The effect of seasonal birth pulses on pathogen persistence in wild mammal populations.
The notion of a critical community size (CCS), or population size that is likely to result in long-term persistence of a communicable disease, has been developed based on the empirical observations of acute immunizing infections in human populations, and extended for use in wildlife populations. Seasonal birth pulses are frequently observed in wildlife and are expected to impact infection dynamics, yet their effect on pathogen persistence and CCS have not been considered. To investigate this issue theoretically, we use stochastic epidemiological models to ask how host life-history traits and infection parameters interact to determine pathogen persistence within a closed population. We fit seasonal birth pulse models to data from diverse mammalian species in order to identify realistic parameter ranges. When varying the synchrony of the birth pulse with all other parameters being constant, our model predicted that the CCS can vary by more than two orders of magnitude. Tighter birth pulses tended to drive pathogen extinction by creating large amplitude oscillations in prevalence, especially with high demographic turnover and short infectious periods. Parameters affecting the relative timing of the epidemic and birth pulse peaks determined the intensity and direction of the effect of pre-existing immunity in the population on the pathogen's ability to persist beyond the initial epidemic following its introduction.
Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK Environmental Futures Research Institute, Griffith University, Brisbane, 4111, Australia alisonpeel@gmail.com.
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AJ
Peel
Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA Department of Biology, University of Florida, Gainesville, FL 32611, USA Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
J R C
JR
Pulliam
Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
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AD
Luis
Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA 16802, USA.
R K
RK
Plowright
US Geological Survey (retired), PO Box 65, Glen Haven, CO 80532, USA.
T J
TJ
O'Shea
Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
D T S
DT
Hayman
Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK.
J L N
JL
Wood
Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
C T
CT
Webb
Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK.
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Restif
D000818:Animals; D000835:Animals, Wild; D003141:Communicable Diseases / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D008322:Mammals; D008962:Models, Theoretical; D036801:Parturition; D011156:Population Density; D012098:Reproduction; D012621:Seasons; D013269:Stochastic Processes
birth pulse; critical community size; seasonality; stochastic model; wildlife epidemiology