Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Do Frogs Get Their Kicks on Route 66? Continental U.S. Transect Reveals Spatial and Temporal Patterns of Batrachochytrium dendrobatidis Infection

  • Michael J. Lannoo ,

    mlannoo@iupui.edu

    Affiliation Indiana University School of Medicine, Terre Haute, Indiana, United States of America

  • Christopher Petersen,

    Affiliation Naval Facilities Engineering Command Atlantic, Norfolk, Virginia, United States of America

  • Robert E. Lovich,

    Affiliation Naval Facilities Engineering Command Southwest, San Diego, California, United States of America

  • Priya Nanjappa,

    Affiliation Association of Fish and Wildlife Agencies, Washington, D. C., United States of America

  • Christopher Phillips,

    Affiliation Illinois Natural History Survey, Institute for Natural Resource Sustainability, University of Illinois, Champaign, Illinois, United States of America

  • Joseph C. Mitchell,

    Affiliation Mitchell Ecological Research Service, Gainesville, Florida, United States of America

  • Irene Macallister

    Affiliation United States Army Corps of Engineers, Construction Engineering Research Laboratory, Champaign, Illinois, United States of America

Do Frogs Get Their Kicks on Route 66? Continental U.S. Transect Reveals Spatial and Temporal Patterns of Batrachochytrium dendrobatidis Infection

  • Michael J. Lannoo, 
  • Christopher Petersen, 
  • Robert E. Lovich, 
  • Priya Nanjappa, 
  • Christopher Phillips, 
  • Joseph C. Mitchell, 
  • Irene Macallister
PLOS
x

Abstract

The chytrid fungus Batrachochytrium dendrobatidis (Bd) has been devastating amphibians globally. Two general scenarios have been proposed for the nature and spread of this pathogen: Bd is an epidemic, spreading as a wave and wiping out individuals, populations, and species in its path; and Bd is endemic, widespread throughout many geographic regions on every continent except Antarctica. To explore these hypotheses, we conducted a transcontinental transect of United States Department of Defense (DoD) installations along U.S. Highway 66 from California to central Illinois, and continuing eastward to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia). We addressed the following questions: 1) Does Bd occur in amphibian populations on protected DoD environments? 2) Is there a temporal pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In these limited human-traffic areas, is Bd acting as an epidemic (i.e., with evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (present without clinical signs of disease)? Bd was detected on 13 of the 15 bases sampled. Samples from 30 amphibian species were collected (10% of known United States' species); half (15) tested Bd positive. There was a strong temporal (seasonal) component; in total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period. There was also a strong spatial component—the eleven temperate DoD installations had higher prevalences of Bd infection (20.8%) than the four arid (<60 mm annual precipitation) bases (8.5%). These data support the conclusion that Bd is now widespread, and promote the idea that Bd can today be considered endemic across much of North America, extending from coast-to-coast, with the exception of remote pockets of naïve populations.

Introduction

One fifth of the world's amphibians may now be facing extinction [1], [2], [3]. In part these declines have been caused by the spread of the chytrid fungus, Batrachochytrium dendrobatidis (Bd) [4], which has been devastating amphibian populations on a global scale [2], [5], [6], [7], [8], [9], [10], [11]. In the United States, this pathogen can now be found from below sea level [12] to the highest elevations where amphibians occur [13], [14]. To date, however, most studies have been conducted locally, on single populations or within regions, and have often used different sampling protocols and analytical techniques [15], [16], [17], [18], [19], [20], [21]. The result is a piecemeal picture of what is most certainly a more widespread pattern [20], [22], [23], [24], [25], [26], [27], although there have been attempts to generalize across broader geographic areas [14], [28], [29], [30], [31], [32], [33], [34], [35].

Because of the variable nature of the available datasets (a situation we do not criticize), there have been questions about the occurrence and spread of Bd. In response, two general scenarios have been proposed that have strong empirical support [36], [37], [38]. In the first scenario, Bd is an epidemic (arising outside the population), spreading as a wave and wiping out individuals, populations, and species in its path. This has been well documented and is occurring in Central America, in eastern Australia, and in parts of California [35], [39], [40], [41], [42], [43], [44], [45]. The second scenario suggests that in certain regions of the world, such as North America, much of the spread of Bd occurred decades ago (when it was an epidemic) and that in these places it is now endemic (arising within the population) [35], [45], [46]. Indeed, Bd is now widespread throughout many geographic regions and is known to occur on every continent inhabited by amphibians (though some land masses and regions appear to remain naïve); therefore, this infection may be considered global [15], [16], [18], [38], [47], [48], [49], [50], [51], [52], [53], [54], [55], [56], [57], [58]. A third scenario, the Bd thermal optimum hypothesis, combines the first two hypotheses and has been more controversial. It suggests widespread benign Bd distribution has been triggered to lethality in regions by increased temperatures due to global warming [59], but this interpretation has been contentious [60].

Exploring the epidemic and endemic hypotheses requires, in part, broad-scale studies using standardized techniques. Further, due to the confounding factor of human disturbance on broad-scale patterns, it is best to examine low-impact (i.e. “natural”), or well-protected areas. Perhaps the most widely available habitats that remain “undisturbed” (a relative term, with perhaps the exception of the deep sea floor it is likely there are no longer any truly undisturbed environments left on earth [61]) in the United States today are United States Department of Defense (DoD) installations, which are secured as a matter of national interest. Military installations are protected against the indiscriminate human traffic experienced by parks, wildlife refuges, and other public areas. Moreover, following the tragic events of September 11th, 2001, access to these installations has been further limited, and in some cases severely restricted. DoD installations encompass over 12 million ha and occur throughout the United States, making continent-wide surveys possible. DoD lands are managed differently than typical surrounding landscapes, using ecosystem management techniques. Indeed, American military lands are thought to harbor the greatest concentrations of endangered and threatened species in the United States [62].

We conducted a transcontinental transect designed to assess the presence of Bd on military lands across the North American continent. DoD installations were sampled from west to east along U.S. Highway 66 (the “Mother Road”) from California into central Illinois, and continuing eastward from there to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia, between 33° and 39° N latitude). We sampled across warm seasons, and used standardized collection and analytical techniques to address the following questions: 1) Does Bd occur in amphibian populations in these relatively undisturbed environments? 2) Is there a temporal (seasonal) pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In secured, limited-traffic areas of the country, is Bd acting as an epidemic (i.e., is there evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (is it present without clinical signs of disease)?

Materials and Methods

Ethics Statement

This research was conducted under IACUC number 3-24-2008 issued by Indiana State University, and Scientific Purposes License Permit numbers 001641 (California Department of Fish and Game), SP783845 (Arizona Game and Fish), 3433 (New Mexico), 4621 (Oklahoma Department of Wildlife Conservation), 14113 (Missouri Department of Natural Resources), 09-0108 (Indiana Department of Natural Resources), SC0911102 (Kentucky Department of Fish and Wildlife), 031168 (Virginia Department of Game and Inland Fisheries). No animals were harmed while collecting Bd samples.

Field Samples

In 2009, a total of 15 DoD installations were sampled as follows (Fig. 1; from west to east): Marine Corps Base Camp Pendleton in California, Camp Navajo in Arizona, Kirtland and Cannon Air Force Bases in New Mexico, Fort Sill and Camp Gruber in Oklahoma, Fort Leonard Wood in Missouri, Sparta Training Center in Illinois, Naval Support Activity Crane in Indiana, Fort Knox in Kentucky, and Radford Army Ammunitions Plant, Fort Lee, Fort A.P. Hill, Fort Belvoir, and Naval Air Station Oceana in Virginia. Each base was sampled three times: once in the spring/early summer (April, May, or the first week in June), once in mid-summer (July, August), and once in the late summer/fall (September, October), conforming to environmental conditions when Bd is most likely detectable [63]. Generally, three wetlands were sampled at each installation. Most sampling occurred at night, when amphibians are active, using dip nets. Captured amphibians were placed in new, individual plastic bags for processing and handling. Bags were discarded after one use; boots and nets were rinsed to clean off mud and debris, and sterilized with a dilute bleach solution between wetland sites.

thumbnail
Figure 1. Department of Defense installations sampled in the present study.

