The causative agent of Newcastle Disease is the Newcastle Disease Virus (Avian Avulavirus 1, APMV-1), a single-stranded RNA virus from the Paramyxoviridae family. NDV is assigned to the genus Avulavirus. A distinction is made between apathogenic, lentogenic (low virulence), mesogenic (moderate virulence) and velogenic (high virulency) virus types. The symptoms depend on the virulence of the pathogen.
In bone marrow and muscles of slaughtered poultry, the NCD virus remains infectious at -20 ⁰C for 6 months, at 1 ⁰C up to 134 days. In contaminated henhouses the virus remains infectious for 30-25 days, depending on the ambient temperature. Dried virus particles can be infectious for years.
The virus is spread directly, by air or by objects. The spread of the disease is favoured by the high tenacity of the virus and the wide host spectrum. Sources of infection are often clinically inapparently infected, diseased animals or animals in the incubation period.
NDV is shed in large quantities in faeces, eye, nose and throat secretions and all other body fluids. Shedding lasts for about 26 days; in vaccinated animals about 40 days. The pathogens are spread directly from animal to animal as well as indirectly via all equipment, stable dust and air, shoes and vehicles. Transovarian virus transmission plays a major role, with infected chicks hatching from NCD virus contaminated eggs.
Trading with live or slaughtered poultry or poultry products plays a role in the new introduction of the disease into disease-free regions (also via frozen poultry!). Virus transmission is also possible via feeding of kitchen waste, litter, feed, housing equipment and transport containers. In comparison, the probability of transmission via wild birds is low. With regard to wild birds, waterfowl and wild poultry are a natural reservoir for epidemics.
Newcastle Disease is spread worldwide. Due to control measures, the disease has lost importance in recent years. In July 2018 an outbreak was reported in Belgium in domestic chickens.