Human Intestinal Worms Types, Symptoms, Pictures

There are many different organisms that can have a parasitic with relationship with humans. This means that the organism drains a person of nutrients or thrives within the body. The organism benefits while the body is harmed, even if it is to a very minor degree. Intestinal worms are one type of parasites that affect humans. There are worms that can occupy and infest other parts of the body like the brain and liver but there are specific types of worms that infest the digestive tract.

What are intestinal worms?

Intestinal worms are multicellular parasitic worms that infest the human gastrointestinal tract. It thrives by consuming food that is within the bowels or sucking on blood from the bowel walls. Most infestations last for months or years with0ut causing any major symptoms or health complications. However, some intestinal worm infestations can be very serious and even life-threatening although these types of infestations are not as common in developed nations.

Human intestinal worms are not isolated to any specific region of the world. It occurs globally but infestations can be drastically reduced by proper control measures, sanitation and hygienic practises. Although prevention is the best measure, human intestinal worms can be effectively treated with modern drugs. Complications can be averted with early diagnosis and prompt treatment. The scientific term for a parasitic worm is helminth. Drugs that kills these worms are known as antihelmintics.

Sources and Spread

Most intestinal worms are contracted by eating food or drinking water that is contaminated with the eggs of the worms. Some types of worms can penetrate the skin and enter the body to migrate to certain organs. There are different stages of the worm life cycle, most of which are similar among the different worm species. In many cases an intermediate host is also necessary for the worm to complete its life cycle. Worms may be contracted by:

  • Eating undercooked meat that is infested with immature worms.
  • Eating raw vegetables and fruit irrigated with contaminated water.
  • Handling soil contaminated with animal feces.
  • Swimming in contaminated water or walking barefoot in contaminated soil.

Common Types of Worms


Roundworms or nematodes are among the common type of human intestinal worms. It can range in size from 1millimeter to 1 meter in length. Most roundworm infestations are contracted from contaminated soil which is then passed into the mouth.

  • Ascaris lumbricoides is the most common and largest of the roundworms that infect humans. It can average around 30cm in length.
  • Hookworms are usually less than 1cm long and the two main species that affects humans are Ancylostoma duodenale and Necator americanus.
  • Threadworms, also known as pinworms, are about 10 to 15mm long on average and the main species are Strongyloides stercoralis and Enterobius vermicularis.
  • Whipworm (Trichuris trichiura) reaches about 4cm in length on average.
  • Trichinella spiralis is the smallest of the roundworms in humans measuring around 1.5mm in length.

Ascaris lumbricoides

Picture of Ascaris roundworms


Flukes or trematodes are another type of parasitic worm. There are many different species of flukes and only a few can cause human infestations. These worms may have a predilection for certain parts of the body like the liver, blood or lung. The intestinal fluke, Fasciolopsis buski, is not a common worm infestation of the digestive tract. The adult worm can reach a length of 75mm and has a lifespan of around one year. It is also referred to as a flatworm due to its shape.



Tapeworms or cestodes are probably the best known of the intestinal parasitic worms. Infections with tapeworms is known as taeniasis. The symptoms are often mild and sometimes even absent so many people do not know that they have tapeworms infesting their gut. Sometimes it can lead to serious complications like seizures when the worm cysts reach the brain tissue but this only happens with certain tapeworm species.

  • Beef tapeworm (Taenia saginata) is acquired by eating undercooked or raw beef.
  • Pork tapeworm (Taenia solium and Taenia asiatica) is acquired by eating undercooked pork.
  • Fish tapeworm (Diphyllobothrium latum) is acquied by eating raw or undercooked fish from certain regions of the world.
  • Pet tapeworm (Dipylidium caninum) infests cats and dogs but in rare instances it may infest humans. It is transmitted by swallowing an infected flea.


Intestinal Worm Symptoms

Many intestinal worm infestations present with mild symptoms. Often there were long periods of time with no symptoms. Although the worms infest the gastrointestinal tract, it does not only present with digestive symptoms. Some infestations may also present with skin, nerve, respiratory and generalized symptoms. Gastrointestinal symptoms of parasitic intestinal worms include:

  • Diarrhea
  • Nausea
  • Abdominal pain
  • Loss of appetite
  • Bloody stool

Other symptoms include:

  • Fever
  • Anemia
  • Weight loss
  • Fatigue
  • Cough
  • Shortness of breath
  • Itchy skin
  • Skin rash or sores
  • Muscle pain
  • Headaches

Diagnosis of Intestinal Worms

Intestinal worms can be diagnosed with stool analysis. A stool sample is collected and examined for the worms, parts of the worm or worm eggs. For some types of worms like pinworms, an adhesive tape applied around the anus may collect eggs which can then be seen under a microscope. A stool test may also reveal the presence of blood which is a sign of certain intestinal worm infections. Other tests may also be done to diagnose anemia, nutritional deficiencies, inflammatory cells and antibodies.

Treatment and Prevention

Ascaris lumbricoides

Intestinal worms can be eradicated from the digestive tract by using antiparasite drugs. The three main drugs used for most intestinal worm infestations are:

  • Medendazole
  • Albdendazole
  • Ivermectin

In addition, other drugs may be used to relieve symptoms (such as antihistamines and painkillers) or to treat complications (such as iron supplements for anemia).

How can intestinal worm infections be prevented?

  • Always wash hands before eating and after using the toilet.
  • Cook meat thoroughly and avoid eating unwashed fruit or vegetables.
  • Children should be taught not to touch their mouth after making contact with soil without first washing their hands.
  • Pets should be dewormed and treated for any flea infestations.
  • Never eat from food outlets with unhygienic practises especially when holidaying in high risk areas.

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