APPEARANCE OF TYPE-B AVIAN PNEUMOVIRUS IN GREAT-BRITAIN

A survey in Britain in 1994/95 has shown that in all cases where avian pneumovirus (APV), was detected in turkeys of over 4 weeks of age, th e virus was of type B. Oesophageal swabs were collected twice-weekly f or up to 14 weeks in seven longitudinal surveys. RNA was extracted and analysed by reverse transcription-nested polymerase chain reaction de signed to discriminate between type A and B APV. Virus of the same typ e as the vaccinal strain applied (type A or B) was detected from 7 and up to 35 days post-vaccination. Subsequently, type B virus only was d etected when the poults were 32 to 67 days old, although in any one gr owing unit the period of detection was maximally one week. Episodes of increased mortality were usually associated with the detection of thi s type B virus a few days previously. In a single experiment inoculati on of poults with virulent type A or B APV induced cross-protection al though that protection was incomplete. Our results confirm that outbre aks of respiratory disease in turkeys in Britain during 1994 to 1995 w ere still associated with APV and that the virus was type B. In contra st, between 1985 and 1990 only APV antigenically similar to type A and B strains had been detected in Britain and in continental Europe resp ectively.