# how to stop chytridiomycosis



## Rain_Frog (Apr 27, 2004)

Ok, yeah. Let's pretend we did get all the funding we need for Amphibian Ark. We captive breed all the frogs in mass numbers. We have ensured plenty of genetic variability. But, how can we release the frogs back into the wild when they'll just die from chytrid?

What have been the proposals to stop the disease in the wild?


----------



## ETwomey (Jul 22, 2004)

I don't know what proposals have been made, but there are few options that seem viable. Getting rid of chytrid in the field or treating adult frogs would be futile. One possibility though would be this: 

1) Captive breed mass numbers of a species of concern
2) Infect all your captive bred individuals with chytrid
3) Hope that some survive, and breed those survivors, essentially selecting for elevated chytrid resistance.

The feasibility of this would likely depend on the species of frog. For example, Jason Brown and I have been observing a post-infection population of Atelopus pulcher for a couple years now. The population is decimated but there are still frogs there, which likely represent survivors, indicating that mortality is not guaranteed and there are at least some frogs there that have elevated resistance to this disease.

Any thoughts?

-Evan


----------



## Guest (Mar 2, 2007)

Evan, just out of curiosity: is there a way to 'test' resistance physiologically in an amphibian (e.g. through necropsy, etc.)?


----------



## Blort (Feb 5, 2005)

Evan,

When you say post-infection does that mean that known infected animals now either test positive and are asymptomatic, that they now test negative and are asymptomatic, or something else?

Marcos


----------



## Ed (Sep 19, 2004)

see http://www.pubmedcentral.nih.gov/articl ... tid=521184 for some comments? 

the only problem is that it appears that the anurans can survive with the fungus until stressed when mortality again beging to emerge. 
Also it appears that some species can either keep the infection at a constant level or temporarily clear it in adults through behavioral fevers (by basking) but still have massive mortality in metamorphs eliminating sufficient recruitment to allow the population to remain at the same levels or even recover? 

Ed


----------



## Rain_Frog (Apr 27, 2004)

If this is the case, would we then have to CB frogs in mass numbers and select metamorphs that are most resistant to the disease?

Is it possible to immunize/vaccinate amphibians? Except I don't believe we have ever made vaccines out of fungus. There's no chance vaccines can be passed on to offspring, can it? (I don't think so, since children need to get the same vaccinations as parents).


----------



## Ed (Sep 19, 2004)

The problem is that is appears that many of the amphibians are not truly resistant but are using behavorial responses to attempt to deal with the infection. 

Typically there needs to be a source of maternal antibodies that are passed onto the tadpole (which could in theory be possible in egg feeders ala the antibodies in milk in mammals) but immunity from vaccines are not handed down through generations. 

Also during metamorphosis the tadpole undergoes significant immunosuppression which means that the immune response is disrupted. 

Even species that are considered to be resistant to chytrid and can act as vectors like bullfrogs (Rana catesbiana) have been shown to undergo massive mortality upon being stressed (like metamorphosis) see http://origin.cdc.gov/ncidod/EID/vol9no8/03-0030.htm for the reference. 

Ed


----------



## ETwomey (Jul 22, 2004)

By post-infection, I mean that the frogs have tested positive for chytrid a few years back. According to what we have heard, the frogs used to occur in many more sites, and were much more common in each site. We have swabbed frogs from our study site but have not tested them yet, although I assume they will test positive since chytrid has recently been confirmed from other amphibians nearby. So it seems that chytrid is still in their site but there are some Atelopus coping with it. However, no sign of reproduction has been witnessed in over three years, so things don't look good. It is possible that some adults can hang on, but are suppressed to the point that reproduction is impossible.

On another note, even if frogs are combating the fungus behaviorally, this behavior would likely have a genetic basis and could therefore be passed to offspring. 

-Evan


----------



## Rain_Frog (Apr 27, 2004)

_However, no sign of reproduction has been witnessed in over three years, so things don't look good. It is possible that some adults can hang on, but are suppressed to the point that reproduction is impossible. _

When you mean no sign of reproduction, are you talking about finding eggs/breeding pairs, or the lack of neonates?

With reference to Ed's remark, then perhaps the metamorphs aren't surviving. Perhaps captive breed frogs to the juvenile stage and then release them into the wild?


----------



## Ed (Sep 19, 2004)

Chytrid (and in other populations ranaviruses) can cause massive (if not total) mortality in metamorphs preventing recruitment while the adults are either not infected or are able to seasonally clear the infection (the first reference is the more indicative). 

see Kerry M. Kriger; Jean-Marc Hero; 2006; Survivorship in Wild Frogs Infected with Chytridiomycosis; EcoHealth 3(3): 171-177 

(abstract at http://www.springerlink.com/content/1207110h865v3482/) 


see Green DE; Converse KA; Schrader AK; 2002; Epizootiology of sixty-four amphibian morbidity and mortality events in the USA, 1996-2001; Ann N Y Acad Sci.Oct;969:323-39. 

(abstract at http://www.annalsnyas.org/cgi/content/a ... /969/1/323 )


and an article on seasonality of chytrid infection 

L BERGER, R SPEARE, HB HINES, G MARANTELLI, AD HYATT, KR MCDONALD, LF SKERRATT, V OLSEN, JMCLARKE, G GILLESPIE, M MAHONY, N SHEPPARD, C WILLIAMS and MJ TYLER; 2004; Effect of season and temperature on mortality in amphibians due to chytridiomycosis; Australian Veterinary Journal Volume 82, No 7

(link at http://www.ava.com.au/avj/private/0407/04070434.pdf)


----------



## creek_frog (Mar 2, 2007)

I love ppl who post references. You rock Ed, thanks for the reading.
Having traveled to some places in South America, I was told that eco tourism is a problem. I bleached my boots countless times. I appreciate that some frogs are stateside waiting out the "fire of chytrid." But when will the fire go out? Will it go out? There are institutions in the UK that have tree seeds on ice so to speak of rare and endangered trees. We an freeze human embyros, why not frogs? Cheaper and more effective than the Noah's Ark approach, and we can make thousands of em, and wait to see what will happen to this nasty fungus. We'll always have em, and if (insert diety of choice here) is willing we can then return them where they belong. Your thoughts?


----------



## Ed (Sep 19, 2004)

There is increasing evidence that the chytrid can survive in the enviroment.. 

See Emerging infectious diseases and amphibian population declines
Emerging Infectious Diseases, Nov-Dec, 1999 by Daszak Peter, Lee Berger, Andrew A. Cunningham, Alex D. Hyatt, D. Earl Green, Rick Speare

the article is online at http://findarticles.com/p/articles/mi_m ... 76081/pg_6

Ed


----------

