Although nearly 50 million commercially raised birds across North America have either been killed or culled due to the recently arrived HPAI H5 viruses, fewer than 100 wild and captive wild birds have tested positive for the virus across the nation (see. Wild Bird Findings confirmed by USDA’s National Veterinary Services Laboratories).
As the map above illustrates, while most of the commercial impact of these viruses (HPAI H5N8, H5N2, H5N1) have centered in the upper Midwest (Iowa, Minnesota, South Dakota, Wisconsin) the bulk of the wild bird detections have so far come from the western states.
Lightly impacted Midwestern states like Michigan, Missouri, and Kentucky have detected HPAI in wild or migratory birds more than once, while Iowa – the hardest hit state – has yet to report finding the virus in the wild. Minnesota – the second hardest hit state – reported the virus in a single Cooper’s Hawk sampled last April, but until yesterday, that was their only announced detection.
This relatively low detection rate is likely due to the fact that many species of birds – particularly waterfowl – can carry these viruses will little or no ill effect. Birds that are infected, are also only likely to shed the virus for a few weeks, providing only a brief window for detection.
Add in the fact that there are billions of birds, and only a few thousand get tested each year, and you wouldn’t expect to find a high rate of positives.
Of interest, the species that Minnesota is reporting infected is the Chickadee, a common songbird in North America. We normally see HPAI in waterfowl and occasionally birds of prey (Hawks & Falcons), but have occasionally seen reports of H5N1 and H7N9 in Passerine birds, which encompasses both `perching birds’ & songbirds (see EID Study & OIE: H5N1 Detected In Crows Again – India)
Because of the low probability of finding HPAI H5 in non-aquatic birds, passerine birds are rarely tested in North America (see Surveillance Plan for the Early Detection of H5N1 Highly Pathogenic Avian Influenza Virus in Migratory Birds: 2009).
While sick or dead passerine birds will undoubtedly be tested this fall and winter, wild bird surveillance efforts will continue to focus on dabbling ducks, and other shorebirds. This from the recently released U.S. Interagency Strategic Plan for Early Detection and Monitoring for Avian Influenzas of Significance in Wild Birds.
Birds should be sampled in conjunction with existing studies when possible (e.g., banding), and additional bird captures should be initiated as necessary to provide a targeted species, geographic and temporal surveillance effort. As with other surveillance methods, sampling should be directed at functional groups rather than particular species. Initial efforts should focus on dabbling ducks. As a functional group, dabbling ducks accounted for 91.5% of the H5 matrix positive samples and 89.7% of the H7 matrix positives in the prior surveillance program which operated from 2006-2010 (Bevins et al. 2014). Diving ducks, shorebirds, gulls June 2015 20 geese, and swans are lower priorities but may be sampled in some cases. These species have also been shown to serve as reservoirs for some avian influenza viruses.
Here is the press release from the Minnesota DNR on their second detection of HPAI H5 (subtype not determined) in a wild bird.
(Released July 10, 2015)
A second confirmed case of highly pathogenic avian influenza (HPAI) has been reported in a wild bird. A chickadee recovered in Ramsey County and delivered on June 10 to a wildlife rehabilitation center later tested positive for avian influenza.
“Since spring, the Minnesota Department of Natural Resources has been conducting wild bird surveillance and we continue to investigate how the virus is impacting birds,” said DNR Commissioner Tom Landwehr. “We are seeking more information about the chickadee, and are continuing plans to conduct expanded surveillance over the summer and fall by testing ducks and geese, and will be sampling hunter-harvested waterfowl throughout the state this fall.”
In April, a Cooper’s hawk from Yellow Medicine County was the first Minnesota wild bird to test positive for the HPAI virus. While waterfowl are known to carry and potentially spread the virus, they don’t get sick or die. However, raptors and songbirds are thought to die from it once infected.
Since December, the U.S. Department of Agriculture reported other individual wild-bird species in other states have tested positive for the virus. Among them are a Cooper’s hawk, several Canada geese, a peregrine falcon, two red-tailed hawks, a snowy owl, and a bald eagle.
Since the discovery of HPAI in domestic poultry, DNR staff have collected almost 4,000 avian influenza samples, including just over 600 geese sampled as part of DNR’s statewide banding program. Until today, the Cooper’s hawk was the only positive sample identified.
“The report of a chickadee testing positive for avian influenza is the first detection of the disease in a songbird,” said Lou Cornicelli, wildlife research manager. “This is further evidence that while waterfowl species can serve as a reservoir for avian influenza, other species are susceptible to the disease.”
Cornicelli added that the chickadee was not turned into the DNR, so the agency does not have complete information about the circumstances surrounding the submission. “It is common for small birds to be sent directly to rehab facilities. We will not be able to determine where or how the bird was infected, but these results highlight the complexity of how this virus is spread, and that it can impact both wild and domestic birds,” Cornicelli said. “Although highly pathogenic H5 was diagnosed, the laboratory was unable to determine the exact virus strain, so we don’t know if was H5N2 or some other highly pathogenic strain.”
The Legislature recently appropriated $350,000 to the DNR for avian influenza testing DNR plans to collaborate with the Minnesota Board of Animal Health and the University of Minnesota on research projects that identify both active virus and virus exposure using serology. For more information on avian influenza and the DNR’s surveillance effort, visit the DNR avian flu Web page.