Intestinal Worms: Gut and Stool Symptoms to Recognize

Intestinal worms are parasites that live in the gut and can make you sick. They are some of the world's most common parasites. As a group, these parasitic worms are called helminths. Because they live in the gut, you can sometimes tell you have an infection of intestinal worms by looking at your stool. 

Seeing worms or eggs in your poop isn't the only way to tell if you have a parasitic infection. You may also have various digestive and non-digestive symptoms triggered by the worms or your body's reaction to them.

This article will review the symptoms of intestinal worms and ways to determine if you have them by examining your stool. It will also cover how intestinal worms are treated. 

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Intestinal Worms: How Do You Know You Have Them?

Intestinal worms are most common in lower-income countries. The symptoms of intestinal worms may vary based on the worm. Often, people will have no symptoms of an intestinal worm infection.

Types of Intestinal Worms

Several types of intestinal worms can infect humans. The general term for these animals is helminths. Several helminths, such as the following, cause illnesses:

Roundworms (nematodes): This group includes Ascaris lumbricoides, threadworms rhabditid nematode (Strongyloides stercoralis), which causes strongyloidiasis, and pinworms (Enterobius vermicularis)—the most common intestinal worms in the United States.
Hookworms (Ancylostoma duodenale and Necator americanus): In the United States, hookworms are the second most common helminthic infection.
Whipworm (Trichuris trichiura): These worms take the shape of a whip, being wider at one end.
Flatworms (platyhelminths) and trematodes (flukes): This group includes tapeworms and species that cause schistosomiasis.
Thorny-headed worms (acanthocephalans): Infections of humans with these parasites are rare and typically asymptomatic.

Stool Signs 

If you have an intestinal worm infection, you may be able to see worms or parts of worms (common with tapeworms) in your stool. Eggs and larvae are harder to see. If you see something in your stool that looks like a worm, bring it to a healthcare provider for diagnosis.

The worms all look different:

Threadworms look like tiny pieces of white cotton. For example, Strongyloides stercoralis worms are slender and measure 2 to 3 millimeters (mm) long (about one-tenth of an inch).
Roundworms look more like earthworms. 
Tapeworms are long, pale yellow, and flat.

You may have gastrointestinal (GI) symptoms that change the look of your stool, making it more watery, mucousy, or even bloody. For example, chronic schistosomiasis and heavy hookworm infections may lead to blood in the stool.

A severe whipworm infection can cause frequent, painful bowel movements of mucus, water, and blood.

GI Symptoms 

Most intestinal worms do not cause symptoms if the infection is light. Gastrointestinal symptoms from heavier infections with intestinal worms can include:

Diarrhea, constipation, abdominal pain, upset stomach, loss of appetite, and weight loss are common with strongyloidiasis, hookworms, schistosomiasis, tapeworms, and ascariasis.
Heavy ascariasis infections can block the intestines.
A gastroenteritis-like syndrome (with symptoms similar to stomach flu) can occur when mature worms attach to the lining of the intestines.
Whipworms can cause the rectum to sag and come out of the anus (rectal prolapse).

Non-GI Symptoms

While intestinal worms live in the gut and cause symptoms there, there are other symptoms to be aware of if you're worried you have these parasites. Some of the most common non-GI signs and symptoms of intestinal worms are:

Rashes are often the first sign of infection with parasitic intestinal worms. For example, hookworms and strongyloidiasis can cause an itchy rash of round red spots where the worm enters the skin. Schistosomiasis can cause a rash or itchy skin days after the initial infection.
Lung and breathing symptoms can occur if the worms enter through the lungs or skin during migration to the gut. People with strongyloidiasis may get a sore throat and develop a dry cough. Ascariasis can also cause a cough.
Malnutrition from intestinal worms can impair growth, physical development, and weakened cognitive development in children with high worm burden (total number of worms in the body). This is especially prevalent in children with a heavy burden of hookworm, ascariasis, or whipworm.
Eosinophilia: Many people with intestinal worms get high counts of white blood cells called eosinophils (eosinophilia), including 30% to 60% of people with hookworm and up to 75% of people with chronic strongyloidiasis.

