Several prominent pathogens and associated EIDs affect amphibian populations worldwide. Some of the research we summarize below focused on how a particular pathogen alone affects a host, whereas some studies addressed how a pathogen may be affected by other variables that may interact with pathogens.Īmong the major threats to amphibians are emerging infectious diseases (EIDs). These include habitat destruction, contaminants, climate change, over-harvesting, invasive species, predation, and infectious diseases, all of which may work independently or synergistically to affect amphibian populations ( Figure 1). Like other groups, amphibians are affected by multiple factors contributing to population declines. Their populations are declining more rapidly than those of birds or mammals. Although numerous species from all taxonomic groups are affected, amphibians are at the forefront of this crisis. Current species extinction rates are higher than pre-human background rates, suggesting this biodiversity crisis is largely attributed to anthropogenic changes. Rapid rates of biodiversity loss have supported the notion that the Earth is heading toward a sixth major extinction event. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease. 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. 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. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies.
These include the fungi Batrachochytrium dendrobatidis and B. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. One major factor affecting amphibian populations is emerging infectious disease.
The causes of amphibian population declines are multifaceted and context-dependent.
These losses are especially illustrated by amphibians, whose populations are declining worldwide. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. Numerous factors are contributing to the loss of biodiversity.
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