Avian Metapneumovirus is Back and it’s Impacting More Than Just Turkeys

Ralco Agriculture
5 hours ago
9 min read

turkey with Avian metapneumovirus (aMPV), also called turkey rhinotracheitis. it has swollen sinuses and head.
Picture credit: Merck Manual, Courtesy of Dr. Rebecca Lindenwald.

Picture credit: Merck Manual, Courtesy of Dr. Rebecca Lindenwald.

Avian metapneumovirus (aMPV), also called turkey rhinotracheitis or, in chickens, a cause of “swollen head syndrome”, has re-emerged in the U.S. with virus subtypes A and B.

This resurgence is changing day-to-day decisions for broiler, layer and turkey operations, especially around day-28 broiler breaks, turkey vaccination logistics and management of secondary bacterial challenges.

To help, Ralco’s poultry team gives insight into what they’re seeing in the field and what’s working for producers.

What is aMPV, and Why the Buzz?

aMPV is a respiratory virus in the Metapneumovirus family that causes respiratory tract infections and significant economic losses for poultry producers.

First detected in South African turkeys in 1978 (Type A), the virus was later classified into additional subtypes: Type B in Europe, Type C in U.S. turkeys in 1996 and Type D, later identified in France from 1985 samples. (1)

After years without aMPV in U.S. commercial flocks, subtypes A and B were first confirmed in early 2024. B in Virginia/North Carolina (turkeys and broilers) and A in California turkeys (from late-2023 samples. (1) This was the first time these virus sub-types had hit U.S. soil.

So why now? It is unknown as to why aMPV is back, but surveillance suggests wild birds can act as reservoirs and long-distance movement (migration, trade) can support spread over time. (2)

When Does aMPV Hit?

The timing of clinical signs can vary depending on the operation, environment and bird type, but some clear patterns have emerged.

Broilers: Day-28 is a common break point in affected systems. Getting interventions in place before that window can pay off.
Turkeys: Susceptibility is frequently noted from 3–12 weeks, but management and environment can shift that.
Layers and Breeders: Clinical disease tends to be milder, but aMPV can lead to egg production drops of up to 70% and egg quality issues. (1)

What Producers Actually Notice First with aMPV

Turkeys tend to show more visible respiratory signs early on, frothy eyes, nasal discharge and swollen sinuses, making the disease easier to spot. Broilers are more subtle. Early signs often look like performance dips, missed production peaks or slower rate of gain, followed by respiratory signs that mimic other diseases.

Turkey with aMPV and swollen sinuses and nasal discharge Picture credit: Penn State

Chick and broiler with aMPV or 'swollen head syndrome'. Picture credit: Poultry DVM

In layer and breeder flocks, aMPV can be even less obvious. Respiratory signs are usually mild, but a drop in egg production or egg quality is often the first sign something is off. Swollen head syndrome can also appear, with swelling around the eyes and sinuses in a small portion of the flock. Mortality rates are typically low, but secondary infections can worsen outcomes if not addressed quickly.

Because these signs can look like a range of other respiratory or management issues, early diagnostic testing is one of the most important steps to get a clear answer. Working with a veterinarian to collect tracheal or sinus swabs shortly after signs appear provides a more accurate picture of what’s circulating. Testing for multiple pathogens can also help identify coinfections, which are common in respiratory breaks, and if subtyping is available, knowing whether you’re dealing with subtype A or B can help guide management and any vaccination strategy.

Unfortunately, once the virus damages cilia, the tiny hairlike projections that protect the respiratory tract, opportunistic bacteria can easily take hold. This often leads to secondary infections like E. coli, Newcastle disease, or Mycoplasma gallisepticum, which can drive much of the observed mortality and economic loss with aMPV. (1)

For most producers, the testing process isn’t complicated. Veterinarians or diagnostic labs can provide swab kits and step-by-step instructions. If you don’t work with a vet regularly, most state or university labs accept direct submissions and can guide you through the process.

For example, both the University of Minnesota and Texas A & M offer aMPV testing and outline their submission requirements online.

Does One Positive Flock Doom the Next Flock?

