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Emerging infectious diseases are a major cause of amphibian declines worldwide. Two of these diseases are amphibian chytridiomycosis caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) and a viral disease caused by different ranaviruses (Rv). Whereas Bd is known to be widespread in Brazil, Rv was only recently detected in natural habitats. We therefore investigated the co‐occurrence of Bd and Rv in wild tadpoles in the southern Brazilian Atlantic Forest from 21 ponds. Because infection by Bd might cause immune suppression in the host, we hypothesized that tadpoles infected with Bd would be more prone to infection with Rv than Bd‐free individuals, hence presenting higher Rv loads. Surprisingly, co‐infection was rare (less than 6% of the sampled specimens), and we did not find evidence that Bd would facilitate Rv infection. On the other hand, we detected Rv in 38% of tadpoles (125 out of 324), representing twice the prevalence of Bd in the same populations. We tested the influence of biotic and abiotic factors on infection by each pathogen on tadpoles, and we detected a positive relationship between forest cover and infection by Rv, whereas no relationship was found for Bd infection. Based on the putatively low rate of co‐infection and high prevalence of Rv in wild anuran populations, we advocate for the inclusion of Rv screening and monitoring in addition to Bd in conservation‐oriented amphibian surveys. Only surveying both diseases will provide a complete picture of amphibian disease‐related declines. [ABSTRACT FROM AUTHOR]

Identifying conservation actions to recover threatened species can be challenging due to many ecological uncertainties. For example, major threats to a species’ conservation are commonly known or suspected, but the specific impacts on population or metapopulation dynamics can be uncertain. This is frequently the case with emerging infectious diseases, including chytridiomycosis, a global driver of amphibian population declines caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans. While these diseases are known to cause amphibian declines and extirpations, the mechanisms of their landscape-scale spread are still largely unknown. Such uncertainty can lead to inaction which may jeopardize timely recovery of a species. Decision analysis is a pragmatic approach to making transparent and defensible decisions while dealing with uncertainties. We investigated whether optimal actions aimed at recovering boreal toad (Anaxyrus boreas boreas) metapopulations in the southern Rocky Mountains are robust to the unknown dynamics of Bd spread using value of information and regret analyses. Value of information is a decision-analytic tool for calculating the value of new information in terms of performance on management objectives, while regret measures the cost of acting under incorrect information. We further conducted a stochastic sensitivity analysis to identify the relative effects of metapopulation parameters on system dynamics. We found optimal actions were robust to the unknown dynamics of Bd spread. While boreal toad breeding occurrence is highly sensitive to Bd distribution, the optimal decision is not. Resolving the unknown dynamics of Bd spread would lead to a minimal gain of less than one breeding toad subpopulation at the end of 50 years, given the currently available management actions. Applying a decision-analytic framework coupled with value of information and regret analyses can help frame how uncertainties affect decisions in a way that empowers decision makers. [ABSTRACT FROM AUTHOR]

Hibernation is often associated with high mortality, especially during early life stages, and losses can be exacerbated by unusual winter conditions or if animals enter hibernation carrying a disease. Here, we examined how overwintering amphibians may be affected by the combined effects of mild winters, which are projected to increase in frequency due to climate change, and of chytridiomycosis, a disease that has contributed to the decline of hundreds of species worldwide. We exposed juvenile agile frogs Rana dalmatina to Batrachochytrium dendrobatidis (Bd), the causative agent of chytridiomycosis, and subsequently subjected them to either a long, cold winter (1.5°C for 91 days) or a short, mild winter (4.5°C for 61 days) under laboratory conditions. Agile frogs proved to be highly resistant to Bd as only 37% of Bd‐exposed individuals became infected as determined before hibernation, and prevalence further decreased to 8% by the end of hibernation, with individuals showing very low infection intensity values. We observed lack of mortality in control and Bd‐exposed groups also, in both types of winter. The two types of winter we simulated did not result in differing body mass loss either alone or in combination with experimental infection. In the Bd‐exposed group, the two types of winter also did not cause differences in prevalence and infection intensity. However, among Bd‐exposed frogs, individuals that were Bd negative when entering hibernation lost more body mass than their conspecifics that carried the fungus at the onset of overwintering. Based on our results, warming winter climate conditions, with or without Bd infection, do not decrease body mass and survival rate of hibernating agile frogs, and do not increase susceptibility of individuals to chytridiomycosis. It remains to be seen to what extent the relatively weak effects of milder winters can be generalized to other amphibians of the temperate climate zone. [ABSTRACT FROM AUTHOR]