From California to Illinois, bases (yellow dots) were located near Route 66; from Illinois east to the coast, sites were chosen near Interstate 64 to hold latitude relatively constant (between 33° and 39° N). Our transect is shown overlain on a redrawn United States portion of the Global Bd-Mapping Project [14], with red pins indicating positive sites, white pins indicating negative sites, and blue pins indicating negative sites with sample sizes unknown.

https://doi.org/10.1371/journal.pone.0022211.g001

Amphibians are the only known animate host for Bd [4], [45], [64], although zoospores can survive for up to 12 weeks under favorable (cool, moist) soil conditions [65], [66], [67], [68], [69]. Therefore our survey effort focused exclusively on amphibian populations. At each installation, postmetamorphic animals were sampled as they were encountered—because we were broadly interested in the presence of Bd we did not discriminate between salamanders and frogs. All animals were handled using sterile techniques and sampled using cotton, wooden-handled swabs. Swabs were rubbed while rolling the cotton over the body surface; five rubs each on the dorsum, flanks, ventrum, cranium, inguinal region, and the palmar/plantar surface of each foot for a total of 50 rubs [64], [70]. The head of the swab was then broken off in an individually labeled 0.5 ml free standing polypropylene screw cap microcentrifuge tube (Fisherbrand 02-681-333) and stored and shipped cold prior to analysis.

Laboratory Analyses

Swabs were analyzed for Bd using conventional PCR (polymerase chain reaction) techniques [71], [72], [73]. Briefly, to extract Bd DNA from field samples, 1 ml of 70% ethanol was added to microcentrifuge tubes containing sample swabs and stored overnight at −20°C. Swabs were removed and the supernatant was centrifuged (16,000× g for 10 min). ATL-PK (Qiagen) tissue lysis buffer (200 ml) was added to the pelleted fraction and incubated overnight (55°C). To detect Bd zoospores, we used a nested PCR approach (18). Amplification products were visualized on a 3% agarose gel (Ameresco agarose 3:1 HRB). Presence or absence of a 300-bp band was compared against the EZ Load 100-bp molecular ruler (Bio-Rad) and a positive control. Negative controls were run with each sample. Samples were analyzed twice; if either sample tested Bd positive the animal was considered infected. Results were recorded on digital spreadsheets (Microsoft Excel).

Temperature and Precipitation Data, and Statistics

Mean monthly and annual temperature and precipitation data for a 30-yr period (1971–2000) were obtained from stations near or at each base by searching National Oceanic and Atmospheric Administration (NOAA) databases (http://cdo.ncdc.noaa.gov/cgi-bin/climatenormals/climatenormals.pl).

We used Akaike's information criterion (AIC) [74], [75] to compare models (general linear mixed models; SPSS v. 17) fitting the pattern of Bd presence to four variables (season [S]—spring/early summer, mid-summer, and late summer/fall; geographic location [G]—east, central, west; mean seasonal rainfall [R]; and mean seasonal temperature) and each possible combination of each of the four variables (23 candidate models in all). Under this model selection framework, one model (see below) was clearly the best fit. However, because of the danger in underfitting models (leaving out models with important biological inferences) [75], we explored the next two models using a hypothesis testing framework. In particular, because only temperature data from among our datasets were normally distributed (Shapiro-Wilk normality test, Program R). We used nonparametric Kruskal Wallis tests (SPSS v. 17) to refine our examination of geographic location by comparing Bd infection prevalences, temperatures, and precipitation values between arid and temperate installations. Arid installations were located west of the 100th meridian, where mean annual precipitation is <60 cm, and included Marine Corps Base Camp Pendleton, Camp Navajo, Kirtland Air Force Base, and Cannon Air Force Base. Temperate bases were Fort Sill, Camp Gruber, Fort Leonard Wood, Sparta Training Center, Naval Support Activity Crane, Fort Knox, Radford Army Ammunition Plant, Fort A.P. Hill, Fort Belvoir, Fort Lee, and Naval Air Station Oceana. Significance levels were set at p≤0.05.

Results

Installations

Each base was visited three times (Table 1). In April, Camp Navajo and Fort Sill were too cold for amphibian activity, and bases were visited but no amphibians were found and therefore no samples were collected. During the mid-summer and late-summer/fall trips the ponds at Fort Belvoir were dry and no amphibians were detected. At all other sites, during all other sampling times, animals were collected and sampled. In total, from all bases, during all visits, 1,306 amphibians were sampled for this project, 217 (16.6%) swabs tested positive for Bd. In general, the more arid the site the more difficult it was to detect amphibians, especially later in the year, and fewer animals were collected from these bases.

thumbnail
Table 1. Summary of percent Bd-positive amphibians detected at each DoD installation for each of the three 2009 sampling periods.

https://doi.org/10.1371/journal.pone.0022211.t001

We did not detect Bd at two bases, Camp Navajo, AZ and Fort Sill, OK. This was not due to sample size, per se. Thirty five samples were taken at Camp Navajo; 34 in July (mid-summer), 1 in September (late-summer/fall). At Fort Sill, a total of 43 samples were taken; 12 during June (mid-summer), 31 during September (late-summer/fall). This result could have been caused, in part, to a lack of samples during the spring/early summer sampling period (due to cold and snow), when the majority of positive samples at other bases were collected (see below).

Bd was detected at the remaining 13 bases (Table 1, Fig. 2). Infection prevalences among these sites ranged from 2% (1 of 46 samples positive) at Kirtland Air Force Base to 39% (7 of 18 samples positive) at Fort Belvoir. Other sites with high Bd prevalences included Sparta Training Center in Illinois (31%; 55 of 180 samples positive), Marine Corps Base Camp Pendleton in California (26%; 5 of 19 samples positive), and Radford Army Arsenal in Virginia (25%; 15 of 60 samples positive). Sparta Training Center had the highest absolute number of positive samples (55), Fort Leonard Wood had the second highest (38).

thumbnail
Figure 2. Prevalence (percentage) of Bd-positive samples by installation.

Bases are arranged from west to east in the order they appear in Figure 1. Right side y-axis indicates both mean annual temperature (°C, yellow line) and mean annual precipitation (cm, red line). Note the generally low percentage of positive samples from the arid western installations.

https://doi.org/10.1371/journal.pone.0022211.g002

Species

Fifteen of the 30 amphibians species sampled tested positive for Bd. Species infected covered a wide phylogenetic range (Table 2) including: four species of plethodontid salamanders (Desmognathus fuscus, Eurycea cirrigera, Eurycea longicauda, and Pseudotriton ruber), three species of toads (Anaxyrus americanus, Anaxyrus fowleri, Anaxyrus woodhousii), five hylid species (Acris blanchardi, Acris crepitans, Hyla cadaverina, Hyla chrysoscelis, and Pseudacris crucifer), and three ranid species (Lithobates catesbeianus, Lithobates clamitans, and Lithobates sphenocephalus). At no point during this study did we observe moribund amphibians.

thumbnail
Table 2. A list of species sampled for the presence of Bd, organized by families (bold); salamanders followed by frogs.

https://doi.org/10.1371/journal.pone.0022211.t002

Temporal Patterns (Seasonality)

Among 23 candidate models based on season, geographic location, mean seasonal rainfall, and mean seasonal air temperature examined individually and in combination, seasonality produce the lowest AICc score (Table 3). We agree there was a strong seasonal component to our results (Table 3, Fig. 3). During the spring/early-summer sampling period, 39.3% of all samples were positive. This number dropped to 6.1% for mid-summer samples, and to 4.5% for late-summer/fall samples. Most bases followed this pattern (Table 1) including Marine Corps Base Camp Pendleton, Cannon Air Force Base, Camp Gruber, Fort Leonard Wood, Sparta Training Center, Naval Support Activity Crane, Fort Knox, and Fort Lee. Camp Navajo and Fort Sill had no positive samples and Fort Belvoir had animals collected only in the spring/early summer period, and therefore these bases had no temporal pattern of infection. Radford Army Arsenal had 15.8% positive in spring/early summer, 33.3% positive samples in mid-summer, and 23.5% positive in late-summer/fall. Three East-Coast installations—Fort A.P. Hill, Fort Lee, and Naval Air Station Oceana—had higher percentages of animals infected during the late-summer/fall than in the mid-summer period.

thumbnail
Figure 3. Temporal pattern (seasonality) of Bd infection incidence across all installations.

