Avian Metapneumovirus (aMPV) Detected in Ontario

On April 17,2024, two turkey flocks in Ontario were detected with aMPV subtype B with one of the flocks experiencing high mortality.

This is the first confirmation of the aMPV subtype B in poultry flocks in the province. Avian metapneumovirus infection (Turkey viral rhinotracheitis) is an immediately notifiable disease which requires all veterinary laboratories in Ontario to notify OMAFRA when the virus is identified by a laboratory test.

Cases in USA:

In recent months, multiple states throughout the USA have documented increased cases of aMPV subtypes A and B with significant economic losses, affecting broilers, broiler breeders, layers, cage free organic birds and turkeys.

aMPV is not a food safety or human health concern. There is 80% structural similarity between human MPV and avian MPV and turkeys are susceptible to hMPV but not the opposite.

Diagnosis updates:

Currently, the Animal Health Laboratory (AHL) is working on updating their PCR testing to include detection of multiple subtypes of aMPV (currently detects type C). If veterinarians have questions about diagnostic testing, we recommend they contact the AHL.


The OAHN poultry veterinary team is conducting a study to determine the prevalence of aMPV in turkeys by serologically testing the flocks processed in Ontario.  This project will provide baseline information for aMPV presence in Ontario turkeys and can be used to determine future monitoring and preventive programs.

Virus etiology:

Avian metapneumovirus is in the family Pneumoviridae and genus Metapneumovirus. It is an enveloped, single-stranded negative-sense RNA and has 4 identified antigenic subtypes (A to D). Subtype A and B are identified in chickens and turkeys while subtype C is identified primarily in turkeys as well as ducks. Other birds at risk include pheasants, game birds, and guinea fowl. Clinically healthy wild birds are considered a reservoir for this organism (waterfowl, sparrows, swallows, pigeons, falcons etc.). Wild birds and game birds have been found to be seropositive in Ontario.

The virus is highly contagious and has tropism to head tissues, upper respiratory and reproductive tracts; there is no evidence of vertical transmission but airborne and close contact via nasal discharges, fomites, affected or recovering birds are the main sources of the virus transmission.

Since this is an enveloped virus, it is sensitive to multiple disinfectants (quaternary ammonia, bleach, etc.) It is stable at pH 3.0 – 9.0 and inactivated at 56°C for 30 minutes. However, it has longer survival times (i.e. weeks) at lower temperatures and that could explain some seasonal occurrences.


The incubation period is 3-7 days and the disease spreads rapidly within and between flocks. An entire flock can become clinical within a day. The birds shed virus for only a few days and there is no latency or carrier state. However, there are species differences in the onset and development of lesions. Unfortunately, clinical signs and lesions are non-specific.

There is variable pathogenicity between strains. Uncomplicated aMPV infection can have mild clinical signs but secondary infection(s) can increase the severity of disease. The virus affects the function of the cilia of the respiratory and reproductive epithelial cells, increasing susceptibility to secondary infections. Uncomplicated infections can clear in 10-14 days. Secondary infections include bacteria (E. coli, ORT, Pasteurella spp., B. avium, R. anatipestifer), mycoplasma (MG), aspergillosis, and viruses (e.g. IBV) resulting in potential development of airsacculitis and pneumonia.

Clinical signs:


Clinical disease caused by aMPV in turkeys has been called turkey rhinotracheitis (TRT) and avian pneumovirus infection of turkeys (APV). Regardless of age, turkey morbidity ranges from 40 to 100% and mortality ranges from 0.4% to 50%. Clinical signs include snicking, rales, nasal discharge, foamy conjunctivitis, swollen infraorbital sinuses, submandibular edema, coughing, open mouth breathing, and head shaking. Severe disease can be identified in 3- to 12-week-old turkeys. In breeders, uterine prolapse can be secondary to coughing. In layers there can be up to 70% drop in egg production (range10-40%) including increased poor shell quality and peritonitis. Recovery can take up to 3 weeks.


Clinical disease caused by aMPV in chickens, guinea fowl and pheasants has been called Swollen Head Syndrome (SHS). The disease is not as well defined in chickens and can be subclinical. Less than 4% of flock can be affected. Mortality is rarely >2%. Egg production in broiler breeder and egg quality in egg layers is affected. Clinical signs can include swelling of the periorbital and infraorbital sinuses, torticollis, disorientation, and opisthotonos.


Clinical signs can include respiratory symptoms (type C), decreased egg production (40-85%), and poor shell quality (i.e. soft, thin-shelled, cracked).


Turkeys: Mucoid exudates in turbinates and trachea; catarrhal inflammation of the upper respiratory tract (i.e. rhinitis, laryngitis, tracheitis); various reproductive tract abnormalities in mature birds (i.e. egg peritonitis, folded shell membranes, misshapen eggs). Secondary infections can result in lesions of airsacculitis, pericarditis, pneumonia, perihepatitis, and in severe cases subcutaneous exudate and osteomyelitis in cranial bones.

Chickens: Severe edema in the subcutaneous tissues of the head, neck and wattles; variable swelling of the infraorbital sinuses.


When deciding on diagnostic testing, it is important to realize that this virus does not persist within birds. The virus is cleared quickly and may only be detectable for 6-7 days post infection, so by the time clinical signs are recognized, it may be undetectable by PCR testing. Combining PCR and ELISA testing will aid in diagnosing and tracking disease within and between flocks. Antibody titres may be detectable 7 days post infection. Recommended samples include nasal secretions and sinus or tracheal swabs of mildly affected birds to test for aMPV and secondary infections. Histopathology requires collection of fresh tissues, but lesions are not pathognomonic.

Treatment and prevention:

There is no treatment for uncomplicated aMPV infection. Suggested interventions include general recommendations for disease management including biosecurity (preventing exposure to wild birds or other infected poultry), disinfection, and dedicated barn clothing. Good barn management involves providing good ventilation, controlling temperature, not overcrowding, maintaining litter quality, and avoiding multiage facilities.  Also, it is strongly recommended to have a preventative program in place to control immunosuppressive disease, anti-Mycoplasma strategies and institute treatment for bacterial respiratory agents.



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