Chytridiomycosis, an emerging disease caused mostly by the pathogen Batrachochytrium dendrobatidis, has caused massive amphibian population declines and extinctions worldwide. The ecology of this disease is mainly explained by the interaction of environmental factors, pathogen biology, and host traits including development. For paedomorphic salamanders, differences in B. dendrobatidis infection may be explained by metamorphosis and water physicochemical conditions. In this study, we aimed to determine the influence of environmental and host factors on B. dendrobatidis prevalence and infection intensity in the facultative paedomorphic salamander Ambystoma altamirani. We determined B. dendrobatidis prevalence and infection load in four populations of A. altamirani along 1 year (four seasons) and assessed their relationship with environmental factors and host metamorphic status (gilled or non‐gilled). We found that B. dendrobatidis prevalence and infection load are largely explained by metamorphic status and environmental factors such as elevation, seasonality, water temperature, pH, conductivity, and dissolved oxygen. To our knowledge, this is the first study to empirically show the effect of metamorphosis on B. dendrobatidis infection status across locations and seasons. This information may be used to understand the temporal dynamics of B. dendrobatidis–host interactions and to identify potential disease outbreaks that may cause cryptic sublethal effects on salamander populations. Our results will help in the development of conservation strategies for paedomorphic salamanders that are already considered threatened by anthropogenic factors such as habitat loss and climate change. [ABSTRACT FROM AUTHOR]

The recently emerged fungal pathogen, Batrachochytrium salamandrivorans (Bsal) causes the lethal skin disease chytridiomycosis in susceptible salamander species and is predicted to emerge within the Americas with devastating consequences. Host responses to Bsal are variable but the factors underlying these differences are unknown. To investigate the role of skin‐associated immune defenses against Bsal and the closely related, B. dendrobatidis (Bd), we sampled skin peptides from wild and captive North American salamanders (spotted salamanders [Ambystoma maculatum], n = 10; hellbenders [Cryptobranchus alleganiensis], n = 2; red‐legged salamanders [Plethodon shermani], n = 18; and Ocoee salamanders [Desmognathus ocoee], n = 15) and conducted in vitro experimental assays to test whether salamander skin peptides inhibit chytrid growth. Interspecies differences in skin defenses against Bsal and Bd, and peptide mixtures were also assessed using a standardized measure and RP‐HPLC, respectively. For A. maculatum, skin peptides inhibited Bsal and Bd growth, consistent with known Bsal resistance. Cryptobranchus alleganiensis skin peptides inhibited the growth of Bsal but not Bd. Plethodon shermani and D. ocoee skin peptides facilitated Bsal growth and had either no effect or inconsistent effects on Bd growth. With the exception of A. maculatum, most species had relatively weak skin defenses against both chytrid pathogens. Collectively, we demonstrate that salamander skin peptide defenses against chytrid pathogens are highly variable and not always equally effective against Bsal and Bd. By advancing knowledge about the factors underlying chytrid susceptibility, particularly Bsal, our findings will help inform conservation initiatives aimed at reducing disease impacts and biodiversity loss. [ABSTRACT FROM AUTHOR]

