Emergence of new sub-genotypes of Newcastle disease virus in Pakistan

Newcastle disease virus (NDV) was first reported in 1926. Since then, the NDV has been prevalent in domestic and wild birds representing a diverse and continually evolving group of viruses, consisting one genotype for class I NDV isolates and eighteen genotypes for class II NDV isolates. The emergence of new virulent genotypes from global epizootics and the year-to-year changes observed in the genomic sequence of NDV of low and high virulence implies that distinct genotypes of NDV are simultaneously evolving at different geographic locations across the globe. This vast genomic diversity may be favoured by the large variety of avian species susceptible to NDV infection and by the availability of highly mobile wild bird reservoirs. In certain countries such as Pakistan, the viruses of sub-genotype VIIi have replaced NDV isolates of genotype XIIIa, which were commonly isolated in 2009-2011, and have become the predominant sub-genotype causing ND outbreaks since 2012, suggesting the existence of a fifth panzootic. The genomic diversity of NDV increases the possibility of diagnostic failures, resulting in unidentified infections. Therefore, continuous monitoring of viral evolution and periodic updates of vaccine seed strains are warranted to achieve efficient control and eradication of ND. This review reports on the emergence and evolution of ND viruses and vaccination strategy in Pakistan.

Duke Scholars

Author Sajid Umar DKU Faculty