Wildlife Health in a Changing Climate: Novel Stressors and Innovative Solutions



Symposia will be available on-demand on their scheduled date, then again at the conclusion of the conference.

Climate change is the ultimate threat to many wildlife populations with a varied suite of proximate risks that have the potential to result in additive or synergistic effects on wildlife populations. Habitat loss, abiotic and biotic changes, including exposure to novel competitors and pathogens has the potential to influence the health of wildlife populations. This symposium will highlight examples of how climate change is influencing pathogens and their wildlife hosts, and will address how the wildlife health paradigm will need to shift to integrate dynamic, novel stressors into a more holistic view of wildlife health. Speakers will expand the concept of health from solely focused on disease status, to a framework that considers all determinants of health for a wildlife population or community. Speakers will also discuss how health surveillance will need to respond to these changing conditions. With this framework in mind, we will consider how climate adaptation and mitigation strategies can contribute to protecting the health of wildlife, as well as our planet and ourselves.

A Health Strategy for Climate Change
Craig Stephen
Climate change health impacts are now inevitable. How we account for and manage climate change vulnerability depends, in part, on how health is defined. Defining health as the absence of specific diseases fails to evoke adequate action. If human health sector experience serves as a warning, significant and unsustainable impacts will arise more through changes in non-communicable diseases and impacts on determinants of health. Climate change will both amplify existing health problems and create unanticipated threats. For amplified problems, adaptation is a matter of ensuring wildlife health services can responsive to locally changing epidemiological situations. Key actions include; (i) adaptable surveillance of expected outcomes or hazards for early warning; (ii) building and sustaining healthy environments; (iii) protecting food and water safety and security; and (vi) reducing inequities that affect access to management actions. However, a hazard-by-hazard approach, on its own, insufficiently ensures climate change preparedness. The complex interaction of global and local forces with climate change will escalate the frequency and severity of unanticipated or unimaginable impacts. Surprise anticipation comes with improving situational awareness of the distribution of and exposure to emerging hazards, or changes in willingness to act on early warning signals. Surprise preparation also comes from bolstering the determinants of health that enhance a population’s capacity to cope with unexpected harms. A strategy concerned with unanticipated impacts requires investment in; (i) identifying and addressing social and ecologic inequities that enhance climate change vulnerability; (ii) building capacity for individuals and populations to cope with multiple interacting threats and stresses before an impact occurs; (iii) resource to adaptively respond to surges in unexpected emergencies or outbreaks; (iv) integrating animal health adaptation into ecosystem climate change management; (iv) promoting climate change health literacy to encourage proactive adaptive and mitigative actions and (v) innovative leadership, partnerships and governance.
Determinants of Health Model for Wildlife
Julie Wittrock; Craig Stephen
Climate change is a growing threat to the resilience and survival of wildlife populations. Despite current wildlife health programs stating the assessment and sustainability of health as a conservation and management goal, the absence of disease continues to be the benchmark for health. In order to address the complex and multifactorial challenges of climate change, it is necessary to adopt a perspective on wildlife health that considers these cumulative effects. Our objectives were to ascertain whether the determinants of health model from human population health could be adapted to wildlife, if it would be applicable to more than one species, and if reflected how fish and wildlife managers conceptualize health in practice. A conceptual model was developed using a scoping review on fish and wildlife health and sustainability combined with a participatory process with experts on caribou (Rangifer tarandus) and Pacific salmon (Oncorhyncus spp.). Both the literature and experts supported the concept of wildlife health as a cumulative effect involving multiple factors that extend beyond the disease and pathogen focus of many wildlife health studies and legislation. Six themes were associated with fish and wildlife health: biological endowment of the individual and population, the animal’s social environment, the quality and abundance of the needs for daily living, their abiotic environment, sources of direct mortality, and changing human expectations. These themes were shared between salmon and caribou and conformed with expert perceptions of health. In public health, determinants of health are used for planning, policy development, and guiding of research. The model produced in this study may also have use as a wildlife health planning tool to help managers identify health protection and promotion actions across the determinants of health.
