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Amebiasis

Table of Contents

Amebiasis

Amebic dysentery; Intestinal amebiasis; Amebic colitis; Amebic dysentery due to Entamoeba histolytica; Amebiasis due to Entamoeba histolytica

Entamoeba histolytica. It can affect anyone, although it is more common in people who live in tropical areas with poor sanitary conditions. Infected people do not always become sick. Learn more about symptoms, diagnosis and treatment.

Entamoeba histolytica

Image by CDC/DPDx

What Is

Amebiasis LifeCycle

Image by CDC/Wikimedia

Amebiasis LifeCycle

Cysts and trophozoites are passed in feces The Number 1. Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Infection by Entamoeba histolytica occurs by ingestion of mature cysts The Number 2 in fecally contaminated food, water, or hands. Excystation The Number 3 occurs in the small intestine and trophozoites The Number 4 are released, which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts The Number 5, and both stages are passed in the feces The Number 1. Because of the protection conferred by their walls, the cysts can survive days to weeks in the external environment and are responsible for transmission. Trophozoites passed in the stool are rapidly destroyed once outside the body, and if ingested would not survive exposure to the gastric environment. In many cases, the trophozoites remain confined to the intestinal lumen (The Letter A: noninvasive infection) of individuals who are asymptomatic carriers, passing cysts in their stool. In some patients the trophozoites invade the intestinal mucosa (The Letter B: intestinal disease), or, through the bloodstream, extraintestinal sites such as the liver, brain, and lungs (The Letter C: extraintestinal disease), with resultant pathologic manifestations. It has been established that the invasive and noninvasive forms represent two separate species, respectively E. histolytica and E. dispar. These two species are morphologically indistinguishable unless E. histolytica is observed with ingested red blood cells (erythrophagocystosis). Transmission can also occur through exposure to fecal matter during sexual contact (in which case not only cysts, but also trophozoites could prove infective).

Image by CDC/Wikimedia

What Is Amebiasis?

Amebiasis is a disease caused by a one-celled parasite called Entamoeba histolytica.

How can I become infected with E. histolytica?

E. histolytica infection can occur when a person:

Puts anything into their mouth that has touched the feces (poop) of a person who is infected with E. histolytica.
Swallows something, such as water or food, that is contaminated with E. histolytica.
Swallows E. histolytica cysts (eggs) picked up from contaminated surfaces or fingers.

Source: Centers for Disease Control and Prevention (CDC)

Additional Materials (4)

Tissue damage caused by E. histolytica is a result of three main events, host cell death, inflammation, and parasite invasion

Tissue damage caused by E. histolytica is a result of three main events: host cell death, inflammation, and parasite invasion.

Image by GLFBM/Wikimedia

Brain

This photomicrograph of a brain tissue specimen depicts the cytoarchitectural changes associated with a free-living, Naegleria fowleri, amebic infection. In this view, you’re able to see a number of N. fowleri trophozoites amongst the brain’s neuropil.

Image by CDC

Entamoeba Histolytica

Video by TheKierstenKaye/YouTube

Amebiasis

Video by DrER.tv/YouTube

Tissue damage caused by E. histolytica is a result of three main events, host cell death, inflammation, and parasite invasion

GLFBM/Wikimedia

Brain

CDC

8:10

Entamoeba Histolytica

TheKierstenKaye/YouTube

4:56

Amebiasis

DrER.tv/YouTube

Risk Factors

Significance of Amebiasis

Image by GLFBM/Wikimedia

Significance of Amebiasis

Significance of Amebiasis

Image by GLFBM/Wikimedia

Who Is at Risk for Amebiasis?

Although anyone can have this disease, it is more common in people who live in tropical areas with poor sanitary conditions. In the United States, amebiasis is most common in:

People who have traveled to tropical places that have poor sanitary conditions
Immigrants from tropical countries that have poor sanitary conditions
People who live in institutions that have poor sanitary conditions
Men who have sex with men

Source: Centers for Disease Control and Prevention (CDC)

Symptoms

Entamoebiasis

Image by Mariana Ruiz Villarreal LadyofHats

Entamoebiasis

Entamoeba histolytica is an anaerobic parasitic protozoan, part of the genus Entamoeba. It infects predominantly humans and other primates

Image by Mariana Ruiz Villarreal LadyofHats

What Are the Symptoms of Amebiasis?

