Newcastle disease virus outbreaks: vaccine mismatch or inadequate application?

Genetic comparisons were made of the fusion protein sequences of 155 Newcastle disease virus isolates collected in South Africa between 1990 and 2002. Their evolutionary relationships and origins are described. All of the lentogenic field isolates were shown to be derived from commercial vaccines. No true South African lentogenic wild type strain was identified. Furthermore, it was shown that almost all mesogenic isolates had avirulent F(0) cleavage site sequences. Three major epizootics occurred in South Africa during the period of this study. The first outbreak (1990/1991) was caused by viruses endemic to South Africa since the 1960's (genotype VIII) but were occasionally also isolated in 2000. Genotype VIIb viruses, implicated in the severe outbreaks during 1993/1994, persisted until 1999. Genotype VIId viruses, responsible for the most recent outbreak in 1999/2000, had their origins in the Far East like those of the two previous outbreaks.

A phylogenetic study of South African Newcastle disease virus strains isolated between 1990 and 2002 suggests epidemiological origins in the Far East.

Forty three Newcastle disease virus (NDV) strains isolated before and during 1997 in Israel from domestic birds were studied by means of the three panels of monoclonal antibodies prepared against all the viral envelope proteins in order to reveal the possible antigenic differences between them and the VH strain used in Israel for poultry vaccination. Three isolates were found to have significant antigenic differences in the hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins as compared to the vaccine strain. As to the matrix protein, almost all the viruses isolated during the year 1997 were found to have considerable differences from the vaccine strain in two of four antigenic sites.

Antigenic heterogeneity amongst the field isolates of Newcastle Disease Virus (NDV) in relation to the vaccine strain. Part II: studies on viruses isolated from domestic birds in Israel.

In order to reveal the viruses strongly differing from the VH NDV strain used in Israel for poultry vaccination, 54 NDV strains isolated during the last 15 years in Israel from feral birds were studied by means of the panels of 39 monoclonal antibodies. Six isolates were found to have considerable antigenic differences in envelope proteins as compared to the vaccine strain. In four cases, the differences were related mostly to the hemagglutinin-neuraminidase glycoprotein, in one case to the fusion glycoprotein, and in one case to the matrix protein.

Antigenic heterogeneity among the field isolates of Newcastle disease virus (NDV) in relation to the vaccine strain

Newcastle disease (ND), caused by avian paramyxovirus type 1, is a highly contagious and devastating viral disease of poultry of worldwide distribution with an enormous economic impact. In this study, the sequences of matrix protein (M) gene of three ND virus strains isolated from outbreak in chickens in poultry farms of Iran in 2011–2012 were determined. Phylogenetic analysis revealed that both strains clustered with the class II viruses, with one phylogenetically close to the genotype VIIb Newcastle disease viruses and the other closer to genotype VIId. This finding is essential for improving the disease control strategies and development of vaccines for ND. The study results thus emphasize the importance of continuous surveillance of this disease and of sharing the information to the global scientific community, which would help to fill the epidemiological gaps in the regions and to validate the robustness of diagnostic screening.

Phylogenetic study base on matrix gene of Iranian Newcastle disease virus isolates, 2011-2012

Summary Between December 1992 and April 1993, Newcastle disease (ND) outbreaks occurred in a broiler flock, a layer flock, in village chickens of two prefectures and in five pigeon lofts in the South Marmara Region of Turkey. Four viruses from chickens and five from pigeons were isolated from these outbreaks, and identified as Newcastle disease viruses (NDV). All were characterized as velogenic strains based on their mean death time in eggs, ability to form plaques in tissue culture and, for some isolates, intracerebral pathogenicity index and intravenous pathogenicity index tests. Monoclonal antibody typing showed that eight of the nine isolates were indistinguishable from each other.

D. J. Alexander

Papers

Characterization of Newcastle disease viruses isolated from chickens and pigeons in the South Marmara region of Turkey.