Pathfinder
Editor, Senior Moderator
Volume 61, Issue 4
October 2025
Article Contents
LETTERS| November 07 2025
Highly Pathogenic Avian Influenza (HPAI) Detected in 41 At-risk Species in Canada
Open Access
Damien O. JolyCorresponding Author;
Yohannes Berhane;
Jeff Bowman;
Jolene A. Giacinti;
Dayna Goldsmith;
Nathan Hentze;
Megan E.B. Jones;
Claire M. Jardine;
Stéphane Lair;
Erin K. Leonard;
Ariane Massé;
Samira Mubareka;
Cynthia Pekarik;
Julie Paré;
Neil Pople;
Margo J. Pybus;
Brian Stevens;
Trevor Thompson;
Amie Enns;
Maeve Winchester
J Wildl Dis (2025) 61 (4): 1120–1124.
https://doi.org/10.7589/JWD-D-25-00048
Article history
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b has impacted wild birds and mammals in Canada since late 2021, including at-risk species. We compared detections and conservation status to highlight the need to integrate disease surveillance with conservation planning when assessing risks and to guide management.
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b (HPAI H5N1, H5N2, and H5N5) has impacted millions of domestic poultry, wild birds, dairy cattle, and wild mammals (Giacinti et al. 2024; Canadian Food Inspection Agency 2025). Avery-Gomm et al. (2024) reported that at least 40,000 birds died of HPAI in Eastern Canada in 2022, including 25,000 Northern Gannets (Morus bassanus), 8,000 Common Murres (Uria aalge), and almost 1,800 Common Eiders (Somateria mollissima).
Our aim here was to identify at-risk species in Canada affected by HPAI H5Nx. These data are currently only available on websites with no guarantee of permanency; we felt there would be value in documenting species affected by HPAI in the scientific literature, providing an additional, permanent, archive of this information.
We downloaded data on HPAI H5Nx virus clade 2.3.4.4b infection in wildlife (November 2022–November 2024) from Canada's Interagency Surveillance Program for Avian Influenza Viruses in Wildlife (2024) HPAI Dashboard. Methods for HPAI surveillance in wildlife are described in Giacinti et al. (2024). In brief, mammals and birds reported as moribund or dead, as well as live-bird samples, were tested for HPAI as part of Canada's Interagency Surveillance Program for Avian Influenza Viruses in Wildlife at regional laboratories. Infection with HPAI was confirmed at Canada’s National Centre for Foreign Animal Disease. Note that these data reflect confirmed cases only, representing only samples submitted for diagnosis. In a die-off event, only a few individuals would be selected for necropsy and testing; therefore data on the total number of individuals affected during an event were not available.
Canadian provincial and territorial species conservation status ranks assigned by provincial and territorial Conservation Data Centres using NatureServe methods (Faber-Langendoen et al. 2012) were downloaded from NatureServe Explorer on 28 November 2024, with the following search criteria: “Classification—Birds or Mammals, Status—S1, S2, or S3, In Canada” (NatureServe 2025a). In brief, species were assigned to a subnational (S) status rank ranging from S1 (“Critically Imperiled”) to S5 (“Secure”) based on evaluation of rarity, trends, and threats. The NatureServe method incorporates uncertainty in the input data by calculating ranks using both lower and upper estimates of uncertain factors. When the resulting rank scores cluster tightly around a single rank (e.g., >95% of the score distribution), a simple rank is assigned (e.g., S1). If the uncertainty is moderate (e.g., 80–95% of the scores fall within one rank), the rank is qualified with a question mark to indicate less confidence in the assignment (e.g., S1?). When the score distribution spans multiple ranks without a clear majority, a range rank is used (e.g., S1S2 or S1S3; Faber-Langendoen et al. 2012). Note that NatureServe Explorer exports “rounded ranks”: When a rank spans adjacent ranks (e.g., S1S2) it is “rounded” to the more imperiled rank (NatureServe 2025b). We followed the categorization criteria for animals used by the British Columbia Conservation Data Centre (2025) to assign species to the following lists: Red (Endangered or Threatened; S1, S1S2, S2, S2?, S1S3), Blue (Special Concern; S2S3, S2S4, S3, S3? S3S4, S3S5), or Yellow (Not at Risk; S4, S4?, S4S5, S5). Qualifiers of “B,” “N,” or “M” after the status rank refer to the Breeding, Nonbreeding, or Migrant population, respectively. When multiple rank qualifiers were assigned in a jurisdiction, we assigned species to a list based on their highest-risk rank (i.e., lowest S number). Insufficient information or substantially conflicting information about status or trends prevented assignment of a status rank for several migratory or nonbreeding populations of species (Table 1); breeding populations for these species were assessed ranks, however, so this did not affect the results. Species were assigned a status rank for the island of Newfoundland and continental Labrador separately; consequently, we determined whether animals with HPAI were detected in Newfoundland (denoted NF) or Labrador (LB) and treated these as if they were separate jurisdictions. Species assigned to the Red or Blue lists were considered Provincial–Territorial (P-T) at-risk species(SAR).
Table 1.
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b detections in at-risk species in Canada by region (province or territory; note that species conservation statuses were available separately for the island of Newfoundland, and continental Labrador (being the province of Newfoundland and Labrador). All detections were of HPAI H5N1 except where noted in parentheses. Red (Endangered or Threatened) and Blue (Special Concern) Lists were determined using NatureServe Conservation Status Ranks, following the BC Conservation Data Centre criteria (British Columbia Conservation Data Centre 2025). NatureServe Conservation Status Ranks (CSR) are indicated in parentheses by subnational (S) status rank ranging from S1 (Critically Imperiled within the subnational jurisdiction) to S5 (Secure within the subnational jurisdiction) based on objective evaluation of rarity, trends, and threats. Species ranked from S1 (Critically Imperiled) to S3 (Vulnerable) are considered “at-risk species.” Additional ranks include SU, unrankable due to lack of information or due to substantially conflicting information about status or trends; SNR, rank not yet assessed. Qualifiers to the CSR are as follows: B, breeding; N, nonbreeding; M, migrant. No at-risk species were found infected with HPAI in Yukon, Northwest Territories, or Nunavut. For data for all species in which HPAI was detected see Supplementary Material, Table S1.
View large
During the period November 2021 to November 2024, HPAI H5Nx was detected in at least 1 individual of 41 SAR across all 10 Canadian provinces, including 20 species on the Red List as Endangered or Threatened (Table 1). No SAR were found with HPAI in the three Canadian Territories (Northwest Territories, Nunavut and Yukon). All 41 species were birds from the following Orders: Accipitriformes (9 species), Anseriformes (11 species), Cathartiformes (1 species), Charadriiformes (8 species), Falconiformes (2 species), Passeriformes (1 species), Pelecaniformes (2 species), Podicipediformes (2 species), Strigiformes (4 species), and Suliformes (1 species), and represented 41% of all species detected with HPAI in this period (n=100) and 44% of bird species (n=93). Although HPAI was detected in eight mammal species, none of these species met the criteria for SAR. Four of the bird species in which HPAI was detected were also assessed as at risk nationally by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Barn Owl (Tyto furcata), Horned Grebe (Podiceps auritus), Snowy Owl (Bubo scandiacus), and Western Grebe (Aechmophorus occidentalis).
This study highlights HPAI as a potential additional conservation threat to species already at risk. However, there are several limitations to this study. First, HPAI surveillance relies on reporting to wildlife authorities, so suffers from the usual limitations of scanning surveillance programs (e.g., Giacinti et al. 2023) and probably underestimates the number of individuals and species affected by HPAI. Specifically, smaller and/or more cryptic species are probably underrepresented, as well as those with habitats away from human occupation. Furthermore, although an informal review of available Canadian Wildlife Health Cooperative data indicated that a majority of HPAI-positive birds had clinical signs indicative of HPAI-associated mortality, detection of HPAI in an individual does not necessarily mean that the individual died of HPAI; more research is necessary to determine species-specific vulnerability to HPAI.
The objective of this study was to document confirmed HPAI detections in at-risk species as a first step toward informing more targeted conservation assessments. Detailed information such as the number of individuals affected, condition at detection, or population-level prevalence was unavailable; therefore this study does not inform broader implications for long-term conservation outcomes. For example, this study does not address the question of the potential role of long-distance migratory species in HPAI transmission. That said, strong connections between disease and conservation research are important for assessing the role of infectious diseases within the broader context of species management and protection.
We thank the members of the public who reported sick and deceased animals, as well as the wildlife rehabilitators, migratory game bird hunters, conservation officers, wildlife biologists, and other personnel who played a crucial role in monitoring and responding to the outbreak. We also acknowledge the collective efforts of all partners contributing to Canada's Interagency Surveillance Program for Avian Influenza Viruses in Wildlife, including the Canadian Wildlife Health Cooperative, as well as federal, provincial, territorial, indigenous, and academic collaborators working across wildlife, domestic animal, and human health sectors.
SUPPLEMENTARY MATERIAL
Supplementary material for this article is online at http://dx.doi.org/10.7589/JWD-D-25-00048.
