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What to Know About Trichinosis (Trichinellosis)

Medically Reviewed by Jabeen Begum, MD on November 10, 2021

Trichinosis, also known as trichinellosis, is a rare type of roundworm infection.

What Causes Trichinosis?

Trichinosis is caused by eating raw or undercooked meat infected with the larvae of the Trichinella worm. Larvae are insects between the stage of hatching from the egg and maturing into adulthood.

There are an estimated 10,000 cases of trichinellosis infection worldwide each year. Between 2011 and 2015, 16 cases a year were reported in the U.S. Most of those infections were among hunters and others who ate meat from wild animals. 

What Are the Symptoms of Trichinosis?

Trichinosis symptoms vary depending on the number of larvae consumed.

Trichinella larvae are encased in a cyst. After you swallow them, your digestive juices dissolve the cysts, and the larvae are released into your body. The larvae move through your small intestinal wall and mature into adult worms and mate. 

At this first stage, some of your symptoms may include:

  • Diarrhea
  • Vomiting
  • Fatigue
  • Fever
  • Nausea
  • Abdominal discomfort

About a week after infection, the adult female Trichinella worms produce larvae for four to six weeks and then die or are excreted. The newborn larvae move through your bloodstream and eventually reach your muscles and other tissues.

The larvae form cysts after one to two months and can live for several years in your body. After they die, they're absorbed or become hardened (calcify).

At this stage, symptoms include:

  • Fever
  • Chills 
  • Swelling of your eyes and face
  • Itchy skin
  • Aching joints and muscle pains,
  • Diarrhea
  • Constipation
  • Headache
  • Cough

If your infection is severe, you may have:

  • Difficulty with coordination of your movements
  • Breathing problems 
  • Heart problems
  • Death 

How Is Trichinosis Diagnosed?

Your doctor may do a physical exam and discuss any symptoms you may have. They may also do a few tests:

Blood tests. Your doctor may take a sample of your blood and have it tested for signs that you may have trichinosis. This includes an increase in a certain type of white blood cells (eosinophils) or the formation of antibodies.

Muscle biopsy. Usually, a blood test is enough to diagnose trichinosis. But your doctor might also recommend a muscle biopsy. They will remove a small piece of your muscle to examine it under a microscope for trichinella larvae.

What Is the Treatment for Trichinosis?

Depending on your symptoms and severity of infection, your doctor may prescribe:

  • Anti-parasitic medication. This is the first line of trichinella infection treatment. If the infection is found early, taking albendazole or mebendazole can eliminate the worms and larvae in your intestine. You may have some mild side effects during the trichinella treatment. But if the infection is discovered after the larvae embed in your muscles, anti-parasitic drugs may be less effective.
  • Pain relievers. If the larvae have moved into your muscles, your doctor may prescribe pain relief medication to help with muscle aches. Over time, the larvae cysts in your muscles will harden, which destroys the larvae. Then your fatigue and muscle aches will go away.
  • Corticosteroids. For some people, trichinellosis may cause allergic reactions. This can happen when the parasites enter your muscles or when the dying larvae release chemicals. Your doctor might prescribe a corticosteroid to help with your inflammation. 

Are You at Risk for Trichinosis?

You are at risk for trichinosis if you eat raw or undercooked meats, especially:

  • Pork
  • Bear
  • Wild cats such as cougar
  • Fox
  • Wolf
  • Dog
  • Horse
  • Seal
  • Walrus

Can Trichinosis Be Prevented?

The best way to prevent trichinella infection is to cook your meat to safe temperatures:

  • Use a food thermometer to check the internal temperature of cooked meat.
  • Cook pork and wild animal meat until it reaches an internal temperature of 160 degrees Fahrenheit (71 degrees Celsius). 
  • For whole cuts of meat and ground poultry, cook until it reaches 165 degrees Fahrenheit (74 degrees Celsius). 
  • Wait for at least three minutes after you've removed meat from heat before you cut or eat it.
  • To kill any parasites, freeze pork that’s less than six inches thick for 20 days at 5 degrees Fahrenheit (-15 degrees Celsius). 
  • Freezing doesn’t work for wild game meat. Some worm species that infect wild animals can’t be killed by freezing.
  • Be aware that meat processing methods like smoking, pickling, and curing don't kill parasites. 
  • If you grind your own meat, clean your meat grinder thoroughly after each use. 

When to See Your Doctor

In most cases, trichinosis will go away on its own. This may take a few months. But some symptoms like fatigue, diarrhea, and mild pain may linger for months or even years.

You might not need to see your doctor if you have a mild case with no symptoms. But you should talk to your doctor if you have gastrointestinal problems or swelling and muscle pain one week after eating wild game meat or pork.

Show Sources

SOURCES: 

Centers for Disease Control and Prevention: “Parasites - Trichinellosis (also known as Trichinosis).”

Mayo Clinic: “Trichinosis.”

Merck Manual: "Trichinosis."

Rawla, P., Sharma, S. StatPearls. “Trichinella Spiralis,” StatPearls Publishing, 2021.

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