Nematodes or nematodes in humans are among the most common infectious agents worldwide. These include parasites such as roundworms, pinworms and whipworms. Infection is usually by eating raw or undercooked foods that are contaminated with eggs or larvae of nematodes. Read more about the possible complaints of roundworms, drugs against the parasites and the chances of recovery in an infestation!

Article overview nematodes

  • description
  • symptoms
  • Causes and risk factors
  • Examinations and diagnosis
  • treatment
  • Disease course and prognosis

Roundworms: description

Roundworms (nematodes) are the parasites that affect humans most often. They occur mainly in tropical developing countries. However, some representatives also live in Europe - which is why you can contract such a worm disease here in Germany as well.

What are nematodes?

Nematodes are long, thread-like worms that reach a length of a few millimeters to a meter - and thus look similar to threads of different lengths. They move snaking forward.

Adult threadworms live mostly in the human intestinal lumen, where they mate and lay eggs. The larvae hatching from the eggs also remain in the intestine in some nematode species, while they wander through the body with other representatives.

The developmental cycle of the animals runs from the egg over several larval stages up to adult male and female worms. Known parasitic representatives of roundworms are roundworms, pinworms, whipworms, Trichinella, hookworms and filaria.


Roundworm infection is the most common human worm disease. How to detect and treat an infestation with these roundworms is described in the article Roundworms.


An infection with the pinwormOxyuris vermicularis (Enterobius vermicularis) is called oxyuriasis (enterobiasis) and affects mainly children - and also in Germany. Read more about these thread worms in the article Pinworms.


Whipworms belong to the species Trichuris trichiura, Tropical and subtropical areas are the main distribution area of ​​these approximately four centimeters long thread worms. Humans and animals (monkeys, pigs, etc.) are possible host organisms, but humans are the main host. Especially children become infected with whipworms.


Various members of the genus Trichinella can lead to infection (trichinellosis) in humans. The larvae of this form of roundworm, with which one is infected, are called Trichinen.

Trichinelles use mammals, birds and as hosts. In addition to the infestation of dogs, cats and horses, domestic animals and wild boars infected with roundworms are of particular importance to humans, and their consumption can be contaminated.

Trichinellosis occurs worldwide, but has become rare in Germany due to the statutory meat inspection meanwhile.


Hookworms that affect humans are Ancylostoma duodenal and Necator americanus, These approximately one centimeter long, blood-sucking thread worms are world-wide spread, particularly in warm regions with bad hygienic conditions. They owe their name to their hook-shaped curved front end.


These tropical roundworms are transmitted by insects and cause different forms of filariasis depending on the species. You will learn more about this in the article Filariasis.

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Roundworms: Symptoms

Not every infestation with roundworms causes discomfort. This depends, among other things, on the number of parasites recorded. The type of symptoms depends on which thread worms are responsible for the infection and where the animals are in the human body.

Infestation with roundworms: symptoms

The migration of roundworms through the human body can cause various discomforts. Keeping the animals in the intestines can cause abdominal pain and nausea. On the other hand, a lung attack triggers allergic reactions such as coughing and mild fever.

Rarely, the roundworms migrate into the bile ducts and move the bile and pancreatic duct. Possible consequences include gallstau (cholestasis) and inflammation of the pancreas (pancreatitis). Other possible complications of infection with these roundworms are:

  • Bowel obstruction (ileus): roundworms can form "balls" in the intestine
  • Appendicitis (appendicitis)
  • cramps
  • shock

Infestation with pinworm: Symptoms

An infection with these roundworms causes nocturnal itching on the anus, because the females lay their eggs in this region. In addition, appendicitis may develop.

Infestation with whipworms: symptoms

These nematodes partially invade the intestinal mucosa, which can lead to bleeding and anemia. With a very strong worm infestation possible symptoms are: abdominal pain, indigestion, colitis and diarrhea. In addition, the nematodes limit the absorption of nutrients in the intestine, which in turn can trigger a deficiency and a growth slowdown (in children).

Infestation with trichinae: symptoms

Experts estimate that symptoms only occur when 100 to 300 Trichinella are taken. Critical to the symptoms is also the stage that the parasites are currently undergoing. The type of Trichinella and the strength of the human defense system also play a role and influence the severity of the disease.

A few days after the infection, diarrhea and abdominal pain are possible with a stronger trichina infestation of the intestine. The patients get high fever (around 40 degrees Celsius), chills, severe muscle pain and swelling (edema) around the eyes.

Other possible symptoms include skin rash, nasal bleeding, conjunctivitis, headache, insomnia, dysphagia, dry cough, punctate skin and mucous membrane bleeding (petechiae), painful movement of the eye muscles and even chronic rheumatic complaints.

Some of these nematode sufferers develop dangerous and sometimes even life-threatening complications. This includes:

  • Heart muscle inflammation (myocarditis), cardiac arrhythmias
  • Brain inflammation (encephalitis)
  • lung infection
  • "Blood poisoning" (sepsis)
  • Circulatory failure
  • Hypofunction of the adrenals (adrenal insufficiency)
  • psychotic states
  • Coma and seizures

Hookworm infestation: symptoms

There, where the larvae of these roundworms have penetrated the skin, itching and reddening of the skin develop. The larvae migrate via blood or lymphatic channels into the lungs, where they cause, for example, shortness of breath, coughing and pneumonia.

By coughing, the larvae enter the larynx and are swallowed. In the small intestine, the parasites develop into sexually mature roundworms, which can survive here for years. They cause symptoms such as upper abdominal pain, bloating, bloating, constipation or diarrhea.

In a serious infection with these bloodsucking nematodes life-threatening iron deficiency anemia (anemia due to iron deficiency) and hypoproteinemia (protein deficiency in the blood) are possible. This slows down the growth and development of children.

Infestation with filariae: symptoms

The symptoms that these nematodes cause depends on the type of parasite and the disease it causes (such as loa-loa filariasis, onchocerciasis, etc.). Possible are, for example, swelling and inflammation of the lymphatic vessels and nodes, fever, massive swelling of the legs, genitals or other body parts (elephantiasis), itching, skin knots or eye disorders.

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Roundworms: causes and risk factors

Threadworms find their way into the human body in different ways:

Food contaminated with roundworm eggs

Often nematodes get into the human organism through food that is contaminated with the eggs of the parasites. So you can get infected with Trichinellen by eating raw or insufficiently cooked meat (especially pork) - these nematodes infested with pleasure domestic pigs.

Salad and raw vegetables can also become sources of infection if they come into contact with contaminated faeces (for example in case of sewage fertilization) - sick people and animals excrete the eggs from roundworms with the stool.

Contaminated items

In case of pinworm, the infection also takes place in other ways:

The females living in the human intestinal lumen deposit their eggs at the intestinal outlet (anus). This itches and causes the patients to scratch themselves there. This is how the eggs of the pinworm reach the fingers and under the nails. In the case of poor hygiene, they can be transferred not only to food, but also to objects (such as doorknobs) and from there to be taken up by other people.

Other infection routes

Some species of nematode worms have other sources of infection: they can enter the human body in larval form (like hookworms), be absorbed into water-borne fleas, or transmitted by insects (such as filariae).

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Roundworms: examinations and diagnosis

Anyone who discovers worms or worm parts in the stool and / or has been suffering from non-specific abdominal pain for a long time should go to the family doctor or pediatrician. The same applies if repeated hitherto unknown afterjumping occurs. With such complaints thread worms could be the cause. To clarify this, the doctor will first describe the patient's complaints in detail and ask questions such as: