Limits...
Disentangling host, pathogen, and environmental determinants of a recently emerged wildlife disease: lessons from the first 15 years of amphibian chytridiomycosis research.

James TY, Toledo LF, Rödder D, da Silva Leite D, Belasen AM, Betancourt-Román CM, Jenkinson TS, Soto-Azat C, Lambertini C, Longo AV, Ruggeri J, Collins JP, Burrowes PA, Lips KR, Zamudio KR, Longcore JE - Ecol Evol (2015)

Bottom Line: We explore factors associated with variance in severity of epizootics focusing on the disease triangle of host susceptibility, pathogen virulence, and environment.Instead of focusing on pathogen "hot spots," we need to identify pathogen "cold spots" so that we can better understand what limits the pathogen's distribution.Finally, we introduce the concept of "the Ghost of Epizootics Past" to discuss expected patterns in postepizootic host communities.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109.

ABSTRACT
The amphibian fungal disease chytridiomycosis, which affects species across all continents, recently emerged as one of the greatest threats to biodiversity. Yet, many aspects of the basic biology and epidemiology of the pathogen, Batrachochytrium dendrobatidis (Bd), are still unknown, such as when and from where did Bd emerge and what is its true ecological niche? Here, we review the ecology and evolution of Bd in the Americas and highlight controversies that make this disease so enigmatic. We explore factors associated with variance in severity of epizootics focusing on the disease triangle of host susceptibility, pathogen virulence, and environment. Reevaluating the causes of the panzootic is timely given the wealth of data on Bd prevalence across hosts and communities and the recent discoveries suggesting co-evolutionary potential of hosts and Bd. We generate a new species distribution model for Bd in the Americas based on over 30,000 records and suggest a novel future research agenda. Instead of focusing on pathogen "hot spots," we need to identify pathogen "cold spots" so that we can better understand what limits the pathogen's distribution. Finally, we introduce the concept of "the Ghost of Epizootics Past" to discuss expected patterns in postepizootic host communities.

No MeSH data available.


Related in: MedlinePlus

Prevalence of Batrachochytrium dendrobatidis and potential distribution of the fungus according to an ensemble species distribution model. Warmer colors indicate higher probability of environmental suitability. Prevalence was computed only for those grid cells with more than 10 samples, wherein the size of the circles represent sample size. Areas exceeding the environmental training range of the SDM are indicated in gray.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4588650&req=5

ece31672-fig-0003: Prevalence of Batrachochytrium dendrobatidis and potential distribution of the fungus according to an ensemble species distribution model. Warmer colors indicate higher probability of environmental suitability. Prevalence was computed only for those grid cells with more than 10 samples, wherein the size of the circles represent sample size. Areas exceeding the environmental training range of the SDM are indicated in gray.

Mentions: In comparison with previous SDMs for Bd, our new model employs an ensemble model approach, which has superior performance when compared to single algorithms (Meller et al. 2014). This enables the prediction of both hot spots and cold spots of environmental suitability for Bd. The new SDM predicts that most parts of eastern and western USA, mountainous areas in Central America, the Northern Andes, lowlands of Chile, the Brazilian Atlantic Forest, and adjacent areas in Uruguay and Argentina provide suitable environmental conditions for Bd (Fig. 2). Most parts of the Amazon basin are not predicted to be suitable for Bd, most likely because their comparatively high annual mean temperatures exceed the critical thermal maximum of the pathogen. Our results highlight similar hot spots for Bd as those predicted by Rödder et al. (2009) and Liu et al. (2013), but allow more differentiation between suitable and unsuitable sites because of increased sampling efforts and the use of analytical methods that are an ensemble of different algorithms (Box 2). A major difference between this new SDM and the previous projections is the lower suitability for Bd in the Amazon basin and higher suitability for Bd in western North America relative to the earlier model by Rödder et al. (2009). Our model also differs from that of Liu et al. (2013) in showing less suitability for eastern North America. We compared the results of the SDM with the prevalence of Bd at given localities for which we had population‐level data (Fig. 3). Overall, Bd prevalence correlates well with the SDM, but neither picture is able to completely explain the epidemiological patterns observed. For example, eastern US amphibian populations have among the lowest mean prevalence (mean = 12.4%), whereas eastern Brazilian populations display among the highest prevalence (mean = 28.5%) (Fig. 3). Yet, both regions show limited evidence for Bd‐related declines.


