More than 17 million poultry have died by disease or depopulation in this year’s U.S. outbreaks of highly pathogenic avian influenza.
About 14.4 million of those birds were chickens, 1.7 million were turkeys, and the rest were a mix of commercial birds not identified by species in data from the U.S. Department of Agriculture Animal and Plant Health Inspection Service. The agency also has cataloged about 480 confirmed infections in 31 types of wild birds as well as more than 40 outbreaks among backyard birds.
The disease also has been widespread, reaching wild and domestic birds in at least 30 states. The infections in commercial flocks alone have been spread across 12 states: Delaware, Indiana, Iowa, Kentucky, Maryland, Minnesota, Missouri, Nebraska, New York, North Carolina, South Dakota, and Wisconsin.
About 480 wild birds, including more than 100 mallards, that were tested in U.S. disease surveillance programs this year have had confirmed infections with highly pathogenic avian influenza. The virus has killed more than 17 million poultry, mostly chickens.
Watching for incursion
Dr. Louise Dufour-Zavala, executive director of the Georgia Poultry Laboratory Network and president of the American Association of Avian Pathologists, said the H5N1 influenza strain circulating in the U.S. this spring is a descendant of a Eurasian strain that has been circulating in Asia for several years as well as in mainland Europe and the United Kingdom for more than a year. The strain in the U.S. is highly contagious and transmissible, and it seems to easily infect chickens.
This strain also is unusually prevalent in waterfowl, she said. About 20% of wild waterfowl tested in surveillance have been positive for the strain, whereas 1% would be typical.
As with past influenza incursions, most of the infections in wild waterfowl have been asymptomatic, Dr. Dufour-Zavala said. But she noted that this strain has been associated with clinical signs of illness in gulls in Canada and a die-off of ducks in Florida, and she noted it was unusual that bald eagles have been among the birds affected—12 of them, according to APHIS data.
Dr. Kate Barger-Weathers, director of animal welfare for poultry breeding company Cobb-Vantress and AAAP representative to the AVMA House of Delegates, said AAAP members across poultry companies, poultry-related industries, and government agencies have been sharing risk information and strengthening their biosecurity measures. Members also have been monitoring the incidence of HPAI infections in poultry flocks and wild birds on the other side of the Atlantic Ocean in anticipation of arrival of the virus in North American flyways.
The heightened biosecurity by Dr. Barger-Weathers’ company at poultry barns, for example, has included limiting entry to essential personnel and increasing the intervals between visits by some personnel. She said it’s also important to make sure farmers, animal caretakers, and even any maintenance or utility workers arriving on a farm hear why the farm is taking precautions, how they can protect the flocks, and why they should avoid contact with any other bird species.
Dr. Dufour-Zavala said it’s also critical that anyone who sees clinical signs of illness or changes in behavior in domesticated birds immediately report those changes to animal health authorities and start the process of testing for influenza. Stamping out the virus requires identifying the first cases, she said.
Dr. Barger-Weathers said a turkey farmer in Indiana, for example, helped identify infections in a flock earlier this year by noticing the birds were drinking less water and realizing that was a possible sign of illness.
Dr. Dufour-Zavala said it’s believed avian influenza most often enters poultry barns on workers’ footwear.
Following the 2014-15 HPAI outbreaks in the U.S. that killed an estimated 50 million birds—again, mostly chickens—the poultry industry added biosecurity standards to the National Poultry Improvement Plan with the intent of creating more barriers between the viruses outside a barn and the poultry inside. Dr. Dufour-Zavala said the response created lines of separation where companies might make workers and visitors don protective gear, change into barn use–only clothing, and disinfect boots and equipment.
The standards also include provisions on controlling rodents as well as ensuring poultry are not drinking water drawn from surface bodies. Since the standards were implemented, farms have seen declines in incidences of other poultry diseases, and the standards should help prevent incursions of avian influenza, Dr. Dufour-Zavala said.
Dr. Barger-Weathers said the AAAP has encouraged veterinarians who work with backyard or mixed poultry flocks to help clients take similar steps, such as limiting contact between owned birds, limiting the flock’s contact with surface waters and waterfowl, and selecting dedicated shoes or boots to wear only when around the flock.Click here to see more...