Roundworms, Pinworms, and Threadworms

By Dr. Loretta Lanphier, ND, CN, HHP, CH

Many of us are not aware of, or we are in denial about, the fact that we share body space with many different types of creatures. We call these uninvited guests parasites, and not all of them are bad. However, roundworm infections, one of the most common types of parasitic conditions, are not one of the friendly kinds of parasites. They invade our systems and feed off of us and the food we eat. Almost everyone has parasites to one degree or another, but we can minimize or eliminate these freeloaders through lifestyle and diet changes that will drastically cut down on the chance of introducing them into our bodies.

What Are Roundworms, Pinworms, and Threadworms?

Pinworms and threadworms are actually both types of roundworms. Roundworm infections are parasitic diseases of the body caused by worms with long, slender bodies called nematodes. Roundworms are hitchhikers who use our bodies and the bodies of animals as a host upon which to feed and reproduce. They typically enter our bodies when we consume infected food or water, or practice poor hygiene, mainly by not properly washing our hands after having a bowel movement or before eating. There are many different types of roundworm infections, so perhaps the best way to learn about them is by studying some of the more common types and their characteristics.


We’ll start with pinworms because they cause the most commonly found form of roundworm infections in the United States. Pinworm infections are found most often in the Southern United States and in tropical countries where it is warm year around. The microscopic eggs find a home in the intestinal tract, where they mature into adult worms (up to a half-inch long) and travel to the anal area where they lay new eggs. The whole process from ingestion of the eggs to laying new eggs by the mature females takes several weeks. They generally migrate from the intestines to the anal area at night while an infected person is sleeping.

Symptoms of pinworm infections include:

  • Anal itching (or vaginal itching in females), sometimes severe.
  • Intermittent nausea and/or abdominal pain
  • Insomnia
  • Irritability and restlessness.

The most common way pinworms are spread is from getting the eggs on your fingers while scratching the anal area. Then when food or food preparation areas are touched, the eggs can be ingested by others or reingested by you. Poor hand washing or dirty fingernails are mostly responsible for spreading the worms.

Occasionally an adult worm can be spotted in the anal area, but there is a very definitive and easily administered test that can detect the presence of pinworms. Place a piece of clear cellophane tape over the anus during the night. Remove the tape first thing in the morning, before bathing or having a bowel movement. You can then take it to your doctor to have it examined under a microscope to look for the presence of pinworm eggs.

Many cases of pinworms are minor, and will run their course after a time, especially in children. However, heavy infections with hundreds of worms can occasionally cause complications such as:

  • Urinary tract and peritoneal cavity infections (in females): Sometimes pinworms can travel into the bladder, and up the vaginal area into the fallopian tubes and other reproductive tract organs. These infections can be potentially serious.
  • Secondary parasitic infections:  These are, in essence, parasites of the parasites. One of the most common parasites that accompany pinworms is called Dientaboeba fragilis infection. It can lead to cramping, diarrhea, fatigue, and poor appetite.
  • Weight loss:  Large pinworm infestations can lead to insufficient nutritional absorption, resulting in malnutrition and weight loss.


Threadworm infection, also known as strongyloidiasis, is commonly found in tropical climates, but can be found in most areas of the world to a lesser degree. It is estimated that about 25% of those in developing nations are infected with threadworms. Here in the U.S., it is rare, with most cases being found in immigrants, world travelers such as returning military personnel, and in the South East, especially in parts of the Appalachian Mountain region. Threadworms can also infect animals such as dogs, cats, horses, pigs, monkeys, rats, and others.

The roundworms that cause threadworm infections can live in soil for many years. In fact, the way that most threadworm infections occur is through walking barefoot on contaminated soil. The Strongyloides stercoralis roundworm has a two-stage life cycle. Stage one is called rhabdoid (rod-shaped), and they are harmless at this point. Stage two is the filariform stage (threadlike), and most infections come by filariform stage worms penetrating the soles of the feet. These aggressive worms quickly move into the lymph tissue once they have broken the skin barrier. From there they travel via the bloodstream into the lungs. They burst out of the capillaries, move upward into the throat, and are swallowed and introduced into the digestive tract. They then hatch into the noninfective rhabdoid stage, and are excreted out of the body in the fecal matter.

Symptoms of threadworm infections include:

  • Swelling, itching, and hives on the soles of the feet (sometimes mistakenly confused with insect bites)
  • Diarrhea
  • Cramps
  • Fever
  • Nausea and vomiting
  • Blood or mucous in the stool

At this point, they may be misdiagnosed as a case of stomach ulcers, due to the similarity in symptoms between the two conditions.

