CHYTRID FUNGUS, FROGS - WORLDWIDE: MECHANISM OF SPREAD
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Date: Mon 7 Nov 2011
Source: New Scientist [edited]
<http://www.newscientist.com/article/dn21133-frogkiller-disease-was-born-in-trade.html?DCMP=OTC-rss&nsref=online-news>
The global amphibian trade spread the lethal chytrid fungus, which is decimating frogs around the planet, and it now looks like it may have created the disease in the 1st place.
The team behind this finding are calling for an amphibian quarantine to help slow the disease's spread.
Rhys Farrer of Imperial College London and colleagues sequenced the genomes of 20 samples of the offending fungus, _Batrachochytrium dendrobatidis_ (_Bd_), collected in Europe, Africa, North and South America, and Australia.
They found that 16 of the 20 samples were genetically identical, belonging to a single strain called BdGPL that had spread to all 5 continents. Tests on tadpoles also revealed that the strain was extremely virulent.
BdGPL's genome showed that it had formed when 2 strains mated, some time in the past 100 years. The best and simplest explanation is that 20th-century trade, which shipped amphibians all over the world, enabled the mating, says Farrer's supervisor Matthew Fisher.
"We have got to restrict trade, or at least make sure that amphibians are not contaminated," says Fisher. One approach would be for countries to quarantine all imported amphibians and only allow them to stay if they are uninfected.
When it emerged that trade was spreading chytrid, the World Organisation for Animal Health made the disease notifiable, meaning that countries must report whether they have it or not. But that doesn't stop it spreading.
The 2 places in most urgent need of protection are Madagascar and south-east Asia, says Fisher: "They're the last redoubts of uninfected amphibian species." Both are hotspots of amphibian diversity, and are clear of BdGPL. Madagascar remains uninfected despite rampant BdGPL in Africa, and a recent survey shows that Asian chytrid strains are not very virulent (PLoS One, DOI: 10.1371/journal.pone.0023179).
If BdGPL reaches these places, it could quickly devastate their frogs.
Within months of it reaching Montserrat, in the West Indies, in early 2009, conservationists had to fly giant ditch frogs -- also known as mountain chickens -- out of the country to save them from extinction.
Countries that already have BdGPL should also institute quarantine, says Peter Daszak, president of EcoHealth Alliance in New York. "This research shows that recombination can occur and give rise to new virulent strains," he says. "Blocking introduction of new strains will cut down on this."
Daszak adds: "It will be hard to stop the spread of new lineages of Bd, but if we look at the devastation that this pathogen has already caused, we desperately need to try."
Journal reference: Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.1111915108 [Farrer RA, Weinerta LA, Bielby J, et al:
Multiple emergences of genetically diverse amphibian-infecting chytrids include a globalized hypervirulent recombinant lineage.
Abstract available at
<http://www.pnas.org/content/early/2011/10/31/1111915108.abstract>]
[Byline: Michael Marshall]
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Communicated by:
ProMED-mail
<promed@promedmail.org>
[Chytrid fungus has had a devastating effect on frogs for more than a decade. It is both sad and somewhat ironic that the very groups who are so passionate about these creatures as to trade them from their natural habitat may have been the perpetrators of the situation.
If this is true, then it is a huge warning. Hopefully those in the amphibian trade and other regulatory agencies will take action. - Mod.TG]
[see also:
2010
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Chytrid fungus, frogs - Worldwide: possible recovery 20101212.4421 Chytrid fungus, frogs - worldwide: review article 20100130.0323
2009
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Chytrid fungus, frog - South Korea 20090920.3301 Chytrid fungus, frog - Philippines: (Luzon) 20090527.1976
2008
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Chytrid fungus, frogs - Panama 20081014.3246 Chytrid fungus, frogs - Spain (Majorca) 20080928.3065
2007
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Chytrid fungus, frogs - Japan (02): wild frogs 20070613.1924 Chytrid fungus, frogs - Japan 20070113.0176
2006
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Chytrid fungus, frogs - worldwide: possible source 20060524.1463 Chytrid fungus, frogs - South Africa 20060203.0344
2005
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Chytrid fungus, frogs - UK (England) 20050916.2741
2004
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Red leg disease, frogs, fatal - UK (02) 20040914.2560 Red leg disease, frogs, fatal - UK 20040912.2542
2002
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Frog deformities - USA (02) 20020425.4030 Frog deformities - USA 20020422.4012 Frog mortality, virus - UK 20020201.3458 2000
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Chytrid fungus, frogs: background 20001201.2096 Frog deformities - USA (Northeast) 20000420.0579] .................................................mhj/tg/mj/mpp/ll
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