Batrachochytrium salamandrivorans

In short:

  1. Bsal infections are restricted to salamanders and newts (Urodela ), but for this group the fungus is highly pathogenic and extremely lethal.
  2. Bsal causes superficial skin erosion, deep ulcerations and skin necrosis.
  3. Bsal originates from Asia.
  4. Asian salamander species have lived in coexistence with Bsal for millions of years (Bsal separated from Bd 67 million years ago).
  5. Recently Bsal arrived in Europe.
  6. An ancient balance between pathogen and host has now been disturbed as a result of the transportation and importation of animals , consequently resulting in the mass mortality of several species.
  7. Bsal is a chytrid fungus that literally eats away at the skin of salamanders and newts.
  8. After exposure the animals die rapidly.
  9. The optimum growth temperature of Bsal is between 10-15 ˚C.
  10. Bsal has caused mass mortality and severe population declines in wild Fire Salamander, Smooth newt and Alpine Newt populations in the Netherlands, Germany and Belgium.
  11. Bsal has also been detected in captive salamanders held in Germany and England

In 2013 it became obvious what had caused the collapse of the Fire salamander in The Netherlands: the newly discovered and identified chytrid fungus Batrachochytrium salamandrivorans (Bsal) was the culprit (Martel et al. 2013). Since this fungus has a relatively low optimal temperature for growth (10 – 15 degrees) and thrives in moist environments, it was expected that soon more salamander and newt populations would fall victim to the fungus. Only salamanders and newts are susceptible to the fungus and once infection occurs the animals experience rapid mortality as a result of the erosive disease eating away at the skin (Martel et al. 2014).

Fire salamander (Salamandra salamandra) infected with the fungal disease, the skin is severely damaged. Photo: Frank Pasmans

In Martel et al.’s (2014) major study, the impact of the fungus on dozens of amphibian species from four continents, were examined. The results indicated that salamanders and newts are extremely susceptible to the deadly fungus, while other amphibians such as frogs and toads remain unaffected.

Batrachochytrium salamandrivorans (salamander-devouring ) kills: 
  • salamanders and newts die rapidly (approximately 12-18 days)
  • after a short period of ataxia, anorexia and apathy.

Bsal is the second fatal chytrid fungus which parasitizes amphibians. Phylogenetic research has shown that Bsal forms a previously unknown branch which forms a group with Bd. The genetic divergence  between the two chytrid fungi is so large that Bsal can be seen as a separate species within the order Rhizophydiales.

Bsal occupies a different niche than Bd. The optimum temperature for growth of Bsal is lower (10-15 ˚C) than that of Bd (17-25 ˚C), which means that Bsal is likely to pose a greater threat to our native salamanders and newts than Bd.

The fungus Bsal is currently on the rise in the Netherlands, Germany and Belgium and will most likely reach other countries in the very near future. Several native salamander species such as the great crested newt and the alpine Newt are, like the fire Salamander, extremely susceptible to the fungus and once infected death ensues rapidly.

The disease is highly contagious and can be easily transferred between different species of salamanders and newts. A common mode of transmission is direct contact of the animals (skin-to-skin), the dispersal of and contact with zoospores is another possible avenue.


Where does the disease come from?

Bsal originated in Asia and is believed to have arrived in Europe via the pet trade, in particularly through the import of Asian salamanders. The importation of Asian salamanders occurs around the world and in large numbers. It was estimated that between 2001-2009 more than 2.3 million Chinese fire-bellied newts were imported into America. Asian salamander species appear to carry the fungus with little or no ill-effect. Research has shown Asian salamanders and the fungus have coexisted for many years and infection records from Asia date back to at least 1861 ( Martel et al. 2014).

SITUATIon in the netherlands

Commissioned by the Ministry of Economic Affairs, the Province of Limburg and Staatsbosbeheer, RAVON has been monitoring the Fire Salamander population and examined whether the fungus was present in the vicinity. The Ministry of Economic Affairs has guaranteed there are opportunities for long-term research.The Dutch Fire Salamander population is not doing well. The latest CBS trend calculations show a decline of 99.9% over the period 1997 - 2014. In 2013 (period 1997-2012 ), the decline was at 96 %, meaning the decline has not stagnated.

Look HERE for the current distribution of the fungal disease.

What can we expect in the near future?

We predict that more outbreaks will follow, this time also involving species other than the fire salamander. Despite encouraging information that healthy looking animals have been observed at all known outbreak sites, we fear for the long term survival of the fire salamander in these regions and eventually elsewhere in Europe; Bsal will put many amphibian species on the path toward extinction.

Fortunately, a great deal of research is currently being carried out at a number of different laboratories. Fire salamander populations where the fungus was previously detected are now being intensively monitored. Hopefully sufficient knowledge can be generated in time so effective mitigation measures can be implemented and the spread of the fungus can be limited.

Mortality as a result of Bsal infections may not be obvious at first. A few dead salamanders could easily go unnoticed and may not seem alarming. Mortality, however, may have occurred as a result of a Bsal infection. So whether you find one or several dead salamanders, we recommend you contact us.

Our American colleagues  launched a website on Bsal (Bsal Taskforce), which is interesting to have a look at so you can follow all overseas developments. There are other sites too such as the webpage from AmphibiaWeb.

Shouldn't the salamander and newt trade be banned?

Based on what we know so far, we do not consider banning the trade of salamanders to be a viable solution. However, both the scientific community and hobbyist groups are pleading for a ban in the trade of wild caught Asiatic salamanders that can easily be bred in captivity. Furthermore, it has been suggested that ‘health certificates’ should be issued for all individuals guaranteeing the animals have not been infected with or do not carry the Bsal fungus. It has also been recommended for salamander keepers/hobbyists to implement hygiene protocols for their own collection which may include: a quarantine period for newly acquired animals and the proper handling of water and terrarium materials. The keeping of salamanders and newts ( as a hobby or professionally) yields information on the ecology and biology of the species, which in turn benefits the protection of these species in the wild.To find out more , please contact the Salamander Association.

  • The import and interstate transport of 201 salamander species will be prohibited in the USA from 28th January onwards.
  • In 2015 the import of salamanders and newts into Switzerland was prohibited: Import verbot für Salamander und Molche in die Schweiz.


Are you keeping salamanders yourself?

If you keep salamanders or newts in your collection , you do not want them to become infected with Bsal, or for your salamanders to spread the fungus by infecting others. Therefore,you will need to be extremely careful when adding new animals to your collection, or when you sell or give away animals to others. When acquiring a new animal, quarantine the animal for a considerable time and be careful with your waste water.

Never purchase salamanders or newts for your garden pond.

It is possible to have your animals tested for Bsal (and Bd and Ranaviruses ). To have animals tested, please contact the University of Ghent directly.

How to treat infected salamanders

Captive animals can be treated if they have been infected with Bsal. In 2015, two articles were