Signs & symptoms of a parasitic worm infestation

Updated April 17, 2017

Parasitic worms are spread to humans through contaminated food and water. These small worms are usually barely visible to the naked eye, but the discomfort level and illnesses caused are varied in intensity and seriousness. An untreated worm infestation can even result in the host's death.

Types of Parasitic Worms

There are three main types of parasitic worms that can grow inside the human digestive tract: roundworm, pork tapeworm and beef tapeworm. Each has different signs and symptoms, and take different amounts of time for the host to realise they are infected.

Symptoms of Intestinal Roundworm

Intestinal roundworm is spread to humans by raw or undercooked pork or wild game. The first symptoms of infestation arrive within one to two days of consumption, and the host experiences nausea, vomiting, diarrhoea, pain in the abdomen and a fever. At this stage, an infestation is often mistaken for the flu, but then additional symptoms set in two to eight weeks later. The host experiences headaches, eye swelling, aches in joints and muscles, feels weak and has itchy skin. A severe infection can be accompanied by additional symptoms of heart and breathing problems, or difficulty with coordination. A severe and untreated case of intestinal roundworm can lead to death.

Symptoms of Pork Tapeworm

Pork tapeworms are spread to humans when raw or undercooked pork infected with the tapeworm larvae is ingested. Infection with adult worms can often be without symptoms, although many will experience abdominal pain, disturbances in the digestive system, weight loss, and possible obstruction of the intestines. These symptoms appear within eight to 12 weeks of ingestion. If the adult worm's eggs hatch and larvae travel throughout the body, infecting other organs, numerous other symptoms will be detected. For example, if the respiratory organs are infected, the host may experience asthma-like symptoms and cough up blood.

Symptoms of Beef Tapeworm

The signs of symptoms of a beef tapeworm infestation is similar to the pork tapeworm. The timing is a bit different, though. Symptoms of beef tapeworms appear within 10 to 14 weeks.

Avoiding a Parasitic Worm Infestation

It is important to practice safe food handling and cooking procedures in order to prevent parasitic worm infestation. Beef, pork and wild game should be cooked to 71.1 degrees C to kill tapeworm larvae that might be present. Water should only be consumed from a treated municipal water supply, and one should avoid drinking swimming pool water. In addition, raw fruits and vegetables should be washed, peeled, or cooked before eating. These rules are especially important to avoid a parasitic worm infestation when visiting developing countries.

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About the Author

Ryan Kelley is a freelance writer, editor and bartender from San Diego. He has developed instructional videos and training materials in industries ranging from manufacturing, alternative medicine and publishing. His film reviews have appeared on, and he is currently the Tequila Examiner at With a passion for life-long learning, Kelley specializes in translating complex concepts to a wide audience.