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

LIFE CYCLE

• Adult worms found in caecum and colon. After fertilization the gravid female wander down to rectum and crawl out through anal opening, eggs are laid in the clusters in the perineal region. Eggs appear as yellowish white streaks – gelatinous.
• Development of egg is rapid usually eggs fall off to the ground and reach infective stage in 3 to 5 days. Sometimes infective stage is reached in perineal region itself. Eggs survive for several weeks in moist surroundings.
• Eggs are commonly found in stable and bedding materials.
• Infection of horse occur by ingestion of embryonated eggs contain L₂, hatch in the intestine. The liberated L₂ moult to L₃ and L₃ migrate to caecal mucosa where it becomes L₄ in 8 – 10 days of infection. L₄ come down to caecal lumen, in which they become adult. Prepatent period is 4 to 5 months.