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Abstract
Mycoplasma gallisepticum (MG) and Mycoplasma synoviae are two importantMycoplasma species in poultry causing huge economic losses directly through the effects
on production or indirectly through the costs of intervention studies. With the recent
changes in limiting the use of antibiotics in this industry, vaccination role becomes more
prominent. Due to issues and challenges with currently available MG vaccines, MG strains
were selected based on the history and analysis of sequencing results from the reservoir at
Poultry Diagnostic and Research Center (PDRC). The safety of the isolates was evaluated
in turkeys as the more sensitive poultry species to MG infection and two (K4110A and
K6067) were selected based on successful colonization of the trachea while showing no
clinical signs or gross lesions at the necropsy. As the next step, the safety and efficacy of
both isolates were evaluated at 2- and 6-weeks post vaccination in chickens, respectively.
Both vaccine candidates significantly protected the chickens from air sac lesions. Further
investigation was performed to find out the most protective route of administration and
dose required for each candidate. The minimum protective doses for both K6067 and
K4110A was 104 ccu/mL via eye drop route of administration. Neither of the strains were
capable of vertical transmission which might be due to the number of birds and the size of
the study. However, the maternal antibodies against MG were transferred to progeny
according to ELISA results on the yolk sac samples. Based on the results, both K6067 and
K4110A could be ideal live vaccine candidates to prevent infection with pathogenic MG
strains. To be able to study the strains and also differentiate both strains in the future,
differentiating qPCR protocols were developed for K4110A and K6067. As mentioned,
MS is another important pathogenic Mycoplasma species in poultry and improving the
current available vaccines and developing vaccines should be also considered for this
pathogen. Therefore, a MS-only challenge model was developed and studied to help with
future vaccine developments while a differentiating qPCR protocol was developed for a
more rapid and more effective differentiation of MS-H vaccine as one of currently available
MS vaccines.