Worms and Intestinal Parasites: Causes, Symptoms and Treatment

Intestinal parasites

Intestinal parasites, commonly called intestinal worms or parasitic worms, are unicellular or multi-cellular organisms that infect the gastrointestinal tract of both humans and other animals and live off their host. Infection with parasitic worms occurs much more frequently than one might believe. While children are often more likely to get parasitic worms, adults that do not keep a rigorous hygiene can also be at risk. If left untreated, intestinal parasites infections can prove life-threatening.

Contaminated food or water, coming into contact with bowel movements and ingesting it as a result of poor hygiene can get one infected with a variety of parasitic worms, ranging from ascaris, giardia, the trichina worm to tapeworms, the hookworm and so on. While an intestinal parasite infection presents symptoms and can be diagnosed through simple tests, many people who are infected are often oblivious to the infection and let it go undiagnosed until the parasite starts causing more serious health problems.

Intestinal worms

What are intestinal parasites?

The key to understanding parasitic infections of the gastrointestinal tract and the reason why they have such a harmful impact on one’s health lies in understanding what intestinal parasites are and what is their mechanism of infection. A parasite is an organism that lives in and feeds off another organism. Intestinal parasites, often referred to as intestinal worms or parasitic worms, are single-cell or multi-cell organisms that can potentially infect humans. They may be as little as a few millimeters or as big as a few meters, depending on their type.

Intestinal parasites go through three main phases of evolution: egg, larvae and adult. Again, depending on their type, they may reside in various animals (fish, rats, pigs, cows, humans, birds) and various parts of the body (intestines, lungs, liver, brain, eyes or lymphatic system).

Where can you find intestinal parasites?

Intestinal parasites can live on fruits and vegetables, especially on crops fertilized naturally with animal manure coming from cows, pigs, sheep and so on. They can be found in the soil, almost everywhere, usually in the first 15 cm from the ground. They can be found in rivers, lakes and puddles. And because they can infect almost every living organism from mosquitoes, ants, wasps, fish, birds, pigs, cows, dogs, cats to humans, intestinal parasites are abundant in the bowel movements of all infected hosts and transmitted further from there.

Types of intestinal parasites

While there are intestinal parasites that prefer certain hosts, most can thrive off any living organism. Here are the most common 5 types of intestinal parasites that can infect humans:

  • Roundworms

Half of roundworm species are parasitic. The most common type of roundworm infection is attributed to Ascaris lumbricoides, an intestinal parasite that causes ascariasis. This type of roundworm infects over 20% of the world’s population and cases occur just as frequently in developed countries with proper sanitation as they occur in developing ones. Children are a high risk category for Ascaris infection because they are more likely to play with pets or stray animals that haven’t been dewormed and thus may come into contact with parasite eggs from their bowel movements.

Ascaris eggs can remain dormant for years and become ‘active’ following ingestion. Ascaris parasites are highly dangerous because once the ingested eggs hatch, the larvae migrate from the intestines to the heart, lungs, liver and even eyes (or get lost in other organs) to then return to the intestines as adults ready to reproduce. If left untreated, ascariasis can lead to death (it is estimated that about 20,000 children die annually as a result of  severe Ascaris infection).

Signs and symptoms of an infection often include eliminating worms or eggs through stools, but more severe cases may include shortness of breath, nausea, diarrhea, bloody stools, fatigue, abdominal pain, vomiting worms. Fortunately, the infection can be detected easily through stool examination and treated successfully with mebendazole, taken orally.

  • Pinworms

The pinworm, also called threadworm or seatworm is another common intestinal parasite and a type of roundworm. Out of three major pinworm species, Enterobius vermicularis is the only one to potentially infect humans and cause what is known as enterobiasis. This type of pinworm completes its life cycle in 8-13 weeks and colonizes the gastro-intestinal tract. A telling sign of pinworm infestation is itching in the perineal area.

If the area is scratched, the eggs of this parasite get attached to fingernails, hands, underwear or bed linen, from where they can easily be transferred to the mouth and ingested. Pinworm infections have extremely high rates of (re)infection, which makes it common for most household member to become carriers of the parasite at one point. Following treatment, strict personal hygiene and household hygiene are imperative.

  • Flatworms

The most problematic types of flatworms for humans (and livestock) are tapeworms and flukes. Tapeworms are the ones that reach menstruous lengths of almost 17 meters. Usually, people become infected with tapeworm larvae after consuming poorly cooked food. The larvae thrives within the intestines by anchoring itself to intestinal walls with hooks and some specimens may live up to 20 years.

