Amebiasis is a disease
caused by a one-celled parasite called Entamoeba histolytica (ent-a-ME-ba
Who is at risk for
Although anyone can
have this disease, it is most common in people who live in developing
countries that have poor sanitary conditions. In the United States,
amebiasis is most often found in immigrants from developing countries. It
also is found in people who have traveled to developing countries and in
people who live in institutions that have poor sanitary conditions. Men
who have sex with men can become infected and can get sick from the
infection, but they often do not get sick.
How can I become infected with E.
- By putting anything
into your mouth that has touched the stool of a person who is infected
with E. histolytica.
- By swallowing
something, such as water or food, that is contaminated with E.
- By touching and
bringing to your mouth cysts (eggs) picked up from surfaces that are
contaminated with E. histolytica.
What are the symptoms of
On average, about one
in 10 people who are infected with E. histolytica becomes sick from
the infection. The symptoms often are quite mild and can include loose
stools, stomach pain, and stomach cramping. Amebic dysentery is a severe
form of amebiasis associated with stomach pain, bloody stools, and fever.
Rarely, E. histolytica invades the liver and forms an abscess. Even
less commonly, it spreads to other parts of the body, such as the lungs or
If I swallowed E.
histolytica, how quickly would I become sick?
Usually 1 to 4 weeks
later but sometimes more quickly or more slowly.
What should I do if I think I
See your health care
How is amebiasis diagnosed?
Your health care
provider will ask you to submit stool samples. Because E. histolytica
is not always found in every stool sample, you may be asked to submit
several stool samples from several different days.
Diagnosis of amebiasis
can be very difficult. One problem is that other parasites and cells can
look very similar to E. histolytica when seen under a microscope.
Therefore, sometimes people are told that they are infected with E.
histolytica even though they are not. Entamoeba histolytica and
another amoeba, Entamoeba dispar, which is about 10 times more
common, look the same when seen under a microscope. Unlike infection with E.
histolytica, which sometimes makes people sick, infection with E.
dispar never makes people sick and therefore does not need to be
If you have been told
that you are infected with E. histolytica but you are feeling fine,
you might be infected with E. dispar instead. Unfortunately, most
laboratories do not yet have the tests that can tell whether a person is
infected with E. histolytica or with E. dispar. Until these
tests become more widely available, it usually is best to assume that the
parasite is E. histolytica.
A blood test is also
available. However, the test is recommended only when your health care
provider thinks that your infection has invaded the wall of the intestines
(gut) or some other organ of your body, such as the liver. One problem is
that the blood test may still be positive if you had amebiasis in the
past, even if you are no longer infected now.
How is amebiasis treated?
Several antibiotics are
available to treat amebiasis. Treatment must be prescribed by a physician.
You will be treated with only one antibiotic if your E. histolytica
infection has not made you sick. You probably will be treated with
two antibiotics (first one and then the other) if your infection has
made you sick.
I am going to travel to a
country that has poor sanitary conditions. What should I eat and drink
there so I will not become infected with E. histolytica or
other such germs?
- Drink only bottled
or boiled (for 1 minute) water or carbonated (bubbly) drinks in cans
or bottles. Do not drink fountain drinks or any drinks with ice
cubes. Another way to make water safe is by filtering it through an
"absolute 1 micron or less" filter and dissolving
iodine tablets in the filtered water. "Absolute 1 micron"
filters can be found in camping/outdoor supply stores.
- Do not eat
fresh fruit or vegetables that you did not peel yourself.
- Do not eat or
drink milk, cheese, or dairy products that may not have been
- Do not eat or
drink anything sold by street vendors.
Should I be concerned about
spreading infection to the rest of my household?
Yes. However, the risk
of spreading infection is low if the infected person is treated with
antibiotics and practices good personal hygiene. This includes thorough
hand washing with soap and water after using the toilet and before
For more information:
Ravdin JI. Amebiasis.
Clin Infect Dis 1995;20:1453-66.
This fact 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.