Ova and Parasite Exam



What is Ova and Parasite Exam?

A variety of parasites can cause infections of the digestive system (gastrointestinal (GI) infections). An ova and parasite (O&P) exam is a microscopic evaluation of a stool sample that is used to look for parasites that may infect the lower digestive tract, causing symptoms such as diarrhea. The parasites and their eggs (ova) are shed from the lower digestive tract into the stool.

When thin smears of fresh or preserved stool are put onto glass slides and stained, the parasites and/or their ova or cysts, the form in which the parasite is surrounded by a resistant cover or capsule, can be detected and identified under the microscope by a trained laboratorian. Different ova and parasites have distinct shapes, sizes, and internal structures that are characteristic of their species.

Why is Ova and Parasite Exam performed?

Your doctor may order an O&P test for a few reasons. For example, they may order the test if you show signs and symptoms of an intestinal infection, such as:

  • Frequent diarrhea
  • Mucus or blood in your stool
  • Nausea or vomiting
  • Severe abdominal pain
  • Headache
  • Fever


What should I know before receiving Ova and Parasite Exam?

This test poses little to no risk. Collecting a stool sample is an easy procedure that you can complete at home. If you experience difficulties producing or collecting a sample, call your doctor.


How to prepare for Ova and Parasite Exam?

In most cases, an O&P test doesn’t require special preparation. In some cases, your doctor may ask you to avoid using certain products before collecting a sample of your stool. For example, they may ask you to avoid taking:

  • Laxatives
  • Antidiarrheal medications
  • Antibiotics
  • Contrast dyes, which are used in imaging studies and X-rays

What happens during Ova and Parasite Exam?

If your doctor orders an O&P test, you will need to provide a sample of your stool. Collect a small sample of your stool using latex gloves or plastic wrap. For example, consider covering the bowl of your toilet with a loose layer of plastic wrap before using it. The plastic wrap will catch your stool, making it easy to collect. Avoid mixing your stool sample with urine or toilet paper.

If you need to collect a sample of stool from your child, it may require additional steps. You may need to help them, especially if they’re not quite potty-trained. You can collect a sample of stool from their diapers, as long as the sample isn’t soiled with urine. In some cases, your doctor may recommend using a clean cotton swab to collect a sample of stool from their rectum.

After you’ve collected a sample of stool, place it in a clean container and seal it. Then take the sealed container to a clinic or laboratory, as instructed by your doctor. A technician will use dye and a microscope to look for parasites and eggs in your stool sample.

What happens after Ova and Parasite Exam?

This test doesn’t require any special aftercare. You may resume your daily activities unless instructed otherwise by your doctor.

If you have any questions about the Ova and Parasite Exam, please consult with your doctor to better understand your instructions.

Explanation of results

What do my results mean?

A “normal” test result means that no eggs or parasites were found in your stool sample. If you receive a normal result but your symptoms haven’t subsided, your doctor may order additional tests or examinations.

An “abnormal” test result means that parasites, eggs, or both have been found in your stool sample.

Typically a person will only have one type of parasite that is causing their symptoms, but there could be more than one.

The most common and frequently detected parasites are:

  • Giardia species—some of the most common intestinal parasites in the United States
  • Cryptosporidium (often called crypto)—one of the leading causes of recreational water-related disease outbreaks in the U.S.
  • Entamoeba histolytica—common but only causes illness in about 10% to 20% of those infected

Other examples include:

  • Dientamoeba fragilis
  • Balantidium coli
  • Cyclospora cayetanensis
  • Roundworms such as Ascaris, Strongyloides
  • Hookworms
  • Tapeworms such as Hymenolepis nana, Taenia solium and Diphyllobthrium latum
  • Flatworms and flukes such as Fasciolopsis buski

Depending on the laboratory and hospital, the normal range for Ova and Parasite Exam may vary. Please discuss with your doctor any questions you may have about your test results.


Hello Health Group does not provide medical advice, diagnosis or treatment.


Review Date: November 5, 2018 | Last Modified: November 5, 2018

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