Reduced Itraconazole Concentration and Durations Are Successful in Treating &lt;em&gt;Batrachochytrium dendrobatidis&lt;/em&gt; Infection in Amphibians

Brannelly, Laura A.

doi:10.3791/51166

Cited by 14 publications

(11 citation statements)

References 17 publications

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“…In addition, if the drug directly affected bacteria, we would expect to see the effect in all frogs, but we saw it only in Bd+ frogs. However, drug treatment could indirectly affect the microbiome if it were to affect immune cell function, cause side effects in the frogs, or affect resident fungi besides Bd [ 46 , 63 ]). Symbiotic fungi and bacteria can engage in facultative and inhibitory interactions, either directly or by influencing host immune responses, which could lead to changes in the bacterial community [ 64 , 65 ].…”

Section: Discussionmentioning

confidence: 99%

“…Three weeks after Bd infection, frogs were treated with itraconazole for 6 days to clear Bd infection [ 45 ]. Itraconazole treatment is a common method for clearing amphibians of Bd infection [ 46 ], and has been used by our group to treat Bd infection in R. muscosa . All frogs (infected and uninfected) were treated with itraconazole to control for any side effects of the drug.…”

Section: Methodsmentioning

confidence: 99%

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The amphibian microbiome exhibits poor resilience following pathogen-induced disturbance

et al. 2021

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Infectious pathogens can disrupt the microbiome in addition to directly affecting the host. Impacts of disease may be dependent on the ability of the microbiome to recover from such disturbance, yet remarkably little is known about microbiome recovery after disease, particularly in nonhuman animals. We assessed the resilience of the amphibian skin microbial community after disturbance by the pathogen, Batrachochytrium dendrobatidis (Bd). Skin microbial communities of laboratory-reared mountain yellow-legged frogs were tracked through three experimental phases: prior to Bd infection, after Bd infection (disturbance), and after clearing Bd infection (recovery period). Bd infection disturbed microbiome composition and altered the relative abundances of several dominant bacterial taxa. After Bd infection, frogs were treated with an antifungal drug that cleared Bd infection, but this did not lead to recovery of microbiome composition (measured as Unifrac distance) or relative abundances of dominant bacterial groups. These results indicate that Bd infection can lead to an alternate stable state in the microbiome of sensitive amphibians, or that microbiome recovery is extremely slow—in either case resilience is low. Furthermore, antifungal treatment and clearance of Bd infection had the additional effect of reducing microbial community variability, which we hypothesize results from similarity across frogs in the taxa that colonize community vacancies resulting from the removal of Bd. Our results indicate that the skin microbiota of mountain yellow-legged frogs has low resilience following Bd-induced disturbance and is further altered by the process of clearing Bd infection, which may have implications for the conservation of this endangered amphibian.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The amphibian microbiome exhibits poor resilience following pathogen-induced disturbance

et al. 2021

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“…We assigned four newts to each of our four treatment groups: To ensure Bd-free status in our Bsal-infected and control groups prior to the experiment, we cleared pre-existing Bd infection only in these groups via daily 0.0025% itraconazole ® exposure for five consecutive days (Brannelly, 2014;Longo et al, 2019). Bdinfected and coinfected groups were left untreated with natural Bd infections.…”

Section: Infection Trial Designmentioning

confidence: 99%

Incapacitating effects of fungal coinfection in a novel pathogen system

et al. 2020

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As globalization lowers geographic barriers to movement, coinfection with novel and enzootic pathogens is increasingly likely. Novel and enzootic pathogens can interact synergistically or antagonistically, leading to increased or decreased disease severity. Here we examine host immune responses to coinfection with two closely related fungal pathogens: Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). Both pathogens have had detrimental effects on amphibian populations, with Bd now largely enzootic, while Bsal is currently spreading and causing epizootics. Recent experimental work revealed that newts coinfected with Bd and Bsal had significantly higher mortality than those infected with either pathogen alone. Here we characterize host immunogenomic responses to chytrid coinfection relative to single infection. Across several classes of immune genes including pattern recognition receptors, cytokines, and MHC, coinfected host gene expression was weakly upregulated or comparable to that seen in single Bd infection, but significantly decreased when compared to Bsal infection. Combined with strong complement pathway downregulation and keratin upregulation, these results indicate that coinfection with Bd and Bsal compromises immune responses active against Bsal alone. As Bsal continues to invade naïve habitats where Bd is enzootic, coinfection will be increasingly common. If other Bd‐susceptible species in the region have similar responses, interactions between the two pathogens could cause severe population and community‐level declines.

