Determination of Humoral Immune Response in Chickens Against Formalin-Inactivated Alum-Precipitated Fowl Cholera Vaccine

We measured the humoral immune response in chickens against a formalin-inactivated alum-precipitated fowl cholera vaccine. The vaccine was administered in 12 weeks old chickens, 5×10 7 CFU/ml/chicken intramuscularly. Booster dose was given with similar dose and route at 15, 30 and 45 days intervals in groups A, B and C, respectively, after primary vaccination. The group D served as unvaccinated control. Pre-vaccination sera were collected from all the groups of birds. Sera of the immunized and control birds were collected at 15, 30, 60, 90, 120, 150 and 180 days post vaccination (DPV). The degree of immunity produced in each group of birds following primary and secondary vaccination were measured by determining their serum antibody level using passive Haemagglutination (PHA) test. Sera sample possessing higher PHA titers after 15 days of primary vaccination manifested a declining tendency at 30 DPV and rapidly fell down at 60 DPV. Boostering of vaccination at this stage elucidated a rapid increase of PHA titers ranging from 128 to 256 at 30 DPV and declined gradually from 60 DPV and reached a titer of approximately 8 to 4 at 180 DPV. Challenge infection was conducted with five randomly selected vaccinates of all the groups of birds along with unvaccinated controls after 15 days of secondary vaccination. The fowl cholera vaccination conferred 100% protection while all the unvaccinated control birds succumbed to such infection.