The outlook is looking much brighter for the bird flu that devastated flocks in 21 Midwest and West Coast states this year, but a team of Penn State poultry experts warns the battle might not be entirely won.
The highly pathogenic strain of the H5 avian flu emerged in wild, captive and commercial flocks in early 2015. To preserve healthy bird populations, the U.S. Department of Agriculture killed an unprecedented 48 million birds since the virus first reached the U.S.
After outbreaks began to subside in the late spring as warmer weather set in, experts predicted the virus could return. In the fall, cooler weather and migrating waterfowl provide a natural reservoir for the less infectious strains of the disease, which can mutate into deadly forms in commercial chickens.
However, according to the USDA, it has not found any outbreaks of the highly pathogenic avian influenza since June, despite southward waterfowl migration coming to its end. As a result, the bans that some states placed on poultry exhibitions and bird gatherings starting at the height of the outbreaks have since been lifted.
Minnesota announced Dec. 15 it had dropped its ban in light of lifting the last of the quarantines placed on the 108 farms infected with HPAI in 2015. With no new confirmed cases of HPAI, many states, including Ohio, lifted their bans months ahead of schedule.
“The outbreaks in June were contained because of all the efforts put in place to make sure it didn’t move around anymore,” said Patricia Dunn, an avian pathologist at Penn State.
In addition to the many statewide bans among affected states and other measures on behalf of the USDA, including increased biosecurity, the virus stayed contained to the Central, Mississippi and Pacific migratory flyways, according to the USDA.
Experts had expected the HPAI virus to reach the Atlantic Flyway in the summer when waterfowl began migrating north for the breeding season. But, Dunn said her team and other researchers have found no evidence of HPAI in the resident wild poultry populations in the Atlantic Flyway, which is a good thing for chicken and turkey farmers in Centre County.
However, the avian influenza could still reach the flyway sometime in the next four years.
“Not all the birds have intermingled on the different flyways,” Dunn said. “It takes almost four to five years for a new strain to infect a large number of wild waterfowl.”
According to the USDA, the decrease in outbreaks the country saw starting in June was a result of summer heat. Warm weather helps quell the virus, Dunn said, so it begs the question whether the warm fall weather is temporarily subduing it.
“It’s probably a couple thing.” said Dunn. “The waterfowl are at the end of the migrating season; the warm weather and all the efforts to clean up the virus on farms,” said Dunn.
The virus strains that some waterfowl might carry with them as they migrate north again in the late winter could interact with other subtypes of the virus, which could lead to HPAI outbreaks in commercial populations, according to a Dec. 18 press release.
Dr. John Takekawa, Audubon’s director of bird conservation, said the combination of winter weather and waterfowl migrating north is a breeding ground for a virulent virus.
If there is an outbreak this year, Takekawa said he predicts to see it in the winter or spring. He said the strength of that outbreak and locations of the outbreak are hard to predict because so much is still unknown about bird migration.
Takekawa encourages farmers to stay on the lookout for any increased deaths among their flocks, which might indicate the presence of infection. Farmers should also follow good biosecurity practices and keep their flocks away from wild waterfowl.
Takekawa said, “Hopefully it was stamped out last year, but if it does come back, hopefully people are alert to the possibility.”
