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Herpetological Review 47(2), 2016
Herpetological Review, 2016, 47(2), 207–209.
© 2016 by Society for the Study of Amphibians and Reptiles
Amphibian: A Case Denition and Diagnostic Criteria for
Batrachochytrium salamandrivorans Chytridiomycosis
A newly described chytrid fungus, Batrachochytrium sala-
mandrivorans (Bsal), has caused several die-offs in salaman-
ders in Europe (Martel et al. 2013; Cunningham et al. 2015).
This pathogen is similar to the species B. dendobatidis (Bd) that
has caused massive amphibian population declines globally. As
the United States is home to the world’s most diverse salaman-
der assemblage, the United States Fish and Wildlife Service has
sought to increase protection of native salamander populations
via an interim rule under the Lacey Act (18 USC 42- USFWS
2016). This rule, effective 28 January 2016, limits international
and interstate movement of 20 genera of salamanders. Concur-
rent with this work, a U.S. Bsal Task Force (Grant et al. 2016)
was formed to help prevent and manage cases that might oc-
cur in North America. The diagnostics committee of this Task
Force developed the following Bsal case definition to promote
standardized communication of results and consistent national
reporting of this invasive pathogen among multiple diagnostic
laboratories in order to provide reliable information to wildlife
Case definitions typically include field, gross, histopatholo-
gy, laboratory, and epidemiologic criteria for assigning an indi-
vidual to a specific disease or condition. The diagnostic criteria
including field signs, gross pathology and histopathology have
been established from Bsal cases in free-ranging salamanders
in Europe and North American species examined during exper-
imental infection trials (Martel et al. 2013; A. P. Pessier, unpubl.
data). As an emerging pathogen some aspects of Bsal ecology,
including variation in species susceptibility and field signs for
North American species, are unknown. The case definition,
therefore, errs on the side of specificity over sensitivity by re-
quiring both histopathologic and laboratory confirmation to be
considered a confirmed Bsal case. However, we also included
a category for reporting the presence of the Bsal fungus in the
absence of corroborating evidence of disease (i.e., histopathol-
ogy) since consistent reporting of this information will be use-
ful for examining pathogen spread in new geographic locations
and susceptibility in new host species.
The case definition presented here represents the current
knowledge of Bsal infection in amphibians and is intended to
provide background information on this new pathogen and the
clinical and histopathogical presentation of the disease. Criteria
for diagnoses are provided and should be used for determining
disease presence. However, it should be noted that since this
disease has not been found in free-ranging North American am-
phibian species, variation in its presentation for these new pop-
ulations is unknown, and the definitions proposed below may
evolve with geographical, environmental, and host expansion.
USGS-National Wildlife Health Center, Madison, Wisconsin 53711, USA
Canadian Wildlife Health Cooperative, Atlantic Veterinary College,
University of Prince Edward Island, Charlottetown,
Prince Edward Island C1A4P3, Canada
Institute for Conservation Research, San Diego Zoo Global,
San Diego, California 92112, USA
Wildlife Epidemiology Lab, Department of Veterinary Clinical Medicine,
University of Illinois, Urbana, Illinois 61802, USA
US Fish and Wildlife Service, Wildlife Health Oce,
Natural Resource Program Center, National Wildlife Refuge System,
Fort Collins, Colorado 80525, USA
Department of Zoology, Southern Illinois University Carbondale,
Carbondale, Illinois 62901, USA
Southeastern Cooperative Wildlife Disease Study, College of
Veterinary Medicine, Department of Population Health,
University of Georgia, Athens, Georgia 30602, USA
Department of Pathology, Bacteriology and Avian Diseases,
Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
Center for Wildlife Health, University of Tennessee, Knoxville,
Tennessee 37996, USA
Department of Population Medicine and Diagnostic Sciences,
Cornell University, Ithaca, New York 14853, USA
USGS-National Wildlife Health Center, Madison, Wisconsin 53711, USA
University of Wisconsin-Madison, School of Veterinary Medicine,
Department of Pathobiological Sciences, Madison, Wisconsin 53706, USA
Department of Biology, University of South Dakota, Vermillion,
South Dakota 57069, USA
*Corresponding author; e-mail:
Herpetological Review 47(2), 2016
CHytrid Fun gus in tHe order rHiZoPHydiaLes, genus
Batrachochytrium , sPeCies sal amandrivoran s
I. Individual, Place, and Time
Individual.—Post-metamorphic amphibians (especially
salamanders) are known to be susceptible. Although larval Fire
Salamanders (Salamandra salamandra) are not susceptible
(Van Rooij et al. 2015), larval susceptibility in other species is
unknown. There is increased index of suspicion for mortality
events involving multiple salamander species (and notably not
involving co-occurring frog species), or North American spe-
cies with laboratory confirmed susceptibility to Bsal chytrid-
iomycosis, specifically Notophthalmus viridescens (Eastern
Newt), Taricha granulosa (Rough-skinned Newt).
