The protective value of monovalent and bivalent adenovirus vaccines against pneumoenteritis was studied in fattening lambs. The monovalent vaccine was prepared from strain ORT/111 which is a sheep isolate, related to bovine adenovirus type 2. The bivalent vaccine contained virus strains ORT/111 and GY/14, which is a local isolate of ovine adenovirus type 1. After administration of monovalent vaccine higher titres of neutralizing antibodies (1:128-1:512) were found than after the bivalent vaccine (1:16-1:128). Following challenge with a homologous virus strain, the lambs vaccinated with monovalent vaccine remained healthy and did not shed the virus. Those vaccinated with the bivalent vaccine and challenged with GY/14 strain also remained healthy, but two out of five lambs shed virus in the faeces. Non-vaccinated challenged controls developed characteristic signs of the disease and shed the virus both in the nasal discharge and the faeces. From the results it can be concluded that experimental adenoviral pneumoenteritis of fattening lambs can be prevented by active immunization.
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