The Newcastle Disease Virus (NDV) is a highly contagious avian virus which is of major economic importance to the poultry industry. NDV is a member of the Paramyxoviridae family, and has a single stranded, negative sense RNA genome. NDV infects via mucosal surfaces of the respiratory and alimentary tract, and its strains can be categorized in accordance to their virulence, from low virulence and mild symptoms (lentogenic), to intermediate forms (mesogenic), through to highly virulent (velogenic) strains which can cause up to 90% mortality. La-Sota is a lentogenic strain, and can be used as a live vaccine.