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Prevalence of Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans in the Gulf Coast Waterdog, Necturus beyeri, from southeast Louisiana

Herpetological Review 48(2), 2017
Herpetological Review, 2017, 48(2), 360–363.
© 2017 by Society for the Study of Amphibians and Reptiles
Prevalence of Batrachochytrium dendrobatidis and
B. salamandrivorans in the Gulf Coast Waterdog,
Necturus beyeri, from Southeast Louisiana, USA
The globally widespread amphibian fungal pathogen
Batrachochytrium dendrobatidis (Bd) has been linked to
amphibian declines worldwide (Lips et al. 2006; Skerratt et
al. 2007). In Louisiana, USA, Bd has been found in several
amphibian species (Chatfield et al. 2012; Rothermel et al. 2008),
but to our knowledge no population-level die-offs have been
observed. Published literature on Bd prevalence in Louisiana is
scant for some amphibian species and completely absent for
many others. This trend is likely driven by the perception that Bd
is not a major problem in this area due to a lack of observed die-
offs attributable to chytridiomycosis.
Batrachochytrium salamandrivorans (Bsal) is an emerging
amphibian fungal pathogen and was first described after
populations of European Fire Salamanders (Salamandra
salamandra) were decimated in the Netherlands (Martel et al.
2013). Since the observations in the Netherlands, Bsal has been
found in wild salamander populations in neighboring Germany
and Belgium (Spitzen-van der Sluijs et al. 2016), and has been
linked to animals in captivity (Cunningham et al. 2015) and trade,
with a proposed origin of Asia (Martel et al. 2014). Occurrence of
Bsal has not been documented in any wild salamanders in North
America, but due to the prolific trade in Asian salamanders, there
is reason to think that it could arrive or may already be in North
America. Prudent surveillance is vital, as a Bsal introduction in
the United States could be devastating to this global hotspot of
salamander diversity (Gray et al. 2015).
The Gulf Coast Waterdog, Necturus beyeri, is a permanently
aquatic neotenic salamander that inhabits sandy spring-fed
streams along the Gulf Coastal Plain, and its global conservation
status is listed by NatureServe as ‘apparently secure’ (G4). In
Louisiana, the Gulf Coast Waterdog is ranked S3 by the Louisiana
Department of Wildlife and Fisheries, which indicates the species
is rare and local throughout the state (21 to 100 known extant
populations). Very little is known about prevalence rates of Bd
in this species. Of two individuals examined by Chatfield et al.
(2012), one tested positive for Bd. To our knowledge, this species
has never been tested for Bsal, and no species of Necturus was
used in challenge experiments by Martel et al. (2014). Therefore,
it is unknown if members of this genus are susceptible to Bsal
infection. Our aim was to conduct additional sampling for Bd
and Bsal in N. beveri in Louisiana.
Gulf Coast Waterdogs were captured in southeast Louisiana
with unbaited minnow traps at sites along ca. 12 km of Bayou
Lacombe as part of an occupancy modelling study (Fig. 1). Al-
though sampling took place over three weeks, all swabs used
in this study were collected in one round of checking all traps
and thus it is certain that each represents a unique individual.
Here we report Bd and Bsal presence and pathogen load, as de-
termined using quantitative polymerase chain reaction (PCR)
results of swabs taken from 76 waterdogs captured 31 March
through 2 April 2015 (Table 1). All captures were of live individu-
als and no other amphibians were captured in the traps.
To test for Bd and Bsal presence, waterdogs were placed
in clear zip-top plastic bags and swabbed by gently rubbing
a rayon-tipped swab (MWE113, Advantage Bundling SP, LLC,
Durham, NC, USA) five times each on the following areas: the
dorsum, each side, the venter, and the bottom of each foot. New
nitrile gloves and new zip-top bags were used for each animal.
Genomic DNA was extracted from the swabs using the
Qiagen DNeasy Blood & Tissue Kit (Qiagen, Inc., Valencia, CA,
USA) and the manufacturer’s recommended protocol for animal
tissue with the following modifications: swabs were incubated
for one hour and were vortexed and spun in a centrifuge after 30
minutes and again at the end of the incubation period; samples
were eluted twice using 100 uL of elution buffer each time instead
of 200 uL once. A multiplexed quantitative (real-time) PCR assay
was used to detect the presence of Bd and Bsal DNA, following
Boyle et al. (2004) and Blooi et al. (2013). Bovine serum albumin
(0.7 mL) was added to each reaction well, as this has been shown
to aid in overcoming problems with inhibition (Garland et al.
