Multi‐scale model of epidemic fade‐out: Will local extirpation events inhibit the spread of white‐nose syndrome?

Abstract

White-nose syndrome (WNS) is an emerging infectious disease that has resulted in severe declines of its hibernating bat hosts in North America. The ongoing epidemic of white-nose syndrome is a multi-scale phenomenon becau.se it causes hibernaculum-level extirpations, while simultaneously spreading over larger spatial scales. We investigate a neglected topic in ecological epidemiology: how local pathogen-driven extirpations impact large-scale pathogen spread. Previous studies have identified risk factors for propagation of WNS over hibernaculum and landscape scales but none of these have tested the hypothesis that separation of spatial scales and disease-induced mortality at the hibernaculum level might slow or halt its spread. To test this hypothesis, we developed a mechanistic multi-scale model parameterized using white-nose syndrome.county and site incidence data that connects hibernaculum-level susceptible-infectious-removed (SIR) epidemiology to the county-scale contagion process. Our key result is that hibernaculum-level extirpations will not inhibit county-scale spread of WNS. We show that over 80% of counties of the contiguous USA are likely to become infected before the current epidemic is over and that geometry of habitat connectivity is such that host refuges are exceedingly rare. The macroscale spatiotemporal infection pattern that emerges from local SIR epidemiological processes falls within a narrow spectrum of possible outcomes, suggesting that recolonization, rescue effects, and multi-host complexities at local scales are not important to forward propagation of WNS at large spatial scales. If effective control measures are not implemented, precipitous declines in bat populations are likely, particularly in cave-dense regions that constitute the main geographic corridors of the USA, a serious concern for bat conservation.

Prelude to a panzootic: Gene flow and immunogenetic variation in northern little brown myotis vulnerable to bat white-nose syndrome

“…Genetic, ecological, and environmental data have been used to model the direction and speed with which bats may facilitate dispersal of P. destructans towards the Pacific Coast of North America (Maher et al 2012;O'Regan et al 2015). However, models cannot fully predict pathogen dispersal, as illustrated by the recent, unexpected emergence of WNS in western Washington State in March 2016 (Lorch et al 2016).…”

Landscape structure and ecology influence the spread of a bat fungal disease

“…Although the effect of landscape structure has been studied in other wildlife diseases (Heard et al., ; Real & Biek, ; Remais, Akullian, Ding, & Seto, ), it has received less attention with WNS as the focal disease (for examples, see Maher et al., ; O'Regan et al., ). Our modelling results show how habitat suitability and landscape structure could influence the invasion rate and prevalence of Pseudogymnoascus destructans , the causative agent of WNS.…”

Microbial inhibitors of the fungus Pseudogymnoascus destructans, the causal agent of white-nose syndrome in bats

“…destructans has decimated eastern North American bat populations and is spreading across the continent [1,3,5]. Saprotrophic growth of P .…”

“…Further, P . destructans has rapidly spread to 32 U.S. states and 5 Canadian provinces [3] and is predicted to continue spreading [5], potentially threatening over half of all North American bat species [3]. Such widespread loss of bats as prominent insectivores will undoubtedly have costly ecological, agricultural, and economic consequences [6].…”