Howden Krista, French Shannon K, Racicot Manon, Signore Anthony V, Best Caitlyn, Perrey Jacklyn, Bourque Troy, Berhane Yohannes
Canadian Food Inspection Agency, Calgary, Alberta T2E 9B2, Canada.
Canadian Food Inspection Agency, Guelph, Ontario N1G 4S9, Canada.
Transbound Emerg Dis. 2025 Jul 15;2025:4099285. doi: 10.1155/tbed/4099285. eCollection 2025.
Highly pathogenic avian influenza (HPAI) virus A (H5N1) was first detected in North America in 2021. Ongoing spillover events from wild to domestic birds and subsequent transmission between domestic birds resulted in Canada's largest recorded epidemic of HPAI. Between December 2021 and April 2024, 422 A (H5N1) outbreaks in domestic birds were confirmed in Canada. Of these, 158 (37%) occurred in British Columbia (BC). This study integrates field and genomic epidemiology (GE) results to investigate the potential for lateral or local spread between infected poultry farms in BC. Five genetically distinct viral clusters were identified during this period. Among the 31 noncommercial premises, 27 (87.1%) were classified as independent introductions, while four premises (12.9%) were attributed to local spread within 10 km of a phylogenetically connected infected premises (IP). No lateral spread events were identified among noncommercial premises. All infected noncommercial premises housed birds with outdoor access, emphasizing their susceptibility to wild bird exposure. Of the 127 infected commercial poultry premises, 21 (16.5%) were classified as independent introductions, 82 (64.6%) as local spread, 18 (14.2%) with potential for lateral spread, five (3.9%) with potential for both local and/or lateral spread, and one (0.8%) for which sequencing was unavailable. Local spread emerged as a prominent feature, with most IP in proximity to one another having genetically similar viruses. Results suggest that proximity (<200 m) to an IP was a more reliable predictor of future infection status than contact with an IP. These findings underscore the critical value of combining field and GE to understand outbreak dynamics comprehensively. This integrative approach improves resource allocation, informs targeted containment strategies, and supports the need for effective biosecurity measures to mitigate future risks, particularly in densely populated poultry production regions. Robust interventions are needed to address both independent introductions and secondary spread pathways.
高致病性禽流感（HPAI）病毒A（H5N1）于2021年首次在北美被发现。从野生鸟类到家养鸟类持续发生的溢出事件以及随后家养鸟类之间的传播，导致了加拿大有记录以来最大规模的HPAI疫情。在2021年12月至2024年4月期间，加拿大确认在家养鸟类中发生了422起A（H5N1）疫情。其中，158起（37%）发生在不列颠哥伦比亚省（BC）。本研究整合了现场和基因组流行病学（GE）结果，以调查BC省受感染家禽养殖场之间横向或局部传播的可能性。在此期间识别出了五个基因不同的病毒簇。在31个非商业场所中，27个（87.1%）被归类为独立引入，而四个场所（12.9%）归因于在系统发育相关的受感染场所（IP）10公里范围内的局部传播。在非商业场所中未识别出横向传播事件。所有受感染的非商业场所都饲养有可接触户外的鸟类，这突出了它们对野生鸟类暴露的易感性。在127个受感染的商业家禽场所中，21个（16.5%）被归类为独立引入，82个（64.6%）为局部传播，18个（14.2%）有横向传播可能性，5个（3.9%）有局部和/或横向传播可能性，1个（0.8%）无法进行测序。局部传播成为一个突出特征，大多数彼此相邻的IP具有基因相似的病毒。结果表明，与IP的接近程度（<200米）比与IP的接触是未来感染状况更可靠的预测指标。这些发现强调了结合现场和GE全面了解疫情动态的关键价值。这种综合方法改善了资源分配，为有针对性的控制策略提供了信息，并支持采取有效的生物安全措施以降低未来风险的必要性，特别是在人口密集的家禽生产地区。需要强有力的干预措施来应对独立引入和二次传播途径。
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