Ecological Traits Driving the Outbreaks and Emergence of Zoonotic Pathogens

Abstract

Infectious diseases that are transmitted from wildlife hosts to humans, such as the Ebola virus and MERS virus, can be difficult to understand because the pathogens emerge from complex multifaceted ecological interactions. We use a wildlife-pathogen system-prairie dogs (Cynomys ludovicianus) and the plague bacterium (Yersinia pestis)-to describe aspects of disease ecology that apply to many cases of emerging infectious disease. We show that the monitoring and surveillance of hosts and vectors during the buildup to disease outbreaks are crucial for understanding pathogen-transmission dynamics and that a community-ecology framework is important to identify reservoir hosts. Incorporating multidisciplinary approaches and frameworks may improve wildlife-pathogen surveillance and our understanding of seemingly sporadic and rare pathogen outbreaks.

Paltry past‐precipitation: Predisposing prairie dogs to plague?

“…We analyzed a long‐term dataset on the fates of individual colonies (Stapp et al , Savage et al , George et al ), an approach that has proven highly useful in prior studies of wildlife (Clutton‐Brock and Sheldon ), and our results support prior findings with prairie dogs and other species of rodents (e.g., Eads et al ; Eads and Hoogland ). Evaluations of factors affecting the occurrence of plague epizootics in prairie dog colonies depend on the definition of an epizootic and the timing of surveys (e.g., most outbreaks are not noticed until a prairie dog colony has collapsed; Salkeld et al ). If possible during future studies, data should be collected in a manner that allows for use of a response variable that reflects a continuum of plague transmission, from devastating epizootics (Savage et al ) to lower‐level transmission in the absence of observable die‐offs (Biggins et al ) to disease fade‐out (Salkeld et al ).…”

“…Evaluations of factors affecting the occurrence of plague epizootics in prairie dog colonies depend on the definition of an epizootic and the timing of surveys (e.g., most outbreaks are not noticed until a prairie dog colony has collapsed; Salkeld et al ). If possible during future studies, data should be collected in a manner that allows for use of a response variable that reflects a continuum of plague transmission, from devastating epizootics (Savage et al ) to lower‐level transmission in the absence of observable die‐offs (Biggins et al ) to disease fade‐out (Salkeld et al ). In our case, the evaluation depended upon weather data collected at stations that were sometimes >10 km from subject colonies (Savage et al ).…”

“…During an epizootic, Y. pestis proliferates in a prairie dog colony. This generative event might allow the bacterium to reach densities that promote dispersal to nearby colonies in infected hosts or fleas (Salkeld et al :125). If Y. pestis disperses to and arrives at a colony where it was not already present, the immigrating bacteria would presumably require time to grow in number and spatial distribution before an epizootic is observed.…”

“…If Y. pestis disperses to and arrives at a colony where it was not already present, the immigrating bacteria would presumably require time to grow in number and spatial distribution before an epizootic is observed. Put differently, an epizootic might not ensue at a colony until the population of Y. pestis has attained a sufficient density for epizootic spread, which takes several months in some cases (St. Romain et al , Salkeld et al ). Thus, we considered connectivity among colonies relative to colonies that experienced a plague epizootic in year t − 1.…”

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