Poultry farms in Virginia's Shenandoah Valley are in the grip of an avian influenza outbreak that has led to the culling of more than four million turkeys and chickens and, as of press time in June, showed no sign of letting up.
Since the virus was first detected in a flock of ill breeder turkeys this past March in Rockingham County near the West Virginia border, infections have been reported at farms in neighboring Shenandoah, Augusta, Page, Greene, and Highland counties. An estimated 167 poultry farms are still quarantined, with 18,700 birds scheduled for depopulation on two of them.
Early in the outbreak, the U.S. Department of Agriculture, at the request of the state, dispatched a team of veterinarians, epidemiologists, and logistic staff to assist with depopulation, surveillance, and decontamination. Although a federal emergency has not been declared, members of AVMA/AVMF Veterinary Medical Assistance Team-4 have helped with these efforts.
Poultry is one of Virginia's most valuable agricultural commodities. Virginia is home to more than 1,300 poultry farms. Nationwide, it ranks fourth and eighth in turkey and broiler chicken production, respectively. The poultry industry provides billions of dollars to Virginia's economy and employs more than 12,000 people.
The estimated 950 poultry farms located in the Shenandoah Valley make it the leading poultry-producing region of the state. Rockingham County leads the nation in turkey production with 213 farms. Most of the poultry operations in the valley are family-owned farms that have contracted with such companies as Pilgrim's Pride, Perdue Farms, and Tyson Foods.
The last avian influenza epornitic in Virginia in 1983-1984 cost farmers around two million birds. The current outbreak dwarfs those figures. And with infections discovered in an average of two to three new flocks every day, state officials are too busy trying to contain the virus to even begin assessing the economic toll.
"Unfortunately, we don't have a sense yet that it's hit the peak," said Elaine Lidholm of the Virginia Department of Agriculture and Consumer Services about the outbreak in May. "Right now, everybody is so busy in the trenches that they aren't necessarily sitting down to do the calculations of what this is costing us. It's just too soon to tell."
Governor Mark R. Warner, along with Virginia's congressional delegation, has asked Agriculture Secretary Ann Veneman to initiate a federal indemnification program to aid farmers and companies that have had to destroy thousands of birds.
"That's critical to our recovery here, and we're very hopeful it will be forthcoming," said Hobey Bauhan, president of the Virginia Poultry Federation, a trade association representing the Virginia poultry industry.
Dr. William Sims, state veterinarian with the agriculture and consumer services department, canceled all public sales and poultry shows throughout Virginia indefinitely to halt the spread of the virus. Biosecurity at all the poultry farms has been stepped up considerably. Visits are prohibited unless absolutely necessary.
Numerous avian influenza viruses exist worldwide. The viruses infect chickens, turkeys, pheasants, geese, duck, and a variety of other birds. Some low-pathogenic forms are not very contagious and cause mild disease with little or no mortality. Highly pathogenic strains are highly contagious and result in death. A unique avian influenza strain in Hong Kong infected humans and birds in 1997 (see JAVMA, Feb. 1, 1998, page 331).
The viruses are spread by contact between healthy and infected birds, and through indirect contact with contaminated equipment and materials. Signs of infection include depression, coughing and sneezing, watery eyes, loss of appetite, edema of the head, and decreased egg production.
The low-pathogenic H7N2 avian influenza strain has been identified at the Virginia farms and is not a threat to human health, according to Lidholm.
The number of birds at any given farm varies but can range from 8,000 to 25,000 birds, depending on the type of operation and the number of houses. Commercial turkey farms can reach as high as 40,000 birds.
The types of operations where the avian influenza virus has been detected so far are turkey breeders, commercial turkeys, broilers, broiler breeders, and layers. Turkeys are hit the hardest, with 146 turkey farms affected, compared with 10 broiler, 25 broiler breeder, and one layer operation.
State officials are not sure how the H7N2 strain was introduced to the Shenandoah Valley. Theories range from infected wild birds to ill poultry imported from New York and New Jersey, where the virus is active. There is no indication this latest epornitic started with the breeder turkeys in Rockingham County, however.
Virginia is considered progressive in its surveillance for avian influenza, according to Bauhan of the poultry federation. Flocks are routinely tested for avian influenza prior to slaughter. There is some serologic testing but the majority is done by tracheal swab. A single case of avian influenza was discovered in 1999 and an outbreak was averted.
Now, the agriculture and consumer services department has implemented a mandatory preslaughter testing policy for all breeder birds, commercial turkeys, and broilers, including required testing of any flocks with respiratory signs.
Samples are divided among the USDA's National Veterinary Services Laboratories in Ames, Iowa, and several regional veterinary diagnostic laboratories.
Farms with a flock that tests positive for the virus are quarantined and the poultry company is responsible for destroying the birds within 24 hours. Carbon monoxide is the most common means of euthanasia.
On-farm burial or composting of carcasses is allowed with a permit from the state Department of Environmental Quality. Other accepted disposal methods are incineration and burial at a sanitary landfill. Bauhan says disposal costs alone are already several million dollars.