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population genetics of the frog-killing fungus batrachochytrium dendrobatidis.global amphibian decline by chytridiomycosis is a major environmental disaster that has been attributed to either recent fungal spread or environmental change that promotes disease. here, we present a population genetic comparison of batrachochytrium dendrobatidis isolates from an intensively studied region of frog decline, the sierra nevada of california. in support of a novel pathogen, we find low diversity, no amphibian-host specificity, little correlation between fungal genotype and geograph ...200717693553
evaluation of tadpole mouthpart depigmentation as a diagnostic test for infection by batrachochytrium dendrobatidis for four california anurans.the objective of this study was to evaluate the utility of gross morphologic examination of larval mouthpart defects as a diagnostic screening test to detect batrachochytrium dendrobatidis infection in four california, usa, anuran species. we examined mouthparts of 2,034 tadpoles of bufo boreas, pseudacris regilla, and rana catesbeiana collected in 2003 and 2004 and bufo canorus collected in 2004. data were recorded for three morphologic features: upper toothrows, lower toothrows, and combined j ...200717984265
prevalence of batrachochytrium dendrobatidis in xenopus collected in africa (1871-2000) and in california (2001-2010).international trade of the invasive south african clawed frog (xenopus laevis), a subclinical carrier of the fungal pathogen batrachochytrium dendrobatis (bd) has been proposed as a major means of introduction of bd into naïve, susceptible amphibian populations. the historical presence of bd in the indigenous african population of xenopus is well documented. however, there are no reports documenting the presence of bd in wild xenopus populations in the us, particularly in california where introd ...201323691097
a reservoir species for the emerging amphibian pathogen batrachochytrium dendrobatidis thrives in a landscape decimated by disease.chytridiomycosis, a disease caused by the fungal pathogen batrachochytrium dendrobatidis (bd), is driving amphibian declines and extinctions in protected areas globally. the introduction of invasive reservoir species has been implicated in the spread of bd but does not explain the appearance of the pathogen in remote protected areas. in the high elevation (>1500 m) sierra nevada of california, the native pacific chorus frog, pseudacris regilla, appears unaffected by chytridiomycosis while sympat ...201222428071
pathophysiology in mountain yellow-legged frogs (rana muscosa) during a chytridiomycosis outbreak.the disease chytridiomycosis is responsible for declines and extirpations of amphibians worldwide. chytridiomycosis is caused by a fungal pathogen (batrachochytrium dendrobatidis) that infects amphibian skin. although we have a basic understanding of the pathophysiology from laboratory experiments, many mechanistic details remain unresolved and it is unknown if disease development is similar in wild amphibian populations. to gain a better understanding of chytridiomycosis pathophysiology in wild ...201222558145
widespread co-occurrence of virulent pathogens within california amphibian communities.the chytrid fungus batrachochytrium dendrobatidis, ranaviruses, and trematodes (ribeiroia ondatrae and echinostomes) are highly virulent pathogens known to infect amphibians, yet the extent to which they co-occur within amphibian communities remains poorly understood. using field surveillance of 85 wetlands in the east bay region of california, usa, we found that 68% of wetlands had ≥2 pathogens and 36% had ≥3 pathogens. wetlands with high pathogen species richness also tended to cluster spatial ...201222766887
bacterial flora on cascades frogs in the klamath mountains of california.amphibians are experiencing global declines due in part to the infectious disease chytridiomycosis. some symbiotic bacteria residents on frog skin have been shown to inhibit the growth of batrachochytrium dendrobatitis (bd) but few studies have attempted to fully describe the resident bacterial flora of frog skin. we cultured and sequenced 130 bacterial isolates from frogs collected from the california klamath range, recovering predominantly gram-negative bacteria from 20 higher order taxa and 3 ...201323969031
prevalence of batrachochytrium dendrobatidis in 120 archived specimens of lithobates catesbeianus (american bullfrog) collected in california, 1924-2007.the chytrid fungus, batrachochytrium dendrobatidis (bd), has been identified as a major cause of the recent worldwide amphibian decline. numerous species in north america alone are under threat or have succumbed to bd-driven population extinctions. the american bullfrog (lithobates catesbeianus) has been reported as a tolerant carrier of bd. in this report, we used a qpcr assay to test 120 archived american bullfrog specimens collected between 1924 and 2007 in california, usa and baja california ...201324419668
