Trichinosis (Trichinellosis)

What is trichinosis?

Trichinellosis, more commonly known as trichinosis, is a parasitic food-borne disease that is caused by eating raw or undercooked meats, particularly pork products infested with the larvae of a type of roundworm called Trichinella.

When you eat food, your stomach acid and enzymes digest what you eat. In the case of infected meat, the acid and enzymes break down the hard outside shell (cyst) of the larvae, freeing the adult worms. The worms then produce larvae which take up residence in your body tissues, especially muscle. Anyone can get trichinosis, regardless of age or health status.

How common is trichinosis?

Trichinosis (trichinellosis) occurs worldwide. An estimated 10,000 people per year get trichinosis worldwide. In the U.S., the numbers have fallen from the estimate of 400 cases per year during the 1940s to 16 cases per year in the time frame from 2011 to 2015.

What causes trichinosis?

The most common ways to get trichinosis (trichinellosis) are:

• Eating raw or undercooked pork products.
• Eating improperly stored meats.
• Unclean kitchen utensils used to prepare meats.
• Eating raw or undercooked meat from wild animals that are infected. These animals include deer, moose, elk, boar, bear, walrus and many birds.

What are the symptoms of trichinosis?

Symptoms of trichinosis range from very mild to severe. Early symptoms, which start a few days after the worms enter your body, may include:

• Nausea and vomiting.
• Diarrhea.
• Pain in your abdomen.

Later symptoms may begin about two weeks after you eat the infected meat and may last as long as several weeks. They include:

• Muscle soreness.
• Fever.
• Headaches.
• Eye swelling.
• Chills.
• Extreme tiredness.
• Diarrhea or constipation.
• Cough.
• Rash or itchy skin.

In severe cases, trichinosis can cause:

• Difficulty with coordination and movement.
• Inflammation of your heart muscles.
• Difficulty breathing.
• Inflammation in your brain (encephalitis).

These symptoms can last from five to 45 days, but they usually begin to appear 10 to 14 days after consuming the infected meat. Abdominal symptoms can occur much sooner at one to two days after infection. Milder cases of trichinosis are often mistaken for the flu or other common illnesses. In extreme cases, trichinosis may result in death.

Is trichinosis contagious?

Trichinosis is an infection, but it’s not one that you pass on by sneezing or coughing. However, there’s some evidence that a pregnant person with trichinosis can pass the infection on to their baby.

How is trichinosis diagnosed?

Your healthcare provider might decide you have trichinosis on the basis of:

• Signs and symptoms.
• Finding out that you’ve eaten meat that may contain larvae.
• Blood tests that show high levels of eosinophils, a type of white blood cell.

Antibodies to Trichinella don’t show up at first, but your provider might order blood tests later that will find the antibodies and confirm the diagnosis. Stool (poop) samples aren’t used to diagnose trichinosis.

In very rare cases, your provider may recommend a biopsy of some of your tissues to confirm the diagnosis.

What is the treatment for trichinosis?

If you’ve eaten raw or undercooked meat and show symptoms of trichinosis, you should contact your healthcare provider. Treatment should begin as soon as possible. Although some cases of trichinosis go away on their own, some cases of untreated trichinosis can be fatal.

Your healthcare provider might prescribe:

• Drugs to rid your body of parasites, including mebendazole and albendazole. If you take these within the first three days of being infected, they stop the infection from getting to the muscles and getting worse.
• Drugs to help with pain, such as nonsteroidal anti-inflammatory drugs (NSAIDS).
• Drugs to help with inflammation, such as steroids.

What are the complications of trichinosis?

Complications of untreated trichinosis can be serious. They might include inflammation and damage to your:

• Heart, which could result in irregular heart rhythm (arrhythmia) and/or heart failure.
• Brain, which could result in seizures.
• Lungs, which could cause severe breathing problems.
• Death (rare).

Even with treatment, there might be long-term complications, including issues with your eyes, muscles and nerves.

How long until I feel better?

It may take weeks for you to feel better if you’ve had trichinosis.

How can I reduce my risk of getting trichinosis?

You can’t tell if the meat you’re eating has worms just by looking at it. Parasites can only be seen with a microscope. However, there are several things you can do to reduce your risk of being infected with trichinosis. One basic thing is to always wash your hands with soap and water before and after you touch raw meat or any food.

Cooking

Be sure you cook any meat you eat, especially pork and wild game, thoroughly. Use a food thermometer to cook it to recommended temperatures, after washing your thermometer with soap and water.

• For pork, the recommended temperature is 160 degrees Fahrenheit.
• For game meat (including deer, elk, moose, bear, bison, rabbit and beaver), the recommended temperature is 165 degrees Fahrenheit.
• For game birds (including turkey, duck, goose, partridge or pheasant), the recommended temperature is 180 degrees Fahrenheit for whole birds.
• For game birds, it’s recommended to cook parts (like breasts or thighs) at 165 degrees Fahrenheit. This includes birds cooked with stuffing inside the bird or dressed in the pan with the bird.

Freezing

Freeze pork, or any meat, that is less than 6 inches thick for 20 days at -15 degrees Centigrade, for 10 days at -23 Centigrade or six days at -30 degrees Centigrade. Freezing may not kill the worms in wild game meat because those particular parasites may be resistant to freezing.

Other processing

U.S. cases of trichinosis in previous years were caused by eating undercooked pork, but a successful education campaign reduced those numbers. However, many people still don’t cook game meats correctly. Also, most people don’t know that salting meat doesn’t kill the cysts of trichinosis and neither does smoking meats. Jerky has caused some of the recent cases of trichinosis in the U.S.

What is the outlook (prognosis) for people with trichinosis?

Most people enjoy a full recovery from trichinosis even though it may take weeks or even months to feel better completely.

The outlook for severe cases of trichinosis that result in brain or heart damage is less positive.

When should I see my healthcare provider?

If you develop symptoms days or weeks after eating pork or wild game meats, be sure to contact your provider. The symptoms of trichinosis depend on the stage of the disease, so try to remember when you had which symptoms.

If you’re being treated for trichinosis and you’re having side effects that are causing problems, let your provider know.

A note from Cleveland Clinic

If you have nausea, diarrhea or stomach pain in the days after eating some type of wild game or some types of pork, contact your healthcare provider. If you do have some type of food poisoning or trichinosis infection, it’s best to be diagnosed and treated early. Remember to cook all the meat you eat thoroughly and at the correct temperature.