Biological and Phylogenetic Characterization of a Genotype VII Newcastle Disease Virus from Venezuela: Efficacy of Field Vaccination

Abstract

Here we report the biological and molecular characterization of a virulent genotype VII Newcastle disease virus (NDV) circulating in Venezuela and the assessment of the vaccination efficacy under field conditions compared to controlled rearing conditions. Biological pathotyping showed a mean embryo dead time of 50 h and an intracerebral pathogenicity index of 1.86. Sequence-based phylogenetic analysis demonstrated that the virus belongs to genotype VII in class II (a genotype often found in Asia and Africa), representing the first report of the presence of this genotype in the continent of South America. A vaccine-challenge trial in commercial broilers reared in fields or in a experimental setting included dual (live/killed) priming of 1-day-old chicks plus two live NDV and infectious bursal disease virus (IBDV) field vaccinations at days 7 and 17, followed by a very stringent genotype VII NDV challenge at day 28. Serology for NDV and IBDV, bursal integrity, and protection against NDV lethal challenge were assessed. At 28 days, field vaccinates showed significantly lower NDV (1,356 versus 2,384) and higher IBD (7,295 versus 1,489) enzyme-linked immunosorbent assay (ELISA) antibody titers than the experimentally reared birds. A lower bursal size and bursa-body weight ratio (P < 0.05) and higher bursa lesion score were also detected in the field set. Only 57.1% of field vaccinates survived the lethal challenge, differing (P < 0.05) from 90.5% survival in the experimental farm. Overall, results confirmed the presence of the genotype VII viruses in South America and suggest that field-associated factors such as immunosuppression compromise the efficacy of the vaccination protocols implemented.

An evolutionary insight into Newcastle disease viruses isolated in Antarctica

“…Severe outbreaks in Western and Southern Europe [26,27], South Africa [28] and Taiwan [29] in the 1990s were caused by genotype VII, the currently circulating genotype in Asia, Africa and Europe [14]. A recent outbreak of NDV in South America (Venezuela) has also been attributed to a genotype VII virus, suggesting that viruses of this genotype are spreading worldwide [30,31].…”

Detection of Inter-Lineage Natural Recombination in Avian Paramyxovirus Serotype 1 Using Simplified Deep Sequencing Platform

“…Several previous studies have shown that genotype V, VI, and VII of class II viruses were the most prevalent viruses presently circulating globally. Out of these, lineage 5 or genotype VII of class II viruses were the most predominantly isolated strains of NDV from Asia, Africa, Middle East, and South America (Khan et al, 2010; Miller et al, 2010; Munir et al, 2012; Perozo et al, 2012). A recent study has classified NDV strains into several new genotypes based on the mean inter-populationary evolutionary distance of 10% as the cutoff value (Diel et al, 2012).…”

Newcastle Disease Virus infection study on duck and chicken in Subang district

“…In reality, sometimes the results are not as expected, mass vaccination using spray method showed that the percentage of group immunity was 53%, whereas vaccination by drinking water showed that the percentage of group immunity was 60% (Degefa et al 2004). Ineffective vaccination also may be affected by immunosuppressive conditions of birds (Perozo et al 2012). Beside live vaccine, inactive vaccine is also often used in layer and breeder farming because it may provide longer high titre than the live vaccine and the antibody can be downgraded to their generation (AlGarib et al 2003).…”