas intestinalis by Lambl in 1859. It was renamed Giardia lamblia by Stiles in 1915 in honor of Professor A. Giard of Paris and Dr. F. Lambl of Prague. However, many consider the name, Giardia intestinalis, to be the correct name for this protozoan. The International Commission on Zoological Nomenclature is reviewing this issue.

Life Cycle:

Go to : http://www.cdc.gov/parasites/images/giardia/giardia_lifecycle.gif

Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages) . The cysts are hardy and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites) . In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites) . Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk . Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces . Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclear.

Disease

Giardia trophozoites stained with trichrome. Credit: Waterborne Disease Prevention Branch, CDC

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:

Diarrhea
Gas
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.

Diagnosis

Giardia trophozoites and cysts. Credit: Waterborne Disease Prevention Branch, CDC

Because Giardia cysts can be excreted intermittently, multiple stool collections (i.e., three stool specimens collected on separate days) increase test sensitivity. The use of concentration methods and trichrome staining might not be sufficient to identify Giardia because variability in the concentration of organisms in the stool can make this infection difficult to diagnose. For this reason, fecal immunoassays that are more sensitive and specific should be use.

Rapid immune-chromatographic cartridge assays also are available but should not take the place of routine ova and parasite examination^. Only molecular testing (e.g., polymerase chain reaction) can be used to identify the subtypes of Giardia.

Treatment

Several drugs can be used to treat Giardia infection. Effective treatments include metronidazole, tinidazole, and nitazoxanide. Alternatives to these medications include paromomycin, quinacrine, and furazolidone. Some of these drugs may not be routinely available in the United States.

Different factors may shape how effective a drug regimen will be, including medical history, nutritional status, and condition of the immune system. Therefore, it is important to discuss treatment options with a health care provider.

Prevention & Control

On This Page

Practice good hygiene.
Avoid water (drinking and recreational) that may be contaminated.
Avoid eating food that may be contaminated.
Prevent contact and contamination with feces (poop) during sex.
Clean up after ill pets and people.

See Giardia and Pets for information on minimizing your exposure to Giardia if you have dogs or cats.

Practice good hygiene.

Everywhere
- Wash hands with soap and clean, running water for at least 20 seconds; rub your hands together to make a lather and be sure to scrub the backs of your hands, between your fingers, and under your nails.
  - Before, during, and after preparing food
  - Before eating food
  - Before and after caring for someone who is sick
  - Before and after treating a cut or wound
  - After using the toilet
  - After changing diapers or cleaning up a child who has used the toilet
  - After blowing your nose, coughing, or sneezing
  - After touching an animal or animal waste
  - After handling pet food or pet treats
  - After touching garbage
- Help young children and other people you are caring for with handwashing as needed.

Practicing good hygiene helps prevent the spread of disease.