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Parasite Diagnosis and Testing

BY: DR. TODD WATTS — 04/04/2021

The average person doesn’t know a whole lot about parasites, nor can they identify the different symptoms or types of parasitic infections. But if you have complex chronic illnesses, you will want to learn about these pathogens and how to treat the different infections.

Most U.S. physicians are unaware how widespread parasitic infections are. They might even tell patients that their idea of being infected with parasites is “all in their head.” (1, 2) In actuality, patients aren’t suffering from a “parasitic delusion disorder.” Quite possibly, parasites are contributing to their health problems.

Parasites are much more common in developed countries than most people realize. For example, it’s estimated that more than 12% of Americans carry Toxoplasma gondii, a microscopic parasite people might get from their cat. (2)

The increasingly toxic environment — including from pollution — could worsen the parasite problem. Toxins can weaken the body’s defenses and alter parasite activity. (3)

Parasites can trigger a wide range of health issues. In some cases, they may be the actual cause behind chronic issues like irritable bowel syndrome and some autoimmune diseases.

(4, 5)

It might be easy for parasites to latch on to hosts, but they do their best to avoid detection.

There are a few different tests that may help check whether you have parasites. But they are far from 100% accurate. That includes standard blood and stool tests, as well as looking inside the gut with special equipment. (60)

Blood and stool tests

You can submit stool samples to a lab to check if you have intestinal parasites or their eggs (ova). These are called ova and parasite (O&P) tests. A lab technician can use special stains to help detect parasites when viewing samples under a microscope. (61)

It’s best to provide at least three different stool samples from separate days to reduce the risk of missing parasites. Still, it’s easy for labs to overlook parasites. And the parasites simply may not be in the tiny bits of stool that the lab analyzes from the larger samples submitted. (62)

Another way to check for parasites is blood tests. But there isn’t such a thing as a blood test that checks for every type of parasite. Instead, the tests are used to check for a few specific types of parasites that the healthcare professional suspects a patient might have. (62)

The blood tests are designed to identify parasites by checking for:

  • Antibodies: When someone is infected with a parasite, their immune system makes specific antibodies to fight them. Blood tests can be used to check for antibodies to a small number of parasites. There aren’t tests for every kind though. (62)

  • Visible parasites: Lab staff may look directly at a specially stained blood smear under a microscope. They’re looking for parasites that reside in the blood. For example, plasmodium (the malaria parasite) and babesia may be found in a blood smear test. (63, 64)

Imaging and other tests

Imaging tests such as CAT scans, MRI scans, and x-rays may pick up signs of parasites in body tissues. The healthcare professional may be looking for something else but could notice parasites in the process.

For example, a swollen liver and spleen could suggest a patient is infected with plasmodium. And these scans could show large ascaris worms in their gut. (62, 65) Another type of test that may reveal parasites is an endoscopy. It may be used to look for parasites, though it would be an invasive and expensive way to do so. (66)

A newer form of testing can look for parasite’s DNA, such as in the blood or stool. This can be compared with databases of known parasites. Not all parasites can be tested in this way, as the DNA of some parasites hasn’t been analyzed. (67)

How accurate is parasite testing?

Typical parasite testing can be inadequate. Several factors contribute to the likelihood of parasite tests being inaccurate.

Some reasons why parasite tests might turn up empty despite having an infection are:

  • Improper storage: If your specimen isn’t handled correctly, you're unlikely to get an accurate result. To detect certain parasites in their active stage, the stool sample must be examined within 30–60 minutes after passing it or be put into a preservative. Otherwise, the parasite will disintegrate before it’s found. (61)

  • Insufficient availability: The right tests or equipment may not be available to you. And due to inadequate parasite training for doctors, they may not even know the best tests for them. On top of that, insurance may not cover the tests. (61)

  • Insufficient training: Is the technician who’s looking at your stool or blood sample highly trained and experienced? The number of truly qualified people to perform these tests is dwindling while the need is going up. (68)

  • Parasites aren’t being expelled: Stool samples don’t necessarily reflect what’s inside you. Some parasites simply may not be making an exit when they test. For example, they could be hiding in your gut or tissues. (69)

  • Rapid DNA destruction: Though genetic tests are available to detect parasites in your samples, parasites can destroy their DNA when they die. For example, leishmania rapidly degrades its DNA in almost any death situation. If a sample isn’t appropriately preserved and transported in a timely fashion, the test results could be invalid. (70, 71)

  • Shortage of time: Medical labs are often very busy with many tests to complete. If a technician is underqualified and rushed, the risk for errors increases. (72)

Click here to learn lab markers that may indicate parasites. Click here to learn more about how to detox parasites naturally.


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