Serological studies on flocks showing depressed egg production.

A serological investigation was undertaken of flocks with depressed egg production. No obvious correlation was found between antibody to adenovirus, infectious bronchitis virus or infectious bursal disease virus and this syndrome. No antibody was detected to Newcastle disease virus, Mycoplasma gallisepticum or in most cases to Mycoplasma synoviae. A relationship was found between the development of antibody to a haemagglutinating virus, 127, and depressed egg production. A retrospective survey of fowl sera for antibody to 127 virus indicated the first evidence of its presence in Northern Ireland was in June 1976. If 127 is the aetiological agent of this syndrome, then it appears to have very limited powers of lateral spread and vertical transmission is postulated. It is further postulated that the widespread dissemination of this condition in Western Europe, coupled with its apparent lack of horizontal transmissibility, can best be explained by contamination of a vaccine with 127 virus.