A paper presented by Dr. Simone T. Stoute and colleagues affiliated to the California Animal Health and Food Safety Laboratory System, Turlock Branch, reported on an outbreak of a disease tentatively ascribed to vvIBD infection. The presentation made at the 2009 Western Poultry Disease Conference documented mortality of 26% and 34% respectively in two pullet flocks aged 11 and 14 weeks.
Based on the post mortem changes which included edematous bursae Fabricius, muscle hemorrhages and supported by microscopic examination, a provisional diagnosis of IBD was made. In view of the severity of mortality and the appearance of the lesions, the IBD isolate was submitted to the Ohio Agriculture Research and Development Center in Wooster OH for examination by Dr. Daral J. Jackwood.
Molecular analysis of the virus showed strong similarity with vvIBD strains isolated in Europe, Asia and Africa. This form of infectious bursal disease is exotic to the U.S. but has been recently isolated in Central America. The very virulent strain is responsible for severe immunosupression and mortality and prevention requires the application of intermediate-plus vaccines. It is noted that the affected flocks had apparently been vaccinated with an intermediate strain product by the aerosol route consistent with accepted U.S. industry practice.
At the present time the outbreak is under active review by the California Department of Agriculture and the USDA.
Critical questions which must be answered within the next few weeks are:
- Is the virus in fact homologous with vvIBD stains which are responsible for severe losses in virtually all countries other than in North America?
- What was the origin of the virus since vvIBD is exotic to the U.S. and emergence of these infections on a small farm presumes introduction from outside the U.S. with obvious implications for security?
Egg Industry will report on findings as released by responsible authorities.