Note the strong tendency for the highest incidences to occur during the spring/early summer sampling period, followed by a precipitous drop off during the mid- to late-summer and fall.

https://doi.org/10.1371/journal.pone.0022211.g003

Spatial Patterns

Among candidate models, seasonality plus mean annual rainfall produced the second lowest AICc score (Table 3). While this model was much less predictive, aridity did appear to have a negative effect on Bd prevalence. Five of the six sites with the lowest prevalences (Camp Navajo, 0%; Fort Sill, 0%; Kirtland Air Force Base, 2%; Cannon Air Force Base, 6%, and Camp Gruber, 8%) occur in the arid southwest (Arizona, New Mexico) or on or near the Great Plains (Oklahoma); the exception was Fort Lee (7%) in Virginia. Remaining sites occur in coastal areas, or inland areas that receive higher levels of precipitation (Table 4). A second way we explored this trend was to compare the data for the western arid bases (Marine Corps Base Camp Pendleton, Camp Navajo, Kirtland Air Force Base, and Cannon Air Force Base) with data for the eastern temperate sites. The prevalence of positive samples for the arid installations was 8.5±11.7% (±95% C.I.)); the prevalence of positive samples for the eastern temperate sites was 20.8±8.4%. This difference was statistically significant (Kruskal-Wallis, p = 0.027). Precipitation levels were also different between the western arid and eastern temperate bases ( = 39.5±13.2 vs. 107.8±11.8 cm annually; Kruskal-Wallis, p = 0.002), although temperatures were not ( = 13.7±2.9 vs. 13.9±1.1°C; Kruskal-Wallis, p = 0.3).

thumbnail
Table 4. Mean annual precipitation (cm) and temperature (°C) at each of the fifteen DoD installations sampled.

https://doi.org/10.1371/journal.pone.0022211.t004

Discussion

We used standardized collection and analytical techniques to address the following questions: 1) Does Bd occur in amphibian populations in these relatively undisturbed environments? 2) Is there a spatial pattern to the presence of Bd? 3) Is there a temporal pattern to the presence of Bd? and 4) In secured, limited-traffic areas of the country, is Bd acting as an epidemic (i.e., is there evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (is it present without clinical signs of disease)?

Before we formally consider these questions, we offer some background on the life history and physiological ecology of Bd. The life history of Bd is composed of two stages: a thallus (body), which is present in amphibian skin and free-living zoospore, which is flagellated and motile in aquatic environments [76]. Zoospores can swim about 2 cm [77] and infect keratinizing squamous epithelial cells [78]. Favorable environments, where the infection can spread, are cool and wet. Hot and dry environments are considered hostile, and temperatures >25°C may assist infected amphibians in clearing the infection [76], [79], [80]. Given this, across amphibian species, behavioral and life history features of the animal, and ecological features of the geographic region (ecoregion), will affect the course and extent of Bd infection [81], [82], [83], [84].

In the present study, Bd was detected in 13 of 15 DoD installations, spanning the width of the North American continent. Fifteen of 30 amphibian species sampled tested positive for Bd. There were both spatial and temporal patterns to Bd prevalence, as follows.

Bd is found in the highly secure environments of U.S. DoD installations

In aggregate, the data for all bases over all three sampling periods (spring/early-summer, mid-summer, late-summer/fall) show a 16.6% prevalence of Bd infection. Bd was found in all but two installations, Camp Navajo in Arizona and Fort Sill in western Oklahoma. Lack of Bd detection on these bases may be the result of insufficient sampling during the first sampling period due to inclement weather (cold/snow). Amphibians were not active during the first sampling period at either of these bases and spring and early-summer was the time when Bd was most likely to be detected (78.5% of our positive samples came from this first sampling period; see below).

During this study we sampled about 10% (30) of all known United States amphibian species and found Bd in half of them, including four plethodontids, three bufonids, five hylids, and three ranids (Table 2). While Bd absence in the remaining species may be due to inherent resistance [85], [86] or ecological avoidance [81], it is most probable that in cases of no detection, individuals sampled happened to be negative, or to test negative at the time of sampling. It is likely that all amphibian species are susceptible to Bd infection, although species-specific variation in susceptibility has been shown [87], as has intraspecific variation in susceptibility [25]. Several of the species that tested Bd positive have tested positive in other studies; salamanders and ranids, including American Bullfrogs (Lithobates catesbeianus), may be carriers of this infection [88], [89], [90], [91].

There is a temporal (seasonal) pattern to the presence of Bd

There was a strong temporal component to our dataset (Table 1; Fig. 3). In total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period, and broken out by sampling period, the percent positive samples were 39.3% (168 of 427), 6.1% (29 of 477), and 4.5% (17 of 374). The data for the majority of bases (Marine Corps Base Camp Pendleton, Cannon Air Force Base, Camp Gruber, Fort Leonard Wood, Sparta Training Center, Naval Support Activity Crane, Fort Knox, and Fort Lee) followed a temporal pattern, but the data from some bases did not (Table 1). For example, three bases had no pattern of infection: Camp Navajo and Fort Sill had no Bd positive samples and Fort Belvoir had positive samples only in the spring/early summer period. Other bases had infection patterns that differed seasonally: Radford Army Arsenal had 15.8% positive in spring/early summer, 33.3% positive samples in mid-summer, and 23.5% positive in late-summer/fall. Interestingly, and perhaps reflecting more favorable conditions for Bd (high moisture), three East-Coast installations—Fort A.P. Hill, Fort Lee, and Naval Air Station Oceana—had higher percentages of animals infected during the late-summer/fall than in the mid-summer period (Table 1). Overall, our data suggest a strong seasonal component to Bd infection, with the earliest sampling period showing the greatest incidence (Fig. 3).

Seasonality in Bd incidence has been previously demonstrated [27], [92], [93], [94]. As summer proceeds, Bd-positive frogs appear to lose their infection [66], [77], [79], [84], [95]. It is also true that infected animals can develop chytridiomycosis and die, and thus be lost to later surveys. Just as we suggest the spatial pattern of Bd presence is due to variations in moisture levels (with moisture promoting infection incidence) we suggest the temporal (seasonal) pattern is due to moisture availability, with Bd present at the highest incidences during the wettest times of the year. Corroborating this hypothesis, our data suggest that Bd prevalence is lower in arid areas (xeric deserts and the arid Great Plains) and during drier times of the year (mid- to late-summer and fall). Temperature may be a covariate, with cooler temperatures promoting the infection, although in our study, by minimizing variation in latitude among sites in the transect [96], we also minimized, as much as possible in a continental transect, temperature differences.

There is a spatial pattern to the presence of Bd

The eleven eastern temperate DoD installations had significantly higher prevalences of Bd infection (20.8%) than the four bases situated in the arid western ecosystems (8.5%). Bd went undetected at one of these bases (Camp Navajo); two arid bases each had single-digit levels of detection (Kirtland Air Force Base, 2%; Cannon Air Force Base, 6%). Marine Corps Base Camp Pendleton was the one exception. It had a 26% prevalence, but this installation is characterized by maritime Mediterranean climate, with more moisture than inland installations. Fort Sill was the second exception; Bd was not found on this eastern Oklahoma base. Bd is known to favor cool, moist conditions [38], [97]. It therefore follows that warm and dry (i.e., arid) conditions may inhibit this pathogen. Our data are consistent with this interpretation (Fig. 2). Further, animals that bask have been shown to have an increased resistance to chytridiomycosis [79], [80]. We find no evidence that particular species are driving geographic trends.

Our data both support and augment data on known distributions of Bd in the United States [14] (Fig. 1). Our data support the observations that Bd is widespread in California and common across portions of the southwest and throughout the eastern half of the country. The relatively few positive samples previously reported from the Great Plains may in part be due to the relatively few samples recorded from this region [14] (Fig. 1). In our study, positive samples from New Mexico, Oklahoma, and Illinois expand upon the sparse reporting from these states. Positive samples from Ft. Knox confirm the presence of Bd in Kentucky.

Our results suggest Bd may be endemic across much of the United States middle latitudes

These data lend support to the conclusion [46] that Bd is now widespread across much of North America. Samples from DoD installations located in mesic habitats show a range of Bd infection from 7% (5/67) positive samples at Fort Lee, in Virginia, to 39% positive samples at Fort Belvoir. This spatial pattern—from coast-to-coast—supports the assertion [46] that Bd, while once likely epidemic, today is endemic across much of the United States. Further, the phylogenetic range of species that tested positive—plethodontid salamanders in three genera, bufonid toads, treefrogs in three genera, and ranid frogs—suggests that this infection has been associated with aquatic ecosystems long enough to infect numerous taxonomic groups.

The exceptions to this generalization of endemism are two arid bases, Camp Navajo in Arizona and Fort Sill in Oklahoma. These installations warrant further study; there would be greater confidence with the conclusion that Bd is absent at these bases had we sampled large numbers of animals during the spring/early-summer period. Our data do not distinguish between “Bd present but not detected” and “Bd absent.” There are known to be pockets of wilderness, for example in regions of the Sierra Nevada that Bd has yet to reach [45]. At these places, when Bd arrives it is predicted to be an epidemic infection, and we suspect amphibian extirpations will follow. Camp Navajo and Fort Sill may be examples of such Bd-negative outposts, but further study is needed.

