title: Injecting epidemiology into population viability analysis: avian cholera transmission dynamics at an arctic seabird colony.
abstract: Infectious diseases have the potential to spread rapidly and cause high mortality within populations of immunologically naïve hosts. The recent appearance of avian cholera, a highly virulent disease of birds caused by the bacterium Pasteurella multocida, at remote Arctic seabird colonies is an emerging conservation concern. Determining disease risk to population viability requires a quantitative understanding of transmission potential and the factors that regulate epidemic persistence. Estimates of the basic (R0) and real-time (Rt) reproductive number are critical in this regard - enumerating the number of secondary infections caused by each primary infection in a newly invaded host population and the decline in transmission rate as susceptible individuals are removed via mortality or immunized recovery. Here, we use data collected at a closely monitored common eider (Somateria mollissima) breeding colony located in the Canadian Arctic to examine transmission and host population dynamics. Specifically, we infer epidemic curves from daily mortality observations and use a likelihood-based procedure to estimate changes in the reproductive number over a series of annual outbreaks. These data are interpreted in relation to concurrent changes in host numbers to assess local extinction risk. Consistent with expectations for a novel pathogen invasion, case incidence increased exponentially during the initial wave of exposure (R0= 2·5; generation time = 6·5 days ± 1·1 SD). Disease conditions gradually abated, but only after several years of smouldering infection (Rt≈ 1). In total, 6194 eider deaths were recorded during outbreaks spanning eight consecutive breeding seasons. Breeding pair abundance declined by 56% from the pre-outbreak peak; however, a robust population of >4000 pairs remained intact upon epidemic fade-out. Overall, outbreak patterns were consistent with herd immunity acting as a mitigating factor governing in the extent and duration of mortality. Disease mortality is frequently modelled as a form of stochastic catastrophe in wildlife population assessments, whereas our approach gives shape to the functional response between transmission and host population dynamics. We conclude that increased emphasis on integrating epidemiological and population processes is essential to predicting the conservation impact of emerging infectious diseases in wildlife.
authors.affiliation: Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada, K1S 5B6. samuel.iverson@canada.ca.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Iverson
authors.affiliation: National Wildlife Research Centre, Environment and Climate Change Canada, 1125 Colonel By Drive, Ottawa, ON, Canada, K1A 0H3.
authors.forename: H Grant
authors.initials: HG
authors.lastname: Gilchrist
authors.affiliation: Science and Technology Branch, Environment and Climate Change Canada, 115 Perimeter Road, Saskatoon, SK, Canada, S7N 0X4.|Department of Veterinary Pathology, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, Canada, S7N 5B4.
authors.forename: Catherine
authors.initials: C
authors.lastname: Soos
authors.affiliation: Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada, K1S 5B6.
authors.forename: Isabel I
authors.initials: II
authors.lastname: Buttler
authors.affiliation: Department of Veterinary Pathology, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, Canada, S7N 5B4.
authors.forename: N Jane
authors.initials: NJ
authors.lastname: Harms
authors.affiliation: Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada, K1S 5B6.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Forbes
mesh_terms: D000818:Animals; D001110:Arctic Regions / Q000453:epidemiology; D001715:Bird Diseases / Q000382:microbiology / Q000401:mortality* / Q000635:transmission*; D004196:Disease Outbreaks / Q000662:veterinary*; D004372:Ducks; D005260:Female; D016013:Likelihood Functions; D008297:Male; D020957:Nunavut / Q000453:epidemiology; D010326:Pasteurella Infections / Q000382:microbiology / Q000401:mortality / Q000635:transmission / Q000662:veterinary*; D016979:Pasteurella multocida / Q000302:isolation & purification
keywords: 
  Pasteurella multocida
  ; 
  R
  
  t
  
  ; 
  R
  0
  ; avian cholera; common eider; disease ecology; epidemic curve; host-pathogen dynamics; population viability