الفهرس 
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Abstract
Despite the great efforts poultry breeding companies made towards eradication of
pathogenic mycoplasmas from poultry flocks, still MG infection is of continuing economic
concern in commercial broiler breeder chicken flocks. The present field study was
concerned with 15 broiler breeders’ flocks of different age ranges between (5 - 51 w) and
showed different healthy status either apparently healthy or diseased. The present study
applied the classical as well as modern diagnostic tools for MG screening, detection, and
characterization. The highest incidence of ELISA positive samples was recorded in the age
group of 20 weeks then DROPped at 27 weeks and increased again to reach max at 51 weeks.
It was found that the antibodies role in protection against MG infection was of low value.
The isolation of Mycoplasma was successful at 27 w and reached its maximum at 51 w.
The first PCR detection for positive flocks was at 27 w of age, while the highest incidence
(50%) was at 51 w of age. The rtPCR was positive in all 15 flocks. Four positive DNA
extracts which typed as MG by rtPCR were sent to USA for mgc2 and IGSR sequencing..
The current molecular study demonstrated presence of 3 wild-type MG strains; RabE1-08,
RabE2-09 and RabE3-09 in vaccinated and diseased flocks, besides related vaccinal Fstrain;
RabE4-08, isolated from non-vaccinated apparently healthy breeder’s flock. The
nucleotide and subsequent amino acids changes gained by field strains have led to
significant antigenic changes. IGSR sequence and phylogenetic analysis were able to
distinguish between MG wild-type and vaccine related strain. Accordingly, there is a need
to revise the control program including vaccine strategy and its application in parallel
biosecurity measures.