Place.—There are currently no specific restrictions for
where Bsal can occur.
Time.—There are currently no specific restrictions for when
Bsal can occur.
II. Diagnostic Description
Field observations.—A clinically compatible case includes
amphibians with skin ulcers and lethargy, leading to a typically
high mortality rate. Weak or erratic swimming may also occur.
Gross necropsy observations.—On post-mortem examina-
tion, clinically compatible cases may present with subtle to
severe skin ulcers or erosions; some cases will have no lesions
visible on gross post-mortem examination. In addition to Bsal
infection, biologists, veterinarians, and diagnosticians are re-
minded to consider differentials for ulcerative or erosive lesions
in amphibians such as viral, bacterial, parasitic or other fungal
infections as well as lesions due to trauma or environmental
conditions (Green 2001). Lesions due to Bsal infection may oc-
cur at any site on the head, body, limbs, or tail of infected in-
dividuals. Chytridiomycosis is not known to be associated with
internal gross lesions (Martel et al. 2013). Although clinical com-
patibility may raise the index of suspicion for a positive diag-
nosis, its presence is not required for diagnostic categorization.
Histopathology.—Histopathological evidence most sugges-
tive of Bsal infection in the epidermis of salamanders is multi-
focal epidermal necrosis with loss of distinction between layers
of keratinocytes associated with myriad intracellular and extra-
cellular chytrid-type fungal thalli (Fig. 1) (Martel et al. 2013; A.
P. Pessier, unpubl. data). Thalli have a diameter of 6.9–17.2 μm
(average 12.2 ± 1.9 μm, N = 50). Lesions multifocally have areas
of erosion or ulceration. In early lesions and at the periphery of
older lesions, chytrid thalli may be observed within keratino-
cyte cytoplasm with margination of cell nuclei.
Necrotizing lesions most suspicious for Bsal (Bsal-type
chytridiomycosis) can be contrasted with those typical of Bd
infection (Bd-type chytridiomycosis) in which the epidermis
is predominantly hyperplastic and hyperkeratotic with many
superficial intracytoplasmic chytrid-type fungal thalli (Fig. 1).
However, there is overlap in these infection patterns.
General histologic features of chytrid (Batrachochytrium
spp.) fungal thalli are 5–20 μm diameter, round to slightly oval
organisms, that may contain 2–3 μm basophilic spores (zoo-
spores) or a discharge tube (giving a flask-like appearance)
(Berger et al. 2005). However, developing thalli or empty thalli
(those that have already discharged zoospores) often predomi-
nate. A highly characteristic feature of chytrid thalli are colonial
thalli that have internal septa. Colonial thalli are most easily
observed when empty or with stains that highlight fungal cell
walls (e.g., Grocott’s methenamine silver or periodic acid-
Schiff). Features of chytrid thalli that are more consistent with
Bsal over than Bd are numerous colonial thalli (compared to
infrequent) with multiple internal septa (rather than single).
However, these two species cannot be definitively distinguished
histologically at this time.
III. Laboratory Criteria for Diagnosis
Current molecular methods for verification of Bsal via poly-
merase chain reactions (PCR) are provided by Martel et al. (2013)
and via quantitative PCR by Blooi et al. (2013). Methods for cul-
turing Bsal are available in Martel et al. (2013).
Fig. 1. Comparison of Bd and Bsal-type chytridiomycosis. Notophthalmus viridescens. Hematoxylin and eosin stain 1000×. Bd-type chy-
tridiomycosis (A) is proliferative with epidermal hyperplasia and hyperkeratosis and numerous chytrid thalli in superficial keratinocytes
(arrows). The keratinocytes are arranged in distinct layers with intact nuclei (N). In contrast, Bsal-type chytridiomycosis (B) has almost
full-thickness necrosis of keratinocytes with myriad chytrid thalli (arrows) that frequently have internal septa (colonial thalli). Note the loss
of distinct layers of keratinocytes. At the periphery of this area of necrosis, a remaining keratinocyte has two intracytoplasmic chytrid thalli
that marginate the nucleus (circle).
