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1. Environmental reservoir dynamics predict global infection patterns and population impacts for the fungal disease white-nose syndrome

   https://doi.org/10.1073/pnas.1914794117  

   Hoyt, Joseph R. ; Langwig, Kate E. ; Sun, Keping ; Parise, Katy L. ; Li, Aoqiang ; Wang, Yujuan ; Huang, Xiaobin ; Worledge, Lisa ; Miller, Helen ; White, J. Paul ; et al ( March 2020 , Proceedings of the National Academy of Sciences)

   Disease outbreaks and pathogen introductions can have significant effects on host populations, and the ability of pathogens to persist in the environment can exacerbate disease impacts by fueling sustained transmission, seasonal epidemics, and repeated spillover events. While theory suggests that the presence of an environmental reservoir increases the risk of host declines and threat of extinction, the influence of reservoir dynamics on transmission and population impacts remains poorly described. Here we show that the extent of the environmental reservoir explains broad patterns of host infection and the severity of disease impacts of a virulent pathogen. We examined reservoir and host infection dynamics and the resulting impacts of Pseudogymnoascus destructans , the fungal pathogen that causes white-nose syndrome, in 39 species of bats at 101 sites across the globe. Lower levels of pathogen in the environment consistently corresponded to delayed infection of hosts, fewer and less severe infections, and reduced population impacts. In contrast, an extensive and persistent environmental reservoir led to early and widespread infections and severe population declines. These results suggest that continental differences in the persistence or decay of P. destructans in the environment altered infection patterns in bats and influenced whether host populations were stable or experienced severe declines from this disease. Quantifying the impact of the environmental reservoir on disease dynamics can provide specific targets for reducing pathogen levels in the environment to prevent or control future epidemics. 

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2. Shifting effects of host physiological condition following pathogen establishment

   https://doi.org/10.1098/rsbl.2022.0574  

   Langwig, Kate E. ; Kilpatrick, A. Marm ; Kailing, Macy J. ; Laggan, Nichole A. ; White, J. Paul ; Kaarakka, Heather M. ; Redell, Jennifer A. ; DePue, John E. ; Parise, Katy L. ; Foster, Jeffrey T. ; et al ( March 2023 , Biology Letters)

   Understanding host persistence with emerging pathogens is essential for conserving populations. Hosts may initially survive pathogen invasions through pre-adaptive mechanisms. However, whether pre-adaptive traits are directionally selected to increase in frequency depends on the heritability and environmental dependence of the trait and the costs of trait maintenance. Body condition is likely an important pre-adaptive mechanism aiding in host survival, although can be seasonally variable in wildlife hosts. We used data collected over 7 years on bat body mass, infection and survival to determine the role of host body condition during the invasion and establishment of the emerging disease, white-nose syndrome. We found that when the pathogen first invaded, bats with higher body mass were more likely to survive, but this effect dissipated following the initial epizootic. We also found that heavier bats lost more weight overwinter, but fat loss depended on infection severity. Lastly, we found mixed support that bat mass increased in the population after pathogen arrival; high annual plasticity in individual bat masses may have reduced the potential for directional selection. Overall, our results suggest that some factors that contribute to host survival during pathogen invasion may diminish over time and are potentially replaced by other host adaptations. 

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3. Field trial of a probiotic bacteria to protect bats from white-nose syndrome

   https://doi.org/10.1038/s41598-019-45453-z  

   Hoyt, Joseph R. ; Langwig, Kate E. ; White, J. Paul ; Kaarakka, Heather M. ; Redell, Jennifer A. ; Parise, Katy L. ; Frick, Winifred F. ; Foster, Jeffrey T. ; Kilpatrick, A. Marm ( June 2019 , Scientific Reports)

