scholarly journals Disease and climate effects on individuals jointly drive post-reintroduction population dynamics of an endangered amphibian

2018 ◽  
Author(s):  
Maxwell B. Joseph ◽  
Roland A. Knapp
Keyword(s):  
Population Dynamics ◽  
Disease Ecology ◽  
Batrachochytrium Dendrobatidis ◽  
Species Conservation ◽  
Infection Intensity ◽  
Host Population ◽  
Negative Effects ◽  
Conservation Actions ◽  
In The Wild ◽  
Amphibian Chytrid Fungus

AbstractThe emergence of novel pathogens often has dramatic negative effects on previously unexposed host populations. Subsequent disease can drive populations and even species to extinction. After establishment in populations, pathogens can continue to affect host dynamics, influencing the success or failure of species recovery efforts. However, quantifying the effect of pathogens on host populations in the wild is challenging because individual hosts and their pathogens are difficult to observe. Here we use long-term mark-recapture data to describe the dynamics of reintroduced populations of an endangered amphibian (Rana sierrae) and evaluate the success of these recovery efforts in the presence of a recently-emerged pathogen, the amphibian chytrid fungus Batrachochytrium dendrobatidis. We find that high B. dendrobatidis infection intensities are associated with increases in detectability, reductions in survival, and more infected adults. We also find evidence for intensity-dependent survival, with heavily infected individuals suffering higher mortality. These results highlight the need in disease ecology for probabilistic approaches that account for uncertainty in infection intensity using imperfect observational data. Such approaches can advance the understanding of disease impacts on host population dynamics, and in the current study will improve the effectiveness of species conservation actions.

scholarly journals Is overwintering mortality driving enigmatic declines? Evaluating the impacts of trematodes and the amphibian chytrid fungus on an anuran from hatching through overwintering

PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0262561
Author(s):  
Olivia Wetsch ◽  
Miranda Strasburg ◽  
Jessica McQuigg ◽  
Michelle D. Boone
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Species Conservation ◽  
Emerging Infectious Diseases ◽  
The Novel ◽  
Chytrid Fungus ◽  
Growth And Survival ◽  
Critical Life Events ◽  
Overwintering Mortality ◽  
Amphibian Chytrid Fungus

Emerging infectious diseases are increasing globally and are an additional challenge to species dealing with native parasites and pathogens. Therefore, understanding the combined effects of infectious agents on hosts is important for species’ conservation and population management. Amphibians are hosts to many parasites and pathogens, including endemic trematode flatworms (e.g., Echinostoma spp.) and the novel pathogenic amphibian chytrid fungus (Batrachochytrium dendrobatidis [Bd]). Our study examined how exposure to trematodes during larval development influenced the consequences of Bd pathogen exposure through critical life events. We found that prior exposure to trematode parasites negatively impacted metamorphosis but did not influence the effect of Bd infection on terrestrial growth and survival. Bd infection alone, however, resulted in significant mortality during overwintering—an annual occurrence for most temperate amphibians. The results of our study indicated overwintering mortality from Bd could provide an explanation for enigmatic declines and highlights the importance of examining the long-term consequences of novel parasite exposure.

scholarly journals Epidemic and endemic pathogen dynamics correspond to distinct host population microbiomes at a landscape scale

2017 ◽  
Vol 284 (1857) ◽  
pp. 20170944 ◽  
Author(s):  
Andrea J. Jani ◽  
Roland A. Knapp ◽  
Cheryl J. Briggs
Keyword(s):  
Infectious Disease ◽  
Fungal Pathogen ◽  
Batrachochytrium Dendrobatidis ◽  
Infection Intensity ◽  
Host Population ◽  
Symbiotic Bacteria ◽  
Skin Microbiome ◽  
Pathogen Infection ◽  
Microbiome Composition ◽  
Pathogen Invasion

