Pathogenesis and Control of Inclusion Body Hepatitis in Broiler chickens
Date
2018-05-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Inclusion body hepatitis (IBH) is an economically important fowl adenovirus (FAdV) disease of broiler chickens. In Canada, FAdV-8a, FAdV-8b, FAdV-11, FAdV-7 and FAdV-2 are the prevalent FAdV serotypes. Currently, there is no commercial vaccine available in Canada to prevent IBH in broiler chickens.
The objectives of this study were to develop live, inactivated or subunit FAdV vaccines to control IBH and to identify a suitable adjuvant for an inactivated FAdV vaccine. In chapter 2, we analyzed the efficacy and safety of live and inactivated bivalent FAdV vaccines (FAdV-8b-SK+FAdV-11-1047) against IBH. We demonstrated significant immunoprotection of broiler chickens (98 – 100%) (P<0.01) against IBH by vaccinating broiler breeders with FAdV-8b-SK+FAdV-11-1047 with either a bivalent live vaccine (1x104 TCID50) at 16 weeks of age or a bivalent inactivated vaccine (1x106 TCID50) at 16 and 19 weeks of age. Both the live and inactivated bivalent FAdV vaccines induced broad-spectrum protection against all common serotypes of FAdV circulating in the Canada. Both the live and inactivated FAdV vaccines were equally efficacious in protecting broiler chickens against IBH by passive transfer of maternal antibodies (MtAb) from broiler breeders to their broiler progeny.
In chapter 3, we demonstrated that FAdV-8b-SK adjuvanted with CpG-ODN induced a long-lasting humoral immunity similar to inactivated FAdV-8b-SK adjuvanted with Emulsigen-D. FAdV-8b-SK adjuvanted with CpG-ODN induced T helper (Th)-1 and Th-2 type immunity. CpG-ODN as an adjuvant enhanced cytotoxic T-cell memory response of FAdV-8b-SK vaccine.
Propagation of some serotypes of FAdVs are difficult in cell lines. Hence, we explored the possibility of developing a subunit FAdV vaccine. In chapter 4, we demonstrated significant protection of broiler chickens against IBH by vaccinating their broiler breeder parents using a FAdV-8b-SK subunit vaccine [fiber protein or virus-like particles (VLPs)]. We also demonstrated that the FAdV-8b-SK fiber and VLPs induce strong cytotoxic T-cell responses in the broiler breeders. The results of this study will help in designing FAdV control strategies for the prevention of IBH in Canada.
Description
Keywords
Fowl adenovirus, Inclusion body hepatitis, Vaccines
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Veterinary Pathology
Program
Veterinary Pathology