Trichinellosis (Trichinosis)



Background

  • Acidic stomach medium dissolve infective Trichinella cysts to release larvae.
  • Larvae mature to adult in small intestine.
  • Adult females lay eggs that develop into larvae, travel through the vascular tree to muscle.
  • Within muscles, the larvae encyst.
  • Transmission of infection with ingestion of cysts.
  • Proper cooking kills the encysted larvae.

Aetiology

  • Trichinellosis is a parasitic disease caused by eating raw or undercooked meat of animals infected with the larvae of a type of worm called Trichinella.
  • Infection occurs commonly in certain wild carnivorous animals but can also occur in domestic pigs.
  • Trichinellosis is a very rare Ireland 9no cases had been reported prior to 2007)
  • In June 2007, an outbreak of trichinellosis in Poland led to the identification of the illness in Ireland in people who had travelled to Poland.
  • Trichinellosis can vary from unnoticed mild condition to fatal infection.
  • In animals trichinellosis rarely presents as a clinical disease.
  • All pigs slaughtered for human consumption have to be tested and shown to be free from this worm
  • No cases detected in Irish pigs for decades.
  • May be found in Irish foxes.

Symptoms of trichinellosis?

  • Incubation period 1 - 6 weeks after ingestion of infected meat
  • The first symptoms can involve swelling of the eyes.
  • GI upset (diarrhoea, vomiting, and abdominal discomfort).
  • Fatigue, fever headaches, shivering, cough, arthralgia & myalgia.
  • Later in-coordination, arrhythmia

Most symptoms subside within a few months. Mild cases of trichinellosis are never specifically diagnosed and are assumed to be the flu or other common illnesses.

Diagnosis

  • Gastroenteritis & Myalgia
  • Facial oedema, or sub-conjunctival haemorrhages
  • Eosinophilia
  • Dx confirmed with serology (occas. muscle Bx)

Differential Dx

  • Influenza
  • Typhoid

Treatment

  • Anti parasitics (e.g. Mebendazole).

Prevention

  • Cook meat products until the juices run clear
  • Freezing pork less than 15cm thick for 20 days at -15°C will kill any larvae
  • Freezing wild game meats is not guaranteed to kill all larvae
  • Curing (salting), fermenting, pickling, drying, smoking, or microwaving meat does not consistently kill infective worms.

Content by Dr Gemma Kelleher, Dr Íomhar O' Sullivan based on the Health Protection Surveillance Centre- Trichinosis fact-sheet..