Chytridiomycosis, amphibian extinctions, and lessons for the prevention of future panzootics.

Centre for Innovative Conservation Strategies, School of Environment, Griffith University, Gold Coast, QLD, Australia.
EcoHealth (Impact Factor: 2.2). 06/2009; 6(1):6-10. DOI: 10.1007/s10393-009-0228-y
Source: PubMed

ABSTRACT The human-mediated transport of infected amphibians is the most plausible driver for the intercontinental spread of chytridiomycosis, a recently emerged infectious disease responsible for amphibian population declines and extinctions on multiple continents. Chytridiomycosis is now globally ubiquitous, and it cannot be eradicated from affected sites. Its rapid spread both within and between continents provides a valuable lesson on preventing future panzootics and subsequent erosion of biodiversity, not only of amphibians, but of a wide array of taxa: the continued inter-continental trade and transport of animals will inevitably lead to the spread of novel pathogens, followed by numerous extinctions. Herein, we define and discuss three levels of amphibian disease management: (1) post-exposure prophylactic measures that are curative in nature and applicable only in a small number of situations; (2) pre-exposure prophylactic measures that reduce disease threat in the short-term; and (3) preventive measures that remove the threat altogether. Preventive measures include a virtually complete ban on all unnecessary long-distance trade and transport of amphibians, and are the only method of protecting amphibians from disease-induced declines and extinctions over the long-term. Legislation to prevent the emergence of new diseases is urgently required to protect global amphibian biodiversity.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The Western Ghats of India harbors a rich diversity of amphibians with more than 77% species endemic to this region. At least 42% of the endemic species are threatened due to several anthropogenic stressors. However, information on amphibian diseases and their impacts on amphibian populations in this region are scarce. We report the occurrence of Batrachochytridium dendrobatidis (Bd), an epidermal aquatic fungal pathogen that causes chytridiomycosis in amphibians, from the Western Ghats. In the current study we detected the occurrence of a native Asian Bd strain from three endemic and threatened species of anurans, Bombay Night Frog Nyctibatrachus humayuni, Leith's Leaping Frog Indirana leithii and Bombay Bubble Nest Frog Raorchestes bombayensis, for the first time from the northern Western Ghats of India based on diagnostic nested PCR, quantitative PCR, DNA sequencing and histopathology. While, the Bd infected I. leithii and R. bombayensis did not show any external symptoms, N. humayuni showed lesions on the skin, browning of skin and sloughing. Sequencing of Bd 5.8S ribosomal RNA gene, and the ITS1 and ITS2 regions, revealed that the current Bd strain is related to a haplotype endemic to Asia. Our findings confirm the presence of Bd in northern Western Ghats and the affected amphibians may or may not show detectable clinical symptoms. We suggest that the significance of diseases as potential threat to amphibian populations of the Western Ghats needs to be highlighted from the conservation point of view.
    PLoS ONE 01/2013; 8(10):e77528. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Extreme overall divergence and high extinction rates are typical of insular endemics. Thus, detecting and understanding nativeness is critical on islands. Resilience to extinction is explored through a mechanistic approach focusing on midwife toads (Anura: Alytidae: Alytinae), an ancient lineage that includes continental and insular species. All alytines need urgent conservation action, including control of emerging diseases and spatially explicit reserve design aimed at ensuring ecosystem health and connectivity. The only extant insular alytine is additionally affected by an introduced continental predator. This alien species acts as a driver of the prey’s near-extinction and has not elicited any evolutionary response. Both IUCN criteria and EDGE scores show that alytines are top conservation priorities. However, there is a need for also considering phenotypic and ecological uniqueness in the assessment of conservation status and urgency. The reason is that phenotypes render ecosystems functional and insular ones uniquely so. In contrast, phylogenetic relatedness is just a constraint upon, not a motor of, evolutionary novelty. Insular species are indeed particularly susceptible, but can be similarly endangered as continental ones. This paradox may be solved by recognizing the insularity syndrome in any isolated or nearly-insular ecosystem, as a function of evolutionary and dispersal potentials. This predictive model may be useful for island biogeography, invasion biology and conservation planning.
    Diversity 01/2014; 6:43-71.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The amphibian disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a major cause of worldwide amphibian declines and extinctions. Although several studies indicate that Bd prevalence and infection intensity vary seasonally, temporal variation of Bd at high-latitude sites, such as the northeastern USA, is still poorly characterized. We screened amphibians for Bd monthly at 2 study sites in New York State from April to October 2011 and used quantitative polymerase chain reaction (qPCR) to detect and quantify temporal variability in Bd infection prevalence and intensity. We found pronounced seasonal variation in both Bd infection prevalence and intensity at the community level, and our data indicate that this pattern is due to a few species (Lithobates catesbeianus, L. clamitans, and Notophthalmus viridescens) that drive temporal variability in disease dynamics. Amphibian body mass and sex were significant predictors of infection intensity but not infection prevalence. Understanding the temporal dynamics of Bd host-pathogen interactions provides important insight into regional, seasonal, and host-specific determinants of disease outbreaks. Further, our study elucidates the most relevant and informative timing for Bd surveys in temperate amphibian assemblages. Seasonal variation of infection dynamics suggests that Bd surveys from different sampling time points are not comparable, and summer surveys to evaluate chytridiomycosis may significantly underestimate Bd prevalence and intensity, leading to false conclusions about the severity of chytridiomycosis-induced amphibian mortality and population decline.
    Diseases of Aquatic Organisms 10/2014; · 1.73 Impact Factor

Full-text (2 Sources)

Available from
May 29, 2014