A mature female tapeworm can lay millions of eggs every day which are then excreted, increasing reinfestation risks. Infestation is dangerous because tapeworm larvae may migrate to the lungs or liver where they form cysts. Pork, beef, fish, dog and sheep tapeworms are the most common potential causes of tapeworm infestation.

While tapeworm infections may be asymptomatic, sometimes, the following signs and symptoms may appear: continuous hunger, weakness, tiredness due to nutrient deficiencies caused by the parasite feeding off its host, nausea, headaches, diarrhea, indigestion, even weight loss or failure to gain weight despite eating well. Taenia solium (the pork tapeworm), Taenia saginata (the beef tapeworm) and Taenis asiatica (the Asian tapeworm) are known to cause the disease known as taeniasis. In the final stages of taeniasis, the parasites reach the brain and may cause severe neurological problems.

  • Whipworms

Trichuris trichiura is a 30-50 millimeter roundworm known as the whipworm. It causes the disease known as trichuriasis, also called whipworm infection. The name of the parasite has to do with its appearance, reminiscent of a whip. Whipworm infection is estimated to affect about 10% of the world’s population annually as a result of oral contact with soil contaminated with whipworm eggs. While the infection may not show symptoms at all in many individuals, when the worm population in the intestines begins to rise, fatigue, abdominal pain and bloody diarrhea may appear.

Trichuriasis is more likely to occur in tropical and subtropical areas of developing countries, where sanitation is practically nonexistent. The infection occurs when people do not wash their fruits and vegetables properly, do not cook their food well or forget to wash their hands, especially after having contact with infected soil, animal or human bowel movements, both of which are often used as fertilizer.

  • Hookworms

Ancylostoma duodenale and Necator americanus are the main parasites causing hookworm infestation, known either as ancylostomiasis, or as necatoriasis. Hookworm infection occurs as a result of poor hygiene and infection rates are visibly higher in rural areas, tropical and subtropical regions, children, adults working in unsanitary conditions and so on. This type of parasite has a lifespan of around 5 years and inhabits the small intestine from where it feeds off blood. As a result, the most telling sign of infestation is anemia, closely followed by iron deficiency.

Unlike other intestinal parasites, hookworms usually infect people by penetrating their skin. For example, if you walk barefoot or handle infected soil, the larvae (and only them) transfer themselves to your skin, penetrate it to reach your circulatory system and then lungs. Their aim is to get to the trachea from where they are swallowed and end up in the intestines where they mature. A single female can lay up to 30,000 eggs in a day and larvae may remain dormant in tissues and become activated when other adult worms die.

Intestinal parasites

Facts about intestinal parasites

Some of these parasites fall into the category of protozoa (single-cell organisms), while the others into the category of helminths (multicellular organisms). An infection with the parasites known as helminths is called helminthiasis. It is estimated there are about 1 million species of parasites that have the potential to infect humans, as well as other animals. Most parasitic worms are thin, either round or flat and have a whitish-yellowish, sometimes transparent color.

While intestinal parasites feed off the nutrients we take from the food we eat, causing visible weight loss and growing hunger, others prefer blood, triggering anemia and iron deficiencies. When parasites grow in numbers, they become less discrete and telling symptoms such as rashes, itching in the groin area or eliminating live worms in stools may occur.

Depending on the type of parasite inhabiting one’s intestines, the degree of infection and the incubation period, intestinal parasite infestations may be more or less hard to detect. Usually, a doctor will examine one or more stool samples under the microscope to identify the parasites. It is also common for a doctor to place some duct tape around the anal region, then remove it to check it under the microscope for eggs. Ultrasounds are rarely used, but aim to locate parasites in the lymphatic system, while colonoscopies are only performed when your doctor suspects you have an intestinal parasite, but cannot find proof in stools (often because you may have only a few adults causing your health problems).

How to tell if you have intestinal parasites?

Here are the most telling 8 signs and symptoms you have an intestinal parasites infection:

  1. Abdominal pain or tenderness.
  2. Itching and rashes in the groin area.
  3. Passing worms in stools.
  4. Tiredness, fatigue.
  5. Visible weight loss.
  6. Increased appetite.
  7. Gas, bloating, nausea and vomiting.
  8. Diarrhea, often with blood.

