AAAP: Spread of avian metapneumovirus in the US
Avian metapneumovirus is highly contagious, causing egg production losses and immunosuppression
3 November 2025
3 minute read
By: Editor's note: the following is from several presentations at the 2025 annual meeting of the American Association of Avian Pathologists.
Avian metapneumovirus (aMPV) is a highly contagious pathogen that causes an upper respiratory tract infection, egg production losses, and immunosuppression in chickens and turkeys. Secondary pathogens and environmental conditions exacerbate the disease and result in major economic losses. Of the four recognized aMPV subtypes (A, B, C, and D), aMPV-A and aMPV-B have been the most common outside the United States, and aMPV-C has only been described in the United States in 1996.
However, during the winter of 2023-2024 aMPV-B was diagnosed in the Southeast of the United States, followed by aMPV-A in the Southwest. By the summer of 2024, both viruses spread and merged in the Midwest, noted researchers from Aviserve LLC, and Veterinary Diagnostic Pathology, LLC.
Researchers at the California Animal Health and Food Safety Laboratory said that the first reported commercial poultry case of aMPV type A in the United States was identified in October 2023. Since then, aMPV-A has not only persisted in commercial broilers, turkeys, and layers in California but also in multiple states in the US.
Private researchers in Georgia and North Carolina studied the evolution of flocks’ exposure to aMPV in the state of Georgia for one year by serological testing as the outbreak unfolded. A total of 289 broiler breeder flocks in the state of Georgia were randomly selected from previously saved sera submitted for health monitoring. Flocks were stratified by months and region in Georgia (Northeast, Northwest and South). Ten sera per flock selected were plated and tested for aMPV using a commercial serology kit. When all flocks were combined and stratified by month, there was a significant increase in the proportion of positive flocks over time and a reduction in the proportion of negative flocks. Comparison of flocks sampled before and after the first confirmed case revealed an increase in titer level by region, with a marked difference in Northeast Georgia. The epidemiologic picture of aMPV in broiler breeder flocks for the state of Georgia indicated an increase of exposure in all regions over time despite fluctuations in positive detections.
Meagan Abraham from Jennie-O Turkey, USA, described aMPV as an enveloped virus of the family Pneumoviridae, genus Metapneumovirus. The virus primarily affects the respiratory system of poultry, and birds often present with swollen heads and sinuses, mucopurulent discharge, snick, and lethargy. aMPV is often associated with secondary colibacillosis, leading to severe mortality, plant condemnations, and financial losses.
Control
According to researchers at Texas A&M University and Wayne-Sanderson Farms, in 2024, aMPV subtypes A and B swept through the country’s flocks of both turkeys and chickens. With traditional biosecurity measures seemingly ineffective and no vaccination options available at the start of the outbreak, veterinarians were limited in their ability to manage the spread and mortality associated with aMPV. This proved no less true across four broiler production complexes in Texas.
Antibody titers from these complexes verified that aMPV subtype A was present in more flocks than suspected. In addition, evaluation of retained serum proved the disease had also been present in the area for longer than previously believed.
With prevention seemingly impossible, controlling the secondary bacterial infections common to aMPV became the best option to reduce mortality. In a world concerned with the judicious use of antimicrobials, treatment was originally withheld until clinical signs appeared. This proved to be inadequate and a policy of treating the entire farm with oxytetracycline as soon as signs appeared in any of the houses was implemented for the breeder farms.
A retrospective analysis of the policy found that treating the entire farm prevented the loss of up to 1.07% of breeders. This translated to a savings of $2,140 in pullet costs per house with the potential to produce an additional 12,947 broiler chicks. An experimental autogenous AMPV vaccine was later implemented to further control clinical signs.
