Hydatidosis in domestic ruminants inflicts enormous economic damage due to the condemnation of affected organs and lowering of the meat, milk and wool production.
Life cycle: The infective eggs containing the oncosphere passed in the faeces are accidentally ingested by cattle, sheep, pigs, other animals or humans which act as a intermediate hosts. After the infective eggs are ingested by these intermediate hosts, the oncospheres in the eggs penetrate the intestine and reach the liver, lungs and other organs including the brain and muscles to develop into hydatid cysts at the end of about five months. These cysts measure commonly 5 - 10 cm and contain fluid. Some may reach up to 50 cm in diameter. Others may produce daughters cysts. The diagnostic features of a hydatid cysts are a concentrically laminated thick outer layer within which is a germinal layer. In fertile hydatids the germinal layer is granular and has brood capsules each containing protoscoleces. When brood capsules become detached and float free in the cysts fluid they are referred to as hydatid sand. In some animals a fair proportion of hydatid may be sterile. The life cycle is completed when a fertile hydatid cyst is eaten by a definitive host, the dog or the appropriate carnivore. Cattle and majority of intermediate hosts show no clinical evidence of infection. However, in humans hydatid cysts can cause serious disease.
Antemortem findings: None of significance
Postmortem findings:
Hydatid cysts as described are found in :
Liver (Fig. 92) , lungs (Fig. 93) , heart, spleen, kidneys ,
Muscle and brain
Any tissue including bone