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

HYDATID CYST

• 5 to 10 cm in diamter, unilobular and consists of two layers
  • Outer laminated membrane and
  • Inner germinal membrane.
• From the germinal membrane, brood capsules develop in about 5 months after infection.
• Each capsule contains a number of protoscolices.
• Sometimes, the brood capsule detaches and float free in the hydatid fluid which is called as “hydatid sand”.
• If the cyst is ruptured, the brood capsule and protoscolices produce “external daughter cysts”.
• All cysts do not produce brood capsules and protoscolices. Cysts which does not have brood capsules and protoscolices are known as “sterile cysts”.
• In sheep, 51% of cysts are sterile.
• D/H acquires infection by ingestion of protoscolices along with infected meat.
• In dog, the protoscolices penetrate between the villi and reach maturity in about 4 to 7 days.
• Man can acquire infection by ingestion of eggs along with contaminated food or entry of protoscolices through cut wounds during slaughter.