Turkey producers are battling a new disease threat that is being blamed for low U.S. inventories of turkey eggs in incubators. According to the National Turkey Federation (NTF), Avian metapneumovirus (aMPV) has been seen in every poultry-producing state in the U.S. and will likely impact supplies heading into the holiday season. Meaning consumers could be stuck paying higher prices for their Thanksgiving birds this year.
Commonly known as “turkey viral rhinotracheitis” in turkeys and “swollen head syndrome” in chickens, aMPV is highly contagious and can spread between all poultry species. The infection from avian metapneumovirus itself is relatively mild but secondary bacterial infections can seriously sicken and kill birds.
Avian metapneumovius has four subtypes named A, B, C, and D. Subtype C has previously been detected in the U.S. when it affected turkeys in Minnesota and Colorado in the 1990s. That outbreak was successfully eradicated and aMPV wasn’t seen again in the U.S. until late 2023. The latest outbreak stems from aMPV-A and -B subtypes. The B subtype is prevalent in the East, the A subtype in the West, and both types have been found in the Midwest.
Lindy Chiaia, Ph.D., vice president of scientific and regulatory affairs for NTF, says her organization estimates that the virus is present in 60-80% of U.S. turkey flocks, with over 1,500 detections since the first cases were confirmed in February 2024. The U.S. Department of Agriculture (USDA) does not officially track avian metapneumovirus cases so this complicates the data collection.
Zoetis senior technical services veterinarian David Rives says the outbreak has delivered a “double whammy” to the U.S. industry with both a shortage of eggs to set in the hatcheries and mortality among older birds resulting in a shortage of turkeys to send to the processing plants.
Symptoms can include sinusitis, watery eyes, depression, and neurological issues. The bacterial infection often concentrates in the head, leading it to its alternative name, “swollen head syndrome.” In broiler breeders, the drop in egg production may be negligible — or as high as 6%. Broilers are usually affected at 4 to 6 weeks of age. In turkeys the disease usually appears between 3 to 12 weeks.
Cumulative mortality in turkeys can be as high as 30%, with mortality most severe among birds 40 weeks and older. Veterinarians say metapneumovirus commonly leads to E. coli infections that are complicated to treat. In general, an aMPV infection makes any secondary infection harder to treat and raises the mortality risk. Keep in mind that producers are also battling the ongoing bird flu virus outbreak that has also led to the loss of millions of turkeys the past few years.
Dr. Kristi Scott of the Virginia Poultry Growers Cooperative suspects metapneumovirus is underdiagnosed in pullet houses. Farmers might see some head shaking or almond-shaped eyes, but clinical signs are rare, she said. Problems become more evident as layers come into production and the secondary bacterial infections kick in. There is no treatment for AMPV infections once they occur.
The U.S. Department of Agriculture approved the use of an autogenous aMPV vaccine for commercial poultry from Cambridge Technologies in August 2024. This is the first aMPV vaccine to receive regulatory approval by the government agency, though it is only designed to target subtype “B”. Outside the U.S., both live and inactivated vaccines are commonly used to immunize chickens and turkeys.
“We have not had U.S. approved vaccines simply because we have not seen this virus circulating the U.S. in almost 20 years,” explains NTF’s Chiaia. “I think it’s important to know that, while other parts of the world have been seeing this disease, they’ve had tools to protect them.”