2nd bird flu outbreak hits Tennessee
Asecond outbreak of bird flu has been identified in Middle Tennessee as the state veterinarian confirmed a flock of chickens at a commercial poultry breeding operation in Giles County tested positive for low pathogenic avian influenza.
However, the company that operates the breeding operation is a different business from the one associated with the recent detection of highly pathogenic avian influenza in nearby Lincoln County, officials said Thursday. At this time, officials do not believe one premises sickened the other.
On Monday, routine screening tests at the premises in Giles County, just west of Lincoln County, indicated the presence of avian influenza in the flock. State and federal laboratories confirmed the existence of H7N9 low pathogenic avian influenza in tested samples.
“This is why we test and monitor for avian influenza,” State Veterinarian Dr. Charles Hatcher said. “When routine testing showed a problem at this facility, the operators immediately took action and notified our lab. That fast response is critical to stopping the spread of this virus.”
As a precaution, the affected flock was depopulated and has been buried, and the premises is under quarantine, officials said. Domesticated poultry within a 6.2-mile radius of the site are also under quarantine and are being tested and monitored for illness, they said.
To date, all additional samples have tested negative for avian influenza and no other flocks within the area have shown signs of illness, according to officials.
The farm in Lincoln County, which is located just outside Fayetteville, produces chickens for Tyson Foods. It was ordered to cull its flock after federal officials last Sunday identified the outbreak, the first time the disease
As a precaution, the affected flock was depopulated and has been buried, and the premises is under quarantine, officials said.
has struck this year.
Some 73,500 birds had to be culled over the weekend at the farm, an operation raising so-called breeder birds, which lay the eggs that become chickens for meat.
The primary difference between the flu strains is the mortality rate in domesticated poultry, officials said. A slight change to the viral structure can make a virus deadly for birds.
Avian influenza virus strains often occur naturally in wild migratory birds without causing illness in those birds. With low pathogenic avian influenza (LPAI), domesticated chickens and turkeys may show little or no signs of illness. However, high pathogenic avian influenza (HPAI) is often fatal for domesticated poultry.
The Giles County LPAI incident is similar to the Lincoln County HPAI incident in that both the low pathogenic and highly pathogenic viruses are an H7N9 strain of avian influenza, according to officials.
The U.S. Department of Agriculture’s National Veterinary Services Laboratories confirmed the H7N9 virus that affected the Lincoln County premises is of North American wild bird lineage. It is not the same as the China H7N9 virus affecting Asia and is genetically distinct, according to officials.
The Lincoln County premises affected by HPAI remains under quarantine, officials said. To date, all additional poultry samples from the area surrounding that site have tested negative for avian influenza and no other flocks within the area have shown signs of illness. Testing and monitoring continues, according to officials.
THE 2015 OUTBREAK
The latest bird flu incidents are far less than two years ago when the USDA reported the largest animal health emergency in U.S. history from the 2015 bird flu outbreak. It cost farmers nearly 50 million birds before it burned out in June 2015. Iowa, the country’s top egg producer, and Minnesota, the No. 1 turkey producer, were by far the hardest hit.
Retail turkey prices weren’t noticeably affected, but egg prices soared. Congressional testimony as the dust was starting to settle conservatively estimated the total economic impact at over $3.3 billion.
HIGH PATH VERSUS LOW PATH
The first symptom of highly pathogenic bird flu, the kind that’s almost always fatal to domestic poultry, is typically birds dying en masse. Scientists learned in 2015 that it’s crucial to euthanize entire infected flocks immediately.
“You want a very rapid response and a very rapid stamping out. … The faster the birds die, the faster the outbreak stops,” said Dr. Carol Cardona, a poultry disease expert at the University of Minnesota.
Low pathogenic is more common. Symptoms are typically mild, if any. Infected birds usually recover.
While response plans differ from state to state, a common and effective approach is “controlled marketing.” Infected flocks are not euthanized but are kept quarantined until they recover and test negative for the virus, and then they can be marketed, Cardona said.
FARMERS’ RESPONSE
U.S. producers have stepped up biosecurity in response to the new cases, as well the ongoing outbreaks in Asia, Europe and Africa that have led to the destruction of hundreds of millions of birds and killed dozens of humans. Bird flu viruses don’t usually spread to people except by close contact with infected birds, but health authorities are always alert to the possibility.
Since wild waterfowl are considered the main reservoirs of bird flu, farmers and scientists get nervous when birds are migrating. Droppings from infected birds flying north in the spring, or south in the fall, can get tracked into barns or carried in on contaminated equipment. So producers are being more vigilant about keeping people and vehicles from entering their farms unless they absolutely need to be there.
“They understand this is a high-risk period with the spring migration period, so they’re watching their flocks closely and doing additional surveillance to make sure that if anything pops up, they’re going to identify it quickly,” said Dr. Shauna Voss, senior veterinarian at the Minnesota Poultry Testing Laboratory in Willmar.
Since 2015, many farmers have built the “Danish entry” system into their barns, said Steve Olson, executive director of the Minnesota Turkey Growers Association. Anyone entering or leaving has to sit on a bench, take their boots off, swing their legs around to the “clean” side of the room, put on new boots and clothing that stay in the barn, and reverse the process when they leave.
WHAT ABOUT VACCINES?
Bird flu viruses keep evolving, like human influenza viruses, so a vaccine that works against one strain might be ineffective against another. While an H5N2 vaccine was developed in 2015, it was never deployed in the field. Producers are wary of vaccines because many countries refuse poultry products from countries that use vaccines. That is because tests for the disease look for the same antibodies that vaccines trigger an animal to produce.