LanguageNewcastle Disease (ND) represents one of the most devastating poultry diseases, caused by a paramyxovirus serotype 1. Although ND virus has various avian hosts, it is of particular economic importance in chickens and turkeys of all ages.
Different strains of ND virus can be classified according to their pathogenicity (velogenic, mesogenic, lentogenic) as well as according to the preference they have for certain organs (pneumotropic, neurotropic, viscerotropic).
Clinical signs of the disease may vary from mild ones, with few or no symptoms, to respiratory infections, diarrhoea and possible nervous symptoms. Mortality can be increased by secondary bacterial infections. In its most severe form ND is characterised by a very short and acute course with sudden death, high mortality of up to 100% and a rapid spread to other flocks in the area. In breeders and layers the disease can lead to a drop in egg production and impairment of eggshell or albumen quality, resulting in serious economic losses.
- Haemorrhagic proventriculus
- Haemorrhagic trachea
Both humoral and mucosal immunity play an important part in the immune response to ND. Infection with ND virus usually results in virus replication and a subsequent systemic response with production of specific circulating antibodies (humoral immunity). There is good correlation between titre and level of protection: the higher the titre, the more complete the protection.
Protection against the disease is induced by vaccination with either live and/or inactivated ND vaccines.