Not necessarily. aMPV can persist in the environment for a period, especially in cool, moist litter, but good management between flock changes that trajectory.

Controlled studies show that aMPV can remain detectable and infectious in litter for days to weeks, influenced by temperature (detection at 46°F/8°C) and other environmental factors. (8)

Because cooler temperatures prolong survival, implementing thorough house clean-out, windrow composting and litter heat-up is critical to lower the risk for the next placement.

Transmission of aMPV: What We Know and Don’t Know

One of the biggest challenges with avian metapneumovirus is that its exact transmission pathways aren’t fully understood. While we know how many respiratory viruses typically behave, this one has proven to be unpredictable at times. It doesn’t always move the same way from one complex, or even one flock, to the next.

What we do know is that aMPV can spread through multiple routes at once. That makes it difficult to pinpoint a single source and easy for the virus to quietly travel between houses, farms or even regions.

So far these are the suspected pathways: (3)

Direct contact with respiratory secretions is the primary route of transmission.
Indirect like equipment, vehicles, clothing or other materials can easily carry the virus between barns.
Rodents can act as mechanical carriers, moving the virus around without showing signs of disease.
Aerosol spread is less likely but can’t be ruled out entirely.
Wild birds are believed to contribute to regional and long-distance spread through migration.

Since the virus can spread in several ways, maintaining strong biosecurity practices is critical.

How the Industry Beat aMPV Once Before

When subtype C emerged in U.S. turkey flocks in the late 1990s, it didn’t take long for the industry to mount a coordinated response. Through widespread vaccination programs that used both live and non-living vaccines, integrators were able to build strong flock immunity and limit the virus’s ability to circulate.

At the same time, biosecurity protocols tightened significantly. Farms focused on better litter management, strict line-of-separation and stronger flock-to-flock sanitation practices. Those measures were reinforced by industry-wide surveillance and rapid reporting, which made it possible to detect and contain new cases quickly.

The combined impact of those strategies was powerful. By the early 2000s, subtype C was no longer circulating in commercial flocks. (1-2)

Today’s subtypes may be different, but the approach that worked then continues to shape how the industry responds now.

Vaccines: Where They Fit, and Don’t Fit (Yet)

Right now, there are no USDA-licensed vaccines for aMPV subtypes A or B in the U.S. However, a modified-live vaccine for subtype A has been granted import permit use and is currently being used only in turkeys. There are no vaccines available for subtype B at this time, and no vaccines approved for broilers or layers. (4, 5, 7)

This imported subtype A vaccine has helped some operations, but how it’s handled and applied makes a big difference. Maintaining proper temperature, mixing correctly and using precise spray or eye-drop techniques are key to achieving consistent protection. (4)

When coverage isn’t even across the flock, producers may see what the industry calls “rolling reactions.” That means some birds respond later than others, stretching out mild clinical signs and making it harder to get control of the break. Uneven coverage can also leave gaps in immunity, giving the virus room to keep moving.

Because vaccine tools are limited, especially for broilers and layers, biosecurity, early testing and secondary challenge management remain the backbone of prevention for most operations.

Important aMPV Vaccine Caveats: (7)

Current access is still turkey-focused. The rollout of modified-live aMPV vaccines has centered on turkey flocks, where the impact of the virus has been most severe. Broiler and layer operations currently don’t have licensed vaccine options.
Vaccine timing and application methods matter. Early field use of spray vaccination showed that the vaccine often didn’t effectively cycle until about three weeks of age, much later than expected. This timing gap meant many flocks showed signs of disease before full protection developed. To address this, vaccination programs have shifted toward hatchery gel application and adjusted boost schedules to improve coverage and consistency.
Vaccines alone aren’t enough, add aggressive temperature control. As field veterinarians have emphasized, vaccination is not a silver bullet. Management practices, especially aggressive temperature control, like increasing temperature by 10-15 degrees when clinical signs appear, remain critical for maintaining bird comfort and reducing mortality.
Field variability is real. Even with vaccination in place, many initial flocks vaccinated early in the rollout still showed clinical signs between the first and second doses, and some experienced significant mortality. This reinforces why it’s critical to manage vaccination timing carefully and layer multiple prevention strategies, not just rely on the vaccine alone.

