Bd population genomics at Asilomar

The bi-annual 26th Fungal Genetics Conference at Asilomar saw a flurry of Bd-related activity being reported. Both Rhys Farrer (Imperial College) and Jason Staijch (UC Riverside) gave talks on the population genomics of Bd from geographically and genetically diverse strains. Both studies report patchy distributions of diversity across Bd's genome, likely owing to loss-of-heterozygosity events. Whether this results from meiotic or mitotic events remains to be seen. Jason reported the release of his comparative genomics tool, FungiDB; this is going to be a great asset to the community, great stuff Jason! Posters were exhibited on putative virulence factors (the CBM18 chitin-binding domain gene expansion: Abramyan & Stajich), the distribution of Bd in British Columbia (LeBlanc, Hintz & Anholt), functional genomics of Bd (Thomas Poorten & Rosenblum), the detection of rhodopsin-like genes in Bd that are indicative of phototactic responses (Medina, Restrepo & Stajich) and the population genomics of Bd (Rhys Farrer et al). Well done to Rhys for winning a poster prize, 'Eukaryotic Cell' is a great bedtime read.....The poster abstracts can be downloaded here.

RACEing ahe.........ah, you know

Currently sitting in the 3rd meeting of the RACE network, rather the extended RACE network, as this meeting is well-attended by extraRACErs (Giulia Tessa, Italy, Vojtech Balaz, Czech Republich, Goncalo Rosa, Portugal, Emilien Luquet, France). The meeting is a success due to the contributions of the PhD students (half of the attendees and the majority of the presentations). Topics range from modelling disease dynamics, mitigation, Bd genomics, spatial epidemiology, assessing effects in wild amphibian populations, trade, policy.....meeting our RACE deliverables is certainly RACEing ahead, thanks to the outstanding science done by these students. However, it's very clear that there are far more issues to hand than those being addressed. More later.....

Shiver Bd! The Mitigators are coming!

Interest and excitement is gathering around the concept of mitigating the lethal effects of Bd by either reducing the threshold burden of infection, or by completely removing Bd from key infected environments. The Zurich Bd mitigation workshop was the first global meeting to address potential mitigation strategies by sharing experience and data, and planning new approaches as well as collaborations. Approaches that were considered in the workshop varied from (i) manipulating pre-epizootic host density; (ii) bioaugmentation with Bd-cidal probiotic bacteria; (iii) antifungal approaches to treating hosts and habitats; (iv) immunisation using recently-discovered hyovirulent/avirulent strains of Bd, or other vaccine technologies; (v) biocontrol with copepods or other zoospore-predators and (vi) ex-situ captive breeding followed by re-introduction with individuals that have undergone 'assisted evolution'. From the meeting, it was clear that not only are there many approaches that can be used, but also several ongoing programs. Indeed, the title for this post is the slogan coined by Jaime Bosch for his new Santander 'Zero' mitigation grant focusing on removing Bd from Mallorca and Alytes muletensis. Indeed, perhaps the time has come to 'Shiver Bd; the mitigators are coming!'. We anticipate appropriate mugs and T-shirts to appear in CafePress soon so stay tuned.....

But hope springs eternal....

Bad news from Mat re: the Pyrenees, but what can be done about it? Recent news articles (Sierra Nevadas: http://www.nytimes.com/2010/10/05/science/05frog.html?_r=1&hpw Mallorca: http://www.nature.com/news/2010/100609/full/465680a.html ) show that some of us are trying some things out. Since mitigating any infectious diseases of wildlife is no small task, we need to share experiences, methods, project ideas and results at a global scale. Doug Woodhams and Benedikt Schmidt have organized a Bd mitigation workshop to run Oct 14/15 in Zuerich, Switzerland. Invitees include Cherie Briggs, Vance Vredenburg, Roland Knapp, Jaime Bosch, Mat Fisher, Reid Harris, Lisa Belden, Brian Gratwicke, Ross Alford, Erin Muths, Ursina Tobler, Leyla Davis, Corina Geiger, Sara Bell, Vicky Flechas, Louis Rollins-Smith and yours truly. Those of you not invited, don't worry, this is merely the first such meeting (and as such numbers had to be kept small) and the plan is to make a book of abstracts, notes and minutes available to all and sundry. This first meeting is global in nature, but herewith a challenge: why not organize your own, regional or even local, workshop on Bd mitigation (heck, on amphibian disease mitigation) to get the process moving for your amphibian assemblages threatened with disease? And remember to communicate the outcome of any meeting widely. Like on this blog, for instance.

More bad news from the Pyrenees as Bd spreads

Bd in the Pyrenees is concentrated into a group of lakes in the Vallee d'Aspe and Ossau. Within this region, one lake in the Ansabere valley, Lescun, has remained Bd free. Lac Lhurs supports a very large population of Alytes, and constitutes one of the main chytridiomycosis-free refuges for these amphibians. However, this has now changed and a low prevalence of infection (~15%) was detected for the first time in 2009. This year, 2010, infection with Bd has increased dramatically to 100% and the first chytridiomycosis mortalities were observed in September. We are still unclear about the mechanism that Bd uses to spread between lakes: Lac Lhurs is shielded from other valleys by a cirque of high peaks that may have limited vector-borne transmission via birds or other vertebrates. This may explain why the Lac remained uninfected in this heavily-infected region for so long. How did Bd arrive? As with so many other aspects of this enigmatic pathogens life-history, we do not know. However, we do know that this otherwise pristine population of amphibians now faces an uncertain future.

A bad year in the Pyrenees for Alytes

2010 has not been a good year for our sentinel species, Alytes, in the outbreak sites of the Pyrenees. The season was hard due to a very cold start - our dataloggers showed that the high altitude Lakes in the Vallee d'Aspe did not thaw until the 1st of June. The amphibians consequently had to hurry their development, and the emergence of Alytes in August was late, and characterised by very high mortality due to chytridiomycosis in several of our study lakes. Lac Arlet, on the GR10 pathway, was the scene of large die-offs and the Imperial College tream found over 350 mortalities in a single day. Die-offs here were still being recorded in early September, detected by local volunteers. Whether the cold early-season is linked to these unusually high mortalities is one of the questions that is currently being worked on.

Endemic v Epizootic Bd in the US Sierra Nevadas

Two papers in PNAS document 13 years work on the emergence of Bd in the Sierra Nevadas by Vance Vredenberg and Cheryl Briggs. The papers contrast two montane scenarios, one where Bd is causing a year-on-year extirpation of mountain yellow-legged frogs Rana muscosa (see picture), and one where Bd has formed a stable persistent association with the frogs. Cheryl and Vance argue, and show using mathematical models, that these dynamics can be explained by density-dependent host-pathogen dynamics. So, if Bd hits a naive high-density population, then individuals are overwhelmed by high-intensity infections and the population is lost. Conversly, lower-density populations can tolerate lower Bd loads and persist. The conclusions from these studies parallel what has been observed in other regions, Australia (Taudactylus eungellensis) and Europe (Alytes obstetricans), where low-density populations persist past the epizootic 'hit'. An idea that is mooted from this work: that mitigation of infection may be possible by manipulating infection loads in the wild, perhaps by removing asymptomatic reservoirs (such as overwintering larvae). So, perhaps the best way to conserve a species is to decrease it to below a predicted critical density in advance of the wave of spread. Could this be used in the Pyrenees where infection is still very local? And, are such population manipulations ethically defensible? Many of these ideas will no doubt be discussed in the upcoming Bd mitigation workshop in Zurich this autumn.