Avian metapneumovirus is proving to be a shape-shifter.
The viral disease, which has surged in the U.S. over the past year, is mostly a problem because it allows secondary bacterial infections to thrive.
The symptoms in birds, which range from swollen heads to death, don’t look the same in every house.
Poultry veterinarians discussed their experiences with the disease on Oct. 2 at the National Meeting on Poultry Health, Processing and Live Production presented by Delmarva Chicken Association.
Dr. Andy Bishop of Wayne-Sanderson Farms has seen broilers develop symptoms at 28 days or older.
Breeders can show signs any time after they begin producing eggs, with mortality most severe among birds 40 weeks and older, he said.
Metapneumovirus symptoms can resemble those of airsacculitis and bronchitis, but with a greater number of swollen heads.
In broiler breeders, the drop in egg production may be negligible — or as high as 6%. A spike in mortality has been Bishop’s biggest concern.
“It was a very variable presentation from one flock to the next,” said Bishop, who has worked in the broiler industry in several Southeastern states.
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.
“A lot of times that was just being attributed to other problems until you would maybe see some sinusitis,” said Scott, who has experience with both turkeys and layers.
Though swollen heads are a hallmark of metapneumovirus, they weren’t always common in the outbreaks Scott handled.
And while infections sometimes ripped through an entire complex, other times they were contained to one house, she said.
Heavy breeds in cage-free houses showed the most pronounced spikes in mortality and drops in egg production.
Multiple treatments were often needed to get the illness under control, Scott said.
Dr. Bob Owen of Best Veterinary Solutions, who works with two turkey companies in Pennsylvania and one in Utah, said diagnosis in turkeys is easy and starts at about 28 days.
“Our first clinical sign is a snick that I call a ‘student snick,’” he said. “It’s so noticeable even a student could pick it up.”
Dr. Eric Orozco of Butterball, who works with turkeys in North Carolina, said he sees the most challenges when turkeys are 6 to 12 weeks old.
Turkey breeders are most vulnerable around 30 weeks old, and often have neurological signs and production drops of 10% to 15%.
Orozco has seen metapneumovirus result in E. coli infections that were complicated to treat. For his first case, he initially suspected mycoplasma because the birds had swollen sinuses.
When responding to an outbreak in broilers, Bishop looks at ways to increase air movement through the house without chilling the birds.
He has had success treating birds with tetracycline, and he commonly doses the water with iodine, which loosens up congestion.
Orozco said his growers like the iodine treatment. He doesn’t have data to show that it works, but he suspects that it does.
For the past few months, he has used a disinfectant fogging.
This treatment needs to be done early, but it can decrease clinical signs.
“Even sometimes no breaks with E. coli, or if you have to treat for E. coli, it’s going to be a really easy case,” he said.
Owen mostly works with organic birds. Antibiotics aren’t an option for him, so he focuses on preventing the secondary infection.
Because organic birds have a high value, the farms Owen works with are careful to keep their water sanitation and ventilation systems in good shape.
He’s trained growers to call the technician the same day they observe the snick.
The tech then comes out to see if the air and water systems, litter or bird comfort need to be tweaked, and to start the birds on mucus-busting treatments.
Owen also treats with aspirin.
“I’m not sure whether I use it to make me feel better or the birds feel better,” he said.
At this point in his career, Owen isn’t sure he would prescribe antibiotics for metapneumovirus even if he could.
When the house systems are working right and the grower is prompt in reporting a problem, he has had few disasters.
Those tend to happen when a grower sees a snick and waits to call the tech until dead birds are piling up — often a delay of just a few days.
“By then, Katie bar the door. You know, it’s too late,” Owen said. “With the antibiotics that we have available to us today, even if we can treat (the birds) with it, it just doesn’t do us any good.”
If a live vaccine were available, the turkey vets said they would be interested in it.
On the broiler side, Bishop said such a vaccine would have a lot of appeal for pullets.
But Scott said metapneumovirus so far hasn’t taken a heavy enough toll for layer companies to justify the expense of a vaccine.
In the meantime, cold weather is returning and bringing ideal conditions for metapneumovirus.
Bishop and Orozco are pushing their farms to maintain a healthful environment, with proper sanitation in drinker lines and good litter management.
Owen is having posters put in feed rooms with a version of a saying attributed to football coach Vince Lombardi — “If you are five minutes early, you are already 10 minutes late.”
Early detection and response will be extremely important, especially until a vaccine is available, he said.
“We’ve just got to be ahead of it,” Owen said. “If we don’t, there’s going to be a lot of problems this winter.”
Source: Philip Gruber, Lancaster Farming