Climate Adaptation: Improving Wildlife Health Outcomes
Olivia LeDee
Climate change impairs wildlife health, affecting reproduction, growth, and survival, and altering the trajectory of wildlife populations. Although climate change is a complex, heterogeneous threat, resource managers have and will continue to implement strategic interventions to reduce harm to wildlife populations. To increase their adaptive capacity, a surrogate for health, resource managers typically employ reserve design and habitat management strategies. Population and disease management are important, underutilized techniques to improve wildlife health outcomes under climate change. Moreover, empirical evidence for guidance and experimental approaches to such interventions are limited. This presentation will review the current landscape of climate adaptation for wildlife health, provide a checklist for optimal design of interventions, and outline conflicts between climate adaptation and wildlife disease management.
Climate change and vector-borne diseases
Robin Russell; Daniel P. Walsh; Tonie E. Rocke
Climate change has the potential to affect both host and vector populations and alter the dynamics of vector-borne diseases. The frequency and severity of vector-borne diseases may change as local environmental conditions are affected by global climate change patterns. We evaluated the effects of local climate factors on host flea abundance at multiple sites across the intermountain west for four species of prairie dog (black-tailed, white-tailed, Utah, and Gunnison’s). We found that several climate related factors including the number of degree days, Normalized Difference Vegetation Index, and precipitation patterns affected host flea loads, and that those factors differ between southern and northern sites. In addition, we have developed a spatially-explicit plague transmission model to investigate the factors influencing the frequency and severity of plague outbreaks including the potential effects of climate change. Plague transmission dynamics are complex, and there are multiple key uncertainties including the mechanics of flea-transmission that we address with our models. We discuss the implications of climate change on plague transmission and extend these ideas to hemorraghic disease and other vector-borne disease.
Assessing Polar Bear Health in a Changing Climate
Tricia Fry; Todd Atwood; Colleen Duncan
Polar bears (Ursus maritimus) from Alaska’s southern Beaufort Sea have been sampled annually since 1984, with few exceptions. This effort has provided long-term data on polar bear demography, habitat use, diet and health. Findings from this long-term data set, in conjunction with relevant sea ice and climate data, afforded us the opportunity to explore how climate-mediated environmental stressors may be influencing polar bear health. Specifically, we discuss how the loss of sea ice habitat has modified bear behavior, resulting in biologic and physiologic cascades that may have adverse implications for population health. Our goal with this synthesis is to explore the opportunities and challenges to moving beyond the predominant conceptualization of wildlife health as the absence of disease to one that recognizes health is the outcome of complex interactions between individuals and their environments. We provide a framework for characterizing polar bear health through the interaction of biological, environmental, and social processes that can be used to provide meaningful measures of progress towards conservation goals and objectives.
Parasite-Host Interactions Associated with Climate Change
Richard Gerhold
Parasites are integrally linked with climate alternations and anthropogenic changes that can influence various aspects of parasite life cycles including relative abundance of definitive and intermediate hosts and vector species. There is even evidence of parasite life cycles being altered by climate changes to reduce parasite maturation intervals that can lead to higher abundance of parasites in hosts or increased frequency of harboring pathogens (i.e. tick borne diseases). Furthermore, precipitation and temperature changes can impact the distribution and density of parasites, parasite sporulation or larvation duration, and even possibly host and vector distribution. Numerous examples of emerging parasite species and community shifts have been noted in various wildlife species with some of these parasites causing substantial population impacts. Various species of arthropods (ticks, mosquitoes, etc), protozoa, nematodes, cestodes, and trematodes have demonstrated previously undocumented geographical shifts that can have negative impacts to ecosystems. Additionally, some parasites species that have evolved with their vertebrate hosts may go extinct or be supplanted by other parasite species that are more pathogenic to the vertebrate hosts. In this lecture we will discuss examples of climate change associated parasite shifts and ecosystem impacts and what the adaptive capacity of select wild animals to these parasites.
The Thermal Mismatchhypothesis Explains Host Susceptibility to the Amphibian Chytrid Fungus
Jeremy Cohen