The amphibian chytrid fungal pathogen (Batrachochytrium dendrobatidis, henceforth Bd) has had a devastating impact on biodiversity, causing the decline or extinction of over 500 amphibian species. Yet, our understanding of Bd transmission pathways remains incomplete, in particular for host species with weak aquatic associations, and between reservoir and susceptible host species. We examined Bd transmission from a potential reservoir host to a potentially susceptible critically endangered host; directly assessing the capacity of the former to transmit Bd, and the susceptibility of the latter as a Bd host. Using cohousing versus sequential use of the same enclosure by the two species, we distinguished the effects of direct versus indirect (environmental) transmission. Our study provides clear evidence that both direct and indirect terrestrial transmission from a reservoir to susceptible host species results in fatal chytridiomycosis. Transmission mode had no effect on overall morbidity or disease progression in the susceptible species. Our results demonstrate that reservoir and susceptible hosts do not need to be in the same place at the same time, or within an aquatic environment for transmission to occur. Our demonstration of indirect terrestrial transmission from a reservoir to susceptible host identifies mechanisms by which Bd may drive ongoing declines in populations where the pathogen is now endemic. Identifying these transmission pathways is important for understanding long‐term extinction vulnerability of remnant populations of declining species challenged by disease. [ABSTRACT FROM AUTHOR]

The emerging fungal pathogen Batrachochytrium salamandrivorans (Bsal) is a major threat to amphibian species worldwide with potential to infect many species if it invades salamander biodiversity hotspots in the Americas. Bsal can cause the disease chytridiomycosis, and it is important to assess the risk of Bsal‐induced chytridiomycosis to species in North America. We evaluated the susceptibility to Bsal of the common and widespread spotted salamander, Ambystoma maculatum, across life‐history stages and monitored the effect of Bsal exposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant to Bsal because they showed no indication of disease or infection, and experienced minor effects on growth upon exposure. While we focused on a single population for this study, results were consistent across conditions of exposure including high or repeated doses of Bsal, life‐stage at exposure, environmental conditions including two temperatures and two substrates, and promoting pathogen infectivity by conditioning Bsal cultures with thyroid hormone. Exposure to high levels of Bsal elicited an acute but not chronic increase in corticosterone in spotted salamanders, and reduced growth. We hypothesize that the early acute increase in corticosterone facilitated mounting an immune response to the pathogen, perhaps through immunoredistribution to the skin, but further study is needed to determine immune responses to Bsal. These results will contribute to development of appropriate Bsal management plans to conserve species at risk of emerging disease. [ABSTRACT FROM AUTHOR]

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), responsible for numerous amphibian declines and extinctions, was previously thought to originate from the African continent. This was based on infected museum specimens from early 20th century South Africa, Cameroon and Uganda. Further research on archived specimens from other continents eventually revealed early 20th century records also in Brazil and Japan. Recent robust analysis of genomic diversity and phylogeny of Bd has shown origin from Asia to be more plausible. This raises the issue that the threat of Bd for African amphibians as a novel pathogen has been underestimated. There are now cases where dramatic amphibian declines in disparate mountains on the continent could be attributed to Bd, and this necessitates an urgent realigning of hypotheses and the research agenda for amphibian conservation on the continent. Notably, hotspots of amphibian host naivety include West Africa where this pathogen has so far not been detected. We discuss research gaps that amphibian conservationists might focus on, notably more genomic sequencing of the BdCAPE (the less virulent) lineage to determine its date of emergence, and assessing the susceptibility of different amphibian species to infection, disease and decline to better prioritize conservation actions. [ABSTRACT FROM AUTHOR]

Hundreds of amphibian species have declined worldwide after the emergence of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd). Despite captive breeding efforts, it is unlikely that wild populations for many species will be reestablished unless Bd resistance increases. We performed a Bd‐challenge study in the functionally extinct southern corroboree frog Pseudophryne corroboree to investigate differences in Bd susceptibility among individuals and populations, identify genetic [major histocompatibility complex (MHC) class I] and genome‐wide variants associated with Bd resistance, and measure genetic diversity and population genetic structure. We found three MHC variants and one MHC supertype associated with Bd infection load and survival along with a suggestively associated single nucleotide polymorphism. We also showed that genome‐wide heterozygosity is associated with increased survival. Additionally, we found evidence of significant population structure among the four P. corroboree populations studied and high MHC genetic diversity. Our results indicate that there are immunogenetic differences among captive southern corroboree frogs; such differences could be manipulated to increase disease resistance and mitigate the significant threat of chytridiomycosis. These results demonstrate a potential long‐term solution to chytridiomycosis that could include breeding more resistant individuals and returning them to the wild. [ABSTRACT FROM AUTHOR]

