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Efficacy of a temperature-sensitive Mycoplasma synoviae live vaccine
J F Markham1, C J Morrow, K G Whithear
1School of Veterinary Science, University of Melbourne, Parkville, Victoria, Australia.
Abstract:
A temperature-sensitive clone of Mycoplasma synoviae (MS), MS-H, derived from the chemical mutagenesis of the Australian field isolate 86079/7NS, was investigated for efficacy as a live vaccine. Titers of MS-H vaccine ranged between 1.16 x 10(8) and 8.4 x 10(8) color changing units/ml when incubated at 33 C and were consistently > or = 10(2) lower when incubated at 39.5 C. Laboratory-produced MS-H vaccine protected 8 out of 10 specific-pathogen-free Webster white leghorn chickens against a combined experimental challenge of aerosols of the virulent wild MS strain 88064/FP and T-strain infectious bronchitis vaccine administered intratracheally. Laboratory and commercially produced vaccines were compared for efficacy against thoracic air sac challenge, with both achieving similar levels of air sac protection. Air sac lesion incidences of five air sacs with lesions out of 32 and four out of 32 were seen in groups vaccinated with laboratory and commercial vaccines, respectively, compared with 13 out of 20 in nonvaccinated specific-pathogen-free hybrid white leghorn chickens. An attempt to determine the dose response of the commercial vaccine was conducted with 0.5, 2, and 4 times the standard dose. Air sac lesion incidences of 16 air sacs with lesions out of 32 in the 0.5 times, 11 out of 32 in the 2 times, and 1 out of 32 in the 4 times dose groups were observed.
Insights
A temperature-sensitive Mycoplasma synoviae (MS) vaccine, MS-H, demonstrated protective efficacy in chickens against virulent MS and infectious bronchitis virus. Both laboratory and commercial MS-H vaccines provided significant air sac protection compared to unvaccinated controls.
Area of Science:
- Veterinary immunology
- Microbiology
- Vaccinology
Background:
- Mycoplasma synoviae (MS) is an avian pathogen causing significant economic losses in the poultry industry.
- Live vaccines are crucial for controlling MS infections, but require careful strain selection for safety and efficacy.
- A temperature-sensitive MS clone, MS-H, was developed for potential vaccine use.
Purpose of the Study:
- To evaluate the efficacy of the temperature-sensitive Mycoplasma synoviae (MS) clone, MS-H, as a live vaccine in chickens.
- To compare the protective effects of laboratory-produced and commercially produced MS-H vaccines against MS challenge.
- To assess the dose-response relationship of the commercial MS-H vaccine.
Main Methods:
- MS-H vaccine titers were determined at different incubation temperatures (33°C and 39.5°C).
- Specific-pathogen-free chickens were vaccinated with MS-H and challenged with virulent MS and infectious bronchitis virus (IBV).
- Vaccine efficacy was assessed by monitoring air sac lesion incidence following thoracic air sac challenge and evaluating dose-response.
Main Results:
- MS-H vaccine titers were significantly lower at 39.5°C compared to 33°C, indicating temperature sensitivity.
- MS-H vaccination protected 80% of chickens against a combined aerosol challenge of virulent MS and IBV.
- Both laboratory and commercial MS-H vaccines showed comparable efficacy, significantly reducing air sac lesions compared to unvaccinated controls.
- A dose-dependent protective effect was observed, with the highest dose (4x) providing the most significant reduction in air sac lesions.
Conclusions:
- The temperature-sensitive Mycoplasma synoviae (MS) clone, MS-H, is a promising candidate for a live MS vaccine.
- Both laboratory and commercial MS-H vaccines offer significant protection against MS-induced air sacculitis.
- The efficacy of the MS-H vaccine is dose-dependent, suggesting optimal vaccination protocols can be established.