| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 96 === Marek’s disease (MD) is one of the most contagious oncogenic lymphotrophic diseases in chicken caused by MDV. In past 30 years, the use of MDV live vaccines have greatly reduced the economic losses from MD. However, vaccines themselves are thought to be responsible for driving the virulence. After the isolation of very virulent MDV (vvMDV) from vaccinated flocks, it is important to evaluate recent vaccine regimes in Taiwan. To investigate the correlation between virus replication kinetics and vaccination, viruses from vaccine strains CVI988 (Rispens), HVT, and very virulent strain DW-1 were used to evaluate virus replication kinetics. We used PCR technique to detect virus in 14 organs in day 1-20 post-vaccination at two-day interval. We also detected the virus of DW-1 and vaccine strains when challenged with or without vaccination. The results showed that the existence of vaccine strains can in vivo reduce the replication of field strain. However, chicken challenged with DW-1 strain enhanced the growth of HVT vaccine strain. It may help us to realize the correlation between vaccine level in different organs and protection. Moreover, we also used the CKC from challenged chickens with or without vaccination to compare the challenge virus yield. Specific plaques were calculated at 14-day after culture from each one, and the plaques of the very virulent DW-1 strain in infected chicken kidney cultures were shown significantly more than other cultures from HVT vaccinated chicken, the results indicated that the growth of field isolate was reduced in vaccinated chicken, in accordance to in vivo test. These findings are useful for developing the vaccine regime of MD in Taiwan.
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