Abstract: Amphibian chytridiomycosis, caused by infection with Batrachochytrium dendrobatidis (Bd), is the most devastating vertebrate disease on record. Reservoir hosts are likely to be important in the Bd‐amphibian system because many amphibian species can carry infections without experiencing mortality. However, while a variety of reservoirs have been proposed, few have been empirically demonstrated to act as competent reservoir hosts. In this study, we investigate whether the common eastern froglet, Crinia signifera, a non‐declining species that is widespread in eastern Australia, is a reservoir host for Bd infection. We conducted a long‐term, large‐scale field survey to investigate disease dynamics in C. signifera at sites where four sympatric, threatened anuran species have severely declined. We also monitored Bd‐infected C. signifera in the laboratory to determine susceptibility and survivorship. Finally, we assessed population age structure to investigate disease impact in the wild. We found that C. signifera is a competent reservoir host, maintaining high prevalence and infection intensities in the wild and in the laboratory, with no signs of sub‐lethal effects or clinical disease. In the wild, the modal age is 4 years with individuals living up to 6 years, indicating that adults can survive across multiple years despite high infection prevalence and intensity. The occurrence of C. signifera at sites with remnant populations of threatened species likely contributes to ongoing disease impact in declining species decades after the arrival of Bd. The presence of C. signifera at sites where threatened species have become extinct inhibits effective reintroductions, and we recommend avoiding sites with high reservoir host abundance when planning reintroductions. [ABSTRACT FROM AUTHOR]

Amphibians are a highly threatened vertebrate group, and populations of these animals have declined drastically. An important global threat to amphibians is the pathogenic fungus Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis. However, not all species develop chytridiomycosis when exposed to Bd. We compared susceptibility to disease in two species of marsupial frogs and found that Gastrotheca nebulanastes is susceptible, whereas its congeneric G. excubitor is resistant. Since Bd is a skin pathogen, it is possible that cutaneous defenses like symbiotic bacteria and antimicrobial peptides protect the resistant species. We tested this hypothesis by comparing the anti-Bd abilities of cutaneous defenses between the two Gastrotheca species. Cultivable bacteria and peptides were isolated from the skin and tested for their abilities to inhibit Bd with in vitro co-culture assays. Twenty-six bacteria were identified by sequencing their 16S rRNA gene and 19 peptides were profiled by MALDI TOF mass spectrometry. We found that bacteria, but not peptides, differed between the two species in their ability to inhibit Bd growth. The resistant G. excubitor harbored more isolates of cultivable anti-Bd bacteria both in number and proportion (6/15 vs. 1/11). Also, the one anti-Bd isolate from G. nebulanastes demonstrated the weakest ability to inhibit Bd growth. Our results highlight the importance of anti-Bd skin bacteria in providing frog species with protection from Bd and can inform mitigation strategies for other wildlife diseases. [ABSTRACT FROM AUTHOR]