...
https://meridian.allenpress.com/jwd...y-Pathogenic-Avian-Influenza-HPAI-Detected-in
October 2025
Article Contents
LETTERS| November 07 2025
Highly Pathogenic Avian Influenza (HPAI) Detected in 41 At-risk Species in Canada
Open Access
Damien O. JolyCorresponding Author;
Yohannes Berhane;
Jeff Bowman;
Jolene A. Giacinti;
Dayna Goldsmith;
Nathan Hentze;
Megan E.B. Jones;
Claire M. Jardine;
Stéphane Lair;
Erin K. Leonard;
Ariane Massé;
Samira Mubareka;
Cynthia Pekarik;
Julie Paré;
Neil Pople;
Margo J. Pybus;
Brian Stevens;
Trevor Thompson;
Amie Enns;
Maeve Winchester
J Wildl Dis (2025) 61 (4): 1120–1124.
https://doi.org/10.7589/JWD-D-25-00048
Article history
- Split-Screen
- Views IconViews Open Menu
- Open thePDFfor in another window
- Share IconShare
- Tools IconTools Open Menu
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b has impacted wild birds and mammals in Canada since late 2021, including at-risk species. We compared detections and conservation status to highlight the need to integrate disease surveillance with conservation planning when assessing risks and to guide management.
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b (HPAI H5N1, H5N2, and H5N5) has impacted millions of domestic poultry, wild birds, dairy cattle, and wild mammals (Giacinti et al. 2024; Canadian Food Inspection Agency 2025). Avery-Gomm et al. (2024) reported that at least 40,000 birds died of HPAI in Eastern Canada in 2022, including 25,000 Northern Gannets (Morus bassanus), 8,000 Common Murres (Uria aalge), and almost 1,800 Common Eiders (Somateria mollissima).
Our aim here was to identify at-risk species in Canada affected by HPAI H5Nx. These data are currently only available on websites with no guarantee of permanency; we felt there would be value in documenting species affected by HPAI in the scientific literature, providing an additional, permanent, archive of this information.
We downloaded data on HPAI H5Nx virus clade 2.3.4.4b infection in wildlife (November 2022–November 2024) from Canada's Interagency Surveillance Program for Avian Influenza Viruses in Wildlife (2024) HPAI Dashboard. Methods for HPAI surveillance in wildlife are described in Giacinti et al. (2024). In brief, mammals and birds reported as moribund or dead, as well as live-bird samples, were tested for HPAI as part of Canada's Interagency Surveillance Program for Avian Influenza Viruses in Wildlife at regional laboratories. Infection with HPAI was confirmed at Canada’s National Centre for Foreign Animal Disease. Note that these data reflect confirmed cases only, representing only samples submitted for diagnosis. In a die-off event, only a few individuals would be selected for necropsy and testing; therefore data on the total number of individuals affected during an event were not available.
Canadian provincial and territorial species conservation status ranks assigned by provincial and territorial Conservation Data Centres using NatureServe methods (Faber-Langendoen et al. 2012) were downloaded from NatureServe Explorer on 28 November 2024, with the following search criteria: “Classification—Birds or Mammals, Status—S1, S2, or S3, In Canada” (NatureServe 2025a). In brief, species were assigned to a subnational (S) status rank ranging from S1 (“Critically Imperiled”) to S5 (“Secure”) based on evaluation of rarity, trends, and threats. The NatureServe method incorporates uncertainty in the input data by calculating ranks using both lower and upper estimates of uncertain factors. When the resulting rank scores cluster tightly around a single rank (e.g., >95% of the score distribution), a simple rank is assigned (e.g., S1). If the uncertainty is moderate (e.g., 80–95% of the scores fall within one rank), the rank is qualified with a question mark to indicate less confidence in the assignment (e.g., S1?). When the score distribution spans multiple ranks without a clear majority, a range rank is used (e.g., S1S2 or S1S3; Faber-Langendoen et al. 2012). Note that NatureServe Explorer exports “rounded ranks”: When a rank spans adjacent ranks (e.g., S1S2) it is “rounded” to the more imperiled rank (NatureServe 2025b). We followed the categorization criteria for animals used by the British Columbia Conservation Data Centre (2025) to assign species to the following lists: Red (Endangered or Threatened; S1, S1S2, S2, S2?, S1S3), Blue (Special Concern; S2S3, S2S4, S3, S3? S3S4, S3S5), or Yellow (Not at Risk; S4, S4?, S4S5, S5). Qualifiers of “B,” “N,” or “M” after the status rank refer to the Breeding, Nonbreeding, or Migrant population, respectively. When multiple rank qualifiers were assigned in a jurisdiction, we assigned species to a list based on their highest-risk rank (i.e., lowest S number). Insufficient information or substantially conflicting information about status or trends prevented assignment of a status rank for several migratory or nonbreeding populations of species (Table 1); breeding populations for these species were assessed ranks, however, so this did not affect the results. Species were assigned a status rank for the island of Newfoundland and continental Labrador separately; consequently, we determined whether animals with HPAI were detected in Newfoundland (denoted NF) or Labrador (LB) and treated these as if they were separate jurisdictions. Species assigned to the Red or Blue lists were considered Provincial–Territorial (P-T) at-risk species(SAR).
