The Thai Journal of Veterinary Medicine


The present study was designed to determine the protection afforded by different vaccination programs against the virulent Newcastle disease virus (vNDV). The chickens were divided into 7 groups, 40 chickens in each. Group 1 did not receive any vaccine and served as a negative control group. Groups 2-7 were vaccinated with different vaccination programs against vNDV. At 1 day old, the chickens in all the vaccinated groups were inoculated with live attenuated vaccine, Ulster strain, followed by different inactivated vaccines including 0.1 ml/chicken of inactivated vaccine A in groups 2 and 4, 0.1 ml/chicken of inactivated vaccine B in groups 3 and 6, 0.25 ml/chicken of inactivated vaccine A in group 5 and 0.25 ml/chicken of inactivated vaccine B in group 7. At 7 days old, revaccination was performed in the vaccinated groups with live attenuated vaccines, B1 strain in groups 2 and 3 and LaSota strain in groups 4-7. The chickens in each group were challenged with vNDV at 14 and 21 days old, 20 chickens at a time. The results at 14 days post-infection (DPI) showed that the mortality rate of the vaccinated groups was significantly lower (p< 0.05) than that of the non-vaccinated group. Body weights were not significantly different between the nonvaccinated group and the vaccinated groups which were challenged at 14 days old (p> 0.05). For the groups which were challenged at 21 days old, the body weights of the vaccinated groups were higher than that of the nonvaccinated group, but only the body weights of vaccinated groups 2, 4 and 6 were significantly different (p<0.05) from the non-vaccinated group. It is indicated that all of the vaccination programs used in this study could alleviate body weight loss and protect the chickens from lethal infection with vNDV.

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