Herpetological Review 47(2), 2016
Case CLassiFiCation
Below we provide criteria for three diagnostic categories of
Bsal based on diagnostic criteria. PCR and culturing methods al-
low for confirmation of the presence of Bsal but do not necessar-
ily indicate infection or the presence of disease. Histopathology
can provide support for chytridiomycosis in the salamander, but
as some histopathological findings such as necrosis and ulcer-
ation in the absence of chytrid fungi are non-specific and can be
caused by a wide variety of pathogens and environmental con-
ditions (Green 2001), a definitive diagnosis must include both
identification of the pathogen and demonstration of disease in
the salamander.
Bsal present.—Positive Bsal PCR or Bsal culture from skin
tissue of an animal for which compatible gross lesions were not
observed and for which histopathology was either not done or
was not consistent with Bsal histopathology (lacking epidermal
necrosis associated with chytrid zoosporangia).
Positive Bsal PCR or Bsal culture from a sample (e.g., swab
from individual or environmental sample) for which gross pa-
thology was not observed or recorded and for which histopathol-
ogy was not done or was not consistent with Bsal histopathology
(lacking epidermal necrosis associated with chytrid zoosporan-
Further verification (via additional samples or alternative
methodology) of a Bsal positive sample in a new area of detec-
tion is highly recommended.
Suspect Bsal chytridiomycosis.—Histopathology consistent
with Bsal infection (epidermal necrosis associated with chytrid
zoosporangia) in the absence of corroborating Bsal PCR or Bsal
fungal culture (either negative results or specimen unsuitable for
Further verification (via additional diagnostics such as PCR
or culture) of a Bsal suspect sample is necessary for a definitive
Confirmed Bsal chytridiomycosis.—Histopathology con-
sistent with Bsal infection (epidermal necrosis associated with
chytrid zoosporangia) and positive Bsal PCR or Bsal culture from
skin samples
Histopathology consistent with chytridiomycosis AND posi-
tive Bsal PCR or Bsal culture and Bd PCR or culture negative.
If Bd is also detected, further investigation into the cause of
the disease is highly recommended.
Conclusion.—As with all emerging diseases there are limited
data and many knowledge gaps for Bsal. This case definition pro-
vides guidelines for reporting Bsal chytridiomycosis. Any diag-
nosis of Bsal should be reported immediately to a regional, state,
or federal wildlife agency. This case definition will be updated as
further information is reported and a current version will be lo-
cated at
Acknowledgments.We thank Julie Ellis, Michael Garner, Deb-
orah Iwanowicz, James Lewis, Steven Lloyd, Jeffrey Lorch, Laura
Sprague, Craig Stephen, Tom Waltzek, John Wood, and Julia Lank-
ton for reviewing drafts of this document. Authors and reviewers are
members of the Bsal Diagnostics Committee of the U.S. Bsal Task
Force. This group was initiated at a meeting hosted by USGS Powell
Center for Analysis and Synthesis, which was supported by the USGS
Ecosystems mission area. The findings and conclusions in this article
are those of the authors and do not necessarily represent the views
of the U.S. Fish and Wildlife Service. Use of trade, product, or firm
names is for descriptive purposes only and does not imply endorse-
ment by the U.S. government.
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... The reporting of amphibian mortality events to this hotline results in diagnostic testing for Bsal. The diagnosis of Bsal chytridiomycosis combines a positive qPCR results with histopathology of dead animals [26]. ...
... For this reason, the OIE guidance explicitly specifies confirmation is needed using an independent diagnostic test (e.g., histopathology, culture) for a definitive Bsal diagnosis in a novel site or host species. The results of the current study support the validity of this requirement [26] and we urge caution interpreting conclusions based on qPCR-only results in novel sites or host species; such results should be treated as "Bsal suspect" until cross-validation has been conducted. ...