Table 1.
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b detections in at-risk species in Canada by region (province or territory; note that species conservation statuses were available separately for the island of Newfoundland, and continental Labrador (being the province of Newfoundland and Labrador). All detections were of HPAI H5N1 except where noted in parentheses. Red (Endangered or Threatened) and Blue (Special Concern) Lists were determined using NatureServe Conservation Status Ranks, following the BC Conservation Data Centre criteria (British Columbia Conservation Data Centre 2025). NatureServe Conservation Status Ranks (CSR) are indicated in parentheses by subnational (S) status rank ranging from S1 (Critically Imperiled within the subnational jurisdiction) to S5 (Secure within the subnational jurisdiction) based on objective evaluation of rarity, trends, and threats. Species ranked from S1 (Critically Imperiled) to S3 (Vulnerable) are considered “at-risk species.” Additional ranks include SU, unrankable due to lack of information or due to substantially conflicting information about status or trends; SNR, rank not yet assessed. Qualifiers to the CSR are as follows: B, breeding; N, nonbreeding; M, migrant. No at-risk species were found infected with HPAI in Yukon, Northwest Territories, or Nunavut. For data for all species in which HPAI was detected see Supplementary Material, Table S1.
View large
During the period November 2021 to November 2024, HPAI H5Nx was detected in at least 1 individual of 41 SAR across all 10 Canadian provinces, including 20 species on the Red List as Endangered or Threatened (Table 1). No SAR were found with HPAI in the three Canadian Territories (Northwest Territories, Nunavut and Yukon). All 41 species were birds from the following Orders: Accipitriformes (9 species), Anseriformes (11 species), Cathartiformes (1 species), Charadriiformes (8 species), Falconiformes (2 species), Passeriformes (1 species), Pelecaniformes (2 species), Podicipediformes (2 species), Strigiformes (4 species), and Suliformes (1 species), and represented 41% of all species detected with HPAI in this period (n=100) and 44% of bird species (n=93). Although HPAI was detected in eight mammal species, none of these species met the criteria for SAR. Four of the bird species in which HPAI was detected were also assessed as at risk nationally by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Barn Owl (Tyto furcata), Horned Grebe (Podiceps auritus), Snowy Owl (Bubo scandiacus), and Western Grebe (Aechmophorus occidentalis).
This study highlights HPAI as a potential additional conservation threat to species already at risk. However, there are several limitations to this study. First, HPAI surveillance relies on reporting to wildlife authorities, so suffers from the usual limitations of scanning surveillance programs (e.g., Giacinti et al. 2023) and probably underestimates the number of individuals and species affected by HPAI. Specifically, smaller and/or more cryptic species are probably underrepresented, as well as those with habitats away from human occupation. Furthermore, although an informal review of available Canadian Wildlife Health Cooperative data indicated that a majority of HPAI-positive birds had clinical signs indicative of HPAI-associated mortality, detection of HPAI in an individual does not necessarily mean that the individual died of HPAI; more research is necessary to determine species-specific vulnerability to HPAI.
The objective of this study was to document confirmed HPAI detections in at-risk species as a first step toward informing more targeted conservation assessments. Detailed information such as the number of individuals affected, condition at detection, or population-level prevalence was unavailable; therefore this study does not inform broader implications for long-term conservation outcomes. For example, this study does not address the question of the potential role of long-distance migratory species in HPAI transmission. That said, strong connections between disease and conservation research are important for assessing the role of infectious diseases within the broader context of species management and protection.
We thank the members of the public who reported sick and deceased animals, as well as the wildlife rehabilitators, migratory game bird hunters, conservation officers, wildlife biologists, and other personnel who played a crucial role in monitoring and responding to the outbreak. We also acknowledge the collective efforts of all partners contributing to Canada's Interagency Surveillance Program for Avian Influenza Viruses in Wildlife, including the Canadian Wildlife Health Cooperative, as well as federal, provincial, territorial, indigenous, and academic collaborators working across wildlife, domestic animal, and human health sectors.
SUPPLEMENTARY MATERIAL
Supplementary material for this article is online at http://dx.doi.org/10.7589/JWD-D-25-00048.
...
https://meridian.allenpress.com/jwd...y-Pathogenic-Avian-Influenza-HPAI-Detected-in