Department of Biology, Carleton University, Ottawa, ON, K1S 5B6, Canada.
Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 391 82, Kalmar, Sweden.
Sci Rep. 2021 Jan 13;11(1):1046. doi: 10.1038/s41598-020-79888-6.
Avian cholera, caused by the bacterium Pasteurella multocida, is a common and important infectious disease of wild birds in North America. Between 2005 and 2012, avian cholera caused annual mortality of widely varying magnitudes in Northern common eiders (Somateria mollissima borealis) breeding at the largest colony in the Canadian Arctic, Mitivik Island, Nunavut. Although herd immunity, in which a large proportion of the population acquires immunity to the disease, has been suggested to play a role in epidemic fadeout, immunological studies exploring this hypothesis have been missing. We investigated the role of three potential drivers of fadeout of avian cholera in eiders, including immunity, prevalence of infection, and colony size. Each potential driver was examined in relation to the annual real-time reproductive number (R) of P. multocida, previously calculated for eiders at Mitivik Island. Each year, colony size was estimated and eiders were closely monitored, and evaluated for infection and serological status. We demonstrate that acquired immunity approximated using antibody titers to P. multocida in both sexes was likely a key driver for the epidemic fadeout. This study exemplifies the importance of herd immunity in influencing the dynamics and fadeout of epidemics in a wildlife population.
禽流感，由多杀巴斯德氏菌引起，是北美的一种常见且重要的野生鸟类传染病。在 2005 年至 2012 年间，在加拿大北极地区努纳武特省米提维克岛最大的聚居地繁殖的北方普通潜鸟（Somateria mollissima borealis）中，禽流感每年造成的死亡率差异很大。尽管群体免疫，即大多数人获得对疾病的免疫力，被认为在传染病消退中发挥了作用，但探索这一假设的免疫学研究却一直缺失。我们研究了禽流感在潜鸭中消退的三个潜在驱动因素的作用，包括免疫力、感染率和聚居地大小。我们研究了每个潜在的驱动因素与米提维克岛潜鸭的多杀巴斯德氏菌的实时繁殖数（R）的关系，该繁殖数是之前计算得出的。每年，我们都会估算聚居地的大小，并对潜鸭进行密切监测，评估其感染和血清学状况。我们证明，使用两性的巴氏杆菌抗体滴度来估计获得的免疫力可能是传染病消退的关键驱动因素。本研究例证了群体免疫对影响野生动物种群传染病动态和消退的重要性。
