Remember that ‘other’ poultry foreign animal disease! Newcastle disease/avian paramyxovirus 1
Emily Martin, Davor Ojkic
Animal Health Laboratory, University of Guelph, Guelph, ON.
AHL Newsletter 2025; 29(3):14.
Considering the ongoing threat of avian influenza circulating in wild birds, it can be easy to develop tunnel vision when it comes to other disease threats to poultry flocks. Recently, in June of 2025, avian paramyxovirus 1 was identified in a commercial pigeon operation in British Columbia. This virus was confirmed to be a pigeon-adapted strain of Newcastle disease (pigeon paramyxovirus 1 (PPMV-1)). The classification and naming of Newcastle disease virus (NDV) has evolved over time. While it is still commonly referred to as NDV, the current term is avian paramyxovirus 1 (APMV-1). The World Organization for Animal Health (WOAH) continues to use both NDV and APMV-1 in its communications.
Because multiple strains of APMV-1 exist, the progression of the disease depends on several factors including the viral strain, the species infected, the age of bird, concurrent infections, stress levels and immune status. As a result, clinical signs are not necessarily pathognomonic. The general organ systems affected include the respiratory tract, digestive tract and nervous system. A few examples of potential signs include high fever, dyspnea, diarrhea, depression, nervous signs, mucosal/serosal bleeding, partial or complete loss of egg production and abnormal egg formation (e.g., abnormal colour, shape, watery albumen). In vaccinated birds, lesions are often absent, or minimal. Transmission occurs rapidly after exposure to infected feces, respiratory secretions or infected fomites (food, water, equipment). The average incubation period is 5-6 days, but it can range from 2-15 days. Mortality rates vary depending on the strain and host, but can be up to 100%. The virus can survive for weeks in the environment. Classification of pathotypes based on clinical signs in chickens is outlined in Table 1.
Table 1. Pathotypes of Newcastle Disease (WOAH Terrestrial Manual 2021)
Wild birds are not all equally susceptible to the virus, but many species can be infected. They can act as reservoirs for the virus, resulting in endemic infection and sporadic outbreaks. According to the Canadian Wildlife Health Centre (CWHC), APMV-1 infection was last detected in Ontario in 2024 in cormorants. The presence of this virus in wildlife represents a potential source of infection for domestic birds. While Newcastle disease is endemic in commercial poultry in many countries around the world, commercial poultry in Canada have remained free of this disease for decades, resulting in its classification as a foreign animal disease (FAD).
APMV-1 is an enveloped RNA virus that utilizes specific viral attachment proteins to bind and enter host cells. The hemagglutinin-neuraminidase (HN) protein facilitates viral attachment to the host cell surface. Along with HN, the fusion (F) protein enables fusion of the viral envelope with the host cell membrane, allowing viral entry. In infected cells, the F protein is initially produced as an inactive precursor, F0, which lacks fusion activity. Activation occurs when host proteases cleave F0 into two subunits, F1 and F2, which are essential for membrane fusion and viral entry. The amino acid sequence at the F protein cleavage site determines whether this cleavage can occur efficiently. The F protein is considered the main virulence determinant of APMV-1. Virulent APMV-1 strains possess multiple basic amino acids at the cleavage site, enabling cleavage by ubiquitous host proteases found in a wide range of tissues. This allows for systemic viral spread and contributes to enhanced pathogenicity.
Tissues, oropharyngeal swabs, and cloacal swabs are used to detect acute APMV-1 infection by PCR. The matrix (M) gene is a standard target for PCR due to its highly conserved nature across all strains, making it suitable for initial screening regardless of APMV-1 pathotype. In Canada, Newcastle disease is reportable due to its significant impact on poultry and trade. A positive APMV-1 M gene PCR result will trigger a mandatory notification to the CFIA, and samples will be sent to the National Centre for Foreign Animal Disease (NCFAD) in Winnipeg for confirmatory testing and further characterization to determine the strain’s virulence and to guide control measures.
References
1. Industry notice – The CFIA detects Newcastle disease in BC pigeons: https://inspection.canada.ca/en/animal-health/terrestrial-animals/diseases/reportable/newcastle-disease/industry-notice-2025-06-19
https://www.woah.org/en/disease/newcastle-disease/
https://ictv.global/report/chapter/paramyxoviridae/paramyxoviridae/orthoavulavirus
2. Miller PJ, Koch G. Newcastle disease. In: Diseases of Poultry, 14th ed. Swayne DE, ed. Wiley Blackwell, 2020;vol I:112-129.
3. Shivaprasad HL, Crespo R. AAAP Slide Study Set #35:An Overview of Exotic Newcastle Disease. AAAP, 2013.
4.Mao Q, et al. Review detection of Newcastle disease virus. Front Vet Sci 2022, 9:936251.
https://doi.org/10.3389/fvets.2022.936251.