U.S. agriculture authorities warn that poultry stocks located along a migratory route between Montana and Texas called the Central Flyway are increasingly more susceptible to contracting a new strain of bird flu.
Virologist Hon Ip of the U.S. Geological Survey (USGS) says the latest influenza strain, known as H5N2, is the result of having multiple bird species in various locations swapping genetic material, leading to several new strains in the process. He says H5N2 is well adapted for transmission among wild birds and poultry stocks and is highly pathogenic, which means it is very potent in producing disease in birds. Authorities, however, believe the risk of infection in humans is low.
"It does represent a higher risk for Texas," said Ip. "There have not been a large number of wild birds that tested positive in the Central Flyway, but that may just represent a low number of birds tested rather than the absence of the virus."
The strain has been found in a mixed-poultry flock in Judith Basin County in Montana and a commercial turkey flock in Beadle County in South Dakota. The Columbus Dispatch reports that this particular strain was identified by the U.S. Department of Agriculture and has spread among turkey and mixed-poultry flocks in the West Coast to Texas, Idaho, Kansas, Missouri, and Minnesota.
The most previous outbreaks were due to a highly pathogenic strain that developed from a mix of a Eurasian strain and a North American strain and quickly affected domestic poultry flocks.
"What's different now is the virus is present in multiple wild bird species, potentially in multiple flyways," Ip said. "There is more opportunity for people tracking that virus into their facility."
Influenza strains are more often transmitted indirectly rather than directly. Ip says species can contract the virus by some form of indirect contact with other species carrying H5N2, such as through bird droppings on the grass, on the roadway, or near a pond located close to the flock.
Dr. Nancy Cox, previously of the Centers for Disease Control and Prevention (CDC), says bird flu from wild migratory birds are very uncommon, and no recent cases of humans infected with any of the strains have been reported, although she says "it is possible that there will be an isolated human case or two" as more humans come in contact with infected birds.
The Texas Animal Health Commission has begun imposing tighter controls and veterinary inspections for poultry entering the state. Other recommendations include anyone who might come in contact with wild birds must change their clothes and footwear when handling other birds. Authorities also say poultry workers must isolate domestic flocks from wild birds and quarantine birds taken to events such as trade fairs and industry shows for 21 days.