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“…However, decreased concentrations and durations have demonstrated efficacy in some species of frogs. 4,5 In our current study, a treatment period of 10 d was adequate for resolution of chytridiomycosis as evaluated by PCR analysis at as long as 6 mo after treatment. However, this 10-d protocol was not completely innocuous for the newts, given that lethargy and closed eyes were observed in a subset of newts beginning on days 3 to 5 of treatment and continuing until treatment concluded.…”

Section: Discussionmentioning

confidence: 69%

“…We chose to use a reduced concentration of itraconazole delivered over 10 d, in light of previously demonstrated efficacy in a frog species. 4 Prior to whole-colony treatment, pilot treatment of a small subset of animals was conducted to assess for potential efficacy and any unanticipated adverse effects.…”

Section: Case Reportmentioning

confidence: 99%

Treatment of Chytridiomycosis in Laboratory Axolotls (Ambystoma mexicanum) and Rough-skinned Newts (Taricha granulosa)

Valle¹,

Eisthen

2019

comp med

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Batrachochytrium dendrobatidis is a fungal pathogen of amphibians that originated in Asia, likely on the Korean peninsula, 27 and is now found on all continents that are home to amphibians. 20 Initial infection of an amphibian host is accomplished by motile, flagellated zoospores. These zoospores encyst within epidermal cells, germinate, and form intracellular sporangia, in which new zoospores develop, within the stratum corneum and stratum granulosum. Epidermal differentiation moves these sporangia to the skin surface, and mature zoospores are released into the external environment. 34 This intracellular proliferation of B. dendrobatidis within the host disrupts electrolyte balance and, in some cases, can lead to cardiac arrest and death. 36 Transmission of B. dendrobatidis between hosts occurs through a variety of methods, including close proximity to infected animals, which can shed considerable loads of infective zoospores into water systems; through direct contact, such as during mating; 34 and possibly through ingestion of infected prey. 15 B. dendrobatidis infects all 3 orders of amphibians (anurans [that is, frogs and toads]; urodeles [salamanders]; and caecilians) 14 and has been reported in more than 700 species of amphibians. 20 The spread of B. dendrobatidis has been linked to an overall global decline in amphibian populations, and this pathogen has contributed to population declines in almost 400 amphibian species that are currently listed as threatened. 20 The virulence of B. dendrobatidis infections varies among both host species and strains of the pathogen. 2,20 B. dendrobatidis has been shown to infect Taricha granulosa in the wild 29 and has been reported in captive-bred axolotls. 11,12,23 In addition, B. dendrobatidis can infect larval zebrafish, 19 creating potential concerns for spread between aquatic animal models when an outbreak is detected within a laboratory setting.A second member of the genus, B. salamandrivorans, was first described in 2013. 21 Like B. dendrobatidis, B. salamandrivorans appears to have originated in Asia 27 and infects epidermal tissue. 21 To date, B. salamandrivorans has been reported in salamanders and fire-bellied toads in the wild and has been shown to be capable of infecting anurans in the laboratory setting. 26,32 No reports of B. salamandrivorans infection in North America have been published. These 2 Batrachochytrium species are the only chytrid fungi known to infect vertebrates. 2 The current case report describes the diagnosis and treatment of chytridiomycosis due to B. dendrobatidis in laboratory colonies of axolotls (Ambystoma mexicanum) and rough-skinned newts

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Reduced Itraconazole Concentration and Durations Are Successful in Treating <em>Batrachochytrium dendrobatidis</em> Infection in Amphibians

Cited by 14 publications

References 17 publications

The amphibian microbiome exhibits poor resilience following pathogen-induced disturbance

The amphibian microbiome exhibits poor resilience following pathogen-induced disturbance

Incapacitating effects of fungal coinfection in a novel pathogen system

Treatment of Chytridiomycosis in Laboratory Axolotls (Ambystoma mexicanum) and Rough-skinned Newts (Taricha granulosa)

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