Amphibians around the world are declining from threats that cannot currently be mitigated, making it impossible to safeguard some species in their natural habitats. Amphibians in the mountainous neotropics are one example where severe disease-related declines prompted calls for the establishment of captive assurance colonies to avoid extinctions. We surveyed experts in Panamanian amphibians to determine the probability of avoiding chytridiomycosis-related extinctions using captive breeding programs. We ranked Panamanian amphibian species by perceived susceptibility to chytridiomycosis, then calculated the likelihood of avoiding extinction as the product of three probabilities, which include (1) finding sufficient founder animals, (2) successfully breeding these species in captivity and (3) becoming extinct in the wild. The likelihood of finding enough animals to create a captive founding population was low for many rare species, especially for salamanders and caecilians. It was also low for frogs which were once regularly encountered, but have already disappeared including Atelopus chiriquiensis, Craugastor emcelae, C. obesus, C. punctariolus, C. rhyacobatrachus, Ecnomiohyla rabborum, Isthmohyla calypsa and Oophaga speciosa. Our results indicate that captive breeding could improve the odds of avoiding extinction for species that have severely declined or are likely to decline due to chytridiomycosis including Atelopus certus, A. glyphus, A. limosus, A. varius, A. zeteki, Anotheca spinosa, Gastrotheca cornuta, Agalychnis lemur and Hemiphractus fasciatus. Priority species that experts predicted were highly susceptible to chytridiomycosis that might also benefit from ex situ management include Craugastor tabasarae, C. azueroensis, C. evanesco, Strabomantis bufoniformis and Colostethus panamansis. In spite of high levels of uncertainty, this expert assessment approach allowed us to refine our priorities for captive amphibian programs in Panama and identify priority conservation actions with a clearer understanding of the probability of success. [ABSTRACT FROM AUTHOR]

Global amphibian decline and extinction has been associated with the spread of the pathogenic chytrid fungus ( B atrachochytrium dendrobatidis, B d). Despite extensive research, there have been no examples of effective management abating the ongoing impact of this pathogen in the wild. The endangered alpine tree frog ( L itoria verreauxii alpina) has been extirpated from 80% of its former range because of B d. We directly tested whether source population or host site influenced the efficacy of a reintroduction of L. v. alpina. We captive reared and released 1241 individuals from three different populations, two with a history of B d exposure and one that was B d-naïve, into two sites where they had historically occurred, and two sites where the species currently persists. Between 6 and 9 months post-release, we recaptured 4.83% of the released animals, and observed breeding at all sites. Both released and extant animals had similar susceptibility to infection; both groups increased in B d infection prevalence and infection intensity throughout the breeding season. We did not detect any effect on survival by site of release; however, population of origin had a relatively large impact ( ω = 0.454), and animals from one B d-exposed population were recaptured significantly more than the animals from the other B d-exposed population and the B d-naive population. Population exposure history to the disease of reintroduced amphibians may be used to increase post-release fitness and conservation success. Selection for mechanisms of resistance should be further explored to help mitigate the impact of chytridiomycosis during reintroduction programmes. [ABSTRACT FROM AUTHOR]

Wildlife disease is an emerging threat to biodiversity. The amphibian chytrid fungus B atrachochytrium dendrobatidis ( Bd), which causes the disease chytridiomycosis, has been documented in over 500 amphibian species globally. Understanding conditions under which amphibians are vulnerable to Bd is important for evaluating species risk and developing surveillance strategies. Here, we investigate the spatial distribution of Bd infection in the ephemeral pond-breeding yellow-bellied toad B ombina variegata, a species of high conservation concern in the European Union. We sampled 550 toads from 60 ponds in a traditional agricultural landscape in Southern Transylvania, Romania. Overall, Bd prevalence was low in B . variegata, but infected toads were widely dispersed through the landscape and were found in a quarter of all sampled ephemeral ponds. At the pond level, increased Bd occurrence was associated with short distances to perennial water sources and high forest cover. These findings suggest that perennial water sources may act as source habitat for Bd, with amphibian movements resulting in Bd spillover into ephemeral ponds. Increased Bd occurrence in ponds surrounded by high levels of forest cover is likely related to cooler and wetter conditions that are more favourable for Bd. Throughout the study landscape, patchy environmental suitability for Bd appears to restrict the pathogen to a subset of B . variegata habitat. Ephemeral ponds in open landscapes, without nearby perennial habitat, likely provide an environmental refuge from Bd, where the risk of infection is low. From a conservation perspective, these findings highlight the importance of maintaining ephemeral ponds in open landscapes, but these are currently threatened by land-use change. [ABSTRACT FROM AUTHOR]

