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Ova and Parasite Test

What is an ova and parasite test?

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

What is it used for?

An ova and parasite test is used to see if intestinal parasites are causing symptoms that appear to be from an intestinal infection. This information helps your health care provider know how to treat your illness. The test may also be used to see if treatment for intestinal parasites is working.

Why do I need an ova and parasite test?

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.

What happens during an ova and parasite test?

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.

Will I need to do anything to prepare for the test?

You don't need any special preparations for an ova and parasite test.

Are there any risks to the test?

There is no known risk to having an ova and parasite test.

What do the results mean?

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.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an ova and parasite test?

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.


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The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.