Routine habitat switching alters the likelihood and persistence of infection with a pathogenic parasite

Animals switch habitats on a regular basis, and when habitats vary in suitability 21 for parasitism, routine habitat switching alters the frequency of parasite exposure 22 and may affect post-infection parasite proliferation. However, the effects of 23 routine habitat switching on infection dynamics are not well understood. 24 2. We performed infection experiments, behavioural observations, and field 25 surveillance to evaluate how routine habitat switching by adult alpine newts 26 (Ichthyosaura alpestris) influences infection dynamics of the pathogenic parasite, 27 Batrachochytrium dendrobatidis (Bd). 28 3. We show that when newts are exposed to equal total doses of Bd in aquatic 29 habitats, differences in exposure frequency and post-exposure habitat alter 30 infection trajectories: newts developed more infections that persisted longer when 31 doses were broken into multiple, reduced-intensity exposures. Intensity and 32 persistence of infections was reduced among newts that were switched to 33 terrestrial habitats following exposure. 34 4. When presented with a choice of habitats, newts did not avoid exposure to Bd, 35 but heavily infected newts were more prone to reduce time spent in water. 36 5. Accounting for routine switching between aquatic and terrestrial habitat in the 37 experiments generated distributions of infection loads that were consistent with 38 those in two populations of wild newts. 39 6. Together, these findings emphasize that differential habitat use and behaviours 40 associated with daily movement can be important ecological determinants of 41 infection risk and severity. 4

Conservation decisions under pressure: lessons from an exercise in rapid response to wildlife disease

Novel outbreaks of emerging pathogens require rapid responses to enable successful mitigation. We simulated a 1‐day emergency meeting where experts were engaged to recommend mitigation strategies for a new outbreak of the amphibian fungal pathogen Batrachochytrium salamandrivorans. Despite the inevitable uncertainty, experts suggested and discussed several possible strategies. However, their recommendations were undermined by imperfect initial definitions of the objectives and scope of management. This problem is likely to arise in most real‐world emergency situations. The exercise thus highlighted the importance of clearly defining the context, objectives, and spatial–temporal scale of mitigation decisions. Managers are commonly under pressure to act immediately. However, an iterative process in which experts and managers cooperate to clarify objectives and uncertainties, while collecting more information and devising mitigation strategies, may be slightly more time consuming but ultimately lead to better outcomes

Captions and references for supplementary tables from Infections on the move: how transient phases of host movement influence disease spread

Animal movement impacts the spread of human and wildlife diseases, and there is significant interest in understanding the role of migrations, biological invasions and other wildlife movements in spatial infection dynamics. However, the influence of processes during the transient phases of host movement on infection is poorly understood. We propose a conceptual framework that explicitly considers infection dynamics during transient phases of host movement to better predict infection spread through spatial host networks. Accounting for host transient movement captures key processes that occur while hosts move between locations, which together determine the rate at which hosts spread infections through networks. We review theoretical and empirical studies of host movement and infection spread, highlighting the multiple factors that impact the infection status of hosts. We then outline characteristics of hosts, parasites and the environment that influence these dynamics. Recent technological advances provide disease ecologists unprecedented ability to track the fine-scale movement of organisms. These, in conjunction with experimental testing of the factors driving infection dynamics during host movement, can inform models of infection spread based on constituent biological processes

Table S2 from Infections on the move: how transient phases of host movement influence disease spread

Animal movement impacts the spread of human and wildlife diseases, and there is significant interest in understanding the role of migrations, biological invasions and other wildlife movements in spatial infection dynamics. However, the influence of processes during the transient phases of host movement on infection is poorly understood. We propose a conceptual framework that explicitly considers infection dynamics during transient phases of host movement to better predict infection spread through spatial host networks. Accounting for host transient movement captures key processes that occur while hosts move between locations, which together determine the rate at which hosts spread infections through networks. We review theoretical and empirical studies of host movement and infection spread, highlighting the multiple factors that impact the infection status of hosts. We then outline characteristics of hosts, parasites and the environment that influence these dynamics. Recent technological advances provide disease ecologists unprecedented ability to track the fine-scale movement of organisms. These, in conjunction with experimental testing of the factors driving infection dynamics during host movement, can inform models of infection spread based on constituent biological processes

Landscape epidemiology of Batrachochytrium salamandrivorans

Starting in 2010, rapid-fire salamander (Salamandra salamandra) population declines in northwestern Europe heralded the emergence of Batrachochytrium salamandrivorans (Bsal), a salamander-pathogenic chytrid fungus. Bsal poses an imminent threat to global salamander diversity owing to its wide host range, high pathogenicity, and long-term persistence in ecosystems. While there is a pressing need to develop further research and conservation actions, data limitations inherent to recent pathogen emergence obscure necessary insights into Bsal disease ecology. Here, we use a hierarchical modeling framework to describe Bsal landscape epidemiology of outbreak sites in light of these methodological challenges. Using model selection and machine learning, we find that Bsal presence is associated with humid and relatively cool, stable climates. Outbreaks are generally located in areas characterized by low landscape heterogeneity and low steepness of slope. We further find an association between Bsal presence and high trail density, suggesting that human-mediated spread may increase risk for spillover between populations. We then use distribution modeling to show that favorable conditions occur in lowlands influenced by the North Sea, where increased survey effort is needed to determine how Bsal impacts local newt populations, but also in hill- and mountain ranges in northeastern France and the lower half of Germany. Finally, connectivity analyses suggest that these hill- and mountain ranges may act as stepping stones for further spread southward. Our results provide initial insight into regional environmental conditions underlying Bsal epizootics, present updated invasibility predictions for northwestern Europe, and lead us to discuss a wide variety of potential survey and research actions needed to advance future conservation and mitigation efforts