2010). All samples were run in triplicate and scored as positive
if at least one replicate tested positive for Bd or Bsal. To confirm
that reactions were not inhibited, an internal positive control
(Applied Biosystems, Inc.) was added to one replicate of each
sample (Hyatt et al. 2007). A seven-fold dilution series of plasmid
standards from Pisces Molecular (Boulder, CO, USA) was run on
every qPCR plate to enable quantification of pathogen load for
both Bd and Bsal. As each assay used only 5 uL of the 200 uL of
genomic DNA extracted, per assay load values were multiplied
by 40 to estimate whole swab pathogen loads.
U.S. Geological Survey, Wetland and Aquatic Research Center,
Lafayette, Louisiana 70506, USA
Department of Ecology and Evolutionary Biology, Tulane University,
New Orleans, Louisiana 70118, USA; Present address:
Department of Biological Sciences, University of Pittsburgh,
Pittsburgh, Pennsylvania 15213, USA
*Corresponding author; e-mail:
taBle 1. Prevalence of Batrachochytrium dendrobatidis (Bd) infection
by size (SVL = snout–vent length) and sex in Necturus beyeri in south-
east Louisiana, USA.
Sex Size range No. No. Bd Prevalence
(SVL, mm) sampled positive
Juvenile Unknown 63–83 7 2 0.29
Adult Male 91–128 52 23 0.44
Female 95–122 17 8 0.47
Total 76 33 0.43
Herpetological Review 48(2), 2017
Fig. 1. Map of the study area showing the sites where Necturus beyeri were captured for assessment of infection with Batrachochytrium den-
drobatidis (Bd) or B. salmandrivorans along Bayou Lacombe, St. Tammany Parish, Louisiana, USA. Solid circles represent sites where at least
one individual tested Bd-positive (Bd+). Open circles represent sites where no individuals tested Bd-positive. The embedded table gives
greater site-level detail: N = no. individuals sampled; Prev = Bd prevalence among individuals sampled at the site. The inset map indicates the
location of the study area within Louisiana.
Herpetological Review 48(2), 2017
Overall, 33 of 76 (43%) waterdogs tested positive for Bd (Glo-
rioso and Waddle 2017). Sixteen of 33 positive results were posi-
tive in all three runs, whereas the remaining 17 were positive in
two of three runs. No difference in prevalence was observed by
adult sex (Table 1). Eleven of 12 traps with three or more wa-
terdogs captured and swabbed contained a mix of positive and
negative results (Fig. 1). Pathogen loads were typically low in Bd-
positive individuals (mean = 364, SD = 298; range 84–1212 plas-
mid equivalents). No waterdogs tested positive for Bsal, and no
clinical signs of chytridiomycosis were observed in any captured
Our prevalence estimate for Bd in Gulf Coast Waterdogs was
nearly twice the rate of all Necturus (N = 17) samples from Chat-
field et al. (2012). The timing of our study coincided with the re-
ported peak infection period found by others for semi-aquatic
species in the southeast (e.g., Kinney et al. 2011; Rothermel et al.
2008). However, the timing of this study also coincides with the
peak time to capture these animals, and captures of this species
in mid-summer are rare. The lower Bd prevalence observed in
Chatfield et al. (2012) may be attributable to warmer water tem-
peratures experienced in summer by some of the permanently
aquatic salamanders they studied (e.g., Amphiuma and Siren).
Water temperatures where these animals live routinely exceed
the optimal growth range of Bd (17°–25°C) in the hottest months
in the Gulf Coastal Plain (Piotrowski et al. 2004).
The relatively cool stable environment that waterdogs inhab-
it suggests that they may serve as year-round hosts of Bd (Chat-
field et al. 2012). Additionally, Bd has been shown to complete
its life cycle in crawfish and transmit Bd infection to amphibians
(McMahon et al. 2013). Crawfish were commonly captured in our
traps and are a known primary prey item of Gulf Coast Waterdogs
in at least some populations (Shoop and Gunning 1967). More
work is needed examining the thermal relationship of Bd, craw-
fish, and Gulf Coast Waterdogs to clarify the possible year-round
host hypothesis.
Currently it is not known if Necturus is susceptible to Bsal.
