Broad spectrum protection of broiler chickens against inclusion body hepatitis by immunizing their broiler breeder parents with a bivalent live fowl adenovirus vaccine

Abstract Historically, fowl adenovirus (FAdV) associated inclusion body hepatitis (IBH) was considered a secondary disease in broiler chickens associated with immunosuppression. However, we previously reported the occurrence of IBH as a primary disease in the broiler chicken industry in Canada as a result of infections with various FAdV serotypes. Therefore, the objectives of this study were to develop an immunization strategy in broiler breeders using live FAdV 11-1047 and FAdV8a-TR59 to confer homologous and heterologous protection in broiler progeny against IBH and to study the efficacy of natural exposure of naive broiler breeders to a vaccine virus from live FAdV vaccinated birds as an immunization technique. Broiler breeders vaccinated orally with FAdV8a-TR59 (1 × 10 4 TCID 50 /bird) and FAdV11–1047 (1 × 10 4 TCID 50 /bird), FAdV8a-TR59 (1 × 10 6 TCID 50 /bird) and FAdV11-1047 (1 × 10 6 TCID 50 /bird) or FAdV8b (1 × 10 6 TCID 50 /bird) transferred substantial levels of neutralizing antibodies to their progeny. The efficacy of maternal antibodies was studied by challenging 14-day old broiler chickens with 1 × 10 7 TCID 50 of FAdV2–685, FAdV7-x11a like, FAdV8a-TR59, FAdV8b-SK or FAdV11-1047 which are the dominant serotypes causing IBH outbreaks in Canada. Broiler chickens from the low and high dose vaccinated breeders were significantly protected against all serotypes of FAdV (P