No abstract

Infectious bronchitis virus (IBV) causes a costly respiratory viral disease of chickens. The role of wild birds in the epidemiology of IBV is poorly understood. We detected diverse coronaviruses by PCR in wildfowl and wading birds in England. Sequence analysis showed some viruses to be related to IBV.

SUMMARYA 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, the virus was of type B. Oesophageal swabs were collected twice-weekly for up to 14 weeks in seven longitudinal surveys. RNA was extracted and analysed by reverse transcriptionnested polymerase chain reaction designed to discriminate between type A and B APV. Virus of the same type 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 detected when the poults were 32 to 67 days old, although in any one growing unit the period of detection was maximally one week. Episodes of increased mortality were usually associated with the detection of this type B virus a few days previously.In a single experiment inoculation of poults with virulent type A or B APV induced cross-protection although that protection was incomplete. Our results confirm that outbreaks of respiratory disease in turkeys in Britain during 1994 to 1995 were still associated with APV and that the virus was type B. In contrast, between 1985 and 1990 only APV antigenically similar to type A and B strains had been detected in Britain and in continental Europe respectively.

SUMMARYGroups of 1-day-old turkey poults from a parent flock free of antibodies to turkey rhinotracheitis virus (TRTV) and the pathogenic mycoplasmas, were infected by eyedrop with virulent TRTV, with Mycoplasma gallisepticum (Mg) or with both agents together. Dual infection resulted in increased morbidity compared with those groups given single infections. The presence of the Mg in the dual infection had no apparent effect on the pathogenesis of the virus, but the virus caused the Mycoplasma to be more invasive.Mg infection caused a transient depression in TRTV ELISA antibody titres at 29 days postinoculation. At 14 days post-infection Mg haemagglutination inhibition (HI) and rapid serum agglutination (RSA) titres were higher (P <0.01) in the mixed infection group compared with those infected with Mg alone, but there was no significant difference between ELISA antibody titres of these two groups.