Genetic characterization of chytrids isolated from larval amphibians collected in central and east Texas

ABSTRACTChytridiomycosis, an emerging infectious disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has caused amphibian population declines worldwide. Bd was first described in the 1990s and there are still geographic gaps in the genetic analysis of this globally distributed pathogen. Relatively few genetic studies have focused on regions where Bd exhibits low virulence, potentially creating a bias in our current knowledge of the pathogen’s genetic diversity. Disease-associated declines have not been recorded in Texas (USA), yet Bd has been detected on amphibians in the state. These strains have not been isolated and characterized genetically; therefore, we isolated, cultured, and genotyped Bd from central Texas and compared isolates to a panel of previously genotyped strains distributed across the Western Hemisphere. We also isolated other chytrids not known to infect amphibians from east Texas. To identify larval amphibian hosts, we sequenced part of the COI gene. Among 37 Bd isolates from Texas, we detected 19 unique multi-locus genotypes, but found no genetic structure associated with host species, Texas localities, or across North America. Isolates from central Texas exhibit high diversity and genetically cluster with Bd-GPL isolates from the western U.S. that have caused amphibian population declines. This study genetically characterizes isolates of Bd from the south central U.S. and adds to the global knowledge of Bd genotypes.

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Composition of symbiotic bacteria predicts survival in Panamanian golden frogs infected with a lethal fungus

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2014.2881 ◽

2015 ◽

Vol 282 (1805) ◽

pp. 20142881 ◽

Cited By ~ 74

Author(s):

Matthew H. Becker ◽

Jenifer B. Walke ◽

Shawna Cikanek ◽

Anna E. Savage ◽

Nichole Mattheus ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

Population Declines ◽

Amphibian Species ◽

Amphibian Population ◽

New Approach ◽

Skin Bacteria ◽

Probiotic Treatment ◽

Host Health ◽

The Face ◽

Inhibitory Bacteria

Symbiotic microbes can dramatically impact host health and fitness, and recent research in a diversity of systems suggests that different symbiont community structures may result in distinct outcomes for the host. In amphibians, some symbiotic skin bacteria produce metabolites that inhibit the growth of Batrachochytrium dendrobatidis (Bd), a cutaneous fungal pathogen that has caused many amphibian population declines and extinctions. Treatment with beneficial bacteria (probiotics) prevents Bd infection in some amphibian species and creates optimism for conservation of species that are highly susceptible to chytridiomycosis, the disease caused by Bd. In a laboratory experiment, we used Bd-inhibitory bacteria from Bd-tolerant Panamanian amphibians in a probiotic development trial with Panamanian golden frogs, Atelopus zeteki , a species currently surviving only in captive assurance colonies. Approximately 30% of infected golden frogs survived Bd exposure by either clearing infection or maintaining low Bd loads, but this was not associated with probiotic treatment. Survival was instead related to initial composition of the skin bacterial community and metabolites present on the skin. These results suggest a strong link between the structure of these symbiotic microbial communities and amphibian host health in the face of Bd exposure and also suggest a new approach for developing amphibian probiotics.

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Infectious disease threats to amphibian conservation

10.37208/tgn27s14 ◽

2018 ◽

Vol 27 (Supplement) ◽

pp. 81-90

Author(s):

A.A. Cunningham

Keyword(s):

Infectious Disease ◽

Batrachochytrium Dendrobatidis ◽

Biodiversity Loss ◽

Amphibian Conservation ◽

Disease Spread ◽

Population Declines ◽

Amphibian Species ◽

Late 20Th Century ◽

Amphibian Population ◽

In The Wild

The unexplained decline of amphibian populations across the world was first recognised in the late 20th century. When investigated, most of these “enigmatic” declines have been shown to be due to one of two types of infectious disease: ranavirosis caused by infection with FV3-like ranavirus or with common midwife toad virus, or chytridiomycosis caused by infection with Batrachochytrium dendrobatidis or B. salamandrivorans. In all cases examined, infection has been via the human-mediated introduction of the pathogen to a species or population in which it has not naturally co-evolved. While ranaviruses and B. salamandrivorans have caused regionally localised amphibian population declines in Europe, the chytrid fungus, B. dendrobatidis, has caused catastrophic multi-species amphibian population declines and species extinctions globally. These diseases have already caused the loss of amphibian biodiversity, and over 40% of known amphibian species are threatened with extinction. If this biodiversity loss is to be halted, it is imperative that regulations are put in place – and enforced – to prevent the spread of known and yet-to-be discovered amphibian pathogens. Also, it is incumbent on those who keep or study amphibians to take measures to minimise the risk of disease spread, including from captive animals to those in the wild.

