Tapeworms are parasitic flatworms that live in the digestive tract of humans and other animals and can achieve lengths of up to ten metres. Several thousand species have been identified, about 25 of which are known to infect humans, most commonly:

  • The beef tapeworm
  • The fish tapeworm
  • The pork tapeworm
  • The dwarf tapeworm

They are a simple organism. The typical tapeworm consists of a head and a chain of identical segments called proglottids. They have no mouth, digestive tract, circulatory system or gas-exchange (breathing) organ, and absorb their food directly through their body covering.

Most tapeworms are hermaphroditic, having reproductive organs of both sexes and are capable of self-fertilisation.

Lifecycle

Despite the simplicity of their construction, tapeworms have a complex lifecycle.

The adult tapeworm lives in the human intestine, attached to the intestinal wall by sharp hooks on its head. Egg-bearing proglottids break off from the end of the worm and are passed in faeces. These eggs find their way into the environment and are ingested by Intermediate hosts – cows, pigs, fish etc.

Inside the intermediate host, the eggs hatch into larvae, burrow through the intestinal wall, and are carried by the bloodstream to various muscle sites, where they anchor and form cysts around themselves.

The larvae remain in this state until the animal is slaughtered and its poorly cooked meat is eaten by humans. The cysts then hatch in the human digestive tract and grow to maturity in the intestine.

Variations on a Theme

While the two-stage lifecycle is the general pattern for tapeworm propagation, there are some variations in the human-infecting tapeworm group.

The Pork Tapeworm

While with other species the human ingestion of tapeworm eggs (as opposed to larval cysts) does not lead to infection, the ingestion of pork tapeworm eggs can lead to the formation of larval cysts in human beings. This condition, known as cysticercosis, can be dangerous as the cysts may form in the organs, spinal muscle, the brain and the eyes.

The Fish Tapeworm

Eggs are first ingested by crustaceans before they are eaten by fish, making this, in effect, a three-stage pathway. Fish tapeworm occurs only in freshwater fish such as salmon, trout, pike and perch.

The Dwarf Tapeworm

Dwarf tapeworms do not need an intermediate host. After ingestion, generally through food contaminated by human faeces, the eggs will mature directly into an adult tapeworm. There is no intermediate cyst stage – the infection is spread by eating food contaminated with eggs, rather than by ingesting cysts in undercooked meat.

Tapeworm Symptoms

The effects of human infection with beef, fish and dwarf tapeworms, although gruesome to contemplate, are relatively innocuous. Most people experience no symptoms. Those that do, report abdominal discomfort, loss of appetite and diarrhoea.

Anaemia may be observed in cases of fish tapeworm infection as the worm absorbs vitamin B12, which red blood cells need to in order to mature.

Pork tapeworm infection, though can cause far more serious symptoms including, headaches, seizures, paralysis, confusion and blindness.

Protection Against the Worm

It should be obvious from the discussion of tapeworm lifecycles above that protection against human tapeworm infection requires only that good personal hygiene standards be observed (washing hands etc.), that care be taken to avoid faeces contaminated food and water, and, most importantly, that meat and fish be thoroughly cooked (at a temperature above 57 degrees Celsius).

Have You Got One?

As, in many cases, there are no immediate symptoms, it can be hard to tell. Worm segments may be visible in stools, or a doctor may analyse stool samples to detect tapeworm eggs.

In the case of pork tapeworm infection or cysticercosis, cysts can be seen with CT and MRI scans. Blood tests for antibodies may also aid diagnosis.

Tapeworm Treatment

Intestinal tapeworms can be killed with a single dose of praziquantel.

Cysticercosis might not be treated unless it involves the brain. If treatment is deemed necessary, anti-parasitic drugs like abendazole and praziquantel may be used. Corticosteroids may be given to reduce inflammation.

Tapeworms are the stuff of nightmares, but cooking food properly is a simple and effective defence against them. Rare steak may be tempting, and salmon sashimi may otherwise be healthy, but next time you order, spare a thought for those gruesome little cysts that might be accompanying your meal.

Learn more about getting rid of tapeworms here.

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Comments

  1. Children are at a higher risk of being infected by worms or any other infection. So have to take good care of them. There are some remedies from which one can protect their children like, dried, pounded leaves of woodworm shrub mixed in honey helps in killing the worms. Freshly grinded cloves are also a great. Fenugreek, licorice and peppermint infusions are known for their anti-bacterial properties. Even capsicum will be helpful.

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