VPA 211: General Veterinary Parasitology and Helminthology (3+1)

LIFE CYCLE OF Toxascaris leonina

• Direct
• Paratenic host

Prenatal and transmammary route of infection is absent.

• Direct
  • Ingestion of embryonated eggs hatch in the intestine. The liberated L₂ enter into the intestinal wall where L₂ moult to become L₃ and L₃ moult to become L₄ in about 10 days and 5 weeks of infection respectively.
  • The L₄ comes to the lumen and moults to become L₅ in 6 weeks after infection. Prepatent period is 74 days.
• Paratenic host
  • Mice acts as a paratenic host. In mice L₂ are distributed to various organs and remain dormant until eaten by dogs and cats.
  • Following ingestion of infected mice by dog, larvae are released in the intestine and develop to adult without migration.