Given that the optimal growth range of Bsal (10–15°C) is lower
than that of Bd (Martel et al. 2013) and that the spring-fed lotic
waters that Necturus beyeri inhabit provide suitable tempera-
tures for Bsal for at least part of the year, there would be cause
for concern if Necturus beyeri were shown to be susceptible to
Bsal. More research into the effect of Bd on Necturus as well as
increased monitoring for Bsal across the range of all taxa in the
genus is warranted.
Acknowledgments.We thank L. Muse and S. Godfrey for as-
sistance with field work. Waterdogs were captured under Louisiana
Department of Wildlife and Fisheries Scientific Collecting Permit
LNHP-15-010002E. All handling of animals was conducted in ac-
cordance with approved IACUC protocols (USGS WARC FY2008-1).
Any use of trade, firm, or product names is for descriptive purposes
only and does not imply endorsement by the U.S. Government. This
is contribution number 578 of the U.S. Geological Survey Amphibian
Research and Monitoring Initiative (ARMI).
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© 2017 by Society for the Study of Amphibians and Reptiles
Batrachochytrium dendrobatidis and Batrachochytrium
salamandrivorans Surveillance in Salamanders of
Southeastern Virginia, USA
The United States (US) has the highest diversity of
salamanders in the world, and many of these are endemic to
only the southeastern states making the US the global hotspot
for salamander biodiversity (Gray et al. 2015). For this reason,
managing disease threats to US salamanders is a high priority
(Grant et al. 2015). Chytridiomycosis is a disease caused by the
pathogenic chytrid fungi Batrachochytrium dendrobatidis (Bd)
and B. salamandrivorans (Bsal). Bd is an emerging infectious
disease that has had a devastating impact on amphibian
populations across Central America, Europe, North America,
and Australia (Skerratt et al. 2007; Cheng et al. 2011; Martel et
al. 2013). All amphibian orders (Anura, Urodela, Gymnophiona)
have experienced disease symptoms and population declines
from (Bd) (Skerratt et al. 2007; Martel et al. 2013; Martel et
al. 2014). Bsal is newly discovered and initial experimental
challenges have reported affects on some urodeles (Martel
et al. 2014; Van Rooij et al. 2015). While Bd has been present
in the US for many years, Bsal has only been found to cause
clinical disease in wild salamanders in Europe to date (Martel
et al. 2013, Richgels et al. 2016), however Bsal surveillance of
wild amphibian populations has been limited elsewhere. Bsal
is significantly affecting both captive and free ranging fire
salamander (Salamandra salamandra) populations in northern
Europe (Martel et al. 2014; Van Rooij et al. 2015). Bsal appears
to have originated in Asia where it likely has remained in
coexistence with salamander hosts for millions of years; spread
to Europe was likely human-mediated through international
trade (Martel et al. 2014). Herein we report the results of
combined Bd and Bsal surveillance of native, wild salamanders
in southeastern Virginia, US.
Salamanders at three sites (Fig. 1) were sampled on
three days in mid- to late-October 2016 for Bd and Bsal: 1)
Sandy Bottom Nature Park, Hampton, Virginia (37.0624°N,
76.4317°W), is a 185-ha public park built around former
borrow pits with created wetlands and a mixed hardwood
and pine forest, and surrounded by suburban development;
2) Grafton Ponds Natural Area Reserve, Yorktown, Virginia
(37.1816°N, 76.5177°W), a 152-ha mixed hardwood and pine
forested wetland complex contiguous with a larger public
park and watershed protection area; and 3) Northwest River
Park, Chesapeake, Virginia (36.5795°N, 76.1529°W), a 309-ha
riverside public park with a mixed hardwood and pine forest.
We opportunistically captured salamanders by searching
under natural cover objects, such as logs and fallen bark, and
restrained specimens in separate moistened plastic bags.
We examined each salamander and collected morphometric
data (e.g., body weight and SVL) (Table 1). Coordinates were
determined using mobile applications, Apple and Google Maps,
with GPS and cellular network assisted locations. We swabbed
salamanders along their ventrum (feet, thighs, abdomen) with
a fine-tipped rayon swab with a plastic handle and placed swabs
Virginia Zoo, 3500 Granby Street, Norfolk, Virginia 23504, USA
Virginia Herpetological Society, 11837 Rock Landing Drive,
Suite 300, Newport News, Virginia 23606, USA
*Current address: ZSL London Zoo, Regent’s Park London,
England NW1 4RY; e-mail:
Fig. 1. Surveillance sites in southeastern Virginia, USA for Batracho-
chytrium dendrobatidis and B. salamandrivorans in native, wild sala-
manders. GPNAR: Grafton Ponds Natural Area Reserve, SBNP: Sandy
Bottom Nature Park, and NRP: Northwest River Park.