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The recent introduction of the chytrid fungus Batrachochytrium salamandrivorans into northeastern Spain threatens salamander diversity on the Iberian Peninsula. We assessed the current epidemiological situation with extensive field sampling of urodele populations. We then sought to delineate priority regions and identify conservation units for the Iberian Peninsula by estimating the susceptibility of Iberian urodeles using laboratory experiments, evidence from mortality events in nature and captivity and inference from phylogeny. None of the 1395 field samples, collected between 2015 and 2021 were positive for Bsal and no Bsal-associated mortality events were recorded, in contrast to the confirmed occurrence of Bsal outbreak previously described in 2018. We classified five of eleven Iberian urodele species as highly susceptible, predicting elevated mortality and population declines following potential Bsal emergence in the wild, five species as intermediately susceptible with variable disease outcomes and one species as resistant to disease and mortality. We identified the six conservation units (i.e., species or lineages within species) at highest risk and propose priority areas for active disease surveillance and field biosecurity measures. The magnitude of the disease threat identified here emphasizes the need for region-tailored disease abatement plans that couple active disease surveillance to rapid and drastic actions.
... First, we performed a structured literature search to update the list of Bsal-susceptible species and used search terms that attempted to capture testing, diagnostics, and laboratory challenge studies in amphibian species (Appendix S1). We categorized the literature results by species based on the case definition categories presented in White et al. (2016): Bsal present (i.e., positive Bsal PCR or culture), suspect Bsal chytridiomycosis (i.e., histopathology consistent with Bsal chytridiomycosis in the absence of positive PCR or culture), confirmed Bsal chytridiomycosis (i.e., both histopathology and PCR or culture positive), or Bsal not detected. Next, we compiled records of all live amphibian imports from 1 January 2010 to 31 October 2019 from the U.S. Fish and Wildlife Service Law Enforcement Management Information System (LEMIS). ...
The emerging amphibian pathogen Batrachochytrium salamandrivorans (Bsal) is a severe threat to global urodelan (salamanders, newts, and related taxa) biodiversity. Bsal has not been detected, to date, in North America, but the risk is high because North America is one of the global hotspots for urodelan biodiversity. The North American and United States response to the discovery of Bsal in Europe was to take a risk-based approach to preventive management actions, including interim regulations on importation of captive salamanders and a large-scale surveillance effort. Risk-based approaches to decision-making can extend to adaptive management cycles by periodically incorporating new information that reduces uncertainty in an estimate of risk or to assess the effect of mitigation actions which reduce risk directly. Our objectives were to evaluate the effects of regulatory action on the introduction of Bsal to the U.S., quantify how a large-scale surveillance effort impacted consequence risk, and to combine other new information on species susceptibility to re-evaluate Bsal risk to the U.S. Import regulations effectively reduced import volume of targeted species, but new research on species susceptibility suggests the list of regulated species was incomplete regarding Bsal reservoir species. Not detecting Bsal in an intensive surveillance effort improved confidence that Bsal was not present, however, the overall risk-reduction impact was limited because of the expansive area of interest (conterminous United States) and limited time frame of sampling. Overall, the preventive actions in response to the Bsal threat did reduce Bsal risk in the U.S. and we present an updated risk assessment to provide information for adaptive decision-making.
... All skin surfaces at each section were evaluated for the presence and distribution of chytrid fungal thalli, and the mean number of Bd-type and Bsal-type lesions per section were calculated. Bd and Bsal-type lesions were as defined by White et al. (2016). Briefly, characteristics of Bd-type lesions are epidermal hyperplasia and hyperkeratosis with chytrid thalli in the outer keratinized layers (stratum corneum), and those of Bsaltype lesions are invasion and necrosis of the epidermis with chytrid-type thalli throughout. ...
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Emerging infectious diseases are among the leading drivers of the sixth mass extinction. The recent invasion of a highly pathogenic chytrid fungus, Batrachochytrium salamandrivorans (Bsal), across Europe has led to salamander mass mortality. To date, it remains unclear whether Bsal will cause salamander mass mortalities in North America. Here, we tested the Bsal susceptibility of eight wild-caught salamander species (Plethodon cinereus, P. glutinosus, P. montanus, P. cylindraceus, Desmognathus fuscus, D. wrighti, Eurycea wilderae, and Notophthalmus viridescens) by inoculating individuals sequentially with a low (10,000 zoospores) and high (500,000 zoospores) Bsal dose. Overall, we found rapid and complete mortality of N. viridescens accompanied with high-Bsal infections (> 200,000 Bsal zoospores) and severe Bsal lesions distributed across the body and deep within the skin. In contrast, we found low mortality of plethodontid salamanders, where only 5 of 60 (8%) Bsal-exposed individuals died over the course of the experiment. In general, plethodontid salamanders experienced moderate Bsal infections (~ 4000 Bsal zoospores) with small numbers of Bsal-type lesions limited to the head and lateral body. Following the first Bsal inoculation, we found that Bd co-infections negatively affected Bsal infections, suggesting cross reactivity of the immune system or competitive exclusion, but this pattern did not persist following the second inoculation. We also found that Bsal infection intensity decreased over time following the second higher Bsal inoculation, suggesting evidence of immune priming. Throughout the experiment, all species and treatments experienced stable or increasing body condition over time. Lastly, ancestral state reconstruction of Bsal susceptibility indicated that although the most recent common ancestor (MRCA) of the family Plethodontidae is resistant to Bsal, the MRCA of the genus Plethodon is tolerant of Bsal. This highlights the variation in Bsal-infection outcomes across Plethodontidae. Collectively, our results suggest that Plethodontidae salamanders differ in their Bsal susceptibility, with some species less impacted than others, which will likely have consequences for their conservation and management.
