Newcastle Disease Virus (Animal)

Primary reference(s)

OIE, 2018. Terrestrial Animal Health Code: Newcastle Disease (Infection with Newcstle Virus). Chapter 3.3.14. World Organisation for Animal Health (OIE). Accessed 4 October 2020.

Additional scientific description

Newcastle disease is a viral disease of birds caused by avian paramyxovirus 1 (APMV-1). For official control purposes, this disease is currently defined as the most severe form of the illness, which is caused only by certain viral strains. Many less virulent strains of APMV-1 also circulate among domesticated and wild birds. These viruses usually cause much milder clinical signs or infect birds asymptomatically. However, they can sometimes evolve to become the highly virulent strains that cause Newcastle disease (Spickler, 2016).

Newcastle disease in birds can vary from no signs of illness to sudden death. Affected birds may have coughing, sneezing, nasal discharge, depression, and diarrhoea. Chicken flocks may have a sudden decrease in egg production or produce thin shelled eggs. Signs of severe illness include swelling of the tissues of the head, muscle tremors, drooping wings, twisted head, circling, paralysis or sudden death (CFSPH, 2008).

Newcastle disease is considered to be one of the most important poultry diseases in the world. Chickens are particularly susceptible and may experience morbidity and mortality rates of up to 100% (Spickler, 2016). Since its recognition in 1926, Newcastle disease is regarded as being endemic in many countries. Outbreaks can have a tremendous impact on village chickens in developing countries, where these birds are a significant source of protein and this disease is endemic (FAO, 2004). In developed countries, where highly virulent APMV-1 strains have usually been eradicated from poultry, trade embargoes and restrictions cause significant economic losses during outbreaks (Spickler, 2016).

Newcastle disease can also affect other commercial poultry, game birds, ratites, and various pet, hobby and zoo birds. Some of these birds become ill, while others carry and shed virulent viruses asymptomatically. Subclinically infected birds, particularly illegally imported psittacines, can introduce Newcastle disease into countries where it does not usually exist (Spickler, 2016).

Newcastle disease is transmitted by direct contact with diseased or carrier birds. Biosecurity measures on farms and in live poultry markets are important to prevent disease spread (FAO, 2015; OIE, 2020).

Prophylactic vaccination is practised in all but a few of the countries that produce poultry on a commercial scale (OIE, 2018).

Newcastle disease virus is a human pathogen and the most common sign of infection in humans is conjunctivitis that develops within 24 hours of exposure to the eye. Although the effect on the eye may be severe, infections are usually transient, and the cornea is not affected. There is no evidence of human-to-human spread (OIE, 2018).

Metrics and numeric limits

Newcastle disease in its virulent form, is notifiable to the World Organisation for Animal Health (OIE) under the Terrestrial Animal Health Code. An intracerebral pathogenicity index (ICPI) in day-old chicks of 0.7 or greater or the presence of multiple basic amino acids in the virus genome determines a strain to be virulent (OIE, 2019).

Examples of drivers, outcomes and risk management

Drivers: introduction of virus to a susceptible flock, via poultry trade-related activities or wild birds.

Outcomes: high mortality in poultry with sudden death of birds, trade ban, livelihoods and food security implications, gender (women and children are often the ones caring for poultry).

Risk management: farm and market biosecurity, vaccination programme (prevention), movement control, depopulation, tracing back/forward.