Population-Level Resistance to Chytridiomycosis is Life-Stage Dependent in an Imperiled Anuran

Waddle, Anthony W.; Levy, Joshua; Rivera, Rebeca; Breukelen, Frank van; Nash, Maliha S.; Jaeger, Jef R.

doi:10.1007/s10393-019-01446-y

Cited by 21 publications

(35 citation statements)

References 45 publications

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“…We observed adult Bd loads well below those considered lethal in other ranids [19,73], but observed extremely high loads in subadults (Fig 2), including one moribund individual. Though our sample sizes are too small to definitively conclude that subadults are more likely to be infected compared to adults, our observation is consistent with high Bd loads and mortality in the subadult stage of other Bd-susceptible ranid species, including R. muscosa and R. boylii in California [16,19], and R. onca in Nevada [35]. The subadult in close proximity to the moribund frog…”

Section: Discussionsupporting

confidence: 77%

“…Variation in host Bd resistance and tolerance can be influenced by host environment [28]; behavior [19]; genetically mediated immune factors [29,30] or the lineage of Bd infecting the host [31,32]. Because reconstruction of the immune system occurs during metamorphosis, immunosuppression can make recently metamorphosed individuals particularly vulnerable to disease [33][34][35].…”

Section: Introductionmentioning

confidence: 99%

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Chytridiomycosis-induced mortality in a threatened anuran

et al. 2020

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Effectively planning conservation introductions involves assessing the suitability of both donor and recipient populations, including the landscape of disease risk. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has caused extensive amphibian declines globally and may hamper reintroduction attempts. To determine Bd dynamics in potential source populations for conservation translocations of the threatened California red-legged frog (Rana draytonii) to Yosemite National Park, we conducted Bd sampling in two populations in the foothills of the Sierra Nevada Mountains, California, U.S.A. At one of two sites, we observed lethally high Bd loads in early post-metamorphic life stages and confirmed one chytridiomycosis-induced mortality, the first such report for this species. These results informed source population site selection for subsequent R. draytonii conservation translocations. Conservation efforts aimed at establishing new populations of R. draytonii in a landscape where Bd is ubiquitous can benefit from an improved understanding of risk through disease monitoring and ex situ infection studies.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Chytridiomycosis-induced mortality in a threatened anuran

et al. 2020

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“…Under certain circumstances, such as in particular species or with repeated priming, it may be possible for this adaptive immune response to function protectively and reduce mortality [163]. Circumstantial evidence concerning experimental animals suggests that adaptive immune memory may be involved in animals that recover from chytridiomycosis after 4-6 weeks post exposure or in animals that persist with low-level burdens indefinitely (as reported by [133,158,[164][165][166]). However, examples of improved survival associated with repeated immune priming may alternatively be due to increased reactivity of the innate response, known as an innate immune memory [167].…”

Section: The Clinical Adaptive Immune Response Is Generally Poor and mentioning

confidence: 98%

Immunological Aspects of Chytridiomycosis

Grogan

Humphries

Robert

et al. 2020

JoF

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Amphibians are currently the most threatened vertebrate class, with the disease chytridiomycosis being a major contributor to their global declines. Chytridiomycosis is a frequently fatal skin disease caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). The severity and extent of the impact of the infection caused by these pathogens across modern Amphibia are unprecedented in the history of vertebrate infectious diseases. The immune system of amphibians is thought to be largely similar to that of other jawed vertebrates, such as mammals. However, amphibian hosts are both ectothermic and water-dependent, which are characteristics favouring fungal proliferation. Although amphibians possess robust constitutive host defences, Bd/Bsal replicate within host cells once these defences have been breached. Intracellular fungal localisation may contribute to evasion of the induced innate immune response. Increasing evidence suggests that once the innate defences are surpassed, fungal virulence factors suppress the targeted adaptive immune responses whilst promoting an ineffectual inflammatory cascade, resulting in immunopathology and systemic metabolic disruption. Thus, although infections are contained within the integument, crucial homeostatic processes become compromised, leading to mortality. In this paper, we present an integrated synthesis of amphibian post-metamorphic immunological responses and the corresponding outcomes of infection with Bd, focusing on recent developments within the field and highlighting future directions.

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“…We obtained 107 juvenile R. onca from a conservation program where frogs were raised in a Bd-free facility from wild-collected eggs. We used R. onca that were at least 2 months post-metamorphosis as earlier life stages may not be immunocompetent (Waddle et al, 2019). Juvenile R. onca were derived from six egg masses from two general areas where this species persists: the Northshore Springs Complex and Black Canyon.…”

Section: Access To Animals and Captive Husbandrymentioning

confidence: 99%