Fighting the salamander-eating fungus

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Recent findings that the salamander-eating chytrid fungus known as Bsal is widespread in the private amphibian trade has further heightened concerns about amphibian conservation in Europe. Liam Fitzpatrick, PhD student at ZSL’s Institute of Zoology, talks what these results might mean for salamanders in captivity and in the wild.

Amphibians are having a tough time, to put it mildly. Of the 6,682 amphibian species listed on the IUCN RedList, almost a third are threatened with extinction and as a group, they are declining more rapidly than birds or mammals. One of the major threats to amphibian biodiversity is “the worst infectious disease ever recorded among vertebrates” – chytridiomycosis. 

A diseased Lissotriton boscai on a towel
Bsal often causes amphibians to be in poor body condition and lose full control of their movements, as was the case in this diseased Bosca’s newt (Lissotriton boscai)

We have known about the fungus that causes chytridiomycosis, Batrachochytrium dendrobatidis or Bd, since the mid-1990s but our efforts to minimise its impact have had only limited success. Scientists from around the world have watched in horror as this disease has caused declines and extinctions in over 200 amphibian species. As if this wasn’t bad enough, in 2010 a second, closely-related chytrid fungus was discovered in the Netherlands where it was decimating fire salamander populations – more than 99% of the population died in a little over four years. Batrachochytrium salamandrivorans, or Bsal for short, is known as the “salamander-eater” for the way that it attacks and erodes amphibian skin. We believe that it was introduced to Europe from Asia via the pet trade, and studies have shown that not only is Bsal lethal to fire salamanders, it can actually kill a wide range of European and North American salamanders. Stopping this disease from spreading into new areas and devastating further salamander populations has a quickly become a key goal in amphibian conservation. 

In order to stop the spread of Bsal into new areas in the wild, we first needed to know more about Bsal in the pet trade – is it widespread or in only a few collections? What sorts of impact is Bsal having on captive salamanders? How is it being transferred from place to place, and can we stop this? Our new paper, published in Scientific Reports last week, tried to answer some of these key questions. 

Scientist checking for Bsal
Liam Fitzpatrick swabs a newt at a private amphibian collection to test for Bsal
As we reported in 2015, Bsal had already been found in a captive amphibian collection in the UK, where three salamanders became sick and either died or were euthanased shortly after being purchased. This seemed like a good place to start our research. From this index case, we identified the source of those infected animals and tested all the newts and salamanders from that source collection. We then identified where those amphibians had come from and, for animals that had been brought into the collection in the last two years, we reached out to the owners of those collections to test their amphibians too. By repeating this process with each new collection that we tested, we began to build up a network of private amphibian collections across Europe that were all linked through recent trade of amphibians. This method is called “contact-tracing” and is widely used in disease outbreaks in humans (you might have heard about it being used to identify potential Ebola cases) and it was very effective in helping us to identify further amphibian collections that we could test for Bsal. The majority of the collectors that we contacted were very keen to work with us on this study, sharing their knowledge and expertise and learning more about this deadly disease.

In total, we tested 11 private amphibian collections in four countries; the United Kingdom, the Netherlands, Spain and Germany. In seven of these collections, we found at least one individual that tested positive for Bsal infection, and five of the positive collections had salamanders dying in numbers they had never seen before. It appeared that infections were being introduced to new collections through the trade of infected salamanders and once introduced, Bsal could have dire impacts on the health and welfare of the collection as a whole. These results are also very concerning for the health of wild amphibians, as having Bsal in captive collections in two countries where it is not known to be in the wild (UK and Spain) increases the risk of the disease spilling over into wild amphibian populations there. Like most of Europe, both of these countries have native amphibian species that are known to be susceptible to Bsal disease, so preventing the fungus from reaching these wild populations is absolutely essential. Our results are likely to only be the tip of the iceberg of Bsal infections in the European pet trade, so it is very important that everyone involved remains vigilant and takes the necessary steps to prevent the disease from being introduced into the wild.

A Lissotriton boscai held in hand, being swabbed
Scientists use a swab to check whether this Bosca’s newt (Lissotriton boscai) is infected with Batrachochytrium salamandrivorans – a fungus that infects amphibian skin with potentially deadly consequences

So, what can be done? How can we help prevent Bsal from spilling over into wild amphibian populations and save the salamanders? Well, for a start, if you have pet amphibians at home, maintaining high levels of biosecurity and testing your animals for Bsal is essential. Quarantining new purchases, disinfecting equipment and wastewater and treating any infected animals are all relatively easy to do and will make a huge difference to the health of your collection and help prevent diseases impacting local wild amphibians.

And if you don’t own amphibians? If you see any sick or dead amphibians in the UK, report it as soon as possible to the Garden Wildlife Health project, and if you can, follow their protocols to submit the carcass for testing. You will receive a detailed report of the findings and will be making a real difference to the conservation of native amphibians.

ZSL is one of several institutions across Europe working to mitigate the impacts of Bsal to European salamanders and newts. For further information on Bsal research, biosecurity and hygiene protocols and ongoing conservation efforts, go to: 

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