How it all started

It has only been a year since the salamander eating killer fungus Batrachochytrium salamandrivorans (hereafter Bs.) has been discovered and described after it brought the Dutch population of fire salamanders, Salamandra salamandra terrestris, to the brink of extinction. An ex situ program was set into place to rescue the survivors of the fungal onslaught. Later in 2014 the disease reared its head in Belgium and caused mortalities in two locations of fire salamander populations. It is to be expected that the disease will spread to other places in Europe and possibly to other continents. This novel disease was found to be lethal and highly transmissible and for now unstoppable, but were did it come from?

Where did it come from?

In the most recent edition (346) of Science an article by the leading author An Martel has been published on the origins of this fungus. After testing five thousand amphibians from four continents, the fungus was only found in Europe and Asia (the Netherlands, Belgium, Japan, Thailand and Vietnam). The fungus has been in Asia for approximately 30 million years. The salamanders and newts in that area are adapted to the fungus deleterious effects due to millions of years of co-evolution. In other words, they have gained resistance to the fungus. So, how did Bs. find its way to Europe?

The authors believe that Bs. Was vectored to Europe by the pet trade from Asia to Europe. Large amounts of Asian salamanders and newts are being traded every year globally. For example, 2.3 million Chinese fire belly newt (Cynops orientalis) were being imported to the US between 2001 and 2009 as pets. This study indicates that this species may be a carrier of Bs. In the case of the first outbreak of the disease in the Netherlands the authors think the culprit is an imported Asian newt. The disease is easily transmitted between individual animals, either by direct contact or substrate. Globalization has its downsides.

Who should be scared?

Now that we know where it comes from, which species are at risk? The authors tested 44 salamander species from Europe and North Africa and found that 41 of these easily succumbed to the disease. Great crested newts (Triturus cristatus), a common European species with a huge distribution, for example readily died after infection. This is just one of many European newt species that could be facing massive declines in the future. But also geographically more restricted and already threatened species like Strinati’s cave salamander (Hydromantes strinatii) from France and Italy die after infection in lab conditions. Anurans do not seem to be susceptible to the disease under lab conditions.

Salamanders and newts in the Americas, the hotspot for salamander diversity globally, are not safe either. As mentioned many Asian salamanders and newts are being imported to the US annually. It just takes some infected animals to spread the disease to indigenous populations. Not much is known yet of the susceptibility of North American salamanders and newts. However, testing has been done abundant and wide spread species like the Easter red-spotted newt (Notophthalmus viridescens) and the rough skinned newt (Taricha granulosa). Mortality rates in these test were 100%. It may be possible that far more American species are susceptible and that when Bs would hit the Continent it could be devastating for hundreds of species. It seems to be the case that it is more of a question of when Bs will arrive in the Americas and not if.

The main thing is that unlike Asian salamanders and newts European and American species are naive to the disease. This means that they haven’t co-evolved with the fungus and have no resistance to it. This is what makes this disease so deadly for species on these two continents.

Future?

Either way, both in Europe as in North America lies a great challenge in mitigating the effects of the disease and reducing its distribution. One way could by regulating wild caught amphibians imports for the global pet trade and screening them for infection with Bs. More research on this disease and legislation concerning importing salamander from Asia for the pet trade are necessary!

References

A. Martel, M. Blooi, C. Adriaensen, P. Van Rooij, W. Beukema, M. C. Fisher, R. A. Farrer, B. R. Schmidt, U. Tobler, K. Goka, K. R. Lips, C. Muletz, K. R. Zamudio, J. Bosch, S. Lotters, E. Wombwell, T. W. J. Garner, A. A. Cunningham, A. Spitzen-van der Sluijs, S. Salvidio, R. Ducatelle, K. Nishikawa, T. T. Nguyen, J. E. Kolby, I. Van Bocxlaer, F. Bossuyt, F. Pasmans. Recent introduction of a chytrid fungus endangers Western Palearctic salamanders. Science, 2014; 346 (6209): 630 DOI: 10.1126/science.1258268