Infectious diseases have serious impacts on human and wildlife populations, but the effects of a disease can vary, even among individuals or populations of the same host species. Identifying the reasons for this variation is key to understanding disease dynamics and mitigating infectious disease impacts, but disentangling cause and correlation during natural outbreaks is extremely challenging. This study aims to understand associations between symbiotic bacterial communities and an infectious disease, and examines multiple host populations before or after pathogen invasion to infer likely causal links. The results show that symbiotic bacteria are linked to fundamentally different outcomes of pathogen infection: host–pathogen coexistence (endemic infection) or host population extirpation (epidemic infection). Diversity and composition of skin-associated bacteria differed between populations of the frog, Rana sierrae , that coexist with or were extirpated by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). Data from multiple populations sampled before or after pathogen invasion were used to infer cause and effect in the relationship between the fungal pathogen and symbiotic bacteria. Among host populations, variation in the composition of the skin microbiome was most strongly predicted by pathogen infection severity, even in analyses where the outcome of infection did not vary. This result suggests that pathogen infection shapes variation in the skin microbiome across host populations that coexist with or are driven to extirpation by the pathogen. By contrast, microbiome richness was largely unaffected by pathogen infection intensity, but was strongly predicted by geographical region of the host population, indicating the importance of environmental or host genetic factors in shaping microbiome richness. Thus, while both richness and composition of the microbiome differed between endemic and epidemic host populations, the underlying causes are most likely different: pathogen infection appears to shape microbiome composition, while microbiome richness was less sensitive to pathogen-induced disturbance. Because higher richness was correlated with host persistence in the presence of Bd, and richness appeared relatively stable to Bd infection, microbiome richness may contribute to disease resistance, although the latter remains to be directly tested.

scholarly journals Systematic shifts in the variation among host individuals must be considered in climate-disease theory

2021 ◽  
Author(s):  
Joseph R Mihaljevic ◽  
David J Páez
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Disease Ecology ◽  
Host Population ◽  
Host Susceptibility ◽  
Disease Spread ◽  
Species Variation ◽  
Trait Variation ◽  
Host Pathogen ◽  
Population Sizes

To make more informed predictions of host-pathogen interactions under climate change, studies have incorporated the thermal performance of host, vector, and pathogen traits into disease models. However, this body of work has ignored the fact that disease spread and long-term patterns of host population dynamics are largely determined by the variation in susceptibility among individuals in the host population. Furthermore, and especially for ectothermic host species, variation in susceptibility is likely to be plastic, influenced by variables such as environmental temperature. Quantifying the relationship between temperature and among-host trait variation will therefore be critical for predicting how climate change and disease will interact to influence host-pathogen population dynamics. Here, we demonstrate how short-term effects of temperature on the variation of host susceptibility drive epidemic characteristics, fluctuations in host population sizes, and probabilities of host extinction. We use this quantitative analysis as a basic framework to suggest that more research is needed in disease ecology to understand the mechanisms that shape trait variation, not just trait averages.

Wild Bird Populations in the Face of Disease

2021 ◽  
pp. 121-144
Author(s):  
Kathryn P. Huyvaert
Keyword(s):  
Population Dynamics ◽  
Disease Ecology ◽  
Population Level ◽  
Host Population ◽  
Infection Prevalence ◽  
Imperfect Detection ◽  
Statistical Parameters ◽  
Bird Populations ◽  
The Face

Parasites and pathogens typically have detectable negative fitness impacts on individual avian hosts, but the role of parasites in driving population dynamics is less straightforward. Questions about whether and under what conditions parasites influence host population dynamics have been long-standing in infectious disease ecology for many years. Understanding the role of parasites in host population dynamics requires estimating statistical parameters such as infection prevalence and host abundance at population scales. Mathematical approaches such as process-based models are also often used to simulate population-level dynamics of host and parasite interactions over time. This chapter first describes tools commonly used in disease ecology to estimate these key parameters, with a focus on accounting for imperfect detection of individual animals or their disease or infection status and mark-recapture approaches. Some of the mathematical approaches, including SIR models, network approaches, and agent-based models, that are commonly used to simulate and predict the population dynamics of host–parasite interactions are presented. Through a series of case studies, the chapter finishes by considering whether and under what conditions parasites affect the overall growth of populations, whether parasites have a tendency to cause cycles or to regulate populations of wild birds, and some examples of parasite-induced local extinctions.

scholarly journals The precarious persistence of the Endangered Sierra Madre yellow-legged frog Rana muscosa in southern California, USA

