Mycoplasma gallisepticum (MG): Laboratory and Field Studies Evaluating the Safety and Efficacy of an Inactivated MG Bacterin

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Abstract
A highly antigenic isolate of M. gallisepticum (MG) was utilized in the production of an inactivated, oil-emulsified MG bacterin (MGB). Laboratory tests indicated that the bacterin was capable of protecting chickens from clinical signs of MG caused by intrasinus challenge with the R, S-6, PG-31 or 1150 strain of MG. Vaccinated turkeys were also protected from clinical signs of disease when challenged with MG. Use of the MGB in chickens under laboratory conditions resulted in a reduction in airsacculitis from 44% in nonvaccinates to 10% in vaccinates and further reduced the number of organisms present in the trachea post-challenge. Commercial chickens vaccinated s.c. midway or lower in the nape of the neck showed no untoward effects due to the bacterin. Those improperly vaccinated at the base of the skull developed a transient edema around the eye(s). This swelling did not appear to affect the performance of the chickens and had been reabsorbed by the next observation period. S.c. inoculation should be at the mid or lower neck region. Field trials at a commercial egg operation comparing production efficiency showed that chickens vaccinated with the MGB had higher egg production, a greater percentage of eggs graded large and over, a smaller percentage of undergrades and better feed conversion than chickens vaccinated with a live culture, low virulence Conn-F strain vaccine. Thus, the oil-emulsified MG bacterin is safe and highly efficacious.