Experimental transmission of hydropericardium syndrome and protection against it in commercial broiler chickens.

Liver collected aseptically from broiler chickens suffering from natural outbreaks of hydropericardium syndrome was homogenised in phosphate buffered saline (1:5) or normal saline (1:10). A dose of 0.25 ml of 800 g supernatant (inoculum S) in the first case or homogenate without centrifugation (inoculum T) in the second case was injected subcutaneously into 12- to 15-day-old broiler chickens. Lesions similar to natural outbreaks of the syndrome appeared in 2 to 5 days. Inoculum S inactivated with 0.1% formalin for 24 h (Vac S) or inoculum T inactivated with 0.5% formalin for 72 h (Vac T) was injected into commercial broiler chickens at 10 or 15 days of age. The birds were challenged with inoculum S or inoculum T at 20 or 25 days of age. Experimentally both vaccines gave satisfactory protection, but under field conditions, Vac T was superior.