Trichinosis, also called trichinellosis, is a parasitic infection caused by roundworms of the Trichinella genus, most commonly Trichinella spiralis. People typically get trichinosis by eating raw or undercooked meat, especially pork or wild game, that contains larvae encased in cysts. Once consumed, these larvae are released in the intestine, mature into adult worms, and produce new larvae that migrate through the bloodstream to muscles, where they encyst. 

Although trichinosis was once a significant global health issue, particularly in areas where pork consumption was high and meat inspection was poor, its prevalence has dropped sharply in many countries. This decline is largely due to improved animal feeding practices, stricter meat inspection laws, and better public awareness of food safety. However, outbreaks still occur in regions where homemade or traditional meat dishes are prepared with undercooked meat or where wild game is consumed. This article provides a comprehensive overview of trichinosis, including its causes, symptoms, diagnosis, treatment, and prevention. 

Trichinosis is a zoonotic (animal-to-human) parasitic infection that occurs when a person ingests Trichinella larvae. The larvae develop into adult worms in the small intestine and produce new larvae that spread through the bloodstream to muscle tissue, where they form cysts. These cysts can persist for years and cause inflammation and muscle pain. 

Key features: 

• Causative agent: Trichinella species, primarily T. spiralis, though other species like T. britovi, T. nativa, T. pseudospiralis, and T. papuae can also infect humans. 

• Transmission: Eating undercooked meat from infected animals, especially pork, wild boar, bear, or walrus. 

• Incubation period: Usually 1–2 weeks, depending on how many larvae are consumed. 

Trichinosis can range from mild or asymptomatic cases to severe infections involving multiple organs such as the heart, brain, and lungs. 

Trichinosis occurs worldwide, though its incidence varies greatly by region. In North America and Western Europe, strict food safety measures have reduced cases. However, it remains more common in Eastern Europe, parts of Asia, and regions where wild game is frequently consumed. 

Outbreaks are often linked to community events or traditional dishes prepared from undercooked meat. The World Health Organization continues to monitor cases to identify new sources and species of Trichinella. 

Trichinosis develops when a person consumes meat contaminated with Trichinella larvae. While improved farming and meat inspection have reduced cases, certain practices still increase risk. 

Major risk factors include: 

• Eating undercooked meat: 

• Raw or undercooked pork products like sausage or smoked meat 

• Wild game such as bear, boar, or walrus 

• Rarely, horse meat (in parts of Europe) 

• Occupational exposure: Hunters, butchers, and trappers who handle raw meat 

• Cultural and culinary traditions: Dishes that use raw or partially cooked meat, such as larb (Southeast Asia) or carne cruda 

• Improper freezing: Some Trichinella species (like T. nativa) are resistant to freezing 

• Home slaughtering: Without proper inspection, infected meat may be consumed unknowingly 

Trichinosis progresses through two distinct phases: 

1. Intestinal Phase (Enteral Phase) 

• Begins within the first week after infection 

• Larvae mature into adult worms in the intestines 

• Females release larvae that penetrate the intestinal lining 

• Causes local inflammation leading to nausea, abdominal pain, and diarrhea 

2. Muscle Invasion Phase (Parenteral Phase) 

• Starts 7–10 days after infection 

• Larvae enter the bloodstream and migrate to muscles 

• Commonly affected muscles include the diaphragm, jaw, neck, and limbs 

• The immune response causes fever, swelling, and muscle pain 

Severe infections can lead to systemic inflammation affecting the heart (myocarditis), brain (encephalitis), and lungs (pneumonitis), sometimes resulting in death if untreated. 

The symptoms of trichinosis depend on the number of larvae ingested and how far the infection has progressed. They typically develop in two phases. 

Early (Intestinal) Symptoms – Days 1–7 

• Diarrhea 

• Abdominal pain 

• Nausea and vomiting 

Later (Muscle Invasion) Symptoms – Days 7–42 

• Fever with chills 

• Muscle pain (especially in muscles used for breathing, chewing, and movement) 

• Swelling around the eyes and face (a hallmark sign) 

• Headache and fatigue 

• Conjunctival bleeding (in the eyes) 

• Rash or itching 

• Eosinophilia (high levels of a specific white blood cell) 

• Splinter hemorrhages under fingernails 

Severe Complications 

• Heart inflammation (myocarditis): May cause irregular heartbeat or heart failure 

• Brain inflammation (encephalitis): Leads to confusion, seizures, or coma 

• Lung inflammation (pneumonitis): Causes coughing and breathing difficulty 

Symptoms usually peak in the third week of infection and gradually improve, though muscle pain may last for months. 