Non-gastrointestinal symptoms that may show up with intestinal worm infections include:

Hookworms can cause anemia from blood loss. This can lead to symptoms like fatigue, weakness, and complications, including protein loss, swelling, pica (eating nonfood substances), and weight loss. This is especially common in people who menstruate.
Chronic strongyloidiasis can cause complications, including arthritis, arrhythmias (abnormal heart rhythms), kidney issues, and recurrent asthma.
Complications of chronic schistosomiasis can include an enlarged liver, blood in the urine, and problems passing urine. People also have an increased risk of liver fibrosis or bladder cancer.
Tapeworm segments can get lodged in the appendix, bile duct, or pancreatic ducts, which can cause serious issues.
The tapeworm T. solium can cause a disease called cysticercosis, which can cause seizures and damage the muscles and eyes.
Pinworm is the most common helminth in the United States. It is spread in daycare and school settings. Pinworm doesn't cause GI symptoms—the most common symptom is nighttime anal itching. Nighttime itching can irritate the anus, perineum, and vagina and disturb sleep, which would make anyone irritable.

Schistosomiasis can produce general malaise, including fever, chills, cough, and muscle aches, within a couple of months of infection

Being Asymptomatic 

Often, people who are otherwise healthy with mild infections and few worms are typically asymptomatic—they usually will not have symptoms of intestinal worms.

Common intestinal worm parasites that are often asymptomatic include:

Chronic strongyloidiasis
Light intestinal hookworm infections
Ascariasis infections
Light whipworm infections
Tapeworms

Treatment to Get Rid of Intestinal Worms 

If you find intestinal worms in your poop, mention it to a healthcare provider. In healthy people, intestinal worms typically go away without treatment.

If you need treatment to deworm your body, most soil-transmitted helminth parasites respond to a single 400 milligram (mg) dose of Albenza (albendazole) or a 500 mg tablet of Vermox (mebendazole).

Infections with strongyloidiasis respond well to Stromectol (ivermectin) treatment.

Pinworm infection is treated with Albenza, Vermox, or Ascarel (pyrantel pamoate). All infested family members should take the drugs at the same time. It is given in two doses—the second dose two weeks after the first.

Intestinal schistosomiasis is treated with one to two days of prescription Biltricide (praziquantel).

Intestinal Worm Diagnosis Process 

If you think you have intestinal worms, a healthcare provider will take a health history and review your hygiene and recent travel to endemic areas.

The only way to diagnose intestinal worm parasites is by seeing eggs, larvae, or adult worms in the stool or, in the case of pinworm, collecting eggs from the perineum.

The fecal (stool) exam is also called an ova and parasite test. It is used to detect the presence of intestinal worms and other gut parasites. You'll need to provide three or more stool samples collected on separate days for the test.

You may need special containers with preservative fluid to collect the samples. If you don't use a special cup with fluid, keep the samples refrigerated but not frozen.

Generally, when doing a stool sample test for intestinal worms, remember to:

Label it with your name, the collection date, and the time.
Collect a stool sample using a clean, dry container. You may also be given a special type of paper or plastic wrap to catch the stool before it goes into the toilet.
Don't include samples mixed with urine, toilet paper, or toilet water.
Make sure to close the container tightly.
Wash your hands well with soap and water after getting the sample.
Follow the instructions to return the container to the lab.

Additional tests that may be used to diagnose intestinal worms or rule out other intestinal parasites include:

Endoscopy or colonoscopy: A tube inserted into the mouth (endoscopy) or rectum (colonoscopy) helps the doctor visualize the intestines and look for signs of worms or other parasites.
Blood tests to look for a specific parasite infection based on the presence of antibodies or the parasites themselves, in the cases of parasitic diseases like filariasis, malaria, or babesiosis.

Instead of a stool test, confirmation of pinworms is usually done by finding eggs using a tape test or visualizing the female adult worm directly. Pinworms are rarely spotted in stool samples. 