Once the larvae reach the respiratory system, common signs may include:

  1. Dry cough
  2. Difficulty breathing
  3. Coughing up blood or pus

A potentially fatal complication that can occur from threadworm infections is called hyperinfection syndrome. Basically, this is a severe threadworm infection that has spread to the point of endangering heart function, or causing other critical conditions such as meningitis, blood poisoning, perforated intestines, and stomach ulcers. Hyperinfection syndrome can lead to system wide shock and in some cases death.


In some ways, this roundworm infection, which infects an estimated 1.3 billion people around the world, is similar to threadworms. It too ends up in the lungs and is then swallowed and travels back to the intestines. But in this case, it is the Ascaris lumbricoides second trip to the intestinal tract. Ascariasis adult worms can grow to a length of a foot or more, and release an astounding 200,000 eggs per day! Initial infestations are usually the result of consuming unwashed vegetables that were grown in contaminated soil that in which animal or human feces were used as fertilizer. Upon reaching the intestines, the eggs mature into larvae that pierce the intestinal wall and enter the liver and bloodstream. From there they travel to the lungs, and then on to the throat where they are swallowed and reintroduced into the intestines. There they finally mature into adult worms. The whole life cycle is about 60-75 days.

Symptoms include intestinal discomfort, and when in the lungs, patients can experience wheezing and difficulty breathing. Severe cases can lead to liver systemic infections in the liver, eyes, lungs, heart, and brain. Large amounts of these foot-long worms can also cause intestinal blockages. In some parts of the world, untreated patients have a very high mortality rate from Ascariasis.


This type of roundworm infection is caused by a critter called anisakid roundworms. People become infected by these worms primarily through the consumption of raw or undercooked seafood.  The anisakid worms initially infect such creatures as whales, seals, and dolphins. Other sea dwellers ingest the feces of these animals, and the anisakids work their way down the food chain. Eventually when people eat fish or squid that is not prepared properly, they too become hosts for this roundworm.

There are two forms of anisakiasis: Acute and chronic. Acute cases can make a person violently ill within several hours after eating contaminated seafood. Chronic cases can cause ongoing intestinal discomfort that is often mistaken for conditions such as irritable bowel syndrome or stomach ulcers. Acute cases will often lead to the chronic form.


Also known as “whipworm” due to its whip-like front end, the roundworm that causes Trichuriasis is called Trichuris trichiura. It is most common in warm weather climates, and is found mostly in the South East here in the United States. It is much more common in other parts of the world, affecting an estimated 800 million worldwide. Ingested eggs mature in the small intestine and then move on to the large intestine where they become attached to the intestinal walls. Most cases are not serious, but severe infestations can result in anemia and even developmental retardation in children.


This particular form of roundworm infection is caused by a worm called Toxocara canis and Toxocara cati, which live in the intestines of dogs and cats, respectively. The eggs can survive in soil contaminated by dog and cat feces for up to seven years, especially in tropical climates. Most victims of toxocariasis are young children who contracted the parasite by playing in contaminated soil or sandboxes. These infections can be dangerous and life threatening in some cases. The eggs hatch in the intestines and the larvae travel throughout the body via the bloodstream. Infected organs can include the eyes, liver, lungs, brain, and heart. Eye infections are very common, and can form ocular larva migrans (OLM), which is often the first discernable sign of toxocariasis in many patients.

What Treatments Are Available for Roundworm Infections?

There are many anti-parasitic drugs that are commonly prescribed for these types of infections, and some of them are needed, especially in severe or life threatening situations. However, as with most medications, many of them can have significant negative side effects, especially on children or pregnant women.

As always, prevention is the best course to take. Be especially careful about what you eat or drink, especially if you are traveling in tropical areas of the developing world. Never go barefoot in areas such as this, and even here in the U.S. wash your vegetables thoroughly before eating. While many people enjoy seafood, be especially careful that any you consume is thoroughly cooked and avoid raw seafood like the plague. Remember that shellfish, in particular, are scavengers, and they consume a lot of unclean things like the feces of other sea creatures. That is why it is easy to get parasites from certain types of seafood. Lobster and crabs may be a delicacy, but they are not the healthiest foods to be putting in your body.

It is also a good idea, and a necessary step in total body health, to undergo a parasite cleanse to rid the body of unwanted intruders like roundworms and other parasites. There are many quality products to choose from on the market. It is hard enough to eat right and get proper nutrition without competing with these opportunistic creatures that seek to use us as a free lunch.

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