Preventive Ounce: Bird-flu checks keep flocks safe
Testing Central: Tyson's Wilkesboro labs on front line of watch for avian-influenza
Saturday, June 17, 2006
By Monte Mitchell
WILKESBORO - Small vials of chicken-blood serum arrive by the thousands each week in FedEx and UPS deliveries to a brick building along U.S. 268.
Seven days a week, workers at the Tyson Foods laboratory conduct screening tests for avian influenza.
There are many types of bird flu, but the issue is getting worldwide attention because of a particular strain, the Asian avian influenza A (H5N1). The World Health Organization says that this strain of the Asian bird flu has killed 129 people since 2003, mostly in Indonesia and Vietnam.
This type of flu has never been detected in North America. According to the Centers for Disease Control and Prevention, the spread of the disease from person to person is rare. Properly cooked chicken is safe to eat, even if it came from an infected bird.
The disease has spread to parts of Europe and Africa, and continues to pose an important and growing public health threat, the CDC says.
Tyson, as other poultry companies, has increased its testing for bird flu.
Every Tyson flock is tested before it leaves the farm. A negative test for avian influenza is required before the chickens can be loaded onto a truck for a trip to the processing plant. A flock would be destroyed and other biomedical safety steps taken if bird flu were ever found.
Tyson conducts 15,000 tests a week for avian influenza, about five times the number the company was conducting a year ago. Most of the companywide testing is done at the Wilkesboro lab already, and the lab will soon do all the company's bird-flu testing for processing operations in 12 states.
"We were doing it before it was popular," said Leonard Brooks, the supervisor for the serology lab, talking about how Tyson has been testing for bird flu for decades. He has worked in the Wilkesboro lab for 40 years, with Holly Farms and then with Tyson. "We did a lot of this stuff before anybody ever thought about it," he said.
A bird-flu outbreak has never been associated with the Tyson Foods complex in Wilkesboro, but public perception is especially important in a county whose plant produces more pounds of chicken meat than any other Tyson processing plant in the nation. Tyson is the biggest employer in Wilkes County. The 91 million broiler chickens grown in Wilkes in 2004 made it the top county in North Carolina for broilers, according to the most recent statewide statistics released by the N.C. Department of Agriculture.
The increased company tests are one step in a line of defense designed to protect people and the chicken supply.
The state agriculture department also has an extensive program that has tested more than 200,000 birds from state poultry flocks in the past year.
Earlier this year, Tyson joined other chicken companies in a comprehensive testing program, announced by the National Chicken Council, the industry's trade association. The companies use procedures approved by the National Poultry Improvement Plan, a federal and state cooperative program. Because of the increased emphasis on the testing, Tyson has renovated a storage room to create more lab space for the avian-influenza tests.
The enclosed, climate-controlled chicken houses of Wilkes and surrounding counties represent a big difference in how chickens are raised, compared to the areas where the Asian bird-flu outbreaks have occurred. For instance, it's not uncommon for chickens in Asia to live closely with humans, wandering through a family's living areas.
Tyson growers here have bio-security measures in place - for example, they step into disinfectant baths before entering the house. They are also required to limit who enters a farm.
Chicken houses vary in size, but it's not unusual for a single broiler house to have 6,000 chickens that live together six to eight weeks. The flocks are raised together in "all-in, all-out" farming, isolating a particular flock to limit its exposure to outside birds and make it possible to trace a flock back to a farm.
Within 10 days of an anticipated slaughter date for the broilers, a service worker will go into the mass of squawking chickens in each house. The worker picks out several birds. In each, he'll do a wing stab to puncture a wing vein and collect two to three cubic centimeters of blood.
Because the bird-flu virus would move rapidly through a flock, a sample of birds is sufficient to see if any of the birds have been exposed to the virus.
Tyson workers deliver local samples to the Wilkesboro lab, which has an advanced international accreditation that requires audits and constant checks.
"Because of that, we have a tremendous quality standard in place," said Beverly Prevette, an associate chemist.
Samples from locally raised birds arrive in vials of whole blood. The vials that are shipped in from other regions contain only blood serum, a yellowish fluid that is separated from a blood clot after coagulation.
Lab workers conduct a basic scientific procedure called the Agar Gel Immunodiffusion Test to check for antibodies that would be produced in the presence of the virus. The test uses petri dishes filled with a clear gel. Workers use a manual hole-punch machine to create seven clusters of seven small wells in the gel. The middle well in each cluster holds an antigen - that's the substance a body reacts to by producing antibodies. A worker uses a pipette to put blood-serum samples into three of the surrounding wells, and the other three wells are filled with positive reference samples.
With three blood samples going into each of the seven clusters, each petri dish can test 21 birds. Each petri dish is labeled with the flock information, and then stored. The liquid from the samples diffuses through the gel. After 24 hours, a lab worker takes the petri dish into a darkened room and looks at it under a high-intensity light.
The worker looks for a thin white line that would appear if the antibodies try to link up to fight the virus. If workers ever do find a positive test, written instructions tell them who to call and what steps to take. The lab is screening for bird flu, and would send the sample to another lab for tests to determine the specific strain of flu
"We've already got procedures in place, what to do, sort of like a fire drill," said Chy Billings II, whose duties include being the lab's safety officer.
The lab building contains many testing rooms for other things besides bird flu. The more than 30 lab workers test chickens for pesticides, they test feed to make sure it provides adequate nutrition, and they analyze meat products being shipped to fast-food restaurants. The lab regularly monitors and tests breeder birds, checking to make sure they pass on maternal antibodies to chicks.
"We found out many years ago that preventative medicine is much better than curative medicine," Brooks said.
• Monte Mitchell can be reached in Wilkesboro at 336-667-5691 or at firstname.lastname@example.org
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