Makindo Medical Notes

🥩 Trichinellosis is a zoonotic parasitic disease caused by eating raw or undercooked meat (especially pork or wild game) containing Trichinella larvae. It is rare in high-income countries but remains important worldwide due to cultural dietary practices and poor meat inspection.

🦠 Aetiology

• Causative agent: Nematodes of the genus Trichinella.
• Trichinella spiralis is the most common species infecting humans; other species (e.g. T. britovi, T. nativa) are found in wild animals.
• Transmission occurs via ingestion of cysts (encysted larvae) in raw/undercooked meat.
• Pigs, wild boar, and bears are common reservoirs.

⚙️ Pathophysiology

• After ingestion, larvae are released in the stomach and mature into adults in the small intestine.
• Adult females release new larvae, which penetrate the intestinal wall and spread via the bloodstream.
• Larvae encyst in striated muscle fibres (diaphragm, tongue, extraocular, intercostal muscles).
• The host inflammatory response contributes to many clinical symptoms.

🩺 Clinical Features

Symptoms depend on the number of larvae ingested and the stage of infection:

• Intestinal phase (1st week):
  • Abdominal pain, diarrhoea, nausea, vomiting.
• Muscle invasion phase (2–6 weeks):
  • Fever, myalgia, and marked eosinophilia.
  • Periorbital oedema (classic sign 👁️).
  • Conjunctivitis, headache, and photophobia.
  • Subungual haemorrhages (splinter haemorrhages).
  • Severe cases: myocarditis, encephalitis, pneumonia → potentially fatal.

🔬 Investigations

• Blood tests: Eosinophilia (hallmark), raised CK, raised ESR.
• Serology: ELISA for Trichinella antibodies (positive after ~3 weeks).
• Muscle biopsy: Demonstrates encysted larvae (rarely required if serology + clinical context are sufficient).
• Imaging: MRI may show muscle inflammation in severe disease.

💊 Management

• Antiparasitic therapy:
  • Albendazole 400 mg BD for 8–14 days OR
  • Mebendazole 200–400 mg TDS for 3 days, then 400–500 mg TDS for 10 days.
• Supportive therapy: Corticosteroids (prednisolone) for severe inflammatory symptoms (e.g. myocarditis, CNS involvement).
• Analgesics/antipyretics for symptomatic relief.

🛡️ Prevention

• Cook pork and wild game meat thoroughly (≥71°C core temperature).
• Meat inspection and control measures in pig farming (rodent control, avoid feeding pigs raw scraps).
• Freezing kills some species but not all (e.g. T. nativa in Arctic regions survives freezing).
• Public health education in endemic areas.

🌐 Public Health Impact

• Now rare in Europe and North America due to strict meat inspection laws.
• Still reported in Eastern Europe, Asia, and areas where wild game is consumed.
• Outbreaks often linked to community feasts or sharing of undercooked meat.

📌 Exam Tip

Classic triad for Trichinellosis: Periorbital oedema 👁️ + myalgia 💪 + eosinophilia 🧪. Always ask about a history of eating raw or undercooked pork/wild game in the stem!