Aquaculture Reuse Water, Genetic Line, and Vaccination Affect Rainbow Trout (Oncorhynchus mykiss) Disease Susceptibility and Infection Dynamics

Infectious hematopoietic necrosis virus (IHNV) and Flavobacterium psychrophilum are major pathogens of farmed rainbow trout. Improved control strategies are desired but the influence of on-farm environmental factors that lead to disease outbreaks remain poorly understood. Water reuse is an important environmental factor affecting disease. Prior studies have established a replicated outdoor-tank system capable of varying the exposure to reuse water by controlling water flow from commercial trout production raceways. The goal of this research was to evaluate the effect of constant or pulsed reuse water exposure on survival, pathogen prevalence, and pathogen load. Herein, we compared two commercial lines of rainbow trout, Clear Springs Food (CSF) and Troutex (Tx) that were either vaccinated against IHNV with a DNA vaccine or sham vaccinated. Over a 27-day experimental period in constant reuse water, all fish from both lines and treatments, died while mortality in control fish in spring water was PPP ≤ 0.001), while risk of death did not differ in spring water (P=0.98). Sham-vaccinated fish had 2.1-fold greater risk of death compared to vaccinated fish (P=0.02). Both IHNV prevalence and load were lower in vaccinated fish compared to sham-vaccinated fish, and unexpectedly, F. psychrophilum load associated with fin/gill tissues from live-sampled fish was lower in vaccinated fish compared to sham-vaccinated fish. As a result, up to forty-five percent of unvaccinated fish were naturally co-infected with F. psychrophilum and IHNV and the coinfected fish exhibited the highest IHNV loads. Under laboratory challenge conditions, co-infection with F. psychrophilum and IHNV overwhelmed IHNV vaccine-induced protection. In summary, we demonstrate that exposure to reuse water or multi-pathogen challenge can initiate complex disease dynamics that can overwhelm both vaccination and host genetic resistance

Context-dependent conservation responses to emerging wildlife diseases

Emerging infectious diseases pose an important threat to wildlife. While established protocols exist for combating outbreaks of human and agricultural pathogens, appropriate management actions before, during, and after the invasion of wildlife pathogens have not been developed. We describe stage-specific goals and management actions that minimize disease impacts on wildlife, and the research required to implement them. Before pathogen arrival, reducing the probability of introduction through quarantine and trade restrictions is key because prevention is more cost effective than subsequent responses. On the invasion front, the main goals are limiting pathogen spread and preventing establishment. In locations experiencing an epidemic, management should focus on reducing transmission and disease, and promoting the development of resistance or tolerance. Finally, if pathogen and host populations reach a stable stage, then recovery of host populations in the face of new threats is paramount. Successful management of wildlife disease requires risk-taking, rapid implementation, and an adaptive approach."Funding was provided by the US National Science Foundation (grants EF-0914866, DGE-0741448, DEB-1115069, DEB-1336290) and the National Institutes of Health (grant 1R010AI090159)."https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/14024

Moving Beyond Too Little, Too Late: Managing Emerging Infectious Diseases in Wild Populations Requires International Policy and Partnerships

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Effects of bird feeder density on the foraging behaviors of a backyard songbird (The house finch, haemorhous mexicanus) subject to seasonal disease outbreaks

Provisioning of wildlife, such as backyard bird feeding, can alter animal behavior and ecology in diverse ways. For species that are highly dependent on supplemental resources, it is critical to understand how variation in the degree of provisioning, as occurs naturally across backyards, alters wildlife behavior and ecology in ways potentially relevant to disease spread. We experimentally manipulated feeder density at suburban sites and tracked local abundance, foraging behaviors, body mass, and movement in House Finches (Haemorhous mexicanus (P.L. Statius Müller, 1776)), the primary host of a pathogen commonly spread at feeders. Sites with high feeder density harbored higher local House Finch abundance, and birds at these sites had longer feeding bouts and total time on feeders relative to sites with low feeder density. House Finches at high-density feeder sites had lower residual body mass despite greater apparent feeder access. Finally, birds first recorded at low-density feeder sites were more likely to move to neighboring high-density feeder sites than vice versa. Because local abundance and time spent on feeders have both been linked with disease risk in this species, the effects of heterogeneity in bird feeder density on these traits may have important consequences for disease dynamics in this system and more broadly

Risk factors associated with mortality from white-nose syndrome among hibernating bat colonies

White-nose syndrome (WNS) is a disease responsible for unprecedented mortality in hibernating bats. First observed in a New York cave in 2006, mortality associated with WNS rapidly appeared in hibernacula across the northeastern United States. We used yearly presence–absence data on WNS-related mortality among hibernating bat colonies in the Northeast to determine factors influencing its spread. We evaluated hazard models to test hypotheses about the association between the timing of mortality and colony-level covariates, such as distance from the first WNS-affected site, colony size, species diversity, species composition and type of hibernaculum (cave or mine). Distance to origin and colony size had the greatest effects on WNS hazard over the range of observations; the type of hibernaculum and species composition had weaker effects. The distance effect showed a temporal decrease in magnitude, consistent with the pattern of an expanding epizootic. Large, cave-dwelling bat colonies with high proportions of Myotis lucifugus or other species that seek humid microclimates tended to experience early mortality. Our results suggest that the timing of mortality from WNS is largely dependent on colony location, and large colonies tend to be first in an area to experience high mortality associated with WNS

Efficacy of a probiotic bacterium to treat bats affected by the disease white‐nose syndrome

The management of infectious diseases is an important conservation concern for a growing number of wildlife species. However, effective disease control in wildlife is challenging because feasible management options are often lacking. White‐nose syndrome (WNS ) is an infectious disease of hibernating bats that currently threatens several North American species with extinction. Currently, no effective treatments exist for WNS . We conducted a laboratory experiment to test the efficacy of probiotic treatment with Pseudomonas fluorescens , a bacterium that naturally occurs on bats, to reduce disease severity and improve survival of little brown bats Myotis lucifugus exposed to Pseudogymnoascus destructans , the fungal pathogen that causes WNS . We found that application of the probiotic bacteria at the time of fungal infection reduced several measures of disease severity and increased survival, whereas bacterial treatment prior to pathogen exposure had no effect on survival and worsened disease severity. Synthesis and applications . Our results suggest that probiotic treatment with Ps. fluorescens has potential for white‐nose syndrome disease management, but the timing of application is critical and should coincide with natural exposure of bats to P. destructans . These results add to the growing knowledge of how natural host microbiota can be implemented as a biocontrol treatment to influence disease outcomes

Data from: Efficacy of a probiotic bacterium to treat bats affected by the disease white-nose syndrome

The management of infectious diseases is an important conservation concern for a growing number of wildlife species. However, effective disease control in wildlife is challenging because feasible management options are often lacking. White-nose syndrome (WNS) is an infectious disease of hibernating bats that currently threatens several North American species with extinction. Currently, no effective treatments exist for WNS. We conducted a laboratory experiment to test the efficacy of treatment with Pseudomonas fluorescens, a bacterium that naturally occurs on bats, to reduce disease severity and improve survival of little brown bats (Myotis lucifugus) exposed to Pseudogymnoacus destructans, the fungal pathogen that causes WNS. Application of the bacteria at the time of P. destructans infection reduced several measures of disease severity and increased survival, whereas bacterial treatment prior to pathogen exposure had no effect on survival and worsened disease severity. Our results suggest that probiotic treatment with Ps. fluorescens has potential for WNS disease management but the timing of application is critical and should coincide with natural exposure of bats to P. destructans. More broadly, these results add to the growing knowledge of how the natural host microbiota can influence disease outcomes