Losing a bet but winning the war: fighting the deadly chytrid fungi

On World Wildlife Day, Grantham Lecturer Dr Kris Murray explains why a US ban on salamander imports is critical to stemming the spread of a new lethal amphibian disease.

I‘m not usually one for gambling, and certainly not for placing bets that I genuinely hope to lose. But last year I made a bet with a colleague that I ended up losing more quickly than I could possibly have hoped for.

The subject of this wager was a petition calling for an emergency ban on imports of all live salamanders, submitted in May last year to the US Department of the Interior by the Centre for Biological Diversity and Save the Frogs.

The US salamander trade is worth about US$10 million a year, and Americans spend over US$60 billion (yes, with a b!) on their pets more broadly. So why and more importantly how would the US impose a ruling that could threaten this lucrative trade with a sudden and expensive halt?

The why – the salamander eater Batrachochytrium salamandrivorans (Bsal)

The story really starts in the 1990s, when a bunch of herpers (the amphibian and reptile obsessed) collectively noticed that many amphibian species were becoming increasingly hard to find.

The culprit, finally identified in 1998, is now considered the most devastating disease to afflict vertebrates, ever. Batrachochytrium dendrobatidis (Bd for short) is a fungus that causes the lethal amphibian skin disease chytridiomycosis. This disease has fuelled amphibian extinctions globally, with an estimated 200 species lost in less than 50 years. This rate of extinction is unbelievable, over 10,000 times higher than normal.

There is no comparison for a similarly catastrophic human disease, since our species wouldn’t be around now to reflect on it if there was.

So when a second species of fungus causing chytridiomycosis was discovered in Europe in 2013, scientists were quick to sound the alarm. The new fungus, Batrachochytrium salamandrivorans (Bsal for short), affects exclusively salamanders. The fear is that if Bsal turns out to be anywhere near as devastating as Bd, then it could wreak havoc on salamander biodiversity globally.

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Alpine salamander. Image credit: Kris Murray

The how – stopping the flow of disease at the border?

Studies on Bd have shown that the global trade in amphibians is the most likely cause of the emergence and spread of an extra-nasty Bd strain, responsible for most of the carnage. Since North America is the centre of global salamander biodiversity, hosting about half of the world’s salamander species, researchers there quickly cobbled together a risk assessment for the importation of Bsal via wildlife trade and called for an immediate precautionary ban on salamander imports.

By the time this assessment was published in Science in July last year, the petition had already been submitted. But could such a ban actually be enacted?

Calling on the Lacey Act – the original wildlife protection law

Fortunately, a couple of little precedents have helped smooth the way for decision-makers to actually consider such a blanket ban on salamander imports.

In 2009, US charity Defenders of Wildlife (DoW) submitted petitions urging two US Departments to regulate amphibian imports to block the threat of Bd. Although Bd was already widespread in the US at that time, the idea was that restricting additional imports and circulation of Bd strains would reduce the risk of further biodiversity impacts.

To support their case, DoW pointed towards the ‘Injurious Wildlife’ listing mechanism of the Lacey Act, the oldest US law that serves to protect wildlife. Species can be listed as injurious if they pose a threat to the health and welfare of humans, agriculture, horticulture, forestry or wildlife. Once listed, imports and transport of species can be regulated.

Although no amphibians had ever been listed as injurious, and for the most part the law has been used to prevent the introduction and spread of dangerous invasive species (although not necessarily the dangerous pathogens they may carry with them), DoW noted that a precedent did in fact exist –  ‘all salmonids’ could be listed for their potential to introduce harmful viruses.

Six years on, however, the Bd case is still pending, most likely due to the mammoth complexity of effectively ruling out trade on all amphibian species to combat a pathogen that is already present.  But that’s another story.

When losing is winning: the ruling on Bsal

With progress on the Bd petition stagnating, I wasn’t optimistic about the prospects of the more recent Bsal petition. I put my money on its rejection, while colleague Prof Mat Fisher, fungal epidemiologist and Batrachochytrium aficionado at the School of Public Health at Imperial College London, bet on its success.

The outcome: on 12 January 2016, the US Fish and Wildlife Service issued an interim notice prohibiting the importation and interstate transportation of 201 species of salamander across 20 genera, dead or alive, in parts or in whole, “to protect the interests of wildlife and wildlife resources” from the potentially devastating impacts of Bsal. The ruling came into effect on 28 January – its success and longevity will now be closely monitored following a solicitation for public comment period, which remains open until March 14.

So while I miserably lost the bet (and the alcoholic beverage at stake), I’m hopeful this ruling is a sign that we’re finally getting serious about waging a war on potentially catastrophic diseases circulating in the wildlife trade.

Now that’s something worth celebrating today on World Wildlife Day, which after all marks the (now 43rd) anniversary of the signing of the Convention on International Trade in Endangered Species (CITES), for which the Lacey Act set a powerful precedent.

 

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