Implications for trade in all exotic animals period pretty big
NEW SCIENTIST (London, UK) 07 November 11 Frog-killer disease was born in
trade (Michael
Marshall)
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 first
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 five continents. Tests on tadpoles also revealed
that the strain was
extremely virulent.
BdGPL's genome showed that it had formed when two 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've 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 two 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
http://www.newscientist.com/article/dn21133-frogkiller-disease-was-born-in-trade.html