Only about 10% to 20% of people who are infected with E. histolytica become sick from the infection. The symptoms are often quite mild and can include loose feces (poop), stomach pain, and stomach cramping. Amebic dysentery is a severe form of amebiasis associated with stomach pain, bloody stools (poop), and fever. Rarely, E. histolytica invades the liver and forms an abscess (a collection of pus). In a small number of instances, it has been shown to spread to other parts of the body, such as the lungs or brain, but this is very uncommon.

If I swallowed E. histolytica, how quickly would I become sick?

Only about 10% to 20% of people who are infected with E. histolytica become sick from the infection. Those people who do become sick usually develop symptoms within 2 to 4 weeks, though it can sometimes take longer.

What should I do if I think I have amebiasis?

See your healthcare provider.

Source: Centers for Disease Control and Prevention (CDC)

Additional Materials (2)

Brain

This photomicrograph of a brain tissue specimen depicts the cytoarchitectural changes associated with a free-living, Naegleria fowleri, amebic infection. In this view, you’re able to see a number of N. fowleri trophozoites amongst the brain’s neuropil.

Image by CDC

Sensitive content

This media may include sensitive content

Patient with invasive extraintestinal amebiasis

This patient presented with a case of invasive extraintestinal amebiasis affecting the cutaneous region of the right flank causing severe tissue necrosis. Here we see the site of tissue destruction, post-debridement, just prior to the wound being covered by skin grafts. Please note PHIL 9926, which depicts the same patient with the pre-debridement appearance of the cutaneous amebiasis lesion.

Image by CDC/ Dr. Kerrison Juniper, Gastroenterologist, University of Arkansas Medical School; George Healy, Ph.D., DPDx, (retired)

Brain

CDC

Sensitive content

This media may include sensitive content

Patient with invasive extraintestinal amebiasis

CDC/ Dr. Kerrison Juniper, Gastroenterologist, University of Arkansas Medical School; George Healy, Ph.D., DPDx, (retired)

Diagnosis

Drawing of hands holding a card containing a stool sample. A drop of liquid is being applied to the stool sample to test for fecal occult blood

Image by NIDDK Image Library

Drawing of hands holding a card containing a stool sample. A drop of liquid is being applied to the stool sample to test for fecal occult blood

Fecal occult blood test.

Image by NIDDK Image Library

How Is Amebiasis Diagnosed?

Your healthcare provider will ask you to submit fecal (poop) 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 ameba, 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 does not make people sick and therefore does not need to be treated.

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 but is only recommended when your healthcare provider thinks that your infection may have spread beyond the intestine (gut) to some other organ of your body, such as the liver. However, this blood test may not be helpful in diagnosing your current illness because the test can be positive if you had amebiasis in the past, even if you are not infected now.

Source: Centers for Disease Control and Prevention (CDC)

Additional Materials (1)

Stool Sample

Gross I know, but hey, somebody somewhere needs a "stool sample" clipart image... and this is for them!

Image by j4p4n

Stool Sample

j4p4n

Ova and Parasite Test

Ova and Parasite Test

Also called: Fecal Smear, O&P Test, Ova and Parasite Exam, Ova and Parasites Examination, Parasitology Examination

An ova and parasite test looks for parasites and their eggs (ova) in a sample of your stool. Parasite infections may be treated with fluids and/or medicine. Infections can be serious for people with weakened immune systems.

Ova and Parasite Test

Also called: Fecal Smear, O&P Test, Ova and Parasite Exam, Ova and Parasites Examination, Parasitology Examination

An ova and parasite test looks for parasites and their eggs (ova) in a sample of your stool. Parasite infections may be treated with fluids and/or medicine. Infections can be serious for people with weakened immune systems.