Producer tip from our team: Optimize your spray programs by choreographing the vaccination application flow. Use two sprayers along the sidewalls and one “bird wrangler” to keep groups of birds bunched along the perimeter. This approach improves coverage of key areas, especially the eyes and nostrils, ensuring the vaccine reaches the surfaces that matter most.

“Guessing at aMPV Solutions” vs. Targeted Management

When vaccines aren’t an option (or are still being developed), reactive “try everything” approaches can get expensive fast. Ralco is seeing poultry producers experience better outcomes when complexes:

Stabilize the environment
- Tighten ventilation, reduce drafts and increase heat for birds with compromised airways and keep litter dry to reduce pathogen pressure.
- Whenever possible, implement disciplined windrow composting and heat up procedures between flocks. Again, research has shown that aMPV can remain active in litter for up to 30 days at cooler temperatures (around 46°F/8°C), making thorough heat-up an important step to reduce carryover between flocks. (8)
Shrink the secondary-infection window
- Support birds through the stress window with electrolyte water programs and tight sanitation. When secondary bacterial infections like E. coli start to move in, veterinarians may prescribe short, targeted antibiotic treatments to help stabilize the flock.
- Keep bacterial pressure down by tightening litter, water and dust management. Since most E. coli episodes are secondary infections, the goal is to make the environment less inviting for bacteria. That often means keeping litter dry, managing ventilation to limit humidity, flushing water lines regularly and controlling dust build-up that can carry pathogens. Small, consistent steps like these can make a big difference in reducing overall infection pressure.
Elevate biosecurity to muscle memory
- Personnel and equipment are the biggest everyday risk factors for moving pathogens between barns. Tighten control by limiting gate access, maintaining clear lines of separation, using Danish entries, changing boots at every entry point and disinfecting all equipment before it moves from one barn to another.
- Route planning: crews should follow clean to dirty movements. Workers start in the healthiest birds (young chicks or recently cleaned barns) and move toward older or potentially more exposed flocks. This reduces the risk of carrying viruses or bacteria backward.
Be proactive around known break points
- For broilers with day-28 risk, proactively implement waterline plans before anticipated breaks to avoid negative dops in production standards.
- For turkeys, schedule vaccination and management events so birds aren’t facing multiple respiratory stressors at once. Try to space out live respiratory vaccines, litter clean-outs or other major handling events by at least several days, giving birds time to recover before introducing another challenge. Coordinating this timing with your veterinarian or service tech can help reduce compounding stress and improve vaccine response.

How Ralco Can Help with aMPV

Strong management and the right support are key to staying ahead of aMPV and reducing the risk of secondary infections. Ralco’s natural, antibiotic-free solutions give poultry producers flexible tools to help birds stay strong before health challenges appear.

We recommend two key products:

Avi-Lyte is natural performance pack for the water that supports hydration and nutrient balance with electrolytes, vitamins and probiotics, helping birds maintain intake during stress events like respiratory pressure or environmental changes.
ProsperEO is a natural feed or water additive that helps strengthen immunity and maintain a balanced gut microflora. Used strategically, it can support gut health and overall resilience to stress.

These products are also OMRI-listed, making them ideal for both conventional and organic poultry operations.

Hear Updates on aMPV Right From the Ralco Poultry Team

Want to dig deeper or hear what’s happening directly in the field with aMPV? Tune in to our Wing it Wisely Spotify episode where the Ralco poultry team shares firsthand insights, practical management tips and what they’re seeing across the industry.

Listen to the aMPV episode on Spotify

Ralco's poultry team talking about aMPV on their podcast Wing it Wisely on Spotify.

Call 1-800-533-5306 to contact our Ralco poultry team for support and talk through your prevention program!

ProsperEO feed and water additive. natural poultry additive for a broad range of health challenges.

ProsperEO - Everyday Immunity & Health ProsperEO is an everyday natural feed or water additive to support a broad range of health challenges. It contains patented Microfused oregano, thyme white and cinnamon essential oils and Actifibe Prebiotic.