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- Cross protection - live vacc.
Cross protection studies - live vaccines
By means of the ciliostasis test cross protection studies were carried out using challenge viruses belonging to serotypes different from those of the vaccines used.
Experimental design
Four groups of specific pathogen free (SPF) chickens, reared in isolators, were used. Each group contained 10 chickens
Each group was vaccinated as follows:
| Group 1 | Nobilis IB Ma5 (Massachusetts type) at one day of age by eye drop |
|---|---|
| Group 2 | Nobilis IB 4/91 at 14 days of age |
| Group 3 | Nobilis IB Ma5 (Massachusetts type) at one day of age and Nobilis IB 4/91 at 14 days of age |
| Group 4 | Unvaccinated control group |
At 5 weeks of age all groups were challenged with different field isolates. At 5-7 days post challenge the ciliostasis test was done.
In all experiments, groups vaccinated and challenged with homologous virus were included.
Results
The lower the average ciliostasis index, the better the protection.
Conclusion
- Protection was complete in the vaccinated groups challenged with the homologous strain (data not shown).
- In some cases either IB Ma5 (e.g. against isolates from the USA, Brazil and Japan) or IB 4/91 (e.g. against all four isolates) alone were able to provide excellent protection against the antigenically different challenge strains.
- The use of both a Massachusetts-type (Ma5) and the 4/91 IB vaccine provided much better cross-protection than did the use of either vaccine alone.
Protection of chickens against renal damage caused by a nephropathogenic infectious bronchitis virus
The ability of the infectious bronchitis (IB) Ma5 and 4/91 live-attenuated vaccines to protect against kidney damage caused by a nephropathogenic strain of IB virus (B1648) was investigated. Protection parameters considered were gross and microscopic renal pathology, and the use of a polymerase chain reaction to detect IB RNA in kidney tissue. By each parameter, Ma5 vaccine alone provided poor protection, but 4/91 alone or the combined program both protected well.
Cook, J. K. A., Chesher, J., Baxendale, W., Greenwood, N., Huggins, M. B. & Orbell, S. J. (2001).
Protection of chickens against renal damage caused by a nephropathogenic infectious bronchitis virus.
Avian Pathology, 30,423-426.