Our results contribute to the recent and widespread literature being generated on the spatial patterns of Bd distribution tied to assessing risks and identifying refugia [98], [99], [100], [101], [102]. In particular, these authors suggest that amphibian species with populations inhabiting the drier interior of the United States may be less at risk than populations inhabiting more mesic regions. Attempts to ameliorate the effects of Bd in the field are being proposed [103]. Our data also suggest that broad geographic surveys, whether they be current or historical, be interpreted in light of seasonality in collection times. For example a directional transect beginning in one region and ending sometime later at a distant region, may interpret a geographic trend, when in fact the cause might be a seasonal trend.

Acknowledgments

The authors recognize the following individuals, without whom this study would not have been possible: Heather Arnold, Sara Bell, John “Chip” Blackburn, Paul Block, Kurt Buhlmann, John Crawford, Megan Dinkins, Mike Dreslik, Nate Engbrecht, Jennifer Heemeyer, Stephanie Keys, Andrew Kuhns, Justin Mitchell, Bill Peterman, Sarah Shepheard, Jeremy Tiemann, Vanessa Kinney, and Dan Wylie for field collection of samples. Neil Wesslund at CERL ran the PCR reactions. Steve Andrews (Naval Support Activity Crane), Jason Applegate, Terry Banks, and Timothy Southerland (Fort A.P. Hill), Bill Berry (Marine Corps Base Camp Pendleton), Dana Bradshaw (Fort Lee), Mike Brandenburg (Fort Knox), Clayton Carmichael (Sparta Training Center), Rick Crow (Cannon Air Force Base), Len DiIoia (Radford Army Ammunitions Plant), Carol Finley (Kirtland Air Force Base), Jeff Howard (Camp Gruber), Kenton Lohraff (Fort Leonard Wood), John Pilcicki (Fort Belvoir), Zach Reichold (Camp Navajo), Glen Wampler and Kevin McCurdy (Fort Sill), and Michael Wright (Naval Air Station Oceana) provided access to their installations and support in the field. Special thanks to Mike Dreslik, Jennifer Heemeyer, Vanessa Kinney, and Nate Engbrecht for the statistical consultation. Danette Pratt created Figure 1. Susie Lannoo proofread early drafts. Thanks also to Allan Pessier and Joe Mendelson for numerous conversations on the nuiances of Bd sampling and interpretation.

Author Contributions

Conceived and designed the experiments: MJL CP REL PN CP JM IM. Performed the experiments: MJL CP REL CP JM IM. Analyzed the data: MJL CP REL PN CP JM IM. Contributed reagents/materials/analysis tools: MJL CP REL PN CP JM IM. Wrote the paper: MJL CP REL IM CP.

