Newcastle diseasevaccineshitherto in vogue are produced from embryonated chickeneggs. Egg-adapted mesogenic vaccines possess several drawbacks such as paralysis and mortality in 2-week-old chicks and reduced eggproduction in the egg-laying flock. Owing to these possible drawbacks, we attempted to reduce the vaccinevirulence for safe vaccination by adapting the virus in a chickenembryofibroblastcell culture (CEFCC) system. Eighteen passages were carried out by CEFCC, and the pathogenicity was assessed on the basis of the mean deathtime, intracerebral pathogenicity index, and intravenous pathogenicity index, at equal passage intervals. Although the reduction in virulence demonstrated with increasing passage levels in CEFCC was encouraging, 20% of the 2-week-old birds showed paralytic symptoms with the virusvaccine from the 18th(final) passage. Thus, a tissue-culture-adapted vaccine would demand a few more passages by CEFCC in order to achieve a complete reduction in virulence for use as a safe and effective vaccine, especially among younger chicks. Moreover, it can be safely administered even to unprimed 8-week-old birds.
Full text:
1
Index:
LILACS
Main subject:
Poultry Diseases
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Newcastle disease virus
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Vaccines, Attenuated
/
Viral Vaccines
/
Chickens
Limits:
Animals
Language:
En
Journal:
Braz. j. microbiol
Journal subject:
MICROBIOLOGIA
Year:
2015
Type:
Article
Consulta Detalhada
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