   Tools for reducing wildlife disease impacts are needed to conserve biodiversity. White-nose syndrome (WNS), caused by the fungusPseudogymnoascus destructans, has caused widespread declines in North American bat populations and threatens several species with extinction. Few tools exist for managers to reduce WNS impacts. We tested the efficacy of a probiotic bacterium,Pseudomonas fluorescens, to reduce impacts of WNS in two simultaneous experiments with caged and free-flyingMyotis lucifugusbats at a mine in Wisconsin, USA. In the cage experiment there was no difference in survival between control andP.fluorescens-treated bats. However, body mass, not infection intensity, predicted mortality, suggesting that within-cage disturbance influenced the cage experiment. In the free-flying experiment, where bats were able to avoid conspecific disturbance, infection intensity predicted the date of emergence from the mine. In this experiment treatment withP.fluorescensincreased apparent overwinter survival five-fold compared to the control group (from 8.4% to 46.2%) by delaying emergence of bats from the site by approximately 32 days. These results suggest that treatment of bats withP.fluorescensmay substantially reduce WNS mortality, and, if used in combination with other interventions, could stop population declines.

    

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4. Body mass and hibernation microclimate may predict bat susceptibility to white‐nose syndrome

   https://doi.org/10.1002/ece3.7070  

   Haase, Catherine G. ; Fuller, Nathan W. ; Dzal, Yvonne A. ; Hranac, C. Reed ; Hayman, David T. S. ; Lausen, Cori L. ; Silas, Kirk A. ; Olson, Sarah H. ; Plowright, Raina K. ( December 2020 , Ecology and Evolution)

   In multihost disease systems, differences in mortality between species may reflect variation in host physiology, morphology, and behavior. In systems where the pathogen can persist in the environment, microclimate conditions, and the adaptation of the host to these conditions, may also impact mortality. White‐nose syndrome (WNS) is an emerging disease of hibernating bats caused by an environmentally persistent fungus,Pseudogymnoascus destructans. We assessed the effects of body mass, torpid metabolic rate, evaporative water loss, and hibernaculum temperature and water vapor deficit on predicted overwinter survival of bats infected byP. destructans. We used a hibernation energetics model in an individual‐based model framework to predict the probability of survival of nine bat species at eight sampling sites across North America. The model predicts time until fat exhaustion as a function of species‐specific host characteristics, hibernaculum microclimate, and fungal growth. We fit a linear model to determine relationships with each variable and predicted survival and semipartial correlation coefficients to determine the major drivers in variation in bat survival. We found host body mass and hibernaculum water vapor deficit explained over half of the variation in survival with WNS across species. As previous work on the interplay between host and pathogen physiology and the environment has focused on species with narrow microclimate preferences, our view on this relationship is limited. Our results highlight some key predictors of interspecific survival among western bat species and provide a framework to assess impacts of WNS as the fungus continues to spread into western North America.

    

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5. Costs and drivers of helminth parasite infection in wild female baboons

   https://doi.org/10.1111/1365-2656.12994  

   Akinyi, Mercy_Y ; Jansen, David ; Habig, Bobby ; Gesquiere, Laurence_R ; Alberts, Susan_C ; Archie, Elizabeth_A ; Cattadori, ed., Isabella ( May 2019 , Journal of Animal Ecology)

   Helminth parasites can have wide‐ranging, detrimental effects on host reproduction and survival. These effects are best documented in humans and domestic animals, while only a few studies in wild mammals have identified both the forces that drive helminth infection risk and their costs to individual fitness.

   Working in a well‐studied population of wild baboons (Papio cynocephalus) in the Amboseli ecosystem in Kenya, we pursued two goals, to (a) examine the costs of helminth infections in terms of female fertility and glucocorticoid hormone levels and (b) test how processes operating at multiple scales—from individual hosts to social groups and the population at large—work together to predict variation in female infection risk.

   To accomplish these goals, we measured helminth parasite burdens in 745 faecal samples collected over 5 years from 122 female baboons. We combine these data with detailed observations of host environments, social behaviours, hormone levels and interbirth intervals (IBIs).

   We found that helminths are costly to female fertility: females infected with more diverse parasite communities (i.e., higher parasite richness) exhibited longer IBIs than females infected by fewer parasite taxa. We also found that females exhibiting highTrichuris trichiuraegg counts also had high glucocorticoid levels. Female infection risk was best predicted by factors at the host, social group and population level: females facing the highest risk were old, socially isolated, living in dry conditions and infected with other helminths.

   Our results provide an unusually holistic understanding of the factors that contribute to inter‐individual differences in parasite infection, and they contribute to just a handful of studies linking helminths to host fitness in wild mammals.

    

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