References

  1. 1. Stuart SN, Chanson JS, Cox NA, Young BE, Rodrigues ASL, et al. (2004) Status and trends of amphibians and extinctions worldwide. Science 306: 1783–1786.SN StuartJS ChansonNA CoxBE YoungASL Rodrigues2004Status and trends of amphibians and extinctions worldwide.Science30617831786
  2. 2. Wake DB, Vredenburg VT (2008) Colloquium paper: are we in the midst of the sixth mass extinction? A view from the world of amphibians. PNAS 105: 11466–11473.DB WakeVT Vredenburg2008Colloquium paper: are we in the midst of the sixth mass extinction? A view from the world of amphibians.PNAS1051146611473
  3. 3. IUCN Red List. IUCN Red List.Available: http://www.iucnredlist.org/initiatives/amphibians. Accessed 2010 Oct. 1. Available: http://www.iucnredlist.org/initiatives/amphibians. Accessed 2010 Oct. 1.
  4. 4. Longcore J, Pessier A, Nichols DK (1999) Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia 91: 219–227.J. LongcoreA. PessierDK Nichols1999Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians.Mycologia91219227
  5. 5. Daszak P, Cunningham AA, Hyatt AD (2003) Infectious disease and amphibian population declines. Divers Dist 9: 141–150.P. DaszakAA CunninghamAD Hyatt2003Infectious disease and amphibian population declines.Divers Dist9141150
  6. 6. Rachowicz LJ, Knapp RA, Morgan JAT, Stice MJ, Vredenburg VT, et al. (2006) Emerging infectious disease as a proximate cause of amphibian mass mortality. Ecology 87: 1671–1683.LJ RachowiczRA KnappJAT MorganMJ SticeVT Vredenburg2006Emerging infectious disease as a proximate cause of amphibian mass mortality.Ecology8716711683
  7. 7. DiRosa I, Simoncelli F, Fagotti A, Pascolini R (2007) The proximate cause of amphibian declines? Nature 447: E4–E5.I. DiRosaF. SimoncelliA. FagottiR. Pascolini2007The proximate cause of amphibian declines?Nature447E4E5
  8. 8. Skerratt LF, Berger L, Speare R, Cashins S, McDonald KR, et al. (2007) Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. EcoHealth 4: 125–134.LF SkerrattL. BergerR. SpeareS. CashinsKR McDonald2007Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs.EcoHealth4125134
  9. 9. Jones , KE , Patel NG, Levy MA, Storeygard A, Balk D, et al. (2008) Global trends in emerging infectious diseases. Nature 451: 990–993.JonesKENG PatelMA LevyA. StoreygardD. Balk2008Global trends in emerging infectious diseases.Nature451990993
  10. 10. Murray KA, Skerratt LF, Speare R, McCallum H (2009) Impact and dynamics of disease in species threatened by the amphibian chytrid fungus, Batrachochytrium dendrobatidis. Cons Biol 32: 1242–1252.KA MurrayLF SkerrattR. SpeareH. McCallum2009Impact and dynamics of disease in species threatened by the amphibian chytrid fungus, Batrachochytrium dendrobatidis.Cons Biol3212421252
  11. 11. Kilpatrick AM, Briggs CJ, Daszak P (2010) The ecology and impact of chytridiomycosis: an emerging disease of amphibians. Trends Ecol Evol 25: 109–118.AM KilpatrickCJ BriggsP. Daszak2010The ecology and impact of chytridiomycosis: an emerging disease of amphibians.Trends Ecol Evol25109118
  12. 12. Lovich R, Ryan MJ, Pessier AP, Claypool B (2008) Infection with the fungus Batrachochytrium dendrobatidis in a non-native Lithobates berlandieri below sea level in the Coachilla Valley, California, USA. Herp Rev 39: 315–317.R. LovichMJ RyanAP PessierB. Claypool2008Infection with the fungus Batrachochytrium dendrobatidis in a non-native Lithobates berlandieri below sea level in the Coachilla Valley, California, USA.Herp Rev39315317
  13. 13. Vredenburg VT, Summers AT (2001) Field identification of chytridiomycosis in Rana muscosa. Herp Rev 32: 151–152.VT VredenburgAT Summers2001Field identification of chytridiomycosis in Rana muscosa.Herp Rev32151152
  14. 14. Bd Maps website. Bd Maps website.Available: http://www.spatialepidemiology.net/bd-maps. Accessed 201 Oct 21. Available: http://www.spatialepidemiology.net/bd-maps. Accessed 201 Oct 21.
  15. 15. Adams MJ, Galvan S, Reinitz D, Cole RA, Payre S, et al. (2007) Incidence of the fungus Batrachochytrium dendrobatidis in amphibian populations along the Northwest Coast of North America. Herp Rev 38: 430–431.MJ AdamsS. GalvanD. ReinitzRA ColeS. Payre2007Incidence of the fungus Batrachochytrium dendrobatidis in amphibian populations along the Northwest Coast of North America.Herp Rev38430431
  16. 16. Frías-Alvarez P, Vredenburg VT, Familiar-López M, Longcore JE, González-Bernal E, et al. (2008) Chytridiomycosis survey in wild and captive Mexican amphibians. EcoHealth 5: 18–26.P. Frías-AlvarezVT VredenburgM. Familiar-LópezJE LongcoreE. González-Bernal2008Chytridiomycosis survey in wild and captive Mexican amphibians.EcoHealth51826
  17. 17. Grant EHC, Bailey LL, Ware JL, Duncan KL (2008) Prevalence of the amphibian pathogen Batrachochytrium dendrobatidis in stream and wetland amphibians in Maryland, USA. Appl Herp 5: 233–241.EHC GrantLL BaileyJL WareKL Duncan2008Prevalence of the amphibian pathogen Batrachochytrium dendrobatidis in stream and wetland amphibians in Maryland, USA.Appl Herp5233241
  18. 18. Deguise I, Richardson JS (2009) Prevalence of the chytrid fungus (Batrachochytrium dendrobatidis) in Western Toads in southwestern British Columbia, Canada. Northwest Nat 90: 35–38.I. DeguiseJS Richardson2009Prevalence of the chytrid fungus (Batrachochytrium dendrobatidis) in Western Toads in southwestern British Columbia, Canada.Northwest Nat903538
  19. 19. Gaertner JP, Forstner MRJ, O'Donnell L, Hahn D (2009) Detection of Batrachochytrium dendrobatidis in endemic salamander species from Central Texas. EcoHealth 6: 20–26.JP GaertnerMRJ ForstnerL. O'DonnellD. Hahn2009Detection of Batrachochytrium dendrobatidis in endemic salamander species from Central Texas.EcoHealth62026
  20. 20. Goldberg CS, Hawley TJ, Waits LP (2009) Local and regional patterns of amphibian chytrid presence on the Osa Peninsula, Costa Rica. Herp Rev 40: 309–311.CS GoldbergTJ HawleyLP Waits2009Local and regional patterns of amphibian chytrid presence on the Osa Peninsula, Costa Rica.Herp Rev40309311
  21. 21. Sadinski W, Roth M, Treleven S, Theyerl J, Dummer P (2010) Detection of the chytrid fungus, Batrachochytrium dendrobatidis, on recently metamorphosed amphibians in the North-Central United States. Herp Rev 41: 170–175.W. SadinskiM. RothS. TrelevenJ. TheyerlP. Dummer2010Detection of the chytrid fungus, Batrachochytrium dendrobatidis, on recently metamorphosed amphibians in the North-Central United States.Herp Rev41170175
  22. 22. Blaustein AR, Romansic JM, Scheessele EA, Han BA, Pessier AP, et al. (2005) Interspecific variation in susceptibility of frog tadpoles to the pathogenic fungus Batrachochytrium dendrobatidis. Cons Biol 19: 1460–1468.AR BlausteinJM RomansicEA ScheesseleBA HanAP Pessier2005Interspecific variation in susceptibility of frog tadpoles to the pathogenic fungus Batrachochytrium dendrobatidis.Cons Biol1914601468
  23. 23. Kriger KM, Hero J-M (2007) The chytrid fungus Batrachochytrium dendrobatidis is non-randomly distributed across amphibian breeding habitats. Divers Dist 13: 781–788.KM KrigerJ-M Hero2007The chytrid fungus Batrachochytrium dendrobatidis is non-randomly distributed across amphibian breeding habitats.Divers Dist13781788
  24. 24. Zellmer AJ, Richards CL, Martens LM (2008) Low prevalence of Batrachochytrium dendrobatidis across Rana sylvatica populations in southeastern Michigan, USA. Herp Rev 39: 196–199.AJ ZellmerCL RichardsLM Martens2008Low prevalence of Batrachochytrium dendrobatidis across Rana sylvatica populations in southeastern Michigan, USA.Herp Rev39196199
  25. 25. Tennessen JA, Woodhams DC, Chaurand P, Reinert LK, Billheimer D, et al. (2009) Variations in the expressed antimicrobial peptide repertoire of Northern Leopard Frog (Rana pipiens) populations suggest intraspecies differences in resistance to pathogens. Develop Comp Immunol 33: 1247–1257.JA TennessenDC WoodhamsP. ChaurandLK ReinertD. Billheimer2009Variations in the expressed antimicrobial peptide repertoire of Northern Leopard Frog (Rana pipiens) populations suggest intraspecies differences in resistance to pathogens.Develop Comp Immunol3312471257
  26. 26. Hossack BR, Adams MJ, Grant EHC, Pearl CA, Bettaso JB, et al. (2010) Low prevalence of chytrid fungus (Batrachochytrium dendrobatidis) in amphibians of U.S. headwater streams. J Herp 44: 253–260.BR HossackMJ AdamsEHC GrantCA PearlJB Bettaso2010Low prevalence of chytrid fungus (Batrachochytrium dendrobatidis) in amphibians of U.S. headwater streams.J Herp44253260
  27. 27. Savage AE, Sredl MJ, Zamudio KR (2011) Disease dynamics vary spatially and temporally in a North American amphibian. Biol Cons. AE SavageMJ SredlKR Zamudio2011Disease dynamics vary spatially and temporally in a North American amphibian.Biol Cons
