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ThePigSite Pig Health

Muscle Worms (Trichinella spiralis)

(500) These are very tiny round worms no more than 2-4mm long. They form cysts in the muscles of the pig. When inadequately cooked pork is eaten by humans they cause disease.

The life cycle

The female worm is found in the intestine where it produces large numbers of larvae which migrate through the intestinal wall into the blood stream Some of these larvae eventually form cysts in the muscles and remain viable for many years. For the cycle to develop further the infected cyst must be eaten by another host, either people, rats or other pigs. The pig therefore can act both as an intermediate host and be involved in a direct cycle through tail and ear biting and cannibalism.

Effect on the pig

It has little effect on the pig but it is important from a public health point of view.

Effects on the human

When the larvae are eaten they migrate from the intestine and burrow into muscles particularly those of the diaphragm and jaw. In severe cases death may occur. The adult worm in the intestine can cause vomiting and diarrhoea.


This is difficult but cysts containing larvae may be found in muscle at meat inspection. A blood test is also available.


  • There is no practical treatment for the cyst but fenbendazole has an effect.
Management control and prevention
  • Control is based on ensuring that pig meat is always well cooked.
  • Control of rats is important .
  • Control human faeces and prevent contact with pigs.
  • See introduction.

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