Mycoplasma gallisepticum strain ts-304 is a safe and effective live attenuated vaccine for use in chickens
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Updated: Sep 17, 2026
Loop-mediated Isothermal Amplification LAMP Assays for the Species-specific Detection of Eimeria that Infect Chickens
Published on: February 20, 2015
Anna Kanci Condello1, Gregory J Underwood2, Pollob K Shil3
1Asia-Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, 3010, Australia.
Abstract:
Vaxsafe MG (strain ts-11) is a live attenuated vaccine against the important poultry pathogen Mycoplasma gallisepticum that has been used globally to improve poultry health. However, the majority of the bacterial cells in Vaxsafe MG do not express the GapA cytadhesin, reducing their capacity to colonise the respiratory tract. Vaxsafe MG (strain ts-304) is a GapA positive clone recovered from Vaxsafe MG (strain ts-11) that has been shown to be safe and efficacious in turkeys, and preliminary studies have suggested that Vaxsafe MG (strain ts-304) may have greater efficacy in chickens than Vaxsafe MG (ts-11). The studies described here aimed to meet the international regulatory requirements for safety and efficacy in chickens. The vaccine colonised the trachea of 3-week-old chickens without inducing signs of respiratory disease or significant lesions in the respiratory tract, and was safe at a tenfold overdose and after repeated administration. It was transmissible from vaccinated to naïve chickens with no evidence of reversion to virulence following multiple in vivo passages. Finally, the superiority of Vaxsafe MG (strain ts-304) was demonstrated by its capacity to induce similar protection against infection with wild type M. gallisepticum at a 40 fold lower dose than the end of shelf life titre dose of Vaxsafe MG (ts-11). The lower effective dose of Vaxsafe MG (strain ts-304) allows it to be freeze-dried, enhancing its stability, making it easier to transport and store the vaccine and increasing its shelf life. Vaxsafe MG (strain ts-304) is, therefore, a highly efficacious and promising live attenuated vaccine candidate suitable for use in chickens.
Insights
Vaxsafe MG (strain ts-304) offers enhanced protection against Mycoplasma gallisepticum in chickens. This improved live attenuated vaccine is safe, transmissible, and more effective than previous versions, simplifying poultry health management.
Area of Science:
- Veterinary immunology
- Poultry health
- Vaccine development
Background:
- Mycoplasma gallisepticum is a significant poultry pathogen.
- Vaxsafe MG (strain ts-11) is a live attenuated vaccine with limited colonization due to low GapA cytadhesin expression.
- Vaxsafe MG (strain ts-304) is a GapA positive clone with potential for greater efficacy in chickens.
Purpose of the Study:
- To evaluate the safety and efficacy of Vaxsafe MG (strain ts-304) in chickens according to international regulatory standards.
- To compare the efficacy of Vaxsafe MG (strain ts-304) with Vaxsafe MG (strain ts-11).
Main Methods:
- Vaccination of 3-week-old chickens with Vaxsafe MG (strain ts-304).
- Assessment of respiratory tract colonization, clinical signs, and lesions.
- Safety evaluations including tenfold overdose and repeated administration.
- Transmission studies and in vivo passages to assess stability and reversion to virulence.
- Comparative efficacy trials against wild-type Mycoplasma gallisepticum challenge.
Main Results:
- Vaxsafe MG (strain ts-304) colonized the trachea without inducing adverse effects or significant lesions.
- The vaccine demonstrated safety at overdose and after repeated administration.
- It was transmissible between chickens with no evidence of virulence reversion after passages.
- Vaxsafe MG (strain ts-304) provided similar protection at a 40-fold lower dose compared to Vaxsafe MG (ts-11).
Conclusions:
- Vaxsafe MG (strain ts-304) is a safe and highly efficacious live attenuated vaccine for chickens.
- Its improved efficacy and lower effective dose facilitate freeze-drying, enhancing stability, transport, storage, and shelf life.
- Vaxsafe MG (strain ts-304) represents a promising candidate for controlling Mycoplasma gallisepticum infections in poultry.
