ABSTRACT

ND is one of the most devastating diseases affecting the poultry industry worldwide (Ganar et al., 2014). It is caused by the highly contagious ND virus (NDV), which is a member of the genus Avulavirus (also known as APMV-1, avian paramyxovirus serotype-1) in the family Paramyxoviridae. They are an extremely diverse group of viruses, and, based on disease severity, NDV strains are classified into velogenic (highly virulent), mesogenic (moderately virulent), lentogenic (mildly virulent) and asymptomatic pathotypes (Alexander et al., 2012). The clinical signs and pathology of ND can range from inapparent infections to severe disease with high mortality, depending on the virus strains and the susceptibility of the host species. Around 250 bird species have been reported to be susceptible to NDV, and virus infections in feral and pet birds can influence virus spread and initiation of major outbreaks and panzootics in poultry. ND is a major global threat to the poultry industry as it has been reported in most countries. While it is endemic in majority of the countries, including some of largest poultryproducing nations, several countries maintain disease-free status despite the accidental incursions of the virus. In NDV-free countries, statutory surveillance measures are in place and outbreaks of NDV are notifiable to the OIE (Office International des Epizooties) and are associated with considerable economic impact including international trade restrictions.