Spatiotemporal heterogeneity decouples infection parameters of amphibian chytridiomycosis
McMillan, K; Lesbarreres, D; Harrison, X; et al.Garner, T
Date: 23 December 2019
Journal
Journal of Animal Ecology
Publisher
Wiley
Publisher DOI
Abstract
1. Emerging infectious diseases are responsible for declines in wildlife populations around the globe. Mass mortality events associated with emerging infectious diseases are often associated with high number of infected individuals (prevalence)
and high pathogen loads within individuals (intensity). At the landscape scale
spatial ...
1. Emerging infectious diseases are responsible for declines in wildlife populations around the globe. Mass mortality events associated with emerging infectious diseases are often associated with high number of infected individuals (prevalence)
and high pathogen loads within individuals (intensity). At the landscape scale
spatial and temporal variation in environmental conditions can alter the relationship
between these infection parameters and blur the overall picture of disease dynamics.
2. Quantitative estimates of how infection parameters covary with environmental
heterogeneity at the landscape scale are scarce. Predicting rates of pathogen
transmission and identifying wild populations at risk of disease epidemics requires
that we elucidate the factors that shape, and potentially decouple, the link between pathogen prevalence and intensity of infection over complex ecological landscapes.
3. Using a network of 41 populations of the amphibian host Rana pipiens in Ontario,
Canada, we present the spatial and temporal heterogeneity in pathogen prevalence
and intensity of infection of the chytrid fungus Batrachochytrium dendrobatidis
(Bd), across a 3-year period. We then quantify how covariation between both
infection parameters measured during late summer, are modified by previously
experienced spatiotemporal environmental heterogeneity across 14 repeat sampled
populations.
4. Late summer Bd infection parameters are governed, at least in part, by different environmental factors operating during separate host life history events. Our results provide evidence for a relationship between Bd prevalence and thermal regimes
prior to host breeding at the site level, and a relationship between intensity of
infection and aquatic conditions (precipitation, hydroshed size and river density) throughout host breeding period at the site level. This demonstrates that
microclimatic variation within temporal windows, can drive divergent patterns of pathogen dynamics within and across years, by effecting changes in host behaviour which interfere with the pathogen’s ability to infect and re-infect hosts.
5. A clearer understanding of the role that spatiotemporal heterogeneity has upon
infection parameters will provide valuable insights into host-pathogen
epidemiology, as well as more fundamental aspects of the ecology and evolution of interspecific interactions.
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