... For example, Muths et al. (2009) addressed the relevance of opportunistic versus systematic sampling efforts, and highlighted the need for sufficient sample sizes in reporting (see also Skerratt et al. 2008;Gray et al. 2017). White et al. (2016) published the Bsal case definition, and Iwanowicz et al. (2017) addressed Bsal diagnostic approaches. Also, two recent articles synthesize general disease sampling approaches and biosecurity issues (Gray et al. 2017), and necropsy methods (Duffus et al. 2017). ...
... La confirmació histològica de la malaltia es va fonamentar en la detecció de característiques microscòpiques fonamentals: la necrosi focal queratinocítica i la presència d'organismes fúngics intracorneals (figura 1). Aquesta darrera característica es pròpia de B. salamandrivorans respecte de B. dendrobatidis (Kriger et al., 2006;White et al., 2016). Quan coincideixen aquests factors es pot concloure que l'organisme patogen està vinculat a la causa de malaltia o mort de l'animal. ...
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In March 2018, was detected the first positive of the fungus Batrachochytrium salamandrivorans in the Montnegre Park in an exotic amphibian (Triturus anatolicus). Since then, among other control measures, exotic amphibians (Triturus anatolicus and Ycthiosaura alpestris) and native (Triturus marmoratus and 2 Salamandra salamandra) were removed from the affected pond. Representatives of these species were deposited in the biosecurity facilities of the CRARC. 18 months later 11 of them are still alive with or without symptoms and 9 have died. The pathological, cytological, blood and PCR results obtained to know the pathogenicity of the disease are presented. The data shows that a subclinical infection of more than one year can occur. Triturus anatolicus seems to be the species most resistent to the infection.
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Batrachochytrium dendrobatidis and B. salamandrivorans are important amphibian pathogens responsible for morbidity and mortality in free-ranging and captive frogs, salamanders, and caecilians. While B. dendrobatidis has a widespread global distribution, B. salamandrivorans has only been detected in amphibians in Asia and Europe. Although molecular detection methods for these fungi are well-characterized, differentiation of the morphologically similar organisms in the tissues of affected amphibians is incredibly difficult. Moreover, an accurate tool to identify and differentiate Batrachochytrium in affected amphibian tissues is essential for a specific diagnosis of the causative agent in chytridiomycosis cases. To address this need, an automated dual-plex chromogenic RNAScope® in situ hybridization (ISH) assay was developed and characterized for simultaneous detection and differentiation of B. dendrobatidis and B. salamandrivorans. The assay, utilizing double Z target probe pairs designed to hybridize to 28S rRNA sequences, was specific for the identification of both organisms in culture and in formalin-fixed paraffin-embedded amphibian tissues. The assay successfully identified organisms in tissue samples from five salamander and one frog species preserved in formalin for up to 364 days and was sensitive for the detection of Batrachochytrium in animals with qPCR loads as low as 1.1 × 102 zoospores/microliter. ISH staining of B. salamandrivorans also highlighted the infection of dermal cutaneous glands, a feature not observed in amphibian B. dendrobatidis cases and which may play an important role in B. salamandrivorans pathogenesis in salamanders. The developed ISH assay will benefit both amphibian chytridiomycosis surveillance projects and pathogenesis studies by providing a reliable tool for Batrachochytrium differentiation in tissues.
This datasheet on Batrachochytrium salamandrivorans infection covers Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Hosts/Species Affected, Diagnosis, Pathology, Epidemiology, Impacts, Prevention/Control, Further Information.
This datasheet on Batrachochytrium salamandrivorans covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Environmental Requirements, Impacts, Further Information.