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Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies

Diversity ◽

10.3390/d10030081 ◽

2018 ◽

Vol 10 (3) ◽

pp. 81 ◽

Cited By ~ 10

Author(s):

Andrew Blaustein ◽

Jenny Urbina ◽

Paul Snyder ◽

Emily Reynolds ◽

Trang Dang ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

Experimental Studies ◽

Emerging Infectious Diseases ◽

Host Susceptibility ◽

Interactive Effects ◽

Life History Stage ◽

Population Declines ◽

Amphibian Population ◽

Amphibian Disease ◽

As Species

Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.

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Baseline amphibian survey and sampling of Batrachochytrium dendrobatidis in the Icaco and Hormiga valleys, Patillas, Puerto Rico

Phyllomedusa Journal of Herpetology ◽

10.11606/issn.2316-9079.v16i1p63-69 ◽

2017 ◽

Vol 16 (1) ◽

pp. 63

Author(s):

Norman Greenhawk ◽

Sara Zlotnik ◽

Lauren Margaret Billy ◽

Sam Boas ◽

Sara Gabel

Keyword(s):

Puerto Rico ◽

Batrachochytrium Dendrobatidis ◽

Population Declines ◽

Amphibian Population ◽

The World

Batrachochytrium dendrobatidis (Bd) is the pathogen responsible for chytridiomycosis, a disease implicated in amphibian population declines around the world. In Puerto Rico, Bd has been shown to cause mortalities in endemic anurans of the genus Eleutherodactylus. In July 2014, we conducted visual-encounter surveys and collected 143 Bd swab samples at 10 locations in Icaco and Hormiga, two remote and understudied valleys in Patillas, Puerto Rico. We found five species of Eleutherodactylus and one species of Leptodactylus. Individuals of four species (E. coqui, E. cooki, E. richmondi, and E. wightmanae) yielded either positive or equivocal results for Bd, but 93.7% of the samples tested negative for Bd

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Historical amphibian declines and extinctions in Brazil linked to chytridiomycosis

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.2254 ◽

2017 ◽

Vol 284 (1848) ◽

pp. 20162254 ◽

Cited By ~ 40

Author(s):

Tamilie Carvalho ◽

C. Guilherme Becker ◽

Luís Felipe Toledo

Keyword(s):

Host Resistance ◽

Batrachochytrium Dendrobatidis ◽

Amphibian Declines ◽

Temporal Association ◽

Population Declines ◽

Amphibian Population ◽

Spatio Temporal ◽

High Diversity ◽

Potential Origin ◽

Temporal Overlap

The recent increase in emerging fungal diseases is causing unprecedented threats to biodiversity. The origin of spread of the frog-killing fungus Batrachochytrium dendrobatidis ( Bd ) is a matter of continued debate. To date, the historical amphibian declines in Brazil could not be attributed to chytridiomycosis; the high diversity of hosts coupled with the presence of several Bd lineages predating the reported declines raised the hypothesis that a hypervirulent Bd genotype spread from Brazil to other continents causing the recent global amphibian crisis. We tested for a spatio-temporal overlap between Bd and areas of historical amphibian population declines and extinctions in Brazil. A spatio-temporal convergence between Bd and declines would support the hypothesis that Brazilian amphibians were not adapted to Bd prior to the reported declines, thus weakening the hypothesis that Brazil was the global origin of Bd emergence. Alternatively, a lack of spatio-temporal association between Bd and frog declines would indicate an evolution of host resistance in Brazilian frogs predating Bd 's global emergence , further supporting Brazil as the potential origin of the Bd panzootic. Here, we Bd -screened over 30 000 museum-preserved tadpoles collected in Brazil between 1930 and 2015 and overlaid spatio-temporal Bd data with areas of historical amphibian declines. We detected an increase in the proportion of Bd -infected tadpoles during the peak of amphibian declines (1979–1987). We also found that clusters of Bd -positive samples spatio-temporally overlapped with most records of amphibian declines in Brazil's Atlantic Forest. Our findings indicate that Brazil is post epizootic for chytridiomycosis and provide another piece to the puzzle to explain the origin of Bd globally.

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