Avian metapneumovirus update
Andrew Brooks, Tanya Rossi, Emily Martin, Davor Ojkic
Animal Health Laboratory, University of Guelph, Guelph, ON
AHL Newsletter 2026;30(2):15.
Since the detection of avian metapneumovirus (aMPV) in Ontario during the winter of 2024, cases in commercial poultry have continued to be identified through 2025 and into 2026 (Fig. 1). A review of laboratory submissions up to May 21, 2026 identified 232 PCR‑positive submissions in turkeys and chickens. Most detections were subtype B (approximately 92%), with subtype A accounting for about 8% of cases. Cases in turkeys primarily involved meat birds, whereas infections in chickens were predominantly identified in broiler breeder flocks, with occasional detections in broilers and layers.
Subtype B was also identified in a single gamebird submission and one small flock. Subgroup C has not been detected in commercial poultry to date. However, surveillance confirms the virus is maintained in the region's wildlife reservoir. Subgroup C was first identified in wild waterfowl in Ontario in 2016, and its continued circulation in the province was recently re-confirmed through a targeted waterfowl surveillance program in 2024.
Live aMPV-A vaccines became available in the second half of 2025. Because standard PCR testing alone does not distinguish between vaccine and wild-type field strains, any positive aMPV-A results recorded in late 2025 and 2026 may reflect detection of the vaccine virus rather than a field infection. Genotyping assays are available to differentiate between field strains and vaccine strains.
Clinically, aMPV infection causes respiratory and reproductive disease, with severity and signs that vary by species. In turkeys, the disease may be more pronounced, with high morbidity and clinical signs such as nasal discharge, swollen infraorbital and periorbital sinuses, conjunctivitis, and reduced egg production. In chickens, clinical signs and lesions (Fig. 2) often include swelling and subcutaneous edema of the head (“swollen head”), sinusitis, tracheitis, as well neurologic signs such as torticollis or stargazing due to inflammation of the middle or inner ear. Secondary bacterial infections are common and exacerbate clinical disease.
From a diagnostic perspective, aMPV infection can be challenging to confirm because the virus may only be present in the upper respiratory tissues for approximately 6–7 days post‑infection. Timing of sampling early in the course of infection is therefore important, ideally selecting multiple acutely affected birds for testing. PCR tests may be performed on swabs of oculo-nasal discharge, the choanal opening, the nasal sinuses and the trachea. Postmortem examination and histopathology may provide supportive findings but are not definitive. Combining PCR with antibody detection (ELISA) can improve case identification, particularly when infection is no longer detectable by PCR. Continued surveillance, prompt diagnosis, and strong biosecurity and flock management remain essential for controlling aMPV in poultry.
Figure 1. AHL submissions positive by PCR for avian metapneumovirus. Cases continue to be detected in poultry flocks, predominantly involving aMPV subtype B in meat turkeys and broiler breeder chickens.
Figure 2. Avian metapneumovirus infection in chickens often produces marked swelling of the head due to subcutaneous edema (left) and sinusitis with discharge that may be clear, mucoid or turbid (right).
References
1. Martin E. Avian metapneumovirus subtype B: First cases confirmed in Canada. AHL Newsletter 2024;28(2):17.
2. Jardine CM, Parmley EJ, Buchanan T, Nituch L, Ojkić D. Avian metapneumovirus subtype C in wild waterfowl in Ontario, Canada. Transbound Emerg Dis. 2018 Aug;65(4):1098-1102.
3. Rautenschlein S. Avian metapneumovirus. In: Diseases of Poultry, 14th ed. Swayne DE, ed. Wiley Blackwell, 2020; vol 1:135-143.