correlates of virulence in a frog-killing fungal pathogen: evidence from a california amphibian decline.the fungal pathogen batrachochytrium dendrobatidis (bd) has caused declines and extinctions in amphibians worldwide, and there is increasing evidence that some strains of this pathogen are more virulent than others. while a number of putative virulence factors have been identified, few studies link these factors to specific epizootic events. we documented a dramatic decline in juvenile frogs in a bd-infected population of cascades frogs (rana cascadae) in the mountains of northern california and ...201525514536
invasion of the fungal pathogen batrachochytrium dendrobatidis on california islands.batrachochytrium dendrobatidis (bd), an amphibian fungal pathogen, has infected >500 species and caused extinctions or declines in >200 species worldwide. despite over a decade of research, little is known about its invasion biology. to better understand this, we conducted a museum specimen survey (1910-1997) of bd in amphibians on 11 california islands and found a pattern consistent with the emergence of bd epizootics on the mainland, suggesting that geographic isolation did not prevent bd inva ...201626493624
citizen scientists monitor a deadly fungus threatening amphibian communities in northern coastal california, usa.ecoclub youth and supervising family members conducted citizen science to assess regional prevalence and distribution of batrachochytrium dendrobatidis (bd) among amphibians at humboldt bay national wildlife refuge (refuge) and redwood national and state parks (parks), humboldt county, california, us, may 2013 through december 2014. using quantitative real-time pcr, 26 (17%) of 155 samples were positive for bd. positive samples occurred in four frog and toad species: foothill yellow-legged frog ...201627195681
recent emergence of a chytrid fungal pathogen in california cascades frogs (rana cascadae).the pathogenic fungus batrachochytrium dendrobatidis (bd) has been associated with global amphibian declines, but it is often difficult to discern the relative importance of bd as a causal agent in declines that have already occurred. retrospective analyses of museum specimens have allowed researchers to associate the timing of bd arrival with the timing of past amphibian declines. cascades frogs (rana cascadae) have experienced dramatic declines in northern california, but it is not clear wheth ...201727957606
do frogs get their kicks on route 66? continental u.s. transect reveals spatial and temporal patterns of batrachochytrium dendrobatidis infection.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 ( ...201121811576
enzootic and epizootic dynamics of the chytrid fungal pathogen of amphibians.chytridiomycosis, the disease caused by the chytrid fungus, batrachochytrium dendrobatidis (bd), has contributed to amphibian population declines and extinctions worldwide. the impact of this pathogen, however, varies markedly among amphibian species and populations. following invasion into some areas of california's sierra nevada, bd leads to rapid declines and local extinctions of frog populations (rana muscosa, r. sierrae). in other areas, infected populations of the same frog species have de ...201020457916
dynamics of an emerging disease drive large-scale amphibian population extinctions.epidemiological theory generally suggests that pathogens will not cause host extinctions because the pathogen should fade out when the host population is driven below some threshold density. an emerging infectious disease, chytridiomycosis, caused by the fungal pathogen batrachochytrium dendrobatidis (bd) is directly linked to the recent extinction or serious decline of hundreds of amphibian species. despite continued spread of this pathogen into uninfected areas, the dynamics of the host-pathog ...201020457913
batrachochytrium dendrobatidis, a novel pathogen approaching endemism in central california.the recent emergence of amphibian chytridiomycosis has precipitated competing hypotheses regarding the endemic versus novel nature of the causative agent, batrachochytrium dendrobatidis (bd). we conducted a retrospective survey of the california academy of sciences' (san francisco, california, usa) amphibian collection, testing for presence of bd in 4 amphibian species collected from central california between 1897 and 2005. the earliest detection of bd was found in 2 rana catesbeiana in 1961, a ...200919301630
disease associated with integumentary and cloacal parasites in tadpoles of northern red-legged frog rana aurora aurora.a total of 6830 northern red-legged frog rana aurora aurora tadpoles were examined under a dissecting microscope for oral disc, integumentary, and cloacal abnormalities in 13 ponds in and near redwood national park in northern california. of these, 163 tadpoles were collected for histopathological investigation, including 115 randomly collected individuals, 38 collected with oral disc abnormalities, and 10 collected due to severe morbidity of unknown etiology. the tadpoles were infected with 8 p ...200718159674
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