الفهرس 
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Abstract
In a study to evaluate the efficacy of some Mycoplasma gallisepticum vaccines in breeding layers flocks; we used three types of vaccines . The first was an inactivated oil emulsion bacterin prepared from virulent S6 strain of MG , the second was a live vaccine prepared from F strain of MG and the third was alive commercial F strain . For evaluation of these vaccines, an experiment was carried out , 125 one day old female chicks ( layers breed) and 25 one day old chicks of the same breed were used .
The chicks reared in complete isolation and were vaccinated against various types of diseases through the rearing period , then at 10 weeks old of age , chickens were grouped into five groups ( A, B, C, D, E) as follows :
1- Group A : represented by 25 female and 4 male chickens were infected with 2 doses of MG oil adjuvant bacterin at 12 and 16 weeks old age ( 0.5 ml of the vaccine was injected subcutaneously at the base of the neck ), then birds were challenged by intranasal inoculation with 0.2 ml of 24 hour broth culture of virulent S6 strain of MG containing 2 x 108 CFU/ml at 20 weeks old age
2- Group B : represented by 25 female and 4 male chickens at 12 weeks old , every bird received 0.2 ml intranasally of 24 hour broth culture of MG — F strain vaccine with titer 10
’
CFU/ml , thettbirds challenged as group A .
Summary
3-Group C : represented by 25 female and 4 male chickens, at 12 weeks old, birds sparied with F strain of MG , then birds challenged as group A .
4-Group D : represented by 25 female and 4 male chickens , birds were not vaccinated but challenged as group A .
5-Group E : represented by 25 female and 4 male chickens , birds were not vaccinated not challenged . Birds were observed for another 25 weeks post challenge .
The efficacy of vaccination in protection against MG was evaluated according to the following parameters :
1-There were no deaths allover the observation period of the experiment (45 weeks ) .
2-Serological response induced in sera of birds after vaccination and post challenge as determined by SPA and ELISA , where antibody response increased suddenly and sharply in non vaccinated challenged birds compared with vaccinated challenged ones, also antibody titers of sera from group A increased gradually and persisted for long period through the time of experiment.
3-Vaccinated birds were markedly protected against the development of clinical signs and air sac lesions after experimental infection with S6 strain.
Birds of group A were markedly protected against the development of air sacculatis after challenge when compared with other groups .
Summary
4-The rate of MG isolation after challenge was reduced in vaccinated birds than in non vaccinated control group (group
D).
5-Body weight gains and livability rate were markedly improved
in vaccinated birds compare to control non vaccinates .
6-The rate of egg production were improved in vaccinated groups than non vaccinated group ( group D).
7-The rate of fertility and hatchability of eggs from vaccinated groups were better than those of group D .
8-There were significant increase in egg weight from vaccinated chickens than non vaccinated group .
9-Percent of vertical transmission of Mg were decreased in hatched chicks from vaccinated groups than those from non vaccinated group ( group D ).
10-Comparing the different types of vaccines used, it was found that the best results were obtained after vaccination with two doses of bacterin then by spraying method with live F strain then by intranasal method.
N. B: There is no significant increase in results between the last two
routes of vaccination with live vaccines.
So, it is recommended to use MG bacterin for the control of Mycoplasma
gallisepticum infection under local conditions because of safety and eventual eradication of the infection accompanied with good sanitation and sound management.