The emergence of a novel infectious disease, chytridiomycosis, is now widely recognized as a major cause of amphibian declines and biodiversity loss across local and global scales. Amphibian mortalities caused by the pathogenic chytrid fungus, Batrachochytrium dendrobatidis ( Bd) were first recorded in Iberia, Europe over a decade ago. In August 2009, hundreds of post-metamorphic common midwife toads ( Alytes obstetricans) were found dead in the water and margins of a pond in the Serra da Estrela Natural Park, north-central Portugal. Histological and genetic analyses confirmed their infection with Bd. Given the likelihood of a new outbreak of chytridiomycosis, we evaluated the possible impacts of this disease on populations of A. obstetricans within the Park by conducting field surveys during 2010 and 2011. We compared the present distribution and abundance of A. obstetricans with historical records, and quantified the present prevalence and intensity of infection by Bd. Results showed that (1) A. obstetricans disappeared from 67% of the 1 × 1 km squares where it was recorded in the past, (2) breeding is currently limited to 16% of the confirmed breeding sites in the past, and that (3) larvae are now less abundant, as well as are highly infected by Bd in the remaining sites. These effects were most pronounced at altitudes above 1200 m. Our findings suggest that an outbreak of chytridiomycosis is responsible for the rapid decline of A. obstetricans in Serra da Estrela, and we believe that urgent conservation measures are needed to prevent local extinction of the species. [ABSTRACT FROM AUTHOR]

Global trade in the North American bullfrog Rana catesbeiana has been implicated in the introduction and spread of the amphibian pathogen Batrachochytrium dendrobatidis. Large-scale production of the North American bullfrog for human consumption has been ongoing since the early part of the 20th century, particularly in Brazil, a pioneer in bullfrog farming following its introduction in the 1930s. In order to determine whether bullfrogs introduced to Brazil and farmed for the food trade serve as reservoirs for amphibian disease, we tested individuals located in the Brazilian states of São Paulo and Pará to determine the prevalence of B. dendrobatidis infections. We were able to confirm B. dendrobatidis on five farms (78.5% infection prevalence overall) by PCR. Isolates were obtained from three of the five farms and genotyped at 17 loci using multilocus sequence typing. Five isolates from the Brazilian farms were genotypically similar to each other as well as to isolates from Central and South America. Isolates from farmed bullfrogs were more similar to isolates from introduced populations in Venezuela than those from the native range of the bullfrog in eastern North America. These results could have important implications for the origin and spread of B. dendrobatidis in Brazil, its neighboring regions and the conservation of native amphibian fauna. They may also suggest a potential for prior recombination within B. dendrobatidis in bullfrogs, which may have implications for the recent emergence of this pathogen. [ABSTRACT FROM AUTHOR]

Amphibians at the global scale are dramatically declining and the pathogenic fungus Batrachochytrium dendrobatidis ( Bd) has been suggested to be an important driver in this biodiversity crisis. Increasing evidence points towards the global emergence of Bd being a panzootic caused by pathogen pollution. Africa has been suggested to be the origin of the pathogen but remains one of the least-studied areas. We have conducted the most comprehensive survey on the continent to date focusing on Kenya for investigating taxonomic and environmental components in the distribution of Bd in tropical Africa. Eleven sites along a 770 km transect from the coast up to the border of Uganda were surveyed. Using quantitative PCR, we screened 861 samples from 23 different species in nine genera. The pathogen was confirmed at all studied sites, with an overall prevalence of 31.5%. No dead or symptomatic specimens were found and no declines have been reported in the region so far. Both prevalence and parasite load ranged from the detection limit to some of the highest ever reported. The parasite load showed a significant taxonomic bias and a strong inverse correlation with temperature. Our findings suggest that Bd may be enzootic in the region. We recommend that further research should focus on comparative experimental studies of susceptibility to Bd in African species. Moreover, we stress the need for improved knowledge on the conservation status of the tropical African amphibian fauna to confirm the enzootic nature of widespread Bd infections. [ABSTRACT FROM AUTHOR]

