Newcastle Disease Viruses Isolated from Racing Pigeons in Japan

Abstract

During the period from September 1983 to October 1984, outbreaks of Newcastle disease (ND) in racing pigeons occurred in Japan. Seven isolates were collected from these outbreaks in 7 prefectures. All of the isolates were found to be identical with ND virus by the hemagglutination inhibition test, and they formed plaques without addition of diethyl-aminoethyl-dextran and MgS0₄ in tissue culture systems. Mean death time of the minimum lethal dose (MDT/MLD) of 7 isolates ranged from 90 to 144 hrs. The intracerebral pathogenicity indices of 5 isolates ranged from 1.3 to 1.7. Five out of 7 isolates were inoculated orally into 1-week-old or 4-week-old chickens. All of the isolates induced clinical signs in 1-week-old chicks, and 3 out of 5 isolates induced death in a few chicks (mortality, 10-30%). However, none of the 5 isolates induced clinical signs in most of the 4-week-old chickens. These results indicated that all the present isolates were of a mesogenic strain while showing a comparatively longer MDT/MLD.