Tuesday, 1 August 2017

More on Bd mitigation

In a new paper published in Scientific Reports (link), Corina Geiger and coauthors describe the results of a field experiments on Bd mitigation. They show that a transient reduction of prevalence is possible.















Here's the abstract:
"Emerging infectious diseases can drive host populations to extinction and are a major driver of biodiversity loss. Controlling diseases and mitigating their impacts is therefore a priority for conservation science and practice. Chytridiomycosis is a devastating disease of amphibians that is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), and for which there is an urgent need to develop mitigation methods. We treated tadpoles of the common midwife toad (Alytes obstetricans) with antifungal agents using a capture-treat-release approach in the field. Antifungal treatment during the spring reduced the prevalence of Bd in the cohort of tadpoles that had overwintered and reduced transmission of Bd from this cohort to the uninfected young-of-the-year cohort. Unfortunately, the mitigation was only transient, and the antifungal treatment was unable to prevent the rapid spread of Bd through the young-of-the year cohort. During the winter, Bd prevalence reached 100% in both the control and treated ponds. In the following spring, no effects of treatment were detectable anymore. We conclude that the sporadic application of antifungal agents in the present study was not sufficient for the long-term and large-scale control of Bd in this amphibian system."

Thursday, 20 April 2017

Bd can infect zebrafish

The amphibian chytrid fungus can infect zebra fish.

The press release: http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_7-4-2017-12-24-44

The paper in Nature Communications: https://www.nature.com/articles/ncomms15048

Batrachochytrium salamandrivorans: The perfect pathogen

A new paper by Gwij Stegen et al. shows that the salamander chytrid fungus may be the 'perfect pathogen'. It kills salamanders rapidly and has a very high transmission. There is apparently no immune response by the salamader. There are reservoir hosts and two types of zoospores.


An infected salamander. Picture by (c) Frank Pasmans.
The paper in Nature.
The News and Views article by Mat Fisher.
The story in Science about the article.

Thursday, 9 February 2017

Did Bd cause historic amphibian population declines in Brazil?

A new paper by Tamilie Carvalho et al. in the Proceedings of the Royal Society shows that there is a link between Bd infection in tadpoles and amphibian population declines in Brazil (primarily in the Atlantic forest). Thus, Bd may have caused population declines a long time ago and even before it was described (1979-1987). The authors argue that these results suggest that Brazil is not the origin of Bd.

The abstract of the paper:
The recent increase in emerging fungal diseases is causing unprecedented threats to biodiversity. The origin of spread of the frog-killing fungus Batrachochytrium dendrobatidis (Bd) is a matter of continued debate. To date, the historical amphibian declines in Brazil could not be attributed to chytridiomycosis; the high diversity of hosts coupled with the presence of several Bd lineages predating the reported declines raised the hypothesis that a hypervirulent Bd genotype spread from Brazil to other continents causing the recent global amphibian crisis. We tested for a spatio-temporal overlap between Bd and areas of historical amphibian population declines and extinctions in Brazil. A spatio-temporal convergence between Bd and declines would support the hypothesis that Brazilian amphibians were not adapted to Bd prior to the reported declines, thus weakening the hypothesis that Brazil was the global origin of Bd emergence. Alternatively, a lack of spatio-temporal association between Bd and frog declines would indicate an evolution of host resistance in Brazilian frogs predating Bd's global emergence, further supporting Brazil as the potential origin of the Bd panzootic. Here, we Bd-screened over 30 000 museum-preserved tadpoles collected in Brazil between 1930 and 2015 and overlaid spatio-temporal Bd data with areas of historical amphibian declines. We detected an increase in the proportion of Bd-infected tadpoles during the peak of amphibian declines (1979–1987). We also found that clusters of Bd-positive samples spatio-temporally overlapped with most records of amphibian declines in Brazil's Atlantic Forest. Our findings indicate that Brazil is post epizootic for chytridiomycosis and provide another piece to the puzzle to explain the origin of Bd globally.

Tuesday, 10 January 2017

Refugia, connectivity, and transmission

Connectivity is bad for Bd and good for frogs. Read more here:
https://parasiteecology.wordpress.com/2016/03/23/refugia-connectivity-and-transmission/











(The cartoon was taken from the parasite ecology blog.)

Thursday, 22 December 2016

"After the epidemic": New review paper on chytrid epidemics in Australian amphibians

Ben Scheele and coauthors review the effects of chytridiomycosis on amphibian populations in Australia in a new paper in Biological Conservation (http://www.sciencedirect.com/science/article/pii/S0006320716310126).
Some highlights from the abstract:
"Chytridiomycosis in amphibians (caused by the fungal pathogen Batrachochytrium dendrobatidis, Bd) is an exemplar, with impacts ranging from rapid population crashes and extinctions, to population declines and subsequent recoveries."
"Population trajectories of declined species are highly variable; six species are experiencing ongoing declines, eight species are apparently stable and 11 species are recovering."
"Our results highlight that while some species are expanding, Bd continues to threaten species long after its emergence."

Monday, 17 October 2016

Tackling emerging fungal threats to animal health, food security and ecosystem resilience

Watch out for the new issue of the Philosophical Transactions of the Royal Society on "Tackling emerging fungal threats to animal health, food security and ecosystem resilience". There will be several papers on chytrids.

Access the articles here: http://rstb.royalsocietypublishing.org/content/371/1709