Oryx ◽  
2013 ◽  
Vol 49 (1) ◽  
pp. 157-164 ◽  
Author(s):  
Adam R. Backlin ◽  
Cynthia J. Hitchcock ◽  
Elizabeth A. Gallegos ◽  
Julie L. Yee ◽  
Robert N. Fisher
Keyword(s):  
Southern California ◽  
Batrachochytrium Dendrobatidis ◽  
Isolated Populations ◽  
Active Season ◽  
Mountain Ranges ◽  
Sierra Madre ◽  
In The Wild ◽  
Rana Muscosa ◽  
Stochastic Events ◽  
Amphibian Chytrid Fungus

AbstractWe conducted surveys for the Endangered Sierra Madre yellow-legged frog Rana muscosa throughout southern California to evaluate the current distribution and status of the species. Surveys were conducted during 2000–2009 at 150 unique streams and lakes within the San Gabriel, San Bernardino, San Jacinto, and Palomar mountains of southern California. Only nine small, geographically isolated populations were detected across the four mountain ranges, and all tested positive for the amphibian chytrid fungus Batrachochytrium dendrobatidis. Our data show that when R. muscosa is known to be present it is easily detectable (89%) in a single visit during the frog's active season. We estimate that only 166 adult frogs remained in the wild in 2009. Our research indicates that R. muscosa populations in southern California are threatened by natural and stochastic events and may become extirpated in the near future unless there is some intervention to save them.

Prioritizing strain insulators for raptor conservation

2021 ◽  
pp. 1-16
Author(s):  
FRANCISCO GUIL ◽  
M. ÁNGELES SORIA ◽  
VÍCTOR ORTEGA ◽  
RUBÉN GARCÍA-SÁNCHEZ ◽  
SILVIA VILLAVERDE-MORCILLO
Keyword(s):  
Methodological Approach ◽  
Risk Index ◽  
Influential Factors ◽  
Negative Effects ◽  
Central Spain ◽  
Novel Approach ◽  
Conservation Actions ◽  
Complete Survey ◽  
Raptor Conservation ◽  
Management And Conservation

Summary Avian species often take advantage of human-made structures, such as perching on power poles, although this can lead to negative effects for both birds and infrastructure. It has been demonstrated that anchor-type pylons, with strain insulators, are amongst the most dangerous of these structures. Our goal was to develop a methodological approach to evaluate the ways in which raptors perch on the six most commonly used strain insulator configurations in Spain, and to build a risk index that can be used to prioritise them. To study the ways raptors perch, we worked with six wildlife rescue centres in central Spain for almost a year assessing these six strain insulator configurations in 83 perch trials with 176 raptors in ample flying pens. We analysed 475 complete survey days, with an approximate number of 258,960 analysed pictures, including 6,766 perchings on strain insulators. We assessed the influential factors for these 6,766 perchings and developed a novel approach to prioritise strain insulator configurations that can be used anywhere. Our results suggest that longer insulator strains (i.e. PECA-1000 and Caon-C3670) are the safest, according to our prioritization criteria, although these results require further assessment in the field. Managers and conservationists should take into account these results to improve management and conservation actions.

scholarly journals Sarcoptic mange in wild ruminants in Spain: solving the epidemiological enigma using microsatellite markers

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Barbara Moroni ◽  
Samer Angelone ◽  
Jesús M. Pérez ◽  
Anna Rita Molinar Min ◽  
Mario Pasquetti ◽  
...  
Keyword(s):  
Microsatellite Markers ◽  
Sarcoptes Scabiei ◽  
Host Population ◽  
Sarcoptic Mange ◽  
Wild Ruminant ◽  
Capra Pyrenaica ◽  
Wild Ruminants ◽  
In The Wild ◽  
Genetic Clusters ◽  
Genetic Strains

