HARRISBURG, Pa. -- A strain of avian influenza that contaminated chickens in east-central Pennsylvania and caused agriculture officials to order the gassing of 135,000 birds appears to have been contained, but poultry farmers say it's too early to let their guard down.
The disease, which also affects turkeys, ducks and geese, can be spread bird-to-bird, and though most strains do not make humans sick, humans can pass the disease to birds. It can also be carried by trucks or equipment exposed to infected fowl.
The virus first appeared in early December in two flocks in Union County, then spread rapidly to four other flocks nearby.
State agriculture officials said Tuesday that testing in two additional flocks -- one in Union County and one in Juniata County -- led them to order quarantines at those farms, though they will not know for sure whether those birds have the same disease until they get final test results back in about 10 days.
The original six Union County farms affected remain quarantined, and state officials are still advising Pennsylvania's nearly 6,000 large-scale poultry farmers to limit access to flocks and disinfect trucks or equipment used on farms other than their own.
Poultry farmers and others linked to the $634 million-a-year industry -- the nation's sixth-largest -- said they can't relax yet. They recall a 1982-83 outbreak, when a more powerful strain of the virus wiped out 16 million chickens and cost about $100 million.
"We're holding our breath," said John Fidler of Pennfield Corp., which sends feed trucks to farms within a 10-mile radius of the infected ones.
"We try to impose procedures to minimize the possibility that we contribute to the spread," Fidler said. Pennfield and other poultry companies are now routinely disinfecting feed trucks and ordering drivers to wear disposable coveralls and boot covers when making deliveries to farms affected by the virus.
Farmers who were ordered to destroy flocks are eligible for reimbursement of up to 66 percent of the value of each bird. The total value of the destroyed chickens is estimated at about $120,000, said John Enck, the state veterinarian.
Although any outbreak of avian influenza should be taken seriously, the virus in Union County is less likely to be fatal to birds than other strains, said Ed Curlett, a spokesman for the U.S. Animal and Plant Health Inspection Service. As a result, no countries have banned imports of Pennsylvania fowl, although China banned poultry from Connecticut recently after the virus turned up in a flock there.
If the Union County problem had not been quickly identified, the disease could have spread and mutated into a more lethal strain, which is what happened in 1982-83, said R. Michael Hulet, a poultry science professor at Penn State University.