Preparation and Serological Evaluation of an Inactivated Trivalent oil emulsion vaccine for Avian Fowl Adenovirus (FAdV) containing -8a, 8b, and 11 serotypes

In recent years, inclusion bodies hepatitis (IBH) caused by fowl adenovirus (FAdV) species D and E led to significant economic losses in the poultry sector, worldwide. Therefore, this study aimed to assess the immunogenicity of an inactivated trivalent FAdV vaccine prepared with different payloads (10 ⁷ TCID ₅₀ , 10 ^6.8 TCID ₅₀ , 10 ^6.5 TCID ₅₀ ) in commercial broiler chickens. The effects of booster immunization and thiomersal addition on the titers of developed antibodies were also evaluated. The virus propagated on liver primary cells for virus isolation and virus infectivity. Our results showed that group which vaccinated with a higher payload of the virus presented a prolonged immune response till the 6th week, compared to birds which were vaccinated with lowest dose of the virus of the trivalent vaccine. Also, birds which were vaccinated with the same vaccine containing thiomersal as a preservative, showed no significant reduction in immune response. For booster immunization, only high payload (10 ⁷ TCID ₅₀ of each serotype/bird) increased the antibodies titers, specially at 2 ^th and 3 ^rd week post-vaccination. The obtained results suggested that the trivalent inactivated FAdv serotype 8a/8b/D vaccine at 10 ⁷ TCID ₅₀ concentration of each serotype/bird at priming and booster vaccination could be used for the prevention and control of IBH.