AI threat re-emerges as outbreaks reported in U.S.

 Penn State University
Thursday, 30 March 2017
By Penn State University
March 30, 2017, University Park, PA — Poultry and animal disease experts in Penn State's College of Agricultural Sciences are urging commercial poultry producers to ramp up their vigilance and biosecurity in the wake of recent outbreaks of avian influenza in several states.

In early March, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS) announced that a commercial flock of breeder chickens in Tennessee tested positive for highly pathogenic avian flu, or HPAI. Since then, USDA-APHIS has revealed another case of the same H7N9 virus at a second Tennessee farm, and Alabama agriculture officials announced an outbreak of suspected low-pathogenic avian flu affecting three premises in that state.

In addition, low-pathogenic avian flu was reported in a Wisconsin turkey flock and a Kentucky broiler breeder flock, and routine surveillance has found the presence of low-pathogenic avian flu in wild waterfowl in various states.

The pathogenicity of a virus refers to its ability to produce disease. Some H5 or H7 viruses have the capacity to mutate into "high-path" strains under certain conditions, according to Eva Wallner-Pendleton, senior research associate and avian pathologist in Penn State's Animal Diagnostic Laboratory.

"Low-path AI viruses can go undiagnosed because they often produce very little illness or death," she said. "The time needed to mutate into high-path viruses varies considerably from weeks to months, or it can occur rapidly."

Infection with North American strains of low-pathogenic avian flu is a common natural occurrence in wild birds, such as ducks and geese, which usually show few or no symptoms, Wallner-Pendleton explained.

"But if these strains get into a poultry flock, they can mutate and become highly pathogenic, causing significant mortality," she said.

She noted that poultry flocks infected with low-pathogenic H5 or H7 avian flu subtypes often will be culled to stop the spread of the virus and to keep it from becoming more virulent.

The recent Tennessee outbreak occurred within the Mississippi flyway, which is one of four paths taken by wild birds when migrating in the spring and fall in North America. During the 2014-15 outbreak of highly pathogenic H5N2 avian flu that led to the loss of about 50 million turkeys and laying hens in the Midwest, the Atlantic flyway – which connects with the Mississippi flyway – was the only migratory flyway not affected.

"In Tennessee, one of the affected poultry houses was near a pond, which may have attracted wild waterfowl," Wallner-Pendleton said. "In cool, wet weather, bird droppings can contain viable virus for a long time, and the pathogen can be spread to poultry flocks on people's shoes or on vehicle tires and so forth. So a key biosecurity recommendation is to prevent any contact between waterfowl and domestic poultry and to take steps to ensure that the virus is not introduced into a poultry house on clothing or equipment."

Gregory Martin, a Penn State Extension poultry science educator based in Lancaster County, pointed out that state and federal agriculture officials are strongly urge producers to develop an HPAI flock plan and augment it with a comprehensive biosecurity plan.

"These plans may be required for producers to receive indemnification for any losses resulting from an avian flu outbreak," he said.

To assist producers in developing a biosecurity plan, Martin said, Penn State poultry scientists and veterinarians have developed a plan template that can be customized for various types of flocks.

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