Key result
Oral vaccination against avian encephalomyelitis in 14-week-old birds was associated with outbreaks of clinical disease, with mortality reaching 2% during weeks 2 to 5 post-vaccination.
Why the study?
Does oral vaccination for avian encephalomyelitis cause clinical disease and mortality in 14-week-old birds?
Does oral vaccination for avian encephalomyelitis cause clinical disease and mortality in 14-week-old birds?
Oral vaccination for avian encephalomyelitis can spread to the CNS and cause clinical disease and mortality, potentially exacerbated by non-CAV-induced immunosuppression.
Oral AE vaccination may induce mild encephalomyelitis; challenges assumptions of non-neurotropism and leaves optimal routes open for study.
Outbreaks of clinical avian encephalomyelitis (AE) which developed after vaccination of 14-week-old birds by the oral route are reported. Mortality during weeks 2 to 5 following vaccination reached 2%. Experimental studies showed that, in contrast to popular opinion, AE vaccine virus given orally can spread to the central nervous system and produce encephalomyelitis (mild). The severity of the vaccine induced lesions was not affected by chicken anaemia virus (CAV) infection 2 weeks before AE vaccination. It is postulated that non-CAV-induced immunosuppression allowed vaccine virus to produce the severe lesions and deaths occurring during the disease outbreaks, and that in one case, Marek's disease virus was the immunosuppressive agent.
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Smyth et al. (1994) studied Avian encephalomyelitis. Oral avian encephalomyelitis vaccination was evaluated on Mortality during weeks 2 to 5 following vaccination. Oral vaccination against avian encephalomyelitis in 14-week-old birds was associated with outbreaks of clinical disease, with mortality reaching 2% during weeks 2 to 5 post-vaccination.
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