NEWCASTLE-DISEASE OUTBREAKS IN DOMESTIC-FOWL AND TURKEYS IN GREAT-BRITAIN DURING 1997

Between January 6 and April 23, 1997, 11 outbreaks of Newcastle diseas e were confirmed in Great Britain, four in broiler chickens and seven in turkeys. Although the viruses isolated gave intracerebral pathogeni city indices in day-old chicks between 1.65 and 1.95, the clinical sig ns of disease in field infections were variable and not always associa ted with high mortality, especially in turkeys. Epidemiological invest igations indicated that the majority of the outbreaks occurred as a re sult of secondary spread by human agency from two or more primary infe cted flocks. The presence of similar outbreaks in Scandinavian countri es in 1996 and the unusual patterns of movement of migratory birds at the end of 1996 and beginning of 1997 suggest they may have been respo nsible for the primary introduction of the causative virus into Great Britain.