Newcastle Disease: Present status and future challenges for developing countries

Abstract

Newcastle disease (ND) is an important infectious disease of the poultry that is caused by virulent strains of Avian Paramyxovirus-1, which is a single strand non segmented negative sense RNA virus. The virus belongs to family Paramyxoviridae and it has 10 serotypes designated as APMV-1 to APMV-10. The Newcastle disease virus (NDV) is endemic in many countries of the world. The first outbreak of Newcastle disease was observed at Newcastle during 1926. Later, it was found in various parts of the world. NDV spreads mostly by the direct contact between healthy and diseased birds or also by the excretions of infected birds. This disease can vary in nature from mild to severe depending upon the type of the virus. NDV can infect both domestic and wild birds. This disease can have a devastating effect on poultry due to high morbidity and mortality rates. In unvaccinated chickens, the morbidity and mortality rates may reach up to 100% each, depending upon the virulence of the NDV. Live virus vaccines and killed oil based vaccines are used in many countries to prevent the disease in chickens. Despite the extensive use of vaccines, outbreaks are continuously occurring in various parts of the world resulting in huge losses since few years. Moreover, extensive use of vaccines has made the situation favorable for genetic modification of the pathogenic virus. Keeping these issues in mind, future challenges are highlighted in detail.