Parasites typically have broader thermal limits than hosts, so large performance gaps between pathogens and their cold- and warm-adapted hosts should occur at relatively warm and cold temperatures, respectively. We tested this thermal mismatch hypothesis by quantifying the temperature-dependent susceptibility of amphibian species to the fungal pathogen Batrachochytrium dendrobatidis (Bd) using laboratory experiments and field prevalence estimates from 88,229 individuals across 3,598 populations. We also tested whether factors such as latitude, body size, preferred habitat and taxonomy influence the importance of thermal mismatches in driving Bd outbreaks. Finally, using a dataset describing 66 recent extinctions in the amphibian genus Atelopus, we asked whether the thermal mismatch hypothesis can predict which species suffered most under a combination of disease and unusually warm conditions.
In both the laboratory and field, we found that the greatest disease susceptibility of cold- and warm-adapted hosts occurred at relatively warm and cool temperatures, respectively, providing support for the thermal mismatch hypothesis. In addition, sensitivity to disease in the presence of thermal mismatches increased for adult amphibians and terrestrial species, likely because these are more exposed to environmental conditions. Consistent with the thermal mismatch hypothesis, Atelopus species from cooler climates were more likely to go extinct when conditions warmed and Bd was present, while those from warm habitats were unaffected. Our results suggest that as climate change shifts hosts away from their optimal temperatures, the probability of increased host susceptibility to infectious disease might increase, but the effect will depend on the host species and the direction of the climate shift. Our findings help explain the tremendous variation in species responses to Bd across climates and spatial, temporal, and species-level variation in disease outbreaks associated with extreme weather events that are becoming more common with climate change.
Drivers of Emerging Hemorrhagic Disease
Sonja Christensen
Hemorrhagic disease (HD) of deer is a vector-borne disease caused by either epizootic hemorrhagic disease virus (EHDV) or bluetongue virus (BTV). These viruses are globally distributed and dependent on specific arthropod vectors and their associated ecological and climatic niche. Climate change has been linked to the emergence of BTV in Europe and is suspected as a driver of emergent disease in North America where in the last 20 years, HD has increased in distribution, severity, and frequency. Our work evaluates the influence of environmental factors on changes in HD reports across the eastern US. Specifically, we are interested in how seasonal weather and climate shifts play a role in the emergence of this important vector-borne disease and potentially other vector-borne diseases like it. Historic data from an annual HD presence-absence survey conducted by the Southeastern Cooperative Wildlife Disease Study has made it possible to evaluate linkages between environmental factors and HD across space and time. For example, in northern latitudes, where immunological naivety is most likely, we’ve demonstrated the increasing strength of drought severity as a determinant of reported HD and established the importance of variation in drought severity as a risk factor over the present range of HD in the eastern United States. We continue to determine what environmental drivers may explain the northern expansion of HD, providing critical insight to the potential vector-host-virus factors influenced by climate.
Invited Speaker
Sonia Altizer
Into Uncharted Waters and Temperatures: Wildlife Professionalsand Climate Change
Danielle Buttke
Climate change is having broad and multi-faceted impacts on natural resources on every continent. At the same time, human populations are impacting these same resources through land development, introduction of non-native species, over-use of many natural resources, and pollution. Climate change impacts to natural resources are therefore one of multiple stressors on a system, making predictions as to the impacts of a changing climate more difficult than in an isolated system. Warmer temperatures and more variable weather patterns can impact disease organisms, particularly those transmitted by arthropod vectors, in multiple ways. At the same time, vector borne diseases are dramatically influenced by ecological factors strongly altered by human settlement and development. We argue that issues of climate change, loss of connectivity, biodiversity loss, and species introductions, including pathogens, must be examined in concert for the best management outcomes and for land-management agencies to adapt policies to promote the precautionary principle in managing risks to conservation. Human behavior and decision-making will determine the success or failure of conservation and climate policies and we argue for a role of wildlife professionals in climate change advocacy to accomplish our conservation goals.

Organizers: Krysten Schuler, Cornell University, Ithaca, NY; Tricia Fry, University of Wisconsin-Madison, Madison, Wisconsin; Michelle Verant, National Park Service, Fort Collins, Colorado; Olivia LeDee, USGS, Minneapolis, MN; Anne Justice-Allen, Arizona Game and Fish Department, Phoenix, AZ; Danielle Buttke, National Park Service, Fort Collins, CO
Supported by: Wildlife Disease Working Group, Climate Change Working Group, American Association of Wildlife Veterinarians

Location: Virtual Date: September 29, 2020 Time: -