What is giardiasis?
Giardiasis is an illness caused Giardia
lamblia, a one-celled, microscopic parasite that lives in the
intestines of people and animals. During the past 15 years, Giardia
lamblia has become recognized as one of the most common
causes of waterborne disease in humans in the United States. This
parasite is found in every region of the United States and
throughout the world.
What are the symptoms of giardiasis?
Diarrhea, abdominal cramps, and nausea are the
most common symptoms of giardiasis. These symptoms may lead to
weight loss and dehydration. However, not everyone infected has
How long after being infected do symptoms
Symptoms usually appear 1-2 weeks after infection
with the parasite.
How long will I have symptoms?
In otherwise healthy persons, symptoms may last
4-6 weeks. Occasionally, symptoms last longer.
How can I get giardiasis?
- By putting
anything into your mouth that has touched the stool of a
person or animal with giardiasis.
- By swallowing
water contaminated with Giardia. A person can swallow
a Giardia cyst, the infectious stage of the parasite,
by consuming water from swimming pools, lakes, rivers,
springs, ponds, or streams contaminated with sewage or feces
from humans or animals.
- By eating
uncooked food contaminated with Giardia cysts.
Thoroughly wash with safe water all vegetables and fruits you
plan to eat raw.
- By touching
and bringing to your mouth cysts picked up from surfaces
(i.e., toys, bathroom fixtures, changing tables, diaper
pails) contaminated with stool from an infected person.
Who is at risk?
Persons at increased risk for giardiasis include
child care workers; diaper-aged children who attend day care
centers; international travelers; hikers; campers; and others who
drink untreated water from contaminated sources. Several
community-wide outbreaks of giardiasis have been linked to
drinking municipal water contaminated with Giardia.
What should I do if I think I have giardiasis?
See your health care provider who will ask you to
submit stool samples to see if you are harboring the parasite.
Because Giardia can be difficult to diagnose, your health
care provider may ask you to submit several stool specimens over
What is the treatment for giardiasis?
Several prescription drugs are available to treat
How can I prevent giardiasis?
- Wash hands
with soap and water after using the toilet and before
- Avoid water or
food that may be contaminated.
- Wash and peel
all raw vegetables and fruits before eating.
- Avoid drinking
water from lakes, rivers, springs, ponds, or streams unless
it has been filtered or chemically treated.
community-wide outbreaks caused by contaminated drinking
water, boil drinking water for 1 minute to kill the Giardia
parasite and make the water safe to drink.
- When traveling
in countries where the water supply may be unsafe, avoid
drinking unboiled tap water and avoid uncooked foods washed
with unboiled tap water. Bottled or canned carbonated
beverages, seltzers, or pasteurized fruit drinks, and
steaming hot coffee and tea are safe to drink. You should
check the label on bottled water to make sure it has been
properly filtered before drinking.
- If you work in
a child care center where you change diapers, be sure to wash
your hands thoroughly with plenty of soap and warm water
after every diaper change, even if you wear gloves.
- Avoid swimming
in pools if you or your child has Giardia. Giardia
cysts are fairly chlorine resistant and are passed in the
stools of infected people for several weeks after they no
longer have symptoms.
My water comes from a well; should I have my
well water tested?
Consider having your well water tested if you
answer yes to the following questions:
- 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
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 Giardia 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
instead of Giardia. Although fecal coliform tests do not
specifically test for Giardia, testing will show if your
well has fecal contamination. If it does, the water is likely to
be contaminated with Giardia, as well as other harmful
bacteria and viruses. Look in your local telephone directory for
a laboratory or cooperative extension that offers water testing.
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 supported 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 effective anti-Giardia
For more information:
- Addiss DG, Juranek DD, Spencer HC. Treatment of
children with asymptomatic and nondiarrheal Giardia
infection. Pediatr Infect Dis J 1991;10:843-6.
- Addiss DG, Davis JP, Roberts JM, Mast EE.
Epidemiology of giardiasis in Wisconsin. Increasing incidence of
reported cases and unexplained seasonal trends. Am J Trop Med Hyg
- Bartlett AV, Englander SJ, Jarvis BA, Ludwig L,
Carlson JF, Topping JP. Controlled trial of Giardia lamblia:
Control strategies in day care centers. Am J Public Health
- Kreuter AK, Del Bene VE, Amstey MS. Giardiasis in
pregnancy. Am J Obstet Gynecol 1981;40:895-901.
- Lengerich EJ, Addiss DG, Juranek DD. Severe
giardiasis in the United States. Clin Infect Dis 1994; 18:760-3.
- Steketee RW, Reid S, Cheng T, et al. Recurrent
outbreaks of giardiasis in a child day care center, Wisconsin. Am
J Public Health 1989;79:485-90.
sheet is for information only and is not meant to be used for
self-diagnosis or as a substitute for consultation with a health
care provider. If you have any questions about the disease
described above or think that you may have a parasitic infection,
consult a health care provider.
Division of Parasitic Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
NCID Home Page
DPD Home Page