2022 Pinniped Unusual Mortality Event in Maine (CLOSED)
The Unusual Mortality Event involving harbor and gray seals along the coast of Maine that began in June 2022 is over.
The Unusual Mortality Event (UME) involving stranded harbor (Phoca vitulina) and gray seals (Halichoerus grypus) along the coast of Maine has ended. NOAA Fisheries and partners investigated the event, which occurred from June 20 to July 20, 2022.
During the event, 181 seals stranded—including 143 harbor seals, 28 gray seals and 10 seals of unidentified species. The UME Investigative Team reviewed necropsy, histopathology, and diagnostic findings. They determined the UME was attributed to spillover events of the highly pathogenic avian influenza H5N1 virus from infected wild birds to harbor and gray seals. An ongoing HPAI H5N1 global outbreak in domestic and wild birds and wild mammals began in 2021.
Live seals showed signs of respiratory and neurological disease including nasal and ocular discharge, coughing, unresponsiveness, and seizures. Eighteen percent of the stranded seals (33 out of 180) were tested for avian influenza via polymerase-chain-reaction. A subset of seals were positive for HPAI H5N1 with preliminary findings confirmed by the United States Department of Agriculture’s National Veterinary Services Laboratories. Of the 33 seals tested during the UME period 19 (58 percent) were positive for H5N1 (17 harbor seals; 2 gray seals) and 14 (42 percent) tested negative. Twelve H5N1 positive seals had histopathology conducted; 11 of those seals had lesions (primarily respiratory and/or neurologic) suspected or consistent with avian influenza infection. Sequencing of the H5N1 virus detected in seals suggests the seals were infected from spillover events from infected wild birds to these seals.
Seal Data
Table 1: Harbor and Gray seal strandings by Maine County from June 20 through July 20, 2022.
| Maine County | Harbor Seal | Gray Seal | Unknown Seal Species | Total |
|---|---|---|---|---|
| York | 14 | 18 | 1 | 32 |
| Cumberland | 60 | 2 | 6 | 68 |
| Sagadahoc | 24 | 3 | 1 | 28 |
| Lincoln | 22 | 0 | 2 | 24 |
| Knox | 10 | 1 | 0 | 11 |
| Waldo | 0 | 0 | 0 | 0 |
| Hancock | 11 | 3 | 0 | 14 |
| Washington | 2 | 1 | 0 | 3 |
| Total | 143 | 28 | 10 | 181 |
Table 2: Summary of HPAI H5N1 test results by county and species from June 20 through July 20, 2022 (n=33). *All positive HPAI cases were confirmed for H5N1 by the USDA National Veterinary Services Laboratory.
| Maine County | Harbor Seal HPAI Positive* | Harbor Seal HPAI Negative | Total Harbor Seal HPAI Tested | Gray Seal HPAI Positive* | Gray Seal HPAI Negative | Total Gray Seal HPAI Tested |
|---|---|---|---|---|---|---|
| York | 4 | 1 | 5 | 1 | 1 | 2 |
| Cumberland | 8 | 4 | 12 | 0 | 1 | 1 |
| Sagadahoc | 2 | 6 | 8 | 1 | 0 | 1 |
| Lincoln | 2 | 0 | 2 | 0 | 0 | 0 |
| Knox | 0 | 1 | 1 | 0 | 0 | 0 |
| Waldo | 0 | 0 | 0 | 0 | 0 | 0 |
| Hancock | 1 | 0 | 1 | 0 | 0 | 0 |
| Washington | 0 | 0 | 0 | 0 | 0 | 0 |
| Total | 17 | 12 | 29 | 2 | 2 | 4 |
Interactive Map
2022 Pinniped Unusual Mortality Event along the Maine Coast Dead Animal Locations
Partners
- Marine Mammals of Maine
- Atlantic Marine Conservation Society
- Allied Whale, College of the Atlantic
- Centers for Disease Control and Prevention
- Maine Department of Marine Resources
- Maine Department of Agriculture, Conservation, and Forestry
- Maine Department of Health and Human Services
- Maine Marine Patrol
- Runstadler Lab at Cummings School for Veterinary Medicine at Tufts University
- USDA Animal and Plant Health Inspection Service, National Veterinary Services Laboratories
- USDA Wildlife Services
- U.S. Geological Survey National Wildlife Health Center