The vertebrate class Amphibia is a diverse group of animals that includes frogs, salamanders, and the lesser‐known caecilians. Evaluation of the integumentary system is especially important in amphibians because of the unique physiologic role of the skin in water absorption, osmoregulation, and respiration. Common clinical samples include skin scrapings, impression smears, and aspirates from cutaneous bacterial and fungal infections including the chytrid fungus Batrachochytrium dendrobatidis, which has been implicated in declines of wild amphibian populations worldwide. Edema syndromes characterized by hydrocoelom and lymphedema are another common clinical presentation. and cytologic examination can be invaluable in differentiating between infectious and noninfectious etiologies.
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Amphibian declines and extinctions are emblematic for the current sixth mass extinction event. Infectious drivers of these declines include the recently emerged fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans (Chytridiomycota). The skin disease caused by these fungi is named chytridiomycosis and affects the vital function of amphibian skin. Not all amphibians respond equally to infection and host responses might range from resistant, over tolerant to susceptible. The clinical outcome of infection is highly dependent on the amphibian host, the fungal virulence and environmental determinants. B. dendrobatidis infects the skin of a large range of anurans, urodeles and caecilians, whereas to date the host range of B. salamandrivorans seems limited to urodeles. So far, the epidemic of B. dendrobatidis is mainly limited to Australian, neotropical, South European and West American amphibians, while for B. salamandrivorans it is limited to European salamanders. Other striking differences between both fungi include gross pathology and thermal preferences. With this review we aim to provide the reader with a state-of-the art of host-pathogen interactions for both fungi, in which new data pertaining to the interaction of B. dendrobatidis and B. salamandrivorans with the host’s skin are integrated. Furthermore, we pinpoint areas in which more detailed studies are necessary or which have not received the attention they merit. Electronic supplementary material The online version of this article (doi:10.1186/s13567-015-0266-0) contains supplementary material, which is available to authorized users.
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THE recently discovered fungal pathogen Batrachochytrium salamandrivorans is causing the rapid loss of infected fire salamander (Salamandra salamandra) populations in continental Europe (Martel and others 2013). The fungus is thought to be endemic to Asia, with introduction to Europe via the pet trade. Many species of salamander and newt (urodeles) have been shown experimentally to be …
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Chytridiomycosis is a lethal fungal disease contributing to declines and extinctions of amphibian species worldwide. The currently used molecular screening tests for chytridiomycosis fail to detect the recently described species Batrachochytrium salamandrivorans. In this study, we present a duplex real-time PCR that allows the simultaneous detection of B. salamandrivorans and Batrachochytrium dendrobatidis. With B. dendrobatidis- and B. salamandrivorans-specific primers and probes, detection of the two pathogens in amphibian samples is possible, with a detection limit of 0.1 genomic equivalent of zoospores of both pathogens per PCR. The developed real-time PCR shows high degrees of specificity and sensitivity, high linear correlations (r2 > 0.995), and high amplification efficiencies (>94%) for B. dendrobatidis and B. salamandrivorans. In conclusion, the described duplex real-time PCR can be used to detect DNA of B. dendrobatidis and B. salamandrivorans with highly reproducible and reliable results.
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An overview of the morphology and life cycle of Batrachochytrium dendrobatidis, the cause of chytridiomycosis of amphibians, is presented. We used a range of methods to examine stages of the life cycle in culture and in frog skin, and to assess ultrastructural pathology in the skin of 2 frogs. Methods included light microscopy, transmission electron microscopy with conventional methods as well as high pressure freezing and freeze substitution, and scanning electron microscopy with critical point drying as well as examination of bulk-frozen and freeze-fractured material. Although chytridiomycosis is an emerging disease, B. dendrobatidis has adaptations that suggest it has long been evolved to live within cells in the dynamic tissue of the stratified epidermis. Sporangia developed at a rate that coincided with the maturation of the cell, and fungal discharge tubes usually opened onto the distal surface of epidermal cells of the stratum corneum. A zone of condensed, fibrillar, host cytoplasm surrounded some sporangia. Hyperkeratosis may be due to (1) a hyperplastic response that leads to an increased turnover of epidermal cells, and (2) premature keratinization and death of infected cells.
Injurious Wildlife Species; Listing salamanders due to risk of salamander chytrid fungus
u.s. FisH and wiLdLiFe serviCe. 2016. Injurious Wildlife Species; Listing salamanders due to risk of salamander chytrid fungus. Federal Register 81(8):1534-1556.
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