Study the Feedback of Mycoplasma Gallisepticum Infection on the Efficacy of Inactivated Viral Vaccines of Poultry

The present study monitored the effect of Mycoplasma gallisepticum infection on the humeral immune response of chickens against the different inactivated bivalent vaccines (ND, AI), (ND, IB), (ND, IBD) and monovalent (Reo Vaccine). These inactivated vaccines were used to inoculate three hundred 3-week-old specific pathogen-free (SPF) chicks by S/C route. They were grouped into nine groups; Groups (1, 3, 5 and 7) pre-infected with MG one week before vaccination and Groups (2,4, 6 and 8)vaccinated and non-infected. Group (9) was kept as control. In this study field infection of Mycoplasma gallisepticum was designed by inoculation of 250uL of the infectious material suspension containing 106cfu of MG was instilled in the nasal sinuses as well as injected subcutaneously one week before vaccination. The immune response was estimated and evaluated by using HI, ELISA and challenge tests. The bacterial stress of M. gallisepticum was recorded by the lesion scores. The results of HI and ELISA tests for the pre-infected groups showed highest antibody titers against (ND, AI), (ND,IB), (ND,IBD), and Reo vaccines which were significantly( at P > 0.05) higher (7.7 log2, 7.8 log2, 7.9 log2, respectively)for ND,(7.1 log2)for AI antigen, andS/P ratio showed non significant increase (1.7, 1.7, 0.3) for IBV, IBDV, and Reovirus antigens respectively28 days post-vaccination. The lowest titer appeared in non-infected vaccinated groups (G2, G4 and G6) (6.5 log2, 6.7 log2, 7.1 log2, respectively) for ND, (6.5 log2)for AI antigen, and S/P ratio was (0.6, 0.8, 0.28) for IBV, IBDV, and Reovirus antigens respectively. This study used serological immune responses to emphasize the results of chicken vaccination with inactivated viral vaccines, particularly in the presence or absence of Mycoplasma infection in chicks. Indeed, there is evidence that vaccinated chicken flocks pre-infected with MG can introduce inaccurate results compared to non infected vaccinated flocks. For the previous conclusion the evaluation of any inactivated viral vaccine must be performed in free Mycoplasma chickens, (SPF chickens as an example) in order to obtain accurate evaluation results