Abstract Background In Spain, sarcoptic mange was first described in native wildlife in 1987 in Cazorla Natural Park, causing the death of nearly 95% of the local native population of Iberian ibex (Capra pyrenaica). Since then, additional outbreaks have been identified in several populations of ibex and other wild ungulate species throughout the country. Although the first epizootic outbreak in wildlife was attributed to the introduction of an infected herd of domestic goats, the origin and the cause of its persistence remain unclear. The main aims of this study are to understand (i) the number of Sarcoptes scabiei “strains” circulating in wild ruminant populations in Spain, and (ii) the molecular epidemiological relationships between S. scabiei and its hosts. Methods Ten Sarcoptes microsatellite markers were used to characterize the genetic structure of 266 mites obtained from skin scrapings of 121 mangy wild ruminants between 2011 and 2019 from 11 areas in Spain. Results Seventy-three different alleles and 37 private alleles were detected. The results of this study show the existence of three genetic strains of S. scabiei in the wild ruminant populations investigated. While two genetic clusters of S. scabiei were host- and geography-related, one cluster included multi-host mites deriving from geographically distant populations. Conclusions The molecular epidemiological study of S. scabiei in wild ruminants in Spain indicates that the spreading and persistence of the parasite may be conditioned by host species community composition and the permissiveness of each host population/community to the circulation of individual “strains,” among other factors. Wildlife–livestock interactions and the role of human-driven introduction or trade of wild and domestic animals should be better investigated to prevent further spread of sarcoptic mange in as yet unaffected natural areas of the Iberian Peninsula.

scholarly journals Prioritizing conservation actions in urbanizing landscapes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. K. Ettinger ◽  
E. R. Buhle ◽  
B. E. Feist ◽  
E. Howe ◽  
J. A. Spromberg ◽  
...  
Keyword(s):  
Coho Salmon ◽  
Predictive Accuracy ◽  
Critical Threshold ◽  
Negative Effects ◽  
Conservation Action ◽  
Critical Thresholds ◽  
Species Response ◽  
Response Data ◽  
Conservation Actions ◽  
Preservation And Restoration

AbstractUrbanization-driven landscape changes are harmful to many species. Negative effects can be mitigated through habitat preservation and restoration, but it is often difficult to prioritize these conservation actions. This is due, in part, to the scarcity of species response data, which limit the predictive accuracy of modeling to estimate critical thresholds for biological decline and recovery. To address these challenges, we quantify effort required for restoration, in combination with a clear conservation objective and associated metric (e.g., habitat for focal organisms). We develop and apply this framework to coho salmon (Oncorhynchus kisutch), a highly migratory and culturally iconic species in western North America that is particularly sensitive to urbanization. We examine how uncertainty in biological parameters may alter locations prioritized for conservation action and compare this to the effect of shifting to a different conservation metric (e.g., a different focal salmon species). Our approach prioritized suburban areas (those with intermediate urbanization effects) for preservation and restoration action to benefit coho. We found that prioritization was most sensitive to the selected metric, rather than the level of uncertainty or critical threshold values. Our analyses highlight the importance of identifying metrics that are well-aligned with intended outcomes.

scholarly journals Pentastomids infecting an invader lizard, Hemidactylus mabouia (Gekkonidae) in northeastern Brazil

2008 ◽  
Vol 68 (3) ◽  
pp. 611-615 ◽  
Author(s):  
LA. Anjos ◽  
WO. Almeida ◽  
A. Vasconcellos ◽  
EMX. Freire ◽  
CFD. Rocha
Keyword(s):  
Feeding Habits ◽  
Infection Intensity ◽  
First Record ◽  
Host Population ◽  
Northeastern Brazil ◽  
Parasitism Rate ◽  
Intensity Of Infection ◽  
New Host ◽  
Single Host ◽  
Hemidactylus Mabouia

From January to April 2006, 37 specimens of Hemidactylus mabouia were collected in houses, in the municipality of Barbalha (7° 20' S and 39° 18' W), Ceará State, Northeast Brazil. Among the individuals captured, 17 were infected with pentastomids, totalling a prevalence of 45.9%, which did not differ between sexes. Host size did not influence the infection intensity. Two species of pentastomids were found: Raillietiella frenatus and R. mottae. The prevalence of R. frenatus (43.2%) was higher than R. mottae (2.7%), whereas the infection intensity of R. frenatus was comparatively lower (1.8 ± 1.4) than R. mottae (36 parasites in a single host). Overall mean intensity of infection was 3.8 ± 8.4 pentastomids. We found no pentastomid infecting juvenile geckos. The parameters of infection in this host population are in accordance to the findings of other studies, in which the high parasitism rate was associated to the feeding habits of geckos living in houses and buildings. Hemidactylus mabouia is a new host to R. mottae and the infection by R. frenatus is the first record of the occurrence this pentastomid species in Brazil.

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