Disentangling host, pathogen, and environmental determinants of a recently emerged wildlife disease: lessons from the first 15 years of amphibian chytridiomycosis research.

James TY, Toledo LF, Rödder D, da Silva Leite D, Belasen AM, Betancourt-Román CM, Jenkinson TS, Soto-Azat C, Lambertini C, Longo AV, Ruggeri J, Collins JP, Burrowes PA, Lips KR, Zamudio KR, Longcore JE - Ecol Evol (2015)

Prevalence of Batrachochytrium dendrobatidis and potential distribution of the fungus according to an ensemble species distribution model. Warmer colors indicate higher probability of environmental suitability. Prevalence was computed only for those grid cells with more than 10 samples, wherein the size of the circles represent sample size. Areas exceeding the environmental training range of the SDM are indicated in gray.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4588650&req=5

ece31672-fig-0003: Prevalence of Batrachochytrium dendrobatidis and potential distribution of the fungus according to an ensemble species distribution model. Warmer colors indicate higher probability of environmental suitability. Prevalence was computed only for those grid cells with more than 10 samples, wherein the size of the circles represent sample size. Areas exceeding the environmental training range of the SDM are indicated in gray.
Mentions: In comparison with previous SDMs for Bd, our new model employs an ensemble model approach, which has superior performance when compared to single algorithms (Meller et al. 2014). This enables the prediction of both hot spots and cold spots of environmental suitability for Bd. The new SDM predicts that most parts of eastern and western USA, mountainous areas in Central America, the Northern Andes, lowlands of Chile, the Brazilian Atlantic Forest, and adjacent areas in Uruguay and Argentina provide suitable environmental conditions for Bd (Fig. 2). Most parts of the Amazon basin are not predicted to be suitable for Bd, most likely because their comparatively high annual mean temperatures exceed the critical thermal maximum of the pathogen. Our results highlight similar hot spots for Bd as those predicted by Rödder et al. (2009) and Liu et al. (2013), but allow more differentiation between suitable and unsuitable sites because of increased sampling efforts and the use of analytical methods that are an ensemble of different algorithms (Box 2). A major difference between this new SDM and the previous projections is the lower suitability for Bd in the Amazon basin and higher suitability for Bd in western North America relative to the earlier model by Rödder et al. (2009). Our model also differs from that of Liu et al. (2013) in showing less suitability for eastern North America. We compared the results of the SDM with the prevalence of Bd at given localities for which we had population‐level data (Fig. 3). Overall, Bd prevalence correlates well with the SDM, but neither picture is able to completely explain the epidemiological patterns observed. For example, eastern US amphibian populations have among the lowest mean prevalence (mean = 12.4%), whereas eastern Brazilian populations display among the highest prevalence (mean = 28.5%) (Fig. 3). Yet, both regions show limited evidence for Bd‐related declines.

Bottom Line: We explore factors associated with variance in severity of epizootics focusing on the disease triangle of host susceptibility, pathogen virulence, and environment.Instead of focusing on pathogen "hot spots," we need to identify pathogen "cold spots" so that we can better understand what limits the pathogen's distribution.Finally, we introduce the concept of "the Ghost of Epizootics Past" to discuss expected patterns in postepizootic host communities.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109.

ABSTRACT
The amphibian fungal disease chytridiomycosis, which affects species across all continents, recently emerged as one of the greatest threats to biodiversity. Yet, many aspects of the basic biology and epidemiology of the pathogen, Batrachochytrium dendrobatidis (Bd), are still unknown, such as when and from where did Bd emerge and what is its true ecological niche? Here, we review the ecology and evolution of Bd in the Americas and highlight controversies that make this disease so enigmatic. We explore factors associated with variance in severity of epizootics focusing on the disease triangle of host susceptibility, pathogen virulence, and environment. Reevaluating the causes of the panzootic is timely given the wealth of data on Bd prevalence across hosts and communities and the recent discoveries suggesting co-evolutionary potential of hosts and Bd. We generate a new species distribution model for Bd in the Americas based on over 30,000 records and suggest a novel future research agenda. Instead of focusing on pathogen "hot spots," we need to identify pathogen "cold spots" so that we can better understand what limits the pathogen's distribution. Finally, we introduce the concept of "the Ghost of Epizootics Past" to discuss expected patterns in postepizootic host communities.

No MeSH data available.


Related in: MedlinePlus