... We treated this as a conditional probability, such that incurring consequences within the postrisk action time period was conditional on the probability of Bsal presence (Fig. 1). The surveillance data was based on extensive sampling from (Waddle et al., 2020), along with other localized sampling that occurred during the post-action risk period (2016-2020) Bales et al., 2015;Glorioso et al., 2017;Parrott et al., 2017;Standish et al., 2018). Bsal was not detected in any of these surveillance efforts. ...
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.
... We weighed Gulf Coast Waterdogs in a disposable cup placed on a tared digital scale (PPS200; Pesola, Schindellegi, Switzerland). We swabbed all Gulf Coast Waterdogs captured on the second sample for a related disease project (Glorioso et al., 2017). Last, we took 50 triangular-shaped tissue samples from near the midpoint of the underside of the tail of a subset of captures (no more than four per site) for a related genetics project. ...
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Few ecological studies have been conducted on Gulf Coast Waterdogs (Necturus beyeri), and published studies have focused on relatively small stream sections of 125 m to 1.75 km. In 2015, we sampled 25 sites along a 13.4-km stretch of Bayou Lacombe (Saint Tammany Parish, Louisiana, USA) to better understand factors that may influence the distribution of Gulf Coast Waterdogs within streams. We checked 250 unbaited traps once per week for 3 weeks, capturing 170 Gulf Coast Waterdogs at 18 of 25 sites. We used hierarchical models of abundance to estimate abundance at each site, as a function of site covariates including pH, turbidity, and distance from headwaters. The abundance of Gulf Coast Waterdogs within Bayou Lacombe was highest toward the center of the sampled stream segment, but we found no evidence that pH or turbidity affected abundance within our study area. Site-level abundance estimates of Gulf Coast Waterdogs ranged from 0 to 82, and we estimated there were 767 (95% Bayesian credible interval [CRI]: 266–983) Gulf Coast Waterdogs summed across all 25 sampling sites. We derived an estimate of 6,321 (95% CRI: 2,139–15,922) Gulf Coast Waterdogs for the entire 13.4-km stream section, which includes our 25 sites and the adjoining stream reaches between sites. Our results suggest that Gulf Coast Waterdogs may be uncommon or absent in the headwaters, possibly because of shallow water and swift currents with limited preferred habitats. Gulf Coast Waterdogs favor the middle stream reaches with adequate depth and abundant preferred microhabitats.
... No life history study has been performed on the Pontchartrain lineage. However, recent study of a dense population in Bayou Lacombe has documented the presence of Batrachochytrium dendrobatidis and B. salamandrivorans in populations of this lineage (Glorioso et al. 2017). Brenes and Ford (2006) provide the only published field study of the Western lineage of N. beyeri. ...
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Recent data from the mitochondrial genome reveal six lineages of Gulf Coast Waterdogs traditionally classified as Necturus beyeri. Here, we use patterns of colour and body size, along with previously published data, to reveal a large, heavily spotted phenotype with an unstriped larva possessing numerous white spots; we re-describe N. beyeri to correspond to this phenotype. We also reveal a small, weakly spotted phenotype possessing an unstriped larva lacking numerous white spots. This phenotype characterises the Apalachicola and Escambia lineages, which current evidence suggests are paraphyletic. We reject taxonomies that place these two lineages in N. lodingi because the type specimen of this species appears to be a melanistic member of N. beyeri. Therefore, we describe the Apalachicola and Escambia lineages as independent new species.
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Infection records of Batrachochytrium dendrobatidis (Bd), a pathogen that has devastated amphibian populations worldwide, have rapidly increased since the pathogen’s discovery. Dealing with so many records makes it difficult to (a) know where, when and in which species infections have been detected, (b) understand how widespread and pervasive Bd is and (c) prioritize study and management areas. We conducted a systematic review of papers and compiled a database with Bd infection records. Our dataset covers 71 amphibian families and 119 countries. The data revealed how widespread and adaptable Bd is, being able to infect over 50% of all tested amphibian species, with over 1000 confirmed host species and being present in 86 countries. The distribution of infected species is uneven among and within countries. Areas where the distributions of many infected species overlap are readily visible; these are regions where Bd likely develops well. Conversely, areas where the distributions of species that tested negative overlap, such as the Atlantic Coast in the USA, suggest the presence of Bd refuges. Finally, we report how the number of tested and infected species has changed through time, and provide a list of oldest detection records per country.
