Wednesday, 20 October 2010

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.....

Wednesday, 6 October 2010

But hope springs eternal....

Bad news from Mat re: the Pyrenees, but what can be done about it? Recent news articles (Sierra Nevadas: Mallorca: ) 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.

Monday, 4 October 2010

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.

Wednesday, 12 May 2010

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.

Friday, 9 April 2010

Filming RACE

Two days of filming have just ended, they will be cut down to 5 minutes by the end of April. Kerala Productions brought over a small team to get explanations on RACE and Chytridiomycosis, focusing on our main sampling area - the Pyrenees. Pierre and Pauline made some nice shots, happily taking all moving amphibians on tape. They got explanations on the whole range of RACE work, starting from sampling , marking and swabbing individuals to the genetic methods and behavioural experiments. They also were part of the world premier - the implementation of ALPHA tags into Alytes tadpoles.

So, lets wait what is the end result. In any case, it was fun and two days did fly by quickly.

Looking forward seeing the result!

Wednesday, 17 February 2010

RACEing ahead (as Mat likes to say)

Yes, the European Bd project is having it's second meeting. Aside from the rather kitch Star Trek allegories, the meeting is extremely informative. Highlights include updates on the Swiss surveillance and mitigation projects, Jaime's work on Iberian endangered species, temporal patterns of Bd infection in adult toads and the Mallorcan mitigation project and a fantastic experiment by Emilien and Sandrine from Lyon examining the interaction between experimental Bd challenge and host population isolation. Currently we are in the midst of a workshop, led by David and Chris, learning how to real time our data into the European (and, by extension, the global) d-base. Our EU network grows: we have at a minimum another ten active Bd research groups in Europe, and several others readying themselves for initiating projects. At least 5 new PhDs in Europe working on Bd!

While it's clear that field projects in France have some time before starting (we are meeting in Grenoble and the snow and temperature are clear indicators of that), we are gearing up for field work at some of the warmer locales. Jaime will soon start another Iberia-wide field trip, interrupted by a collaborative project with Judit Voros (sorry, Judit, no idea how to do umlauts in Blogger) in Hungary, and Jon Bielby and I should be heading to Sardinia soon to continue our collaborative project with Zirichiltaggi and Ente Foreste Sarda.

A challenge to our North American counterparts: start blogging!

Thursday, 4 February 2010

Living the high life is risky business for midwive's in Iberia

Walker et al. have published their long-awaited survey of the prevalence of Bd across the Iberian peninsula in Ecology Letters. The study focuses on common midwives, Alytes muletensis, and combines multilocus genotyping with bayesian analyses to show that Bd is not at equilibrium within Iberia, but is still spreading. While lowland populations of Alytes appear to co-exist with the chytrid, high-altitude populations exhibit chytridiomycosis and seasonal die-offs, demonstrating a very strong interaction between altitude/temperature and disease. Within a key region, the Pyrenean mountain range, Bd is absent across the majority of the range except for a tight cluster of genotypically-identical Bd strains in the western Pyrenean National Park. How Bd arrived in this region is not known: there are no known introduced non-native amphibian species in this area however the montane lakes are regularly 'seeded' with salmonid fish for the angling industry. Efforts now need to focus on the process of introduction and spread, as it is a key concern to prevent the wider spread of Bd throughout this ecologically sensitive region.

Tuesday, 19 January 2010

Terrestrial chytridiomycosis

Sara Weinstein has published an exciting study of Bd infecting and affecting a strictly terrestrial plethodontid salamander in the Western US (Weinstein Copeia 2009(4): 653-660). She provides strong evidence for a historical relationship between Batrachoseps attenuatus and Bd, going back as far as 1973, that seems to involve mortality of the species in the field. Her experiments convincingly show that Bd infection leads to death in the species and some insight into the link between environmental moisture and mortality. Fascinating work on a host species not expected to be so strongly affected by a supposedly aquatic parasite. This, along with the recent paper in Molecular Ecology by Goka et al. (2009, vol 18(23): 4757-4774) are the most significant papers on chytridiomycosis, caudate hosts and historical interactions to come along for quite some time.