Study the effect of Mycoplasma contamination of eggs used in virus titration and efficacy of some live attenuated poultry viral vaccines

Abstract

Objective: The study of Mycoplasma gallisepticum (MG) infection is needed, not only to understand the disease process but also to understand the interference with the evaluation of some live viral poultry vaccines. This study aims to investigate the titration and potency of some live attenuated poultry viral vaccines; Newcastle disease, infectious bronchitis, infectious bursal disease, and Reo in both specific pathogen-free (SPF) embryonated chicken eggs (ECEs) and chickens. Methods: Titration of live attenuated viral poultry vaccines in ECEs was carried out by dividing the inoculated eggs into four groups; the pre-, simultaneously-, post-, and non-MG contaminated. MG effect on the potency test was carried out using seventeen groups of SPF chickens (25 chicken/ group) placed into separate isolators. Each live attenuated viral poultry vaccine was inoculated into 4 groups. Results: The highest titer of these vaccines that appeared in MG pre- contaminated ECEs were 1011, 107.5, 107.9, and 107.5, respectively. The lowest vaccine titers that appeared in non-MG contaminated ECEs were 108, 106, 106.8, and 106, respectively. Although the potency of these previous vaccines indicated that the highest antibodies titer that appeared in MG pre-infected vaccinated chickens were 7.5 log2, 36 enzyme-linked immunosorbent assay unit (EU), and 42 EU, respectively; the lowest antibodies titer that appeared in non-MG infected vaccinated chickens were 6.5 log2, 12 EU, 17 EU, and 10 EU, respectively. Conclusion: The present study findings underline the importance of using Mycoplasma -free eggs or chicken for the production of virus vaccines.