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Emerging fungal diseases can drive amphibian species to local extinction. During 2010-2016, we examined 1,921 urodeles in 3 European countries. Presence of the chytrid fungus Batrachochytrium salamandrivorans at new locations and in urodeles of different species expands the known geographic and host range of the fungus and underpins its imminent threat to biodiversity.
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Significance Chytridiomycosis has resulted in the serious decline and extinction of >200 species of amphibians worldwide and poses the greatest threat to biodiversity of any known disease. This fungal disease is currently known to be caused by Batrachochytrium dendrobatidis , hitherto the only species within the entire phylum of the Chytridiomycota known to parasitize vertebrate hosts. We describe the discovery of a second highly divergent, chytrid pathogen, Batrachochytrium salamandrivorans sp. nov., that causes lethal skin infections in salamanders, which has resulted in steep declines in salamander populations in northwestern Europe. Our finding provides another explanation for the phenomenon of amphibian biodiversity loss that is emblematic of the current global biodiversity crisis.
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Batrachochytrium dendrobatidis, a pathogenic chytrid fungus implicated in worldwide amphibian declines, is considered an amphibian specialist. Identification of nonamphibian hosts could help explain the virulence, heterogeneous distribution, variable rates of spread, and persistence of B. dendrobatidis in freshwater ecosystems even after amphibian extirpations. Here, we test whether mosquitofish (Gambusia holbrooki) and crayfish (Procambarus spp. and Orconectes virilis), which are syntopic with many amphibian species, are possible hosts for B. dendrobatidis. Field surveys in Louisiana and Colorado revealed that zoosporangia occur within crayfish gastrointestinal tracts, that B. dendrobatidis prevalence in crayfish was up to 29%, and that crayfish presence in Colorado wetlands was a positive predictor of B. dendrobatidis infections in cooccurring amphibians. In experiments, crayfish, but not mosquitofish, became infected with B. dendrobatidis, maintained the infection for at least 12 wk, and transmitted B. dendrobatidis to amphibians. Exposure to water that previously held B. dendrobatidis also caused significant crayfish mortality and gill recession. These results indicate that there are nonamphibian hosts for B. dendrobatidis and suggest that B. dendrobatidis releases a chemical that can cause host pathology, even in the absence of infection. Managing these biological reservoirs for B. dendrobatidis and identifying this chemical might provide new hope for imperiled amphibians.
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Little is known about the impact that the pathogenic amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), has on fully aquatic salamander species of the eastern United States. As a first step in determining the impacts of Bd on these species, we aimed to determine the prevalence of Bd in wild populations of fully aquatic salamanders in the genera Amphiuma, Necturus, Pseudobranchus, and Siren. We sampled a total of 98 salamanders, representing nine species from sites in Florida, Mississippi, and Louisiana. Overall, infection prevalence was found to be 0.34, with significant differences among genera but no clear geographic pattern. We also found evidence for seasonal variation, but additional sampling throughout the year is needed to clarify this pattern. The high rate of infection discovered in this study is consistent with studies of other amphibians from the southeastern United States. Coupled with previously published data on life histories and population densities, the results presented here suggest that fully aquatic salamanders may be serving as important vectors of Bd and the interaction between these species and Bd warrants additional research.
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The global emergence and spread of the pathogenic, virulent, and highly transmissible fungus Batrachochytrium dendrobatidis, resulting in the disease chytridiomycosis, has caused the decline or extinction of up to about 200 species of frogs. Key postulates for this theory have been completely or partially fulfilled. In the absence of supportive evidence for alternative theories despite decades of research, it is important for the scientific community and conservation agencies to recognize and manage the threat of chytridiomycosis to remaining species of frogs, especially those that are naive to the pathogen. The impact of chytridiomycosis on frogs is the most spectacular loss of vertebrate biodiversity due to disease in recorded history.
