Global Flyways – Credit FAO
As regular readers of this blog already know, Europe is embroiled in their 3rd major avian epizootic of the past 5 years (see DEFRA: Highly pathogenic avian influenza (HPAI) in the UK, and Europe (Update #8)) - driven primarily by the Eurasian HPAI H5N1 clade 18.104.22.168b virus - spread primarily by migratory birds.
While mainly a threat to wild birds, poultry, and captive birds, this Eurasian lineage of HPAI H5Nx has recently been linked to increased mammalian infections (see Netherlands: WBVR Diagnoses Avian H5N1 In Another Fox), and sporadic, and thus far mild, human infections (see UKHSA Statement On Human H5 Infection In England).
These Eurasian HPAI H5Nx viruses - while sharing the same subtype as their more pathogenic Asian counterparts (H5N1, H5N6) - are from a different lineage, and have not shown anywhere near the same level of pathogenicity in humans as their more famous cousins.
Although North America is normally protected against the incursion of infected migratory birds from both Europe and Asia by vast oceans, we have seen evidence that - on rare occasions - long distance flyers have made the journal.
In late 2014, (see EID Journal: Novel Eurasian HPAI A H5 Viruses in Wild Birds – Washington, USA), an earlier version of the virus currently plaguing Europe arrived in North America, presumably crossing the the Northern Pacific into Alaska, then making its way south through Canada to the Pacific Northwest.
This unfortunate arrival sparked North America's the largest Avian Epizootic on record, eventually impacting 15 U.S. states and several provinces in Canada (see map below).
While involving longer distances, the same scenario has long been believed possible from European migratory birds (see 2014's PLoS One: North Atlantic Flyways Provide Opportunities For Spread Of Avian Influenza Viruses), and three weeks ago we saw multiple reports of Eurasian HPAI H5 in Newfoundland and Labrador (see Update: More Reports of HPAI H5N1 in Eastern Canada), presumably brought in by migratory birds.
Published: Jan 14, 2022
WASHINGTON, January 14, 2022 – The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed highly pathogenic Eurasian H5 avian influenza (HPAI) in a wild American wigeon in Colleton County, South Carolina.
Eurasian H5 HPAI has not been detected in a wild bird in the United States since 2016. There was a case of HPAI (H7N3) in one commercial meat turkey flock in South Carolina in 2020 due to a North American lineage virus.
The Centers for Disease Control and Prevention considers the risk to the general public from HPAI H5 infections to be low. No human infections with Eurasian H5 viruses have occurred in the United States. As a reminder, the proper handling and cooking of poultry and eggs to an internal temperature of 165˚F kills bacteria and viruses, including HPAI.
Anyone involved with poultry production from the small backyard to the large commercial producer should review their biosecurity activities to assure the health of their birds. APHIS has materials about biosecurity, including videos, checklists, and a toolkit available at https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/defend-the-flock-program/dtf-resources/dtf-resources
The United States has the strongest AI surveillance program in the world, and USDA is working with its partners to actively look for the disease in commercial poultry operations, live bird markets, and in migratory wild bird populations. APHIS Wildlife Services collected the sample from the hunter-harvested American wigeon, and it was initially tested at the Clemson Veterinary Diagnostic Center (a member of the National Animal Health Laboratory Network). The presumptive positive samples were then sent to APHIS’ National Veterinary Services Laboratories (NVSL) for confirmatory testing.
Since wild birds can be infected with these viruses without appearing sick, people should minimize direct contact with wild birds by using gloves. If contact occurs, wash your hands with soap and water, and change clothing before having any contact with healthy domestic poultry and birds. Hunters should dress game birds in the field whenever possible and practice good biosecurity to prevent any potential disease spread. Biosecurity information is available at: https://www.aphis.usda.gov/publications/animal_health/2015/fsc_hpai_hunters.pdf.
In addition to practicing good biosecurity, all bird owners should prevent contact between their birds and wild birds and report sick birds or unusual bird deaths to State/Federal officials, either through their state veterinarian or through USDA’s toll-free number at 1-866-536-7593. Additional information on biosecurity for backyard flocks can be found at http://healthybirds.aphis.usda.gov.
Avian influenza (AI) is caused by an influenza type A virus which can infect poultry (such as chickens, turkeys, pheasants, quail, domestic ducks, geese, and guinea fowl) and is carried by free flying waterfowl such as ducks, geese and shorebirds. AI viruses are classified by a combination of two groups of proteins: hemagglutinin or “H” proteins, of which there are 16 (H1–H16), and neuraminidase or “N” proteins, of which there are 9 (N1–N9). Many different combinations of “H” and “N” proteins are possible. Each combination is considered a different subtype and can be further broken down into different strains which circulate within flyways/geographic regions. AI viruses are further classified by their pathogenicity (low or high)—the ability of a particular virus strain to produce disease in domestic chickens.