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Tracheal populations of Mycoplasma gallisepticum after challenge of bacterin-vaccinated chickens
Abstract:
Chickens vaccinated once or twice with inactivated oil-emulsion vaccine against Mycoplasma gallisepticum (MG) or left unvaccinated were challenged intratracheally with the R strain of MG. The population of MG organisms was determined by enumerating tracheal cultures periodically up to 28 weeks postchallenge (PC). The number of organisms in the respiratory tract increased rapidly after 4 days PC, and the number tended to decrease after 4 weeks PC. Tracheal populations of MG varied considerably among individual chickens. Bacterin-vaccinated chickens had numerically lower populations of MG in their tracheas up to 8 weeks PC, but the differences were small and considered of little practical significance.
Insights
Chicken vaccination with inactivated Mycoplasma gallisepticum (MG) oil-emulsion vaccines showed minimal impact on tracheal bacterial populations post-challenge. While vaccinated birds had slightly lower MG counts early on, the differences were not practically significant.
Area of Science:
- Veterinary Immunology
- Avian Pathology
- Bacteriology
Background:
- Mycoplasma gallisepticum (MG) is a significant respiratory pathogen in chickens.
- Effective vaccination strategies are crucial for controlling MG outbreaks in poultry flocks.
- Assessing vaccine efficacy requires understanding pathogen load dynamics post-challenge.
Purpose of the Study:
- To evaluate the efficacy of inactivated oil-emulsion Mycoplasma gallisepticum (MG) vaccines.
- To quantify the impact of vaccination on MG organism populations in chicken tracheas.
- To determine the duration of any observed vaccine effect post-challenge.
Main Methods:
- Chickens were vaccinated once or twice with an inactivated MG oil-emulsion vaccine or remained unvaccinated.
- All chickens were intratracheally challenged with the R strain of Mycoplasma gallisepticum.
- Tracheal cultures were enumerated periodically up to 28 weeks postchallenge (PC) to determine MG populations.
Main Results:
- MG organism numbers in the respiratory tract rapidly increased within 4 days PC.
- Tracheal MG populations generally decreased after 4 weeks PC.
- Bacterin-vaccinated chickens exhibited numerically lower MG populations up to 8 weeks PC, but these differences were small and not practically significant.
Conclusions:
- Single or double vaccination with inactivated MG oil-emulsion vaccine provided limited protective effect against MG challenge.
- The observed reduction in MG tracheal populations in vaccinated birds was not substantial enough for practical significance.
- Further research may be needed to explore alternative or combination vaccination strategies for improved MG control.