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To fully comprehend chytridiomycosis, the amphibian disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), it is essential to understand how Bd affects amphibians throughout their remarkable range of life histories. Crawfish Frogs (Lithobates areolatus) are a typical North American pond-breeding species that forms explosive spring breeding aggregations in seasonal and semipermanent wetlands. But unlike most species, when not breeding Crawfish Frogs usually live singly--in nearly total isolation from conspecifics--and obligately in burrows dug by crayfish. Crayfish burrows penetrate the water table, and therefore offer Crawfish Frogs a second, permanent aquatic habitat when not breeding. Over the course of two years we sampled for the presence of Bd in Crawfish Frog adults. Sampling was conducted seasonally, as animals moved from post-winter emergence through breeding migrations, then back into upland burrow habitats. During our study, 53% of Crawfish Frog breeding adults tested positive for Bd in at least one sample; 27% entered breeding wetlands Bd positive; 46% exited wetlands Bd positive. Five emigrating Crawfish Frogs (12%) developed chytridiomycosis and died. In contrast, all 25 adult frogs sampled while occupying upland crayfish burrows during the summer tested Bd negative. One percent of postmetamorphic juveniles sampled were Bd positive. Zoospore equivalents/swab ranged from 0.8 to 24,436; five out of eight frogs with zoospore equivalents near or >10,000 are known to have died. In summary, Bd infection rates in Crawfish Frog populations ratchet up from near zero during the summer to over 25% following overwintering; rates then nearly double again during and just after breeding--when mortality occurs--before the infection wanes during the summer. Bd-negative postmetamorphic juveniles may not be exposed again to this pathogen until they take up residence in crayfish burrows, or until their first breeding, some years later.
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Batrachochytrium dendrobatidis is a pathogen of amphibians that has been implicated in severe population declines on several continents. We investigated the zoospore activity, physiology and protease production of B. dendrobatidis to help understand the epidemiology of this pathogen. More than 95% of zoospores stopped moving within 24 h and swam less than 2 cm before encysting. Isolates of B. dendrobatidis grew and reproduced at temperatures of 4-25 C and at pH 4-8. Growth was maximal at 17-25 C and at pH 6-7. Exposure of cultures to 30 C for 8 d killed 50% of the replicates. B. dendrobatidis cultures grew on autoclaved snakeskin and 1% keratin agar, but they grew best in tryptone or peptonized milk and did not require additional sugars when grown in tryptone. B. dendrobatidis produced extracellular proteases that degraded casein and gelatin but had no measurable activity against keratin azure. The proteases were active against azocasein at temperatures of 6-37 C and in a pH range of 6-8, with the highest activity at temperatures of 23-30 C and at pH 8. The implications of these observations on disease transmission and development are discussed.
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From 1999 to 2006, we sampled > 1200 amphibians for the fungal pathogen Batrachochytrium dendrobatidis (Bd) at 30 sites in the southeastern USA. Using histological techniques or PCR assays, we detected chytrid infection in 10 species of aquatic-breeding amphibians in 6 states. The prevalence of chytrid infection was 17.8% for samples of postmetamorphic amphibians examined using skin swab-PCR assays (n = 202 samples from 12 species at 4 sites). In this subset of samples, anurans had a much higher prevalence of infection than caudates (39.2% vs. 5.5%, respectively). Mean prevalence in ranid frogs was 40.7%. The only infected salamanders were Notophthalmus viridescens at 3 sites. We found infected amphibians from late winter through late spring and in 1 autumn sample. Although we encountered moribund or dead amphibians at 9 sites, most mortality events were not attributed to Bd. Chytridiomycosis was established as the probable cause of illness or death in fewer than 10 individuals. Our observations suggest a pattern of widespread and subclinical infections. However, because most of the sites in our study were visited only once, we cannot dismiss the possibility that chytridiomycosis is adversely affecting some populations. Furthermore, although there is no evidence of chytrid-associated declines in our region, the presence of this pathogen is cause for concern given global climate change and other stressors. Although presence-absence surveys may still be needed for some taxa, such as bufonids, we recommend that future researchers focus on potential population-level effects at sites where Bd is now known to occur.
The seasonal activity and movements of Necturus maculosus louisianensis and N. b. beyeri were studied in Louisiana from 1959 to 1962 and again in December 1965 and January 1966. Cover preferences were similar in both forms, the animals usually being found in and around obstructions in streams; both species are active throughout the year. There was a negative correlation between fish activity and foraging away from cover by both species. There was no indication of summer dormancy. Fifteen N. beyeri were recaptured within 215 ft of their original capture and release point after up to 724 days. Twenty-three N. maculosus were captured within 840 ft of their original capture point after up to 2089 days. Of 33 N. maculosus displaced downstream, four were recaptured near the release area; one animal returned to its previous capture point. Most of the displaced animals headed upstream instead of seeking shelter as do animals released near original capture sites.