In 2002, a commercial layer flock in Japan was initially diagnosed as being infected with infectious bronchitis (IB) based on clinical signs, virus isolation and serological analysis, report Hiromitsu Katoh of Poultry Products Quality Control (PPQC Co. Ltd.) and colleagues in the current issue of the journal, Poultry Science.

Along with co-authors at the University of the Philippines Los Baños as well as Tottori University and Yamaguchi University in Japan, Hatoh reports that molecular diagnosis subsequently identified the cause to be atypically infected with velogenic Newcastle disease virus (NDV).

The flock had slightly decreased egg production and an increased occurrence of soft-shelled eggs without significant mortality.

IB-like viruses were isolated, which caused dwarfing and curling in 12-day-old chicken embryos.

Ten years after this case, retrospective genetic analyses showed that apart from the IB virus, the flock was also infected with NDV.

Mean death time, intracerebral pathogenicity index (ICPI) and deduced amino acid sequence of the cleavage site of the fusion-protein gene revealed that the NDV isolate was velogenic (112RRQKR116).

Katoh and co-authors conclude from their results that poultry clinicians should look out for atypical velogenic ND, especially in vaccinated commercial chicken flocks, which may harbour hidden NDV infection.

Reference

Umali D.V., H. Ito, K. Shirota, T. Ito and H. Katoh. 2015. Atypical velogenic Newcastle disease in a commercial layer flock in Japan. Poultry Science. 94:890-897.

May 2015