Thursday, 20 April 2017

Bd can infect zebrafish

The amphibian chytrid fungus can infect zebra fish.

The press release:

The paper in Nature Communications:

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:

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