Biological and molecular characterization of Newcastle disease virus isolates from surveillance of live bird markets in the northeastern United States.

Newcastle disease virus (NDV) is frequently recovered from surveillance samples collected by U.S. Department of Agriculture, Animal and Plant Health Inspection Service personnel in live bird markets. Six NDV isolates, five from chickens and one from a pheasant, were characterized for comparison with reference NDV isolates from poultry and other birds. All isolates tested were of low virulence for chickens. Four of the six isolates were similar to reference lentogens B1 and La Sota, but two isolates, one from a chicken and one from a pheasant, were different. The aberrant chicken isolate had a monoclonal antibody-binding profile like an unusual Canadian pigeon isolate. Sequence analysis of the matrix gene of this isolate demonstrated that it differed from all isolates included in the comparison and therefore may represent a third phylogenetic NDV group. The pheasant isolate had a monoclonal antibody-binding profile typical of other U.S. NDV lentogens but had a matrix gene sequence and hemagglutinin thermostability similar to strains Ulster and Queensland V4 (QV4), viruses originally isolated in Northern Ireland and Australia, respectively. The pheasant virus is the first lentogen isolated in the United States known to be closely related phylogenetically to Ulster and QV4. The unusual chicken and pheasant isolates were readily shed from the intestinal tract during chicken passage, whereas the other isolates were shed from the respiratory tract with little or no intestinal shedding. The frequency in live bird markets of viruses similar to those previously thought to be exotic to the United States in unknown.