Less common signs and symptoms associated with a severe intestinal parasite infestation may include:

  1. Irritable bowel syndrome symptoms.
  2. Difficulty falling asleep.
  3. Screeching teeth during sleep.
  4. Unexplained skin rashes, hives, rosacea or eczema.
  5. Muscle aches or muscle pain and joint pain.
  6. Frequent feelings of apathy, depression, chronic fatigue, anxiety.
  7. Constant feeling of hunger.
  8. Hypoglycemia.
  9. B vitamins deficiency.
  10. Excessive mucus in stools, often accompanied by visible (or invisible) traces of blood.
  11. A cough.
  12. Jaundice.
  13. Night sweats or chills.
  14. Colitis.

Some of these symptoms are caused by parasites releasing toxins or their bowel movements into the host’s bloodstream and are the result of a severe infestation. For this reason, they rarely occur in individuals in developed countries, but are more common in poor, developing countries lacking sanitation and good hygiene education.

Sources of infection

What causes an intestinal parasite infection? Where can you acquire a parasitic infection?

  1. Contaminated water.
  2. Contaminated and unwashed fruits and vegetables.
  3. Raw or uncooked contaminated meat.
  4. Walking barefoot or handling contaminated soil.
  5. Working with natural fertilizers such as human and animal manure.
  6. Lack of good personal hygiene (hand washing) and sanitation (lack of toilets).

Tips to prevent intestinal parasites infection

Once a person acquires an intestinal parasite and remains untreated, it is only a matter of time until he or she infects other members of the household, coworkers and so on. Seeing that transmission can occur fairly easily, prevention remains crucial in reducing both infection and reinfection rates. Here is how to prevent intestinal parasites:

  • Practice good hygiene

The most important thing you can do to prevent a great number of diseases, including intestinal parasites infections is to wash your hands thoroughly before you eat as well as before and after you use the toilet. Changing your bed linen and underwear regularly and washing them at high temperatures can help destroy excreted eggs and prevent infection of other people as well as reinfestation.

  • Drink clean water

Whether you have a certified clean water source, drink bottled water (which is best), filter or even boil and cool you drinking water, it is important to keep to your practice to avoid consuming contaminated water.

  • Wash your food and cook it well

Wash fruits and vegetables well before eating them and avoid consuming undercooked meat such as pork, beef or fish. Also, you may want to avoid foods fertilized with untreated human and animal manure.

  • Disinfect your shoes and house regularly

If you went for a walk in the park, leave your shoes at the door and change into a clean pair you use only inside the house. Disinfect your outsoles with diluted chlorine and do the same with the floors once in a while.

  • Avoid playing with unwormed animals

Stray cats and dogs and even household pets that have not been dewormed are very likely to carry one or more intestinal parasites that can infect humans. Being an adult, you will most likely wash your hands well after petting an unwormed animal, but children might put their hands into their mouth soon after touching the fur or tail of a stray animal, which might lead to the transmission of a potentially dangerous parasite.

How to treat intestinal parasites?

  • Antiparasitic medication

Medication used to treat intestinal parasites is called antihelmintic medication. It includes Benzimidazoles (mebendazole, albendazole, fenbendazole), Ivermectin, Praziquantel and so on. The most effective is mebendazole therapy, often prescribed in one dose or smaller doses taken over a period of three days, twice a day, with a last dose recommended 10-14 days after the completion of the first treatment (to kill remaining eggs).

What is interesting is that mebendazole has shown promising results in cancer treatment as well, with testimonies showing that it can induce partial and total remission in terminal cancer patients. It was shown to help reduce tumor size and prevent further cancer spread.

  • Surgery

This is a last resort and is recommended only in cases of extremely severe intestinal parasites infestation, when worms clump together in the abdomen, for example, expanding it visibly and putting great strain on the host’s body. Such cases are only seen in individuals living in extreme poverty, lacking hygiene possibilities. If the condition is left untreated and ends up in worms clumping together in various parts of the body (intestines, lymphatic system), medication is no longer effective and surgery becomes imperative.


While it may not seem as much of an issue, remember that intestinal parasites are extremely dangerous and can lead to long-term health problems. For example, Toxocara canis, an ascarid found in unwormed pet cats and dogs, which can infect humans as well, can damage the heart muscle, the liver, the retina, cause seizures and coma. Another parasite appears to increase bladder cancer risks in adults, while many cause retarded physical and cognitive development in children. Basic hygiene rules and prevention can mean the world.