How a Tapeworm Infection Is Diagnosed

It’s important to get a diagnosis and seek treatment for a tapeworm infection, even though in many cases a tapeworm infection does not cause any symptoms and most people will not know that they are infected.

Diagnosis for tapeworm infection is usually done through detection of eggs and proglottids (worm segments) via a stool test, although many patients’ tapeworms are detected when they find proglottids in their own stool or in the toilet.

Infection with certain species, specifically the pork tapeworm (Taenia solium), carry the potential for serious complications with long-lasting effects on the central nervous system, making a proper diagnosis and treatment crucial.

Self-Checks

Tapeworms or tapeworm segments may be visible in the stool when they are passed along with a bowel movement. In particular, a head-like part of the tapeworm that has suckers and hook-like structures that attach to the intestine, called a scolex, may be seen.

Scolices (more than one scolex) can appear round, in the shape of a diamond, or elongated, depending on the species. It's important to bring a stool sample containing any scolices to a physician or to a lab for a stool test.

Labs and Tests

Stool Tests

Tapeworm infection may be diagnosed through a stool test. Tapeworms or eggs leave the body by passing through the intestines and ultimately end up in the stool. The part of the worm that leaves the body will differ based on the type of tapeworm that is causing the infection.

An ova and parasite exam may be used because it looks for eggs (ova) and parasites (which includes tapeworms). In order to test the stool, a patient will need to collect a stool sample which will be sent to a lab for analysis. The technicians will use a microscope to look for worm parts such as eggs or worm segments called proglottids. Each type of worm can be identified based on certain characteristics, including size, shape, and internal structures. It may take a few days for this test to be completed and the results to be returned to a physician.

Stool tests may be completed in a variety of ways but in most cases done by placing fecal matter in a sterile plastic container. In many cases, the lab will have a bathroom which patients can use to provide the sample. If done at home, the lab will ask that the stool sample be delivered within an hour or two of its collection unless it can be stored properly—either through refrigeration or with a liquid preservative. Samples might also need to be collected over a few days, as the Centers for Disease Control recommends that three different samples be tested.

Blood Tests

Infection with the fish tapeworm (Diphyllobothrium latum) may lead to a lack of vitamin B12 which may cause anemia. A physician may order a blood test to check for these complications. Other blood tests may also be used, but this is not common.

Physical Exam

A physical exam may not turn up anything for most tapeworm infections, although it's important to discuss any new signs and symptoms, even if they're not related to the digestive tract. In the case of cysticercosis (infection with pork tapeworm) there’s the potential for cysts to form under the skin. A physician might be able to feel these cysts during a physical exam.

In the case of an infection with the beef tapeworm, Taenia saginata, it’s possible that eggs could be found during an examination of the perianal area (the skin around the anus). The eggs might be collected by applying a piece of cellophane tape to the perianal area. The eggs will stick to the tape, and the tape can be put on a slide for examination under a microscope.

Imaging

In the case of a pork tapeworm infection that has spread beyond the intestine and into other organs and body tissues, imaging tests might be needed to look for cysts and determine if there is any other damage.

According to the Merck Manual, stool tests might not be positive for pork tapeworms in 50 percent or more of people who have cysticercosis. Two imaging tests that are often used to diagnose cysticercosis or neurocysticercosis in people that have symptoms of infection in the nervous system are computed tomography (CT) scan and magnetic resonance imaging (MRI).

CT Scan

A CT scan is a type of X-ray that is used to take images of the organs, tissues, and structures inside the body. The preparation for this test may include fasting for a few hours beforehand. Contrast dye may be given through an IV in order to better see certain parts of the body.

This test usually involves lying on a table that will slide into the CT machine. The machine will rotate around to take the images, and it will be important to stay still or hold the breath at times as instructed by a technician. 

MRI

An MRI is an imaging test that can be used to see structures inside the body, including the spine and the brain. It’s painless and non-invasive, although in some cases contrast dye may be given in an IV to get a better view of certain areas of the body.

Patients will lie on a table which slides into the MRI machine, which is a large tube. Earplugs or headphones may be offered as the machine may make a certain amount of noise.

Differential Diagnoses

Most people with a tapeworm infection don’t have symptoms, but if there are gastrointestinal symptoms such as diarrhea and abdominal pain it may be necessary to rule out other digestive conditions such as:

• appendicitis
• enteritis (inflammation of the small intestine)
• gallbladder inflammation
• gastroenteritis
• irritable bowel syndrome (IBS)

In the case of cysticercosis and neurocysticercosis (when the central nervous system is affected because the infection spread), it may be necessary to rule out conditions that could be causing symptoms in other areas of the body outside of the digestive tract and/or in the central nervous system, including:

• brain abscess
• encephalitis
• epilepsy
• meningitis
• tumors