What is Trichinosis?

Trichinosis is an infection caused by a species of parasitic roundworm known as Trichinella. They are usually found in carnivorous animals such as foxes, pigs, wild boars, bears, and walruses. People can contract trichinosis if they consume undercooked or raw meat from an infected animal. This happens most frequently with pork products.

It is a relatively rare condition in the United States due to strict meat processing and animal feed laws. However, there are still about ten thousand cases reported worldwide every year, usually in rural areas.

The parasite first takes root within a person’s intestines, where the larvae grow into adult roundworms over the course of several weeks. From there, the adult worms produce additional larvae that make their way into the bloodstream to be transported to other bodily tissues, usually the muscles.

Once there, the worms embed themselves into the muscle tissue, where they can survive for extended periods of time.

What are the Symptoms of Trichinosis?

Patients may not experience any symptoms at first, especially in mild cases. By the time the roundworm reaches the muscles, it is usually clear there is an infection.

Symptoms include:

  • Diarrhea
  • Fatigue
  • Lack of energy
  • Vomiting
  • Nausea
  • Abdominal cramps
  • Muscle aches
  • Muscle pain
  • Facial swelling
  • Eye infections
  • Chills
  • Headaches
  • Unexplained rashes
  • Light sensitivity
  • High fever
  • Pink eye
  • Weakness

In rare cases, severe trichinosis infections can lead to complications like encephalitis, bronchopneumonia, meningitis, sinusitis, and myocarditis.

Trichinosis Causes

Trichinosis, also called trichinellosis, is caused by ingesting the larval form of a Trichinella worm species. The worm infects carnivorous and omnivorous animals, especially those in the wild such as bear and wild boar.

Humans are infected by eating raw or undercooked meat from infected animals such as domestic pigs, wild feline (such as a cougar), fox, dog, wolf, horse, seal, or walrus. Animals contract the infection by feeding on tainted meat. Pigs or horses can be infected by consuming garbage that contains infected meat. Although cattle eat no meat, beef can be a source of infection if it is mixed with infected pork or placed in a grinder used with contaminated meat.

Until recently, pork was the primary cause of trichinosis in humans. Stiffer regulations of pork feed, however, have decreased the chance of contracting the infection from pigs.

How is a Trichinosis Treated?

Trichinosis does not always require treatment. Mild cases might clear up on their own without medical intervention within a few months after the initial onset of infection. Despite this, medications are often used to control symptoms and prevent future complications. Doctors will prescribe anti-parasitic drugs to treat the infection itself.

Additionally, patients may be given steroids to manage inflammation and pain relievers for muscle aches.

Trichinosis Prevention

The most effective way to prevent trichinosis is to properly cook and handle meat products.

How to cool and handle meat products:

  • Do not eat undercooked meat.
  • Use a food thermometer to ensure the internal temperature of a meat product meets the guidelines for recommended cooking temperatures.
  • Do not “taste-test” uncooked meat.
  • Freeze pork to kill worms. The meat must be under 6 inches thick and remain frozen at 5°F (-15°C) for 20 days to kill the worms.
  • Thoroughly clean meat grinders after every use.
  • Dispose of uncooked meat scraps and carcasses properly so that animals cannot consume them. This helps prevent the spread of trichinosis in animal populations, including rats.
  • Freeze or irradiate wild-animal meat. Irradiation kills parasites, and three weeks of deep freezing kills the worms in some meats. Freezing bear meat does not kill Trichinella worms. If these are not practical options, cook the meat to recommended temperatures.

Microwaving, curing (salting), pickling, drying, or smoking will not necessarily kill Trichinella parasites. The Centers for Disease Control and Prevention report multiple cases of the infection from homemade jerky and sausage in recent years.

Although freezing pork products kills worms, wild game may harbor certain freeze-resistant species. As a result, freezing may not kill all the worms contained in wild game.

Using a food thermometer, cook all meats to the temperatures recommended by the USDA:

  • Whole cuts of meat: minimum 145° F (63° C). Allow meat to rest at least three minutes to complete the cooking process.
  • Ground meat: minimum 160° F (71° C). No rest time needed.
  • Whole cuts and ground wild game: minimum 160° F (71° C).
  • Whole cuts and ground poultry: minimum 165° F (74° C). Allow to rest for at least three minutes to complete the cooking process.
Last Reviewed:
October 11, 2016
Last Updated:
September 10, 2017