  28. 28. Green DE, Converse KA, Schrader AK (2002) Epizootiology of sixty-four amphibian morbidity and mortality events in the USA, 1996–2001. Ann New York Acad Sci 969: 323–339.DE GreenKA ConverseAK Schrader2002Epizootiology of sixty-four amphibian morbidity and mortality events in the USA, 1996–2001.Ann New York Acad Sci969323339
  29. 29. Garner TWJ, Walker S, Bosch J, Hyatt AD, Cunningham AA, et al. (2005) Chytrid fungus in Europe. Emerg Infect Dis 11: 1639–1641.TWJ GarnerS. WalkerJ. BoschAD HyattAA Cunningham2005Chytrid fungus in Europe.Emerg Infect Dis1116391641
  30. 30. Partners in Amphibian and Reptile Conservation, Southeastern Regional Working Group, 2010 meeting. Partners in Amphibian and Reptile Conservation, Southeastern Regional Working Group, 2010 meeting.Available: http://www.parcplace.org/Bd_conference.html. Accessed 2010 Nov 7. Available: http://www.parcplace.org/Bd_conference.html. Accessed 2010 Nov 7.
  31. 31. Murray KA, Retallick R, McDonald K, Mendez D, Aplin K, et al. (2010) The distribution and host range of the pandemic disease chytridiomycosis in Australia spanning surveys from 1956 to 2007. Ecology. 91. : 1557. E091–108.KA MurrayR. RetallickK. McDonaldD. MendezK. Aplin2010The distribution and host range of the pandemic disease chytridiomycosis in Australia spanning surveys from 1956 to 2007.Ecology911557. E091108
  32. 32. Goka K, Yokoyama J, Une Y, Kuroki T, Suzuki K, et al. (2009) Amphibian chytridiomycosis in Japan: distribution, haplotypes and possible route of entry into Japan. Molecular Ecology 18: 4757–4774.K. GokaJ. YokoyamaY. UneT. KurokiK. Suzuki2009Amphibian chytridiomycosis in Japan: distribution, haplotypes and possible route of entry into Japan.Molecular Ecology1847574774
  33. 33. Kriger KM, Hero J-M (2007) Large-scale seasonal variation in the prevalence and severity of chytridiomycosis. J Zool 271: 352–359.KM KrigerJ-M Hero2007Large-scale seasonal variation in the prevalence and severity of chytridiomycosis.J Zool271352359
  34. 34. Skerratt LF, McDonald KR, Hines HB, Berger L, Mendez , D , et al. (2010) Validation of the mapping protocol for Batrachochytrium dendrobatidis in Queensland, Australia. Dis Aquat Org 92: 117–129.LF SkerrattKR McDonaldHB HinesL. BergerMendezD2010Validation of the mapping protocol for Batrachochytrium dendrobatidis in Queensland, Australia.Dis Aquat Org92117129
  35. 35. Cheng TL, Rovito SM, Wake DB, Vredenburg VT (2011) Coincident mass extirpation of Neotropical amphibians with the emergence of the infectious fungal pathogen Batrachochytrium dendrobatidis. PNAS doi/10.1073/pnas 1105538108. TL ChengSM RovitoDB WakeVT Vredenburg2011Coincident mass extirpation of Neotropical amphibians with the emergence of the infectious fungal pathogen Batrachochytrium dendrobatidis.PNAS doi/10.1073/pnas 1105538108
  36. 36. Briggs CJ, Vredenburg VT, Knapp RA, Rachowicz LJ (2005) Investigating the population-level effects of chytridiomycosis: an emerging infectious disease of amphibians. Ecology 86: 3149–3159.CJ BriggsVT VredenburgRA KnappLJ Rachowicz2005Investigating the population-level effects of chytridiomycosis: an emerging infectious disease of amphibians.Ecology8631493159
  37. 37. Rachowicz LJ, Hero J-M, Alford RA, Taylor JW, Morgan JAT, et al. (2006) The novel and endemic pathogen hypotheses: competing explanations for the origin of emerging infectious diseases of wildlife. Cons Biol 19: 1441–1449.LJ RachowiczJ-M HeroRA AlfordJW TaylorJAT Morgan2006The novel and endemic pathogen hypotheses: competing explanations for the origin of emerging infectious diseases of wildlife.Cons Biol1914411449
  38. 38. Fisher MC, Garner TWJ, Walker SF (2009) Global emergence of Batrachochytrium dendrobatidis and amphibian chytridiomycosis in space, time, and host. Ann Rev Microbiol 63: 291–310.MC FisherTWJ GarnerSF Walker2009Global emergence of Batrachochytrium dendrobatidis and amphibian chytridiomycosis in space, time, and host.Ann Rev Microbiol63291310
  39. 39. Berger L, Speare R, Daszak P, Green DE, Cunningham AA, et al. (1998) Chytridiomycosis causes amphibian mortality associated with population decline in the Rain Forests of Australia and Central America. PNAS 95: 9031–9036.L. BergerR. SpeareP. DaszakDE GreenAA Cunningham1998Chytridiomycosis causes amphibian mortality associated with population decline in the Rain Forests of Australia and Central America.PNAS9590319036
  40. 40. Lips KR (1998) Decline of a tropical montane amphibian fauna. Cons Biol 12: 106–117.KR Lips1998Decline of a tropical montane amphibian fauna.Cons Biol12106117
  41. 41. Lips KR (1999) Mass mortality and population declines of anurans at an upland site in western Panama. Cons Biol 13: 117–125.KR Lips1999Mass mortality and population declines of anurans at an upland site in western Panama.Cons Biol13117125
  42. 42. Lips KR, Green DE, Papedick R (2003) Chytridiomycosis in wild frogs from southern Costa Rica. J Herp 37: 215–218.KR LipsDE GreenR. Papedick2003Chytridiomycosis in wild frogs from southern Costa Rica.J Herp37215218
  43. 43. Lips KR, Brem F, Brenes R, Reeve JD, Alford RA, et al. (2006) Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community. Ecology 103: 3165–3170.KR LipsF. BremR. BrenesJD ReeveRA Alford2006Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community.Ecology10331653170
  44. 44. James TY, Litvintseva AP, Vilgalys R, Morgan JAT, Taylor JW, et al. (2009) Rapid global expansion of the fungal disease chytridiomycosis into declining and healthy amphibian populations. PLoS Path 5: e1000458.TY JamesAP LitvintsevaR. VilgalysJAT MorganJW Taylor2009Rapid global expansion of the fungal disease chytridiomycosis into declining and healthy amphibian populations.PLoS Path5e1000458
  45. 45. Vredenburg VT, Knapp RA, Tunstall TS, Briggs CJ (2010) Dynamics of an emerging disease drive large-scale amphibian population extinctions. PNAS. pnas.0914111107 p.VT VredenburgRA KnappTS TunstallCJ Briggs2010Dynamics of an emerging disease drive large-scale amphibian population extinctions.PNASpnas.0914111107
  46. 46. Ouellet M, Mikaelian I, Pauli BD, Rodrigues J, Green DM (2005) Historical evidence of widespread chytrid infection in North American amphibian populations. Cons Biol 19: 1431–1440.M. OuelletI. MikaelianBD PauliJ. RodriguesDM Green2005Historical evidence of widespread chytrid infection in North American amphibian populations.Cons Biol1914311440
  47. 47. Waldman B, van de Wolfshaar KE, Klena JD, Andjic V, Bishop PJ, et al. (2001) Chytridiomycosis in New Zealand frogs. Surveillance 28: 9–11.B. WaldmanKE van de WolfshaarJD KlenaV. AndjicPJ Bishop2001Chytridiomycosis in New Zealand frogs.Surveillance28911
  48. 48. Retallick RWR, McCallum H, Speare R (2004) Endemic infection of the amphibian chytrid fungus in a frog community post-decline. PLoS Biol 2: 1965–1971.RWR RetallickH. McCallumR. Speare2004Endemic infection of the amphibian chytrid fungus in a frog community post-decline.PLoS Biol219651971
  49. 49. Carnival ACOQ, Puschendorf R, Peixoto OL, Verdade VK, Rodrigues MT (2006) Amphibian chytrid fungus broadly distributed in the Brazilian Atlantic Rain Forest. EcoHealth 3: 41–48.ACOQ CarnivalR. PuschendorfOL PeixotoVK VerdadeMT Rodrigues2006Amphibian chytrid fungus broadly distributed in the Brazilian Atlantic Rain Forest.EcoHealth34148
  50. 50. Adams MJ, Galvan S, Scalera R, Grieco C, Sindaco R (2008) Batrachochytrium dendrobatidis in amphibian populations in Italy. Herp Rev 39: 324–326.MJ AdamsS. GalvanR. ScaleraC. GriecoR. Sindaco2008Batrachochytrium dendrobatidis in amphibian populations in Italy.Herp Rev39324326
  51. 51. Lampo M, Sánchez D, Nicolás A, Márquez M, Nava-González F, et al. (2008) Batrachochytrium dendrobatidis in Venezuela. Herp Rev 39: 449–454.M. LampoD. SánchezA. NicolásM. MárquezF. Nava-González2008Batrachochytrium dendrobatidis in Venezuela.Herp Rev39449454
  52. 52. Longcore JR, Longcore JE, Pessier AP, Halteman WA (2007) Chytridiomycosis widespread in anurans of northeastern United States. J Wildl Manage 71: 435–444.JR LongcoreJE LongcoreAP PessierWA Halteman2007Chytridiomycosis widespread in anurans of northeastern United States.J Wildl Manage71435444
  53. 53. Pearl CA, Bull EL, Green DE, Bowerman J, Adams MJ, et al. (2007) Occurrence of the amphibian pathogen Batrachochytrium dendrobatidis in the Pacific Northwest. J Herp 41: 145–149.CA PearlEL BullDE GreenJ. BowermanMJ Adams2007Occurrence of the amphibian pathogen Batrachochytrium dendrobatidis in the Pacific Northwest.J Herp41145149
  54. 54. Rothermel BB, Walls SC, Mitchell JC, Dodd CK, Irwin LK, et al. (2008) Widespread occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in the southeastern USA. Dis Aquat Org 82: 3–18.BB RothermelSC WallsJC MitchellCK DoddLK Irwin2008Widespread occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in the southeastern USA.Dis Aquat Org82318
