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Trichinosis

Medically reviewed by Drugs.com. Last updated on May 25, 2022.

Overview

Trichinosis (trik-ih-NO-sis), sometimes called trichinellosis (trik-ih-nuh-LOW-sis), is a type of roundworm infection. These roundworm parasites (trichinella) use a host body to live and reproduce. These parasites infect animals such as bears, cougars, walruses, foxes, wild boars and domestic pigs. You get the infection by eating the immature form of the roundworm (larvae) in raw or undercooked meat.

When humans eat raw or undercooked meat containing trichinella larvae, the larvae grow into adult worms in the small intestine. This takes several weeks. The adult worms produce larvae that travel through the bloodstream to different parts of the body. They then bury themselves in muscle tissue. Trichinosis is most widespread in rural areas throughout the world.

Trichinosis can be treated with medication, though it's not always needed. It's also easy to prevent.

Symptoms

Signs and symptoms of trichinosis infection and how severe the infection is can vary. This depends on the number of larvae eaten in the infected meat.

Possibly no signs or symptoms

Mild cases of trichinosis — those with only a small number of parasites in your body — may cause no signs or symptoms. Symptoms can develop with moderate or heavy infestation — a large number of parasites in your body. These symptoms sometimes get worse as the roundworm (trichinella) larvae travel through your body.

Initial signs and symptoms

You swallow roundworm (trichinella) larvae in tiny sacks (cysts) containing the parasite. Your digestive juices dissolve the cysts, releasing the larvae into your body. The larvae then enter the wall of your small intestine, where they grow into adult worms and mate. Digestive symptoms can begin 1 to 2 days after infection. At this stage, you may experience:

Later signs and symptoms

About a week after infection, the adult female worms produce larvae. The larvae go through the wall of your intestine and enter your bloodstream, They travel around the body and bury themselves in muscle tissue. Here, each larva coils up and forms a cyst around itself.

The larvae can live for months to years inside the muscle tissue.

Symptoms caused by muscle tissue invasion usually start 2 to 8 weeks after infection and include:

With a large number of parasites, muscle pain and weakness can be severe. This can limit moving, breathing and speaking.

Symptoms last for several months. But symptoms generally lessen when the larvae form cysts. Even after the infection is gone, fatigue, mild pain, weakness and diarrhea may last for months or years.

Trichinella cysts

After you eat roundworm (trichinella) larvae, they grow into adult worms in your small intestine. The adults then produce larvae that move through the bloodstream to muscle tissues, shown here.

When to see a doctor

If you have a mild case of trichinosis with no symptoms, you might not need medical care. If you have digestive problems or muscle pain and swelling about a week after eating pork or wild-animal meat, talk to your health care provider.

Causes

People get trichinosis when they eat raw or undercooked meat that is infected with the larvae of the trichinella roundworm parasite. You can't pass the parasite on to another person.

Animals are infected when they feed on other infected animals. Infected meat anywhere in the world can come from wild animals such as bear, cougar, wolf, wild boar, walrus or seal. Domestic pigs and horses can become infected with trichinosis when they feed on garbage containing infected meat scraps.

In the United States, pigs have become a less common source of infection due to increased control of pork feed and products. Wild-animal meat is the source of most cases of trichinosis in the U.S.

You can't get trichinosis from beef, as cows don't eat meat. But some cases of trichinosis in people have been linked to eating beef that was mixed with infected pork.

You can also get trichinosis when beef or other meat is ground in a grinder previously used to grind infected meat.

Risk factors

Risk factors for trichinosis include:

Complications

Except in severe cases, complications related to trichinosis are rare. In cases with a large number of roundworm (trichinella) larvae, larvae can move through the body to muscle tissue in and around organs. This can cause potentially dangerous, even fatal, complications, such as pain and swelling (inflammation) of the:

Prevention

The best defense against trichinosis is proper food preparation. Follow these tips to avoid trichinosis:

Diagnosis

Your health care provider can diagnose trichinosis by discussing your symptoms and doing a physical exam. You provider may also ask if you've eaten raw or undercooked meat.

To diagnose your infection, your health care provider might use these tests:

Trichinella larvae travel from the small intestine through your bloodstream to bury themselves inside muscle tissue. Because of this, stool sample tests don't often show the parasite.

Treatment

Trichinosis usually gets better on its own. In cases with a mild or moderate number of larvae, most signs and symptoms typically go away within a few months. However, fatigue, mild pain, weakness and diarrhea may stay for many months or years. Infection with a large number of larvae can cause more-severe symptoms that need treatment right away.

Your health care provider may prescribe medications depending on your symptoms and the severity of infection.

Preparing for your appointment

You're likely to start by seeing your family health care provider. In some cases, you may be referred to an infectious disease specialist.

Here's some information to help you get ready for your appointment.

What you can do

For trichinosis, some questions to ask include:

Don't hesitate to ask other questions during your appointment.

What to expect from your doctor

Your health care provider is likely to ask you a number of questions, including:

Preparing for your appointment will help you make the most of your time with your health care provider.

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