Bald eagle mortality and nest failure due to clade 2.3.4.4 highly pathogenic H5N1 influenza a virus

Abstract

The bald eagle (Haliaeetus leucocephalus) is a culturally and ecologically vital species in North America that embodies conservation success but continues to face threats that include emerging pathogens. The introduction of A/goose/Guangdong/1/1996 lineage highly pathogenic (HP) clade 2.3.4.4b H5N1 influenza A virus (IAV) in North America in late 2021 resulted in high rates of mortality among bald eagles. Here we show an alarming rate of bald eagle nest failure and mortality attributed to HP IAV. We documented fatal, systemic HP IAV infection in breeding adult and nestling bald eagles along the southeastern U.S. coast. Concurrently, annual bald eagle nest surveys in Georgia and Florida revealed a precipitous drop in success in coastal counties compared with previous years, portending negative impacts on population recruitment. As an apex predator and efficient scavenger, it is likely that bald eagles become infected through consumption of infected waterfowl. These results and similar reports of raptor mortality in Europe, Asia, and Africa, indicate a clear threat to raptor health. The possible long-term persistence of HP H5N1 IAV in North America poses an impending threat to bald eagle populations not only related to direct mortality but also decreased recruitment and warrants continued efforts to understand these potential impacts.

Figure 1

Regional highly pathogenic influenza. A virus in wild birds during Spring 2022 in the southeastern USA. Counties in North Carolina, South Carolina, Georgia, and Florida where H5 influenza A virus (IAV) (A/goose/Guangdong/1/1996 lineage HP clade 2.3.4.4b H5N1) was detected in wild birds during Spring 2022, as reported by the U.S. Department of Agriculture (USDA; https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/hpai-2022/2022-hpai-wild-birds; website accessed July 22, 2022), with additional detections by the Southeastern Cooperative Wildlife Disease Study, University of Georgia. Detections were made through wild bird mortality investigations, or USDA surveillance of hunter-harvested waterfowl. The map shows counties with bald eagle H5 IAV mortality (red), as detected by SCWDS and reported on the USDA website from January 1 through May 15, 2022; detections of H5 IAV in dead or hunter-harvested waterfowl (hash lines) as reported on USDA website from January 1 through April 1, 2022; H5 IAV detection or mortality in wild bird species other than bald eagle or waterfowl (yellow border) as detected by SCWDS and reported on USDA website from January 1 through May 15, 2022. Duck silhouettes identify locations with confirmed H5 IAV waterfowl mortality coincident with peak bald eagle nesting activity from January 1 through April 1, 2022, as detected by SCWDS and reported on USDA website.

Figure 2

Images illustrating severe disease and mortality from H5 influenza A virus infection in bald eagles (Haliaeetus leucocephalus). (a) An attentive nesting pair of bald eagles (nest BE106) with an apparently healthy nestling on February 17, 2022, in Brevard County, Florida (photo by Bob Glover). (b) Nestling bald eagle from the same nest (BE106) taken February 18, 2022, after being found dead under the nest and later confirmed to have died from H5 IAV infection (photo by Bob Glover). (c) A Florida Fish and Wildlife Conservation Commission law enforcement officer collecting the carcass of the adult female from the same nest (BE106) after being found dead under the nest on February 24, 2022, after succumbing to H5 IAV infection (Photo by Bob Glover). (d) Adult bald eagle from Davidson County, North Carolina infected with H5 IAV and presented to a wildlife rehabilitation facility with severe neurologic signs (e.g., severe lethargy, seizures, partial paralysis); the eagle was administered oxygen, subcutaneous fluids, antibiotics, diazepam (valium®) but died the following morning (photograph by Jackie Schaible).

Figure 3

Reproductive indices for nesting bald eagles in Georgia, USA in 2022. (a) Regional bald eagle percent nest success in Georgia during 2022. (b) Bald eagle nest success in Atlantic coastal counties of Georgia during 2022. Aerial nest surveys are performed annually during March by the Georgia Department of Natural Resources. N = number of occupied nest territories surveyed.

Figure 4

Bald eagle nest metrics (2015–2022) in selected counties of Georgia and Florida, USA where H5 highly pathogenic influenza A virus mortality in bald eagles was confirmed January—April 2022. (a) Bald eagle nest success. (b) Brood size (mean fledged bald eagles/successful nest). (c) Productivity (mean fledged bald eagles/occupied territory (GA) or /occupied nest (FL)). Red dots represent values for 2022. Duck symbols represent those counties with documented mortality among overwintering waterfowl (e.g., lesser scaup).