  55. 55. Scalera R, Adams MJ, Galvan SK (2008) Occurrence of Batrachochytrium dendrobatidis in amphibian populations in Denmark. Herp Rev 39: 199–200.R. ScaleraMJ AdamsSK Galvan2008Occurrence of Batrachochytrium dendrobatidis in amphibian populations in Denmark.Herp Rev39199200
  56. 56. Chatfield MWH, Rothermel BB, Brooks CS, Kay JB (2009) Detection of Batrachochytrium dendrobatidis in amphibians from the Great Smoky Mountains of North Carolina and Tennessee, USA. Herp Rev 40: 176–179.MWH ChatfieldBB RothermelCS BrooksJB Kay2009Detection of Batrachochytrium dendrobatidis in amphibians from the Great Smoky Mountains of North Carolina and Tennessee, USA.Herp Rev40176179
  57. 57. de Queiroz Carnival ACO, Puschendorf R, Peixoto OL, Verdade VK, Rodrigues MT (2009) Amphibian chytrid fungus broadly distributed in the Brazilian Atlantic Rain Forest. EcoHealth 3: 41–48.ACO de Queiroz CarnivalR. PuschendorfOL PeixotoVK VerdadeMT Rodrigues2009Amphibian chytrid fungus broadly distributed in the Brazilian Atlantic Rain Forest.EcoHealth34148
  58. 58. Briggs CJ, Knapp RA, Vredenburg VT (2010) Enzootic and epizootic dynamics of the chytrid fungus pathogen of amphibians. PNAS. pnas.0912886107 p.CJ BriggsRA KnappVT Vredenburg2010Enzootic and epizootic dynamics of the chytrid fungus pathogen of amphibians.PNASpnas.0912886107
  59. 59. Pounds JA, Bustamante MR, Coloma LA, Consuegra JA, Viteri MP, et al. (2006) Widespread amphibian extinctions from epidemic disease driven by global warming. Nature 439: 161–167.JA PoundsMR BustamanteLA ColomaJA ConsuegraMP Viteri2006Widespread amphibian extinctions from epidemic disease driven by global warming.Nature439161167
  60. 60. Lips KR, Diffendorfer J, Mendelson JR III, Sears MW (2008) Riding the wave: reconciling the roles of disease and climate change in amphibian declines. PLoS Biol 6: 441–454.KR LipsJ. DiffendorferJR Mendelson IIIMW Sears2008Riding the wave: reconciling the roles of disease and climate change in amphibian declines.PLoS Biol6441454
  61. 61. Hester RE, Harrison RM (2007) Biodiversity Under Threat. Royal Society of Chemistry, London. RE HesterRM Harrison2007Biodiversity Under Threat.Royal Society of Chemistry, London
  62. 62. Stein BA, Scott C, Benton N (2008) Federal lands and endangered species: the role of military and other federal lands in sustaining biodiversity. BioScience 58: 339–347.BA SteinC. ScottN. Benton2008Federal lands and endangered species: the role of military and other federal lands in sustaining biodiversity.BioScience58339347
  63. 63. Skerratt LF, Berger L, Hines HB, McDonald KR, Mendez D, et al. (2008) Survey protocol for detecting chytridiomycosis in all Australian frog populations. Dis Aquat Org 80: 85–94.LF SkerrattL. BergerHB HinesKR McDonaldD. Mendez2008Survey protocol for detecting chytridiomycosis in all Australian frog populations.Dis Aquat Org808594
  64. 64. Pessier AP, Mendelson JR III (2010) A manual for control of infectious diseases in amphibian survival assurance colonies and reintroduction programs. Proceedings from a Workshop 16–18 February 2009, San Diego Zoo, San Diego, California, USA. AP PessierJR Mendelson III2010A manual for control of infectious diseases in amphibian survival assurance colonies and reintroduction programs.Proceedings from a Workshop 16–18 February 2009, San Diego Zoo, San Diego, California, USA
  65. 65. Johnson ML, Speare R (2003) Survival of Batrachochytrium dendrobatidis in water: quarantine and disease control implications. Emerg Infect Dis 9: 922–925.ML JohnsonR. Speare2003Survival of Batrachochytrium dendrobatidis in water: quarantine and disease control implications.Emerg Infect Dis9922925
  66. 66. Johnson ML, Speare R (2005) Possible modes of dissemination of the amphibian chytrid Batrachochytrium dendrobatidis in the environment. Dis Aquat Org 65: 181–186.ML JohnsonR. Speare2005Possible modes of dissemination of the amphibian chytrid Batrachochytrium dendrobatidis in the environment.Dis Aquat Org65181186
  67. 67. Rachowicz LJ, Vredenburg VT (2004) Transmission of Batrachochytrium dendrobatidis within and between amphibian life stages. Dis Aquat Org 61: 75–83.LJ RachowiczVT Vredenburg2004Transmission of Batrachochytrium dendrobatidis within and between amphibian life stages.Dis Aquat Org617583
  68. 68. Berger L, Hyatt AD, Speare R, Longcore JE (2005) Life cycle stages of the amphibian chytrid Batrachochytrium dendrobatidis. Dis Aquat Org 68: 51–63.L. BergerAD HyattR. SpeareJE Longcore2005Life cycle stages of the amphibian chytrid Batrachochytrium dendrobatidis.Dis Aquat Org685163
  69. 69. Mitchell KM, Churcher TS, Garner TWJ, Fisher MC (2008) Persistence of the emerging pathogen Batrachochytrium dendrobatidis outside the amphibian host greatly increases the probability of host extinction. Proc Royal Soc Biol Sci B 275: 329–334.KM MitchellTS ChurcherTWJ GarnerMC Fisher2008Persistence of the emerging pathogen Batrachochytrium dendrobatidis outside the amphibian host greatly increases the probability of host extinction.Proc Royal Soc Biol Sci B275329334
  70. 70. Skerratt LF, Berger L, Hines HB, McDonald KR, Mendez D, et al. (2008) Survey protocol for detecting chytridiomycosis in all Australian frog populations. Dis Aquat Org 80: 85–94.LF SkerrattL. BergerHB HinesKR McDonaldD. Mendez2008Survey protocol for detecting chytridiomycosis in all Australian frog populations.Dis Aquat Org808594
  71. 71. Annis SL, Dastoor FP, Ziel H, Daszak P, Longcore JE (2004) A DNA-based assay identifies Batrachochytrium dendrobatidis in amphibians. J Wildl Dis 40: 420–428.SL AnnisFP DastoorH. ZielP. DaszakJE Longcore2004A DNA-based assay identifies Batrachochytrium dendrobatidis in amphibians.J Wildl Dis40420428
  72. 72. Kriger KM, Hero J-M (2006) Survivorship in wild frogs infected with chytridiomycosis. EcoHealth 3: 171–177.KM KrigerJ-M Hero2006Survivorship in wild frogs infected with chytridiomycosis.EcoHealth3171177
  73. 73. Hyatt AD, Boyle DG, Olsen V, Boyle DB, Berger L, et al. (2007) Diagnostic assays and sampling protocols for the detection of Batrachochytrium dendrobatidis. Dis Aquat Org 73: 175–192.AD HyattDG BoyleV. OlsenDB BoyleL. Berger2007Diagnostic assays and sampling protocols for the detection of Batrachochytrium dendrobatidis.Dis Aquat Org73175192
  74. 74. Anderson DR, Burnham KP, Thompson WL (2000) Null hypothesis testing: problems, prevalence, and an alternative. J Wildl Manage 64: 912–923.DR AndersonKP BurnhamWL Thompson2000Null hypothesis testing: problems, prevalence, and an alternative.J Wildl Manage64912923
  75. 75. Mills LS (2008) Conservation of Wildlife Populations: Demography, Genetics, and Management. Blackwell, Malden, Massachusetts. LS Mills2008Conservation of Wildlife Populations: Demography, Genetics, and Management.Blackwell, Malden, Massachusetts
  76. 76. Morgan JAT, Vredenburg VT, Rachowicz LJ, Knapp RA, Stice MJ, et al. (2007) Population genetics of the frog-killing fungus Batrachochytrium dendrobatidis. PNAS 104: 13845–13850.JAT MorganVT VredenburgLJ RachowiczRA KnappMJ Stice2007Population genetics of the frog-killing fungus Batrachochytrium dendrobatidis.PNAS1041384513850
  77. 77. Piotrowski JS, Annis SL, Longcore JE (2004) Physiology of Batrachochytrium dendrobatidis, a chytrid pathogen of amphibians. Mycologia 96: 9–15.JS PiotrowskiSL AnnisJE Longcore2004Physiology of Batrachochytrium dendrobatidis, a chytrid pathogen of amphibians.Mycologia96915
  78. 78. Pessier AP, Nichols DK, Longcore JE, Fuller MS (1999) Cutaneous chytridiomycosis in Poison Dart Frogs (Dendrobates spp.) and White's Tree Frogs (Litoria caerulea). J Vet Diagn Invest 11: 194–199.AP PessierDK NicholsJE LongcoreMS Fuller1999Cutaneous chytridiomycosis in Poison Dart Frogs (Dendrobates spp.) and White's Tree Frogs (Litoria caerulea).J Vet Diagn Invest11194199
  79. 79. Woodhams DC, Alford RA, Marantelli G (2003) Emerging disease of amphibians cured by elevated body temperature. Dis Aquat Org 55: 65–67.DC WoodhamsRA AlfordG. Marantelli2003Emerging disease of amphibians cured by elevated body temperature.Dis Aquat Org556567
  80. 80. Richards-Zawacki CL (2010) Thermoregulatory behaviour affects prevalence of chytrid fungal infection in a wild population of Panamanian Golden Frogs. Proc Royal Soc Biol Sci B 277: 519–528.CL Richards-Zawacki2010Thermoregulatory behaviour affects prevalence of chytrid fungal infection in a wild population of Panamanian Golden Frogs.Proc Royal Soc Biol Sci B277519528
  81. 81. Lips KR, Reeve JD, Witters LR (2003) Ecological traits predicting amphibian declines in Central America. Cons Biol 17: 1078–1088.KR LipsJD ReeveLR Witters2003Ecological traits predicting amphibian declines in Central America.Cons Biol1710781088
