Trichinellosis: Epidemiology, Clinical Features, and Prevention

Trichinellosis (trichinosis) is a foodborne zoonosis caused by Trichinella spp. nematodes, acquired by eating raw/undercooked meat containing encysted larvae.

Epidemiology

• Species: T. spiralis (pigs, cosmopolitan), T. nativa (arctic wildlife), T. britovi (Eurasian wildlife), T. pseudospiralis (non-encapsulated, birds/mammals).
• Global burden: ~10,000 cases/year reported; true incidence higher. Outbreaks linked to pork, wild boar, bear, horse, walrus meat.
• Low-prevalence regions: Scandinavia, UK, Japan, USA (commercial pork) — due to controlled housing, feed regulation, meat inspection, freezing requirements.

Life Cycle and Pathogenesis

1. Ingestion of infected meat → larvae released in stomach.
2. Larvae invade small intestinal mucosa → mature to adults (2-4 days).
3. Females release newborn larvae (L1) → enter circulation → disseminate to striated muscle.
4. Encystment in muscle (except T. pseudospiralis) → viable for years.

Clinical Phases

Phase	Timing	Features
Enteral (intestinal)	1-2 days post-ingestion	Nausea, diarrhea, abdominal pain (often mild/missed)
Parenteral (invasive)	1-4 weeks	Fever, periorbital/facial edema, myalgia, rash, eosinophilia, elevated CK/LDH
Convalescent	Months	Cachexia, persistent myalgia; cardiac/CNS involvement rare but severe

Diagnosis

• Serology: ELISA/Western blot (detects 2-3 weeks post-infection).
• Muscle biopsy: Rarely needed; shows encysted larvae.
• Eosinophilia >1000/μL + exposure history = high suspicion.

Treatment

• Albendazole 400 mg BID × 10-14 days (or mebendazole).
• Corticosteroids (prednisone 0.5-1 mg/kg) for severe myositis, myocarditis, CNS involvement.
• Early treatment (<14 days) prevents muscle encystment.

Prevention

• Cook pork/wild game to 71°C (160°F) internal temperature.
• Freeze pork <15 cm thick at -15°C (5°F) × 20 days (kills T. spiralis; T. nativa freeze-resistant).
• Irradiation, curing (salt/drying) not reliably effective.
• Biosecurity: Rodent control, no raw meat waste to pigs.