Avian Metapneumovirus Update

March 1, 2024

Consistent with our efforts to communicate with our stakeholders and partners early and often when we identify events of national concern, we are sharing an update about an emerging disease issue that APHIS is monitoring.  

On January 23, the National Veterinary Services Laboratories (NVSL) confirmed avian metapneumovirus (aMPV) subtype B in samples from a National Animal Health Laboratory Network (NAHLN) laboratory. These samples originated from turkeys and broilers in Virginia and North Carolina. On February 1, APHIS also confirmed the presence of aMPV subtype A in turkeys in California from samples collected between November and December 2023. While aMPV subtype C was known to exist in the United States, subtypes A and B had not previously been identified in the United States.  

Over the past few months, diagnostic laboratories in several states have indicated an increase in serologic positives using a pan-aMPV assay. The positive serologic samples have increased since the early fall of 2023, however some serologic assays used do not distinguish among the subtypes. The positive serologic samples have been associated with high mortality events in turkeys and broilers accompanied by respiratory or reproductive clinical signs. The NVSL and USDA Agricultural Research Service Southeast Poultry Research Laboratory are engaged in virus isolation attempts, assay evaluation, and virus characterization. The U.S. Geological Survey National Wildlife Health Center plans to test wild bird samples from the 2023 summer/fall period along the Atlantic flyway for aMPV. 

APHIS does not expect trade impacts beyond restrictions to impacted (affected, vaccinated) flocks and does not recommend or anticipate any regulatory response activities to restrict movement or stamp out disease.  

The Center for Veterinary Biologics (CVB) has received several inquiries, but only partial information from two manufacturers to date. Most manufacturers are focused on modified live products, but CVB is looking first for information to support import of a killed vaccine due to the increased risk that comes with importing live products. If vaccines meet requirements for use, the CVB will contact State Animal Health Officials (SAHOs) to approve the import into and use of any vaccine in their state as part of title 9, Code of Federal Regulations104.4 (import) and 103.3 (domestic shipping) research and evaluation permitting process. On February 6, 2024, CVB published Notice No. 24-03 to inform interested parties that CVB is accepting product license and import permit applications for vaccines and diagnostic products for aMPV research and evaluation permitting process. At the request of the National Turkey Federation, CVB provided a presentation to federation members, representatives of the National Chicken Council, and other interested parties on the veterinary biologics import process on March 1, 2024. 

Considering these detections, APHIS recommends the following: 

  • APHIS encourages laboratories receiving samples with compatible clinical signs, including high mortality and reproductive losses, to consider conducting testing for aMPV and report positive PCR or virus isolation findings to the SAHOs in the state where the positive flock is located.
    • APHIS will send additional guidance to SAHOs to report findings voluntarily to support national monitoring. APHIS’ requested information will include test type, production type, test result date, and clinical signs in reports, and provide a tool to share this information.
  • While confirmatory testing by NVSL is not necessary for reporting, NVSL will support virus monitoring efforts by offering whole genome sequencing at no cost to the submitter for samples with Ct values of 30 and lower.

Additional general disease information on aMPV can be found at: 

We will share additional information and guidance about the aMPV situation as it becomes available. We appreciate your continued partnership with APHIS.