Trichinelloidea - pigs

Question 1

Why is Trichinella so important worldwide?

Answer 1

• It is a zoonotic disease

Question 2

What is unique about the life cycle of Trichinella?

Answer 2

• There is no production of eggs or loss of egg / larva to the environment through feces
• L1 encyst in muscle, which is then ingested by another animal
• Adult in SI produces L1, which then penetrates the SI mucosa
• L1 travels to muscle via lymph and bloodstream where it encysts
• The muscle (containing the encysted L1) is ingested by another animal
• L1 infects the SI mucosal epithelium and matures to an adult (within 2 days!)

Question 3

What are some modes of infection of Trichinella?

Answer 3

• Predation
• Carrion - ingestion of rotting carcass; encysted L1 capable of living in this state for months
• Cannibalism
• Ingestion of feces - from animals with patent infection

Question 4

What are the two cycles of Trichinell?

Answer 4

1. Sylvatic cycle - wild animals
2. Domestic cycle - pigs from production systems (usually extensive). (also rats)

• Sylvatic cycle - predominantly in carnivores (fox, rodent, bear, badger, wild pig, polar bear, wolves, lions, leopards, hyaena). Also, eating wild game is a source of infection for man.
• Domestic cycle - pig to pig in production system by infected swill (food scraps fed to pigs), tail biting, and rats. Man gets infected by eating undercooked meat.

Question 5

What are the predilection sites for Trichinella in pigs?

Answer 5

• Diaphragm, intercostal muscles, tongue, masseters
• Look at these sites for possible larva

Question 6

What are some methods of control for Trichinella?

Answer 6

• Mandatory meat inspection
• Prohibition of uncooked food waste (swill) to pigs
• Control of rodent population
• Proper carcass disposal
• Consumer education - cooking of pork, wild game