The Value of Well-Designed Experiments in Studying Diseases with Special Reference to Amphibians

Blaustein, Andrew R.; Alford, Ross A.; Harris, Reid N.

doi:10.1007/s10393-009-0266-5

Cited by 7 publications

(7 citation statements)

References 29 publications

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“…Climate modeling should be fortified with both laboratory and field experiments. Experimental studies should be bolstered with molecular work, especially using molecular tools that can provide clues as to how amphibians are affected at the physiological level [222]. Molecular biologists, ecologists and modelers working together may be able to help us understand the broad impacts of climate change on amphibians.…”

Section: Discussionmentioning

confidence: 99%

Direct and Indirect Effects of Climate Change on Amphibian Populations

et al. 2010

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Abstract:As part of an overall decline in biodiversity, populations of many organisms are declining and species are being lost at unprecedented rates around the world. This includes many populations and species of amphibians. Although numerous factors are affecting amphibian populations, we show potential direct and indirect effects of climate change on amphibians at the individual, population and community level. Shifts in amphibian ranges are predicted. Changes in climate may affect survival, growth, reproduction and dispersal capabilities. Moreover, climate change can alter amphibian habitats including vegetation, soil, and hydrology. Climate change can influence food availability, predator-prey relationships and competitive interactions which can alter community structure. Climate change can also alter pathogen-host dynamics and greatly influence how diseases are manifested. Changes in climate can interact with other stressors such as UV-B radiation and contaminants. The interactions among all these factors are complex and are probably driving some amphibian population declines and extinctions. OPEN ACCESSDiversity 2010, 2 282

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Section: Discussionmentioning

confidence: 99%

Direct and Indirect Effects of Climate Change on Amphibian Populations

et al. 2010

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“…Nevertheless, with the random method that we used to assign the tadpoles to their respective experimental groups, we should have evenly distributed tadpoles with preinfections by any type of pathogen among the groups, such that the average state of health of all tadpoles upon initiation of the experiment was equal. Thus, while we cannot state unequivocally that none of our control tadpoles harboured Bd infections prior to the experimental exposures, we are confident that our results demonstrate effects of the experimental exposures to Bd and the pesticides on the initial state of tadpole health, as all other conditions were equal (see Blaustein et al 2009 for a discussion on well-designed disease studies).…”

Section: Discussionmentioning

confidence: 74%

“…Exposure to Bd, even without manifestation of infection or disease, can prove detrimental to the health and survival of larval amphibians (Blaustein et al 2005;Blaustein et al 2009;Garner et al 2009). However, amphibian larvae exhibit interspecific variability in susceptibility to Bd and bullfrog tadpoles can display resistance to lethal infections (Blaustein et al 2005).…”

Section: Discussionmentioning

confidence: 99%

“…The former possibility could raise questions regarding whether opportunities actually arose for within-host interactions to occur between Bd and G. jennyae. However, exposure to Bd may adversely affect larval amphibian health with or without establishment of infection (Blaustein et al 2009). In one instance, Blaustein et al (2005) reported higher rates of mortality in larval western toads Bufo boreas exposed to Bd than in controls, yet none of the Bd-exposed larval toads that died provided histologic evidence of chytrid infection.…”

Section: Discussionmentioning

confidence: 99%

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Mortality of American Bullfrog Tadpoles Lithobates catesbeianus Infected by Gyrodactylus jennyae and Experimentally Exposed to Batrachochytrium dendrobatidis

Paetow¹,

McLaughlin²,

Pauli

et al. 2013

J Aqua Anim Hlth

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The fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis in postmetamorphic amphibians, has been linked to amphibian population declines. Different amphibian species, however, exhibit different susceptibility to Bd pathogenicity. At the same time, agricultural pesticides commonly found contaminating aquatic habitats have been reported to increase the susceptibility of amphibians to pathogens. To investigate whether certain pesticides are able to alter the pathogenicity of Bd to larval amphibians, we exposed larval American bullfrogs Lithobates catesbeianus to end-use formulations of the herbicides atrazine or glyphosate, and then exposed them to Bd. Following the experimental exposures, a preexisting infection of the tadpoles by the monogenean ectoparasite Gyrodactylus jennyae was detected in all experimental and control tadpoles. Gyrodactylus jennyae infection intensity varied, and individuals with heavy G. jennyae infections suffered more skin erosion due to grazing by the parasite. Tadpoles experimentally exposed to Bd, or to Bd and either herbicide, had significantly reduced survival rates compared with untreated tadpoles that were only infected by G. jennyae. Increased mortality was also correlated with degree of skin erosion; survival of tadpoles with severe skin erosion was significantly reduced compared with that of tadpoles with no, or mild, skin erosion. While infected with G. jennyae, the group of tadpoles with the lowest survival rate (exposed only to Bd) included significantly more individuals exhibiting severe skin erosion and significantly fewer individuals without skin erosion, compared with the control group. These results emphasize the potential pathogenicity of gyrodactylid infections in larval amphibian hosts and suggest that concomitant exposures to Bd may enhance infections and effects of G. jennyae in bullfrog tadpoles.

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“…Although amphibians are hosts to an assortment of pathogens/parasites, including bacteria, viruses, fungi, water molds and helminths [13,[24][25][26][27], we focus on Bd, Bsal and Rv, given accumulating evidence of their potentially devastating effects on amphibian populations worldwide. In particular, we focus on reviewing the literature that report the results of experiments (manipulation of key variables [28]) conducted with Bd, Bsal, and Rv concentrating on papers that used live amphibian hosts. Given the complexity of these host-pathogen systems, experimental approaches are crucial for disentangling potential mechanisms driving patterns of transmission and examining variation in lethal and sublethal effects due to host species, host life-history traits, pathogen strain, host populations, and environmental conditions.…”

Section: Introductionmentioning

confidence: 99%

Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies

et al. 2018

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Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.

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The Value of Well-Designed Experiments in Studying Diseases with Special Reference to Amphibians

Cited by 7 publications

References 29 publications

Direct and Indirect Effects of Climate Change on Amphibian Populations

Direct and Indirect Effects of Climate Change on Amphibian Populations

Mortality of American Bullfrog Tadpoles Lithobates catesbeianus Infected by Gyrodactylus jennyae and Experimentally Exposed to Batrachochytrium dendrobatidis

Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies

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