  82. 82. Rowley JJL, Alford RA (2007) Behaviour of Australian rainforest stream frogs may affect the transmission of chytridiomycosis. Dis Aquat Org 77: 1–9.JJL RowleyRA Alford2007Behaviour of Australian rainforest stream frogs may affect the transmission of chytridiomycosis.Dis Aquat Org7719
  83. 83. Rödder D, Veith M, Lötters S (2008) Environmental gradients explaining prevalence and intensity of infection with the amphibian chytrid fungus: the host's perspective. Anim Cons 11: 513–517.D. RödderM. VeithS. Lötters2008Environmental gradients explaining prevalence and intensity of infection with the amphibian chytrid fungus: the host's perspective.Anim Cons11513517
  84. 84. Woodhams DC, Alford RA, Maraentelli G (2005) Ecology of chytridiomycosis in rainforest stream frog assemblages of tropical Queensland. Cons Biol 19: 1449–1459.DC WoodhamsRA AlfordG. Maraentelli2005Ecology of chytridiomycosis in rainforest stream frog assemblages of tropical Queensland.Cons Biol1914491459
  85. 85. Woodhams DC, Ardipradja K, Alford RA, Harris R, Marantelli G, et al. (2007) Resistance to chytridiomycosis varies among amphibian species and is correlated with skin peptide defenses. Anim Cons 10: 409–417.DC WoodhamsK. ArdipradjaRA AlfordR. HarrisG. Marantelli2007Resistance to chytridiomycosis varies among amphibian species and is correlated with skin peptide defenses.Anim Cons10409417
  86. 86. Lauer A, Simon MA, Banning JL, André E, Duncan K, et al. (2007) Common cutaneous bacteria from the eastern red-backed salamander can inhibit pathogenic fungi. Copeia 2007: 630–640.A. LauerMA SimonJL BanningE. AndréK. Duncan2007Common cutaneous bacteria from the eastern red-backed salamander can inhibit pathogenic fungi.Copeia2007630640
  87. 87. Woodhams DC, Hyatt AD, Boyle DG, Rollins-Smith LA (2007) The Northern Leopard Frog Rana pipiens is a widespread reservoir species harboring Batrachochytrium dendrobatidis in North America. Herp Rev 39: 66–68.DC WoodhamsAD HyattDG BoyleLA Rollins-Smith2007The Northern Leopard Frog Rana pipiens is a widespread reservoir species harboring Batrachochytrium dendrobatidis in North America.Herp Rev396668
  88. 88. Daszak P, Strieby A, Cunningham AA, Longcore JE, Brown CC, et al. (2004) Experimental evidence that the Bullfrog (Rana catesbeiana) is a potential carrier of chytridiomycosis, an emerging fungal disease of amphibians. Herp J 14: 201–207.P. DaszakA. StriebyAA CunninghamJE LongcoreCC Brown2004Experimental evidence that the Bullfrog (Rana catesbeiana) is a potential carrier of chytridiomycosis, an emerging fungal disease of amphibians.Herp J14201207
  89. 89. Hanselmann R, Rodríguez A, Lampo M, Fajardo-Ramos L, Aguirre AA, et al. (2004) Presence of an emerging pathogen of amphibians in introduced Bullfrogs Rana catesbeiana in Venezuela. Biol Cons 120: 115–119.R. HanselmannA. RodríguezM. LampoL. Fajardo-RamosAA Aguirre2004Presence of an emerging pathogen of amphibians in introduced Bullfrogs Rana catesbeiana in Venezuela.Biol Cons120115119
  90. 90. Garner TWJ, Walker S, Bosch J, Hyatt AD, Cunningham AA, et al. (2006) The emerging amphibian pathogen Batrachochytrium dendrobatidis globally infects introduced populations of the North American Bullfrog, Rana catesbeiana. Biol Lett 2: 455–459.TWJ GarnerS. WalkerJ. BoschAD HyattAA Cunningham2006The emerging amphibian pathogen Batrachochytrium dendrobatidis globally infects introduced populations of the North American Bullfrog, Rana catesbeiana.Biol Lett2455459
  91. 91. Peterson JD, Wood MB, Hopkins WA, Unrine JM, Mendonca MT (2007) Prevalence of Batrachochytrium dendrobatidis in American Bullfrog and Southern Leopard Frog larvae from wetlands on the Savannah River site, South Carolina. J Wildl Dis 43: 450–460.JD PetersonMB WoodWA HopkinsJM UnrineMT Mendonca2007Prevalence of Batrachochytrium dendrobatidis in American Bullfrog and Southern Leopard Frog larvae from wetlands on the Savannah River site, South Carolina.J Wildl Dis43450460
  92. 92. Berger L, Speare R, Hines HB, Marantelli G, Hyatt AD, et al. (2004) Effect of season and temperature on mortality in amphibians due to chytridiomycosis. Aust Vet J 82: 434–439.L. BergerR. SpeareHB HinesG. MarantelliAD Hyatt2004Effect of season and temperature on mortality in amphibians due to chytridiomycosis.Aust Vet J82434439
  93. 93. Gaertner JP, Gaston MA, Spontak D, Forstner MR, Hahn D (2009) Seasonal variation in the detection of Batrachochytrium dendrobatidis in a Texas population of Blanchard's Cricket Frog (Acris crepitans blanchardi). Herp Rev 40: 184–187.JP GaertnerMA GastonD. SpontakMR ForstnerD. Hahn2009Seasonal variation in the detection of Batrachochytrium dendrobatidis in a Texas population of Blanchard's Cricket Frog (Acris crepitans blanchardi).Herp Rev40184187
  94. 94. Longo AV, Burrowes PA, Joglar RL (2010) Seasonality of Batrachochytrium dendrobatidis infection in direct-developing frogs suggests a mechanism for persistence. Dis Aquat Org 93: 253–260.AV LongoPA BurrowesRL Joglar2010Seasonality of Batrachochytrium dendrobatidis infection in direct-developing frogs suggests a mechanism for persistence.Dis Aquat Org93253260
  95. 95. Kinney VC, Heemeyer JL, Pessier AP, Lannoo MJ (2011) Seasonal pattern of Batrachochytrium dendrobatidis infection and mortality in Lithobates areolatus: affirmation of Vredenburg's “10,000 Zoospore Rule.” PLoS One 6(3): e16708.VC KinneyJL HeemeyerAP PessierMJ Lannoo2011Seasonal pattern of Batrachochytrium dendrobatidis infection and mortality in Lithobates areolatus: affirmation of Vredenburg's “10,000 Zoospore Rule.”PLoS One63e16708
  96. 96. Kriger KM, Pereoglou F, Hero J-M (2007) Latitudinal variation in the prevalence and intensity of chytrid (Batrachochytrium dendrobatidis) infection in Eastern Australia. Cons Biol 21: 1280–1290.KM KrigerF. PereoglouJ-M Hero2007Latitudinal variation in the prevalence and intensity of chytrid (Batrachochytrium dendrobatidis) infection in Eastern Australia.Cons Biol2112801290
  97. 97. Ribas L, Li M-S, Doddington BJ, Robert J, Seidel JA, et al. (2009) Expression profiling the temperature-dependent amphibian response to infection by Batrachochytrium dendrobatidis. PLoS One 4: e8408.L. RibasM-S LiBJ DoddingtonJ. RobertJA Seidel2009Expression profiling the temperature-dependent amphibian response to infection by Batrachochytrium dendrobatidis.PLoS One4e8408
  98. 98. Murray KA, Retallick RWR, Puschendorf R, Skerratt LF, Rosauer D, et al. (2011) Assessing spatial patterns of disease risk to biodiversity: implications for the management of the amphibian pathogen, Batrachochytrium dendrobatidis. J Appl Ecol 48: 163–173.KA MurrayRWR RetallickR. PuschendorfLF SkerrattD. Rosauer2011Assessing spatial patterns of disease risk to biodiversity: implications for the management of the amphibian pathogen, Batrachochytrium dendrobatidis.J Appl Ecol48163173
  99. 99. Muths E, Pilliod DS, Livo LJ (2008) Distribution and environmental limitations of an amphibian pathogen in the Rocky Mountains, USA. Biol Cons 141: 1484–1492.E. MuthsDS PilliodLJ Livo2008Distribution and environmental limitations of an amphibian pathogen in the Rocky Mountains, USA.Biol Cons14114841492
  100. 100. Puschendorf R, Carnaval AC, VanDerWal J, Zumbado-Ulate H, Chaves G, et al. (2009) Distribution models for the amphibian chytrid Batrachochytrium dendrobatidis in Costa Rica: proposing climatic refuges as a conservation tool. Divers Distrib 15: 401–408.R. PuschendorfAC CarnavalJ. VanDerWalH. Zumbado-UlateG. Chaves2009Distribution models for the amphibian chytrid Batrachochytrium dendrobatidis in Costa Rica: proposing climatic refuges as a conservation tool.Divers Distrib15401408
  101. 101. Rohr JR, Raffel TR, Romansic JM, McCallum H, Hudson PJ (2008) Evaluating the links between climate, disease spread, and amphibian declines. PNAS 105: 17436–17441.JR RohrTR RaffelJM RomansicH. McCallumPJ Hudson2008Evaluating the links between climate, disease spread, and amphibian declines.PNAS1051743617441
  102. 102. Ron SR (2005) Predicting the distribution of the amphibian pathogen Batrachochytrium dendrobatidis in the New World. Biotropica 37: 209–221.SR Ron2005Predicting the distribution of the amphibian pathogen Batrachochytrium dendrobatidis in the New World.Biotropica37209221
  103. 103. Woodhams DC, Bosch J, Briggs CJ, Cashins S, Davis LR, et al. (2011) Mitigating amphibian disease: strategies to maintain wild populations and control chytridiomycosis. Front Zool 8: 8.DC WoodhamsJ. BoschCJ BriggsS. CashinsLR Davis2011Mitigating amphibian disease: strategies to maintain wild populations and control chytridiomycosis.Front Zool88