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CHICAGO, March 16 (Reuters) - U.S. authorities are considering imposing tougher restrictions in Arkansas to contain a virulent strain of avian flu in the heart of America's poultry region in a bid to minimize international trade disruptions and contain the virus.
The H5N2 flu discovered in Arkansas last week is the state's first case of a strain that causes massive internal hemorrhaging in poultry, can kill nearly every bird in an infected flock within 48 hours, and is prone to mutate. Such strains are sometimes called "chicken Ebola."
In response, Arkansas is working with the U.S. Department of Agriculture (USDA) to create new rules for commercial poultry producers and owners of backyard flocks alike, Reuters has learned.
The rules will spell out how often poultry within a quarantine zone must test negative for bird flu before the quarantine can be lifted, Brandon Doss, Arkansas' assistant state veterinarian, said. Until the quarantine is lifted, no poultry within 10 km (6 miles) around the farm that was infected with bird flu can move in or out of the area.
The rules being revised were previously used to deal with less deadly strains of the bird flu in Arkansas.
U.S. authorities are seeking to reassure major buyers of U.S. chicken, such as Mexico, which imposed new import restrictions last week. The export market for companies like Tyson Foods Inc and JBS SA unit Pilgrim's Pride Corp is worth $5.7 billion annually.
Already, Arkansas has established a quarantine zone around a farm infected with H5N2 and ordered a 24-hour guard to monitor trucks and people entering and leaving the site and block unauthorized access.
"In all likelihood it will be our largest response effort to date," Doss said. Arkansas has 42 commercial operations and at least two dozen backyard flocks to monitor within its quarantine zone.
Other states with recent H5N2 cases, including Minnesota and Missouri, have also established quarantine zones around infected farms and are testing nearby flocks in line with existing U.S. requirements.
Kansas last week imposed a quarantine in two counties even before a case of the flu was confirmed on Friday. They took action because of worry about an infection in neighboring Missouri.
But it is the Arkansas infection, in particular, that is causing concern among poultry producers and investors in chicken companies like Tyson and Sanderson Farms Inc, because the state is among the top chicken and turkey producers and is near other major poultry states like Mississippi and Alabama.
Arkansas poultry have previously suffered from milder cases of low pathogenic avian flu, which can cause reduced egg production and respiratory difficulties, among other symptoms. During those outbreaks, flocks needed to test negative for the virus in a minimum of two tests administered 10 days apart before quarantines were lifted, Doss said.
For the more deadly strain discovered last week, "we have not set that time frame or that protocol yet," he said. "It is still in development with USDA."
It is not known whether states other than Arkansas are working with the USDA on new surveillance protocols.
Butterball LLC, the largest U.S. producer of turkey products, contracts to buy birds from the Arkansas farm infected with the virus.
Arkansas livestock inspectors, divided into six teams of two people, are going door-to-door to nearly 1,900 properties within the quarantine zone to search for backyard flocks that could potentially be infected, Doss said.
As of late on Friday, they had visited 256 properties and identified 24 with backyard flocks. All will be subject to the new protocols under discussion by the USDA and the state. (Reporting by Tom Polansek, editing by Ross Colvin)