Giardiasis (GEE-are-DYE-uh-sis) is a diarrheal illness caused by
(also known as
a one-celled, microscopic parasite that lives in the intestine of
people and animals. The parasite is passed in the stool of an
infected person or animal. The parasite is protected by an outer
shell that allows it to survive outside the body and in the
environment for long periods of time. During the past two decades,
has become recognized as one of the most common
causes of waterborne disease (drinking and recreational) in humans
in the United States. The parasite is found in every region of the
United States and throughout the world.
What are the symptoms of giardiasis?
Symptoms include diarrhea, loose or watery stool, stomach
cramps, and upset stomach. These symptoms may lead to weight loss
and dehydration. Some people have no symptoms. Symptoms generally
begin 1-2 weeks after being infected. In otherwise healthy persons,
symptoms may last 2-6 weeks. Occasionally, symptoms last
How is giardiasis spread?
lives in the intestine of infected humans or
animals. Millions of germs can be released in a bowel movement from
an infected human or animal. You can become infected after
accidentally swallowing the parasite.
may be found
in soil, food, water, or surfaces that have been contaminated with
the feces from infected humans or animals.
spread by contact with blood.
can be spread by:
Putting something in your mouth or accidentally swallowing
something that has come in contact with the stool of a person or
animal infected with
Swallowing recreational water contaminated with
(Recreational water is water in swimming pools, hot tubs, jacuzzis,
fountains, lakes, rivers, springs, ponds, or streams that can be
contaminated with sewage or feces from humans or animals.)
Eating uncooked food contaminated with
picked up from surfaces
(such as toys, bathroom fixtures, changing tables, diaper pails)
contaminated with stool from an infected person
Who is at risk?
Everyone. Persons at increased risk for giardiasis include:
Child care workers
Children who attend day care centers, including diaper-aged
Others who drink or accidentally swallow water from
contaminated sources that are untreated (no heat inactivation,
filtration, or chemical disinfection)
Several community-wide outbreaks of giardiasis have been linked
to drinking municipal water or recreational water contaminated with
can be very contagious. If you have
, follow these guidelines to avoid spreading it to
Wash your hands with soap and water after using the toilet,
changing diapers, and before eating or preparing food.
Avoid swimming in recreational water (pools, hot tubs, lakes or
rivers, the ocean, etc.) while you have
and for at
least two weeks after diarrhea stops. You can pass
in your stool and contaminate water for several weeks after your
symptoms have ended. This has resulted in outbreaks of
among recreational water users.
Avoid fecal exposure during sex.
How is a
Your health care provider will likely ask you to submit stool
samples to see if you have the parasite. Because
be difficult to diagnose, he or she may ask you to submit several
stool specimens over several days.
What is the treatment for giardiasis?
Several prescription drugs are available to treat
. Consult with your health care provider. Although
can infect all people, young children and pregnant
women may be more susceptible to the dehydration resulting from
diarrhea. They should drink plenty of fluids while ill.
How can I prevent
Practice good hygiene.
Wash hands thoroughly with soap and water.
Wash hands after using the toilet and before handling or eating
food (especially for persons with diarrhea).
Wash hands after every diaper change, especially if you work
with diaper-aged children, even if you are wearing gloves.
Protect others by not swimming if experiencing diarrhea
(essential for children in diapers).
Avoid water that might be contaminated.
Avoid swallowing recreational water.
Avoid drinking untreated water from shallow wells, lakes,
rivers, springs, ponds, and streams.
Avoid drinking untreated water during community-wide outbreaks
of disease caused by contaminated drinking water. In the United
States, nationally distributed brands of bottled or canned
carbonated soft drinks are safe to drink. Commercially packaged
noncarbonated soft drinks and fruit juices that do not require
refrigeration until after they are opened (those that are stored
unrefrigerated on grocery shelves) also are safe.
Avoid using ice or drinking untreated water when traveling in
countries where the water supply might be unsafe. If you are unable
to avoid drinking or using water that might be contaminated, then
treat the water yourself by:
Heating the water to a rolling boil for at least 1 minute,
Using a filter that has an absolute pore size of at least 1
micron or one that has been NSF rated for "cyst removal."
If the methods above cannot be used, then try chemical
by chlorination or iodination.
Chemical disinfection may be less effective than other methods
because it is highly dependent on the temperature, pH, and
cloudiness of the water.
Avoid food that might be contaminated.
Wash and/or peel all raw vegetables and fruits before
Use uncontaminated water to wash all food that is to be eaten
Avoid eating uncooked foods when traveling in countries with
minimal water treatment and sanitation systems.
Avoid fecal exposure during sex.
My water comes from a well; should I have my well water
If you answer yes to the following questions, consider having
your well water tested:
Are other members of your family or users of your well water
ill? If yes, your well may be the source of infection.
Is your well located at the bottom of a hill or is it
considered shallow? If so, runoff from rain or flood water may be
draining directly into your well causing contamination.
Is your well in a rural area where animals graze? Well water
can become fecally contaminated if animal waste seepage
contaminates the ground water. This can occur if your well has
cracked casings, is poorly constructed, or is too shallow.
Tests specifically for
are expensive, difficult,
and usually require hundreds of gallons of water to be pumped
through a filter. If you answered yes to the above questions,
consider testing your well for fecal coliforms or
. Although fecal coliforms or
tests do not specifically test for
will show if your well has fecal contamination. These tests are
only useful if your well is not routinely disinfected with chlorine
since chlorine kills fecal coliforms and
. If the
tests are positive, the water may also be contaminated with
, as well as other harmful bacteria and viruses. Look
in your local telephone directory for a laboratory or cooperative
extension that offers water testing. If the fecal coliform test
comes back positive, indicating that your well is fecally
contaminated, contact your local water authority for instructions
on how to disinfect your well.
My child was recently diagnosed as having giardiasis, but does
not have any diarrhea. My health care provider says treatment is
not necessary. Is this true?
In general, the answer by the American Academy of Pediatrics is
that treatment is not necessary. However, there are a few
exceptions. If your child does not have diarrhea, but is having
nausea, or is fatigued, losing weight, or has a poor appetite, you
and your health care provider may wish to consider treatment. If
your child attends a day care center where an outbreak is
continuing to occur despite efforts to control it, screening and
treatment of children without obvious symptoms may be a good idea.
The same is true if several family members are ill, or if a family
member is pregnant and therefore not able to take the most
Centers for Disease Control and
Prevention, May 2001
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a