{"label":"Ova and parasite reference range","scale":"lin","step":0.25,"hideunits":true,"items":[{"flag":"negative","label":{"short":"Negative","long":"Negative","orientation":"horizontal"},"values":{"min":0,"max":1},"text":"A negative result means that no ova or parasites were found in the stool sample. However, this could mean that the infection may be caused by another microorganism, such as bacteria or viruses. It can also mean that the parasite was not present in the stool sample at the time of collection; this happens because some of them are shed into the stool intermittently. Repeat or further testing may be ordered.","conditions":[]},{"flag":"positive","label":{"short":"Positive","long":"Positive","orientation":"horizontal"},"values":{"min":1,"max":2},"text":"A positive result will report the name and number of the parasite and their ova. It can also identify co-infections (more than one parasite present at the time of testing).","conditions":["Parasitic gastrointestinal infection","Cryptosporidiosis","Amebiasis","Giardiasis","Strongyloidiasis","Taeniasis",""]}],"value":0.5,"disclaimer":"Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are \"within normal limits.\""}[{"negative":0},{"positive":0}]
Use the slider below to see how your results affect your health.
Your result is Negative.
A negative result means that no ova or parasites were found in the stool sample. However, this could mean that the infection may be caused by another microorganism, such as bacteria or viruses. It can also mean that the parasite was not present in the stool sample at the time of collection; this happens because some of them are shed into the stool intermittently. Repeat or further testing may be ordered.
Related conditions
An ova and parasite test looks for intestinal parasites and their eggs (ova) by checking a sample of your stool (poop) under a microscope. The test is also called an O&P.
Intestinal parasites are tiny life forms that can live and reproduce in your digestive system. They most commonly infect your intestines (the long, tube-shaped organ in your belly that helps digest food). A parasitic infection can cause diarrhea, gas, stomach cramps, and other abdominal (belly) symptoms.
When people and animals have intestinal parasites, eggs and parasites are found in their stool. Tiny amounts of contaminated stool that you can't see, smell, or taste can get into water, soil, food, and beverages. If a person with an infection doesn't wash their hands well after using the bathroom, parasites can also get on any surfaces that they touch.
If you swallow parasites or their eggs in contaminated water or food, you can develop an infection. You can also become infected if you put anything in your mouth that has touched contaminated surfaces.
There are many types of intestinal parasites. The most common types in the U.S. include:
- Giardia
- Cryptosporidium
- Entamoeba histolytica, which causes a disease called "amebiasis." In the US, amebiasis happens mostly in people who have been in countries where it is common. This includes tropical areas with poor sanitary conditions.
These parasites are often found in water, including rivers, lakes, ponds, and streams. They are also found in swimming pools, hot tubs, and drinking water. That's because certain types of intestinal parasites are not easily killed by chlorine in water.
Other intestinal parasites that aren't common in the U.S. include many types of worms, such as pinworms. These parasites also spread through contaminated soil, water, food, and drink. But some of them, such as hookworms, can infect you by getting into your skin, especially if you walk barefoot on contaminated ground or other surfaces.
Healthy people often recover from intestinal parasite infections without treatment. When treatment is needed, it usually works to get rid of the parasites.
But intestinal parasites can cause severe, long-lasting diarrhea and other serious conditions in people with weakened immune systems. This includes people with HIV, cancer, certain genetic disorders, and people who take certain medicines that affect their immune systems. Infants and older adults also have weaker immune systems.
Other names: parasitic examination (stool), stool sample exam, stool O&P, fecal smear, egg cyst
Your provider may order an O&P test if you have symptoms that could be caused by an intestinal parasite, and the symptoms have lasted for a few days. They include:
- Diarrhea
- Abdominal pain
- Blood and/or mucus in the stool
- Unusually foul-smelly, greasy stools that float
- Nausea and vomiting
- Gas
- Fever
- Weight loss
Sometimes these symptoms go away without treatment, so testing is not always needed. Your provider will be more likely to order a test for parasites if:
- You have developed serious symptoms, including an electrolyte imbalance or dehydration.
- You have a weakened immune system because of disease, medicines you take, or your age. Older adults and very young children often have weaker immune systems.
- You could have been exposed to parasites. This includes:
  Drinking or accidentally swallowing water from a stream and/or lake.
  Traveling to another country where intestinal parasites are more common.
  Being around another person who has an intestinal parasite infection.
You will need to provide a stool sample for your test. Your provider will probably give you a container or kit with instructions on how to collect the sample. There are different ways to collect stool samples so follow the instructions carefully. In general, you'll need to:
- Label the container with your name, the collection date, and time.
- Collect a stool sample as instructed. This usually involves using a clean, dry container, or special paper or plastic wrap placed over the toilet to catch the stool.
- Make sure the stool doesn't mix with any urine, toilet paper, or water from the toilet.
- Close the container tightly.
- Wash your hands well with soap and water.
- Return the container according to the instructions.
If you're collecting a sample from diapers, you'll get special instructions for using plastic wrap inside of a clean diaper. In certain cases, a provider may use a swab to take a stool sample from the rectum.
To get accurate test results, you may need to collect several stool samples over a few days. That's because parasites may not show up in your stool every day. Testing several samples will increase the chance that the parasites will be found.
A negative or normal test result means that no parasites or eggs were found in your stool sample. This may mean:
- You don't have parasites.
- There were not enough parasites in your sample to show up in a test.
Your provider may order another test and/or different tests to help find out what's causing your symptoms.
A positive or abnormal test result means that parasites and/or eggs were found in your stool sample. You have intestinal parasites. The results will also show the type of parasites you have and how many were in your sample.
Treatment for an intestinal parasite infection will depend on the type of parasite you have and your general health. Treatment may include medicines that get rid of the parasites and/or relieve symptoms. You will also need to drink plenty of fluids to prevent dehydration (the loss of too much fluid from your body) from the diarrhea and vomiting.
You may be told not to swim until all your symptoms have been gone for at least two weeks. That can help make sure you don't spread parasites to others.
If you have questions about your results, talk with your provider.
There are many steps you can take to protect yourself from getting infected with intestinal parasites. For example:
- Wash your hands with warm water and soap, which work better than hand sanitizers. Always wash:
  Before, during, and after preparing food
  Before and after eating and caring for someone who is or may be infected with parasites
  After going to the bathroom, changing a diaper, handling animals, and gardening or working with soil
- Don't drink untreated water from lakes, streams, or rivers. And be careful not to swallow water when you swim.
- When camping or traveling to countries where the water may not be safe, avoid tap water, ice, and uncooked foods washed with tap water. Bottled water is safe.
- If you are unsure if water is safe, boil it before drinking. Boiling water for one to three minutes will kill the parasites. Wait until the water cools before drinking.
1. Ova and Parasite Test: MedlinePlus Medical Test [accessed on Jan 28, 2024]
2. Stool ova and parasites exam: MedlinePlus Medical Encyclopedia [accessed on Jan 28, 2024]
3. Ova and Parasite Exam - Testing.com. Nov 9, 2021 [accessed on Jan 28, 2024]
4. Ova and Parasites (Stool) - Health Encyclopedia - University of Rochester Medical Center [accessed on Jan 28, 2024]

Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

Treatment

Bottle of Doxycycline

Image by NIAID

Bottle of Doxycycline

Capsules of the antibiotic doxycycline spill from a medication bottle. Oral antibiotics, such as doxycycline or amoxicillin, are often prescribed after exposure to tickborne Lyme disease.

Image by NIAID

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.

Source: Centers for Disease Control and Prevention (CDC)

Prevention

Bottled Water

Image by CDC/ Debora Cartagena

Bottled Water

This image depicts six plastic bottles filled with spring drinking water, bottled for human consumption.

Image by CDC/ Debora Cartagena

How Can Amebiasis Be Prevented?

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?

The following items are safe to drink:

Bottled water with an unbroken seal
Tap water that has been boiled for at least 1 minute
Carbonated (bubbly) water from sealed cans or bottles
Carbonated (bubbly) drinks (like soda) from sealed cans or bottles

You can also make tap water safe for drinking by filtering it through an “absolute 1 micron or less” filter and dissolving chlorine, chlorine dioxide, or iodine tablets in the filtered water. “Absolute 1 micron” filters can be found in camping/outdoor supply stores.

The following items may NOT be safe to drink or eat:

Fountain drinks or any drinks with ice cubes
Fresh fruit or vegetables that you did not peel yourself
Milk, cheese, or dairy products that may not have been pasteurized.
Food or drinks sold by street vendors

Should I be concerned about spreading the infection to others?

Yes, but the risk of spreading infection is low if the infected person is treated with antibiotics and practices good personal hygiene. This includes thorough handwashing with soap and water after using the toilet, after changing diapers, and before handling or preparing food.

Source: Centers for Disease Control and Prevention (CDC)

Related HealthJournals

Parasitic Diseases

Parasites are living things that use other living things - like your body - for food and a place to live. Parasitic diseases are diseases transmitted by parasites, usually via contaminated food, water, or through bug bites. Some parasitic diseases are easily treated and some are not. Get tips to protect yourself from parasitic diseases.

Foodborne Illness

Many pathogens and bacteria can contaminate what we eat and cause food poisoning. Find out the food and germs most associated with foodborne illness.

Sappinia Infection

<em>Sappinia</em> is a free-living ameba (a single-celled living organism), found in the environment. There are two known species of <em>Sappinia</em>: <em>Sappinia diploidea</em> and <em>Sappinia pedata</em>. This ameba causes amebic encephalitis, which is an infection of the brain.

Naegleria Fowleri Infection

<em>Naegleria fowleri</em>, commonly called the "brain-eating ameba", is a single-celled living organism that lives in soil and warm fresh water, such as lakes and rivers. This ameba causes amebic encephalitis, a rare brain infection that is usually fatal. Get your questions answered about the "brain-eating ameba."

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Amebiasis

Entamoeba histolytica. It can affect anyone, although it is more common in people who live in tropical areas with poor sanitary conditions. Infected people do not always become sick. Learn more about symptoms, diagnosis and treatment.

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