Diagnosing trichinosis involves recognizing characteristic symptoms, exposure history, and laboratory findings. 

Laboratory Tests 

• Eosinophilia: Elevated eosinophil count is one of the earliest indicators. 

• Muscle enzymes: Elevated creatine kinase (CK), lactate dehydrogenase (LDH), and AST suggest muscle involvement. 

• Serologic tests: ELISA or Western blot to detect antibodies (positive 2–3 weeks after infection). 

Muscle Biopsy 

• A biopsy from a painful muscle may show cysts and inflammation. 

• Most helpful when performed after three weeks of infection. 

Imaging 

• MRI or ultrasound can detect muscle inflammation. 

• Chest X-rays may reveal lung changes in severe cases. 

Trichinosis can mimic other conditions, including: 

• Influenza or other viral infections 

• Polymyositis or dermatomyositis 

• Eosinophilic myositis 

• Cysticercosis or other parasitic infections 

• Autoimmune diseases or sepsis 

A clear history of consuming undercooked meat is often key to making the diagnosis. 

Effective management of trichinosis aims to eliminate the parasite, reduce inflammation, and relieve symptoms. The choice of treatment depends on the stage of the infection and its severity. Early diagnosis is crucial, as antiparasitic medications work best before larvae become encysted in muscle tissue. Supportive therapies help control pain, fever, and inflammation, while severe cases may require hospitalization for monitoring. Below are the main approaches used in treating trichinosis. 

Antiparasitic Medications 

• Albendazole: 400 mg twice daily for 8–14 days 

• Mebendazole: 200–400 mg three times daily for 3 days, then 400–500 mg three times daily for 10 days 

Treatment is most effective when started early, before larvae encyst in the muscles. 

Supportive Therapy 

• Pain relievers and antipyretics: For fever and muscle pain 

• Corticosteroids (e.g., prednisone): For severe infections with inflammation of the heart, brain, or lungs 

• Hydration and nutrition: To support recovery during prolonged illness 

Monitoring 
Patients with cardiac or neurological complications require close monitoring and sometimes hospitalization. With timely treatment, most cases resolve completely. 

Severe or untreated trichinosis can cause life-threatening complications: 

• Myocarditis: Irregular heart rhythm, heart failure, sudden death 

• Encephalitis: Seizures, coma, or paralysis 

• Pneumonitis: Respiratory failure 

• Thrombophlebitis and embolic events 

• Chronic muscle pain or weakness 

Mortality is rare (less than 1%), but complications are more likely in people with heavy infections or delayed treatment. 

The prognosis is generally favorable. Most mild to moderate infections resolve completely within weeks to months. Factors affecting recovery include: 

• The number of larvae ingested 

• How early treatment begins 

• The presence of complications 

• The patient’s age and immune status 

Encysted larvae can persist for years, but they eventually die and are absorbed by the body. Chronic fatigue or muscle aches may persist but usually improve gradually. 

Preventing trichinosis depends on careful food handling and awareness. 

Safe Cooking 

• Cook all pork and wild game to at least 160°F (71°C). 

• Avoid tasting meat before it is fully cooked. 

• Freezing meat can kill T. spiralis, but not freeze-resistant species. 

Meat Inspection and Hygiene 

• Ensure meat is inspected by veterinary authorities. 

• Avoid consuming uninspected or home-slaughtered meat. 

Public Awareness 

• Educate hunters and consumers about the risks of eating raw meat. 

• Promote safe cooking and preparation practices. 

Animal Management 

• Prevent pigs from eating raw meat scraps. 

• Control rodent populations around farms. 

Global surveillance programs continue to monitor and manage outbreaks effectively. 

Most people recover completely from trichinosis, but ongoing muscle pain or fatigue can occur in the months following infection. Supportive care and rehabilitation may help with recovery. 

Tips for recovery: 

• Rest and gradual return to activity 

• Maintain hydration and nutrition 

• Continue prescribed medications fully 

• Follow up with healthcare providers to monitor heart or neurological symptoms 

Support groups and educational resources can also provide reassurance and practical advice for patients and families. 

Trichinosis is a preventable parasitic infection that still poses a risk in regions where undercooked or wild game meat is consumed. Recognizing the symptoms—especially fever, muscle pain, and swelling after eating meat—is crucial for early diagnosis and effective treatment. With prompt medical care, most people recover completely. However, prevention through proper cooking, meat inspection, and public awareness remains the best strategy to eliminate trichinosis worldwide. 

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