Chydridiomycosis is an infectious emerging disease in amphibians that has been directly linked to mass mortality, drastic population decline and extinction. The understanding of the factors limiting the distribution and the abundance of its biological agent, the amphibian chytrid fungus Batrachochytrium dendrobatidis ( Bd ), is still limited. It has been suggested that climate plays a key role. A recent study conducted infection surveys at 31 lowland sites on the Australian East coast and searched for climatic variables explaining Bd prevalence and intensity in Stony creek frogs Litoria lesueuri (complex). A link between the prevalence of infections and latitude was advocated, exclusively focusing on the pathogen. Beyond this, the prevalence and intensity of Bd infection may also depend on the climatic suitability of a given site for the amphibian host. Herein, we extend the previous study using a set of long-term bioclimatic variables and assess climatic suitability for Stony creek frogs at the sites previously studied for Bd. We ran a Climatic Envelope Model for our target amphibian based on those variables with the most explanatory power for prevalence and intensity, thus representing the link between climatic suitability for both the pathogen and the host. Our findings allow the hypothesis that there exists a significant correlation between climatic suitability for Stony creek frogs at the previously studied sites and latitude. At the same time, this was congruent with the latitudinal gradient of the number of zoospores per frog. [ABSTRACT FROM AUTHOR]

Innate immune mechanisms of defense are especially important to ectothermic vertebrates in which adaptive immune responses may be slow to develop. One innate defense in amphibian skin is the release of abundant quantities of antimicrobial peptides. Chytridiomycosis is an emerging infectious disease of amphibians caused by the skin fungus, Batrachochytrium dendrobatidis. Susceptibility to chytridiomycosis varies among species, and mechanisms of disease resistance are not well understood. Previously, we have shown that Australian and Panamanian amphibian species that possess skin peptides that effectively inhibit the growth of B. dendrobatidis in vitro tend to survive better in the wild or are predicted to survive the first encounter with this lethal pathogen. For most species, it has been difficult to experimentally infect individuals with B. dendrobatidis and directly evaluate both survival and antimicrobial peptide defenses. Here, we demonstrate differences in susceptibility to chytridiomycosis among four Australian species ( Litoria caerulea, Litoria chloris, Mixophyes fasciolatus and Limnodynastes tasmaniensis) after experimental infection with B. dendrobatidis, and show that the survival rate increases with the in vitro effectiveness of the skin peptides. We also observed that circulating granulocyte, but not lymphocyte, counts differed between infected and uninfected Lit. chloris. This suggests that innate granulocyte defenses may be activated by pathogen exposure. Taken together, our data suggest that multiple innate defense mechanisms are involved in resistance to chytridiomycosis, and the efficacy of these defenses varies by amphibian species. [ABSTRACT FROM AUTHOR]

In this article, the author discusses reservoir of Batrachochytrium dendrobatidis in Australia. It mentions the use of disease mitigation strategies such as culling, environmental disinfection and immunization, for protection of amphibians from decline. it also mentions importance of amphibian chytridiomycosis as a threat to biodiversity.

In this article, the author discusses impact of chytridiomycosis, which is caused by the chytrid fungi Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), and leading global amphibian declines. it mentions the use of applications such as vaccination, disinfection, and bioaugmentation for mitigation of the impact of amphibian chytridiomycosis.

This article contends that there is a potential interplay between climate change and the emergence of amphibian chytridiomycosis. It explains that host-pathogen dynamics are influenced by environmental conditions and that variation in environment can be a principal driver underlying the emergence of infectious disease in amphibians. It points out that being ectotherms amphibians' physiology is determined by their external environment. Their immune system is easily affected by environmental temperature.

This article discusses the basis scientific issues involved in research about amphibian immune defenses and the emergence of the disease chytridiomycosis threatening the survival of the species. It mentions several hypothesis advanced by herpetologists and immunologists to account for the interaction between amphibian immunity, climate change and the fungus Batrachochytrium dendrobatidis that causes the disease chytridiomycosis. It explores the issue of whether or experimental evidence of innate immunity in amphibians is just a matter of design or constraints. It points out that the practical problem remains the preservation of amphibians.