To find a female worm, look around the anal area or in pajamas about two to three hours after falling asleep. If the worm is out, you'll see it with the naked eye. It is between one-quarter to one-half inch long.

If you don't see the worm, you'll want to do a tape test as soon as you wake up in the morning, before washing, bathing, going to the toilet or getting dressed.

Firmly press a piece of transparent tape against the folds of skin around the anus. The tape will pick up eggs or worms on the perineum. Repeat this for three days in a row. You'll need to seal the tape in a plastic bag and take it to your healthcare provider, who can have the lab look at it under a microscope.

It's also possible that you could find pinworm eggs in samples taken from under the fingernails.

Repeat Infection From Intestinal Worms 

Helminths live in the soil or the environment. They may pass through the skin or enter the intestines through something you eat or drink. They can even be breathed in. 

For example, hookworm eggs hatch in the soil and attach to bare feet and ankles. They penetrate the skin, migrate around the body, and end up in the intestine, where they attach to the lining and gorge on blood.

Threadworms get into the body through the skin from contaminated soil, but their eggs hatch in the intestine.

If you find yourself repeatedly getting infections with soil-based intestinal worms, there are some steps you can take to decrease your risk, such as:

Avoid touching the soil in areas where sanitation is poor.
Wash your hands (including under fingernails) regularly after touching soil that may be contaminated.
Carefully wash, peel, and cook fruits and vegetables that may be contaminated.
Avoid potentially contaminated water sources.
Don't drink untreated water from lakes, streams, or rivers when camping. Be careful not to swallow water when you swim.
When traveling to countries where the water may not be safe, avoid tap water, ice, and uncooked foods washed with tap water.
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. 
Wear shoes outside or anywhere that is potentially contaminated with hookworm and threadworm.

Raw Meat

Avoid eating raw or uncooked pork or beef. Tapeworms live in the flesh of cows and pigs.

To decontaminate and avoid reinfection with pinworm during and after treatment, the entire household must take precautions to reduce the spread of the pinworm eggs. These include:

Encourage children to avoid scratching their bare bottoms.
Wash daily. Showering is preferred to avoid contaminating the bathwater and spreading the infection.
Change and wash clothing and bedding frequently.
Avoid co-bathing and the reuse or sharing of washcloths.
Keeping good hand and fingernail hygiene, especially after using the restroom, changing a diaper, and before eating.
Trim the nails very short to avoid scratching and nail-biting.
Wash all clothing, bedding, and towels in hot water and machine dry at high temperatures to destroy eggs.
Let as much light into the bedrooms as possible during the day.
Wipe down all surfaces with an oiled cloth and vacuum carefully to avoid scattering the light eggs

Pinworm Sources

Pinworms can live up to two or three weeks at room temperature, so it's possible to be reinfected after deworming the entire house. Pinworms spread from the bare anal area to the hands or fingernails, then onto surfaces. They spread easily when:

Kids scratch their anus and touch playmates or toys, spreading eggs.
Eggs spread to clothing or bedding and then spread around the home.
Eggs are swept into the air and breathed into the mouth. 
Eggs drop onto food and are eaten.

If pinworm reinfection continues, consider if other playmates, schoolmates, or close contacts outside the home may be re-introducing the eggs. Ensure everyone infected—even those outside the home—gets the two-dose treatment and decontaminates their environment.

Summary

Parasitic intestinal worms include roundworms, pinworms, hookworms, and tapeworms. These worms infect humans and can cause various illnesses.

Symptoms range from gastrointestinal issues like diarrhea and abdominal pain. You may see parts of a worm in your stool or changes in stool appearance. Non-gastrointestinal symptoms of intestinal worms include rashes, respiratory problems, anemia, and malnutrition.

Diagnosis involves stool sample testing to look for worms, eggs, or larvae. The healthcare professional may run other tests depending on the worm. Treatment includes medicines.

Prevention strategies include:

Maintaining hygiene
Cooking food properly
Avoiding contaminated water sources

Reinfection with parasitic intestinal worms can occur. Take precautions to avoid reinfection, especially of pinworms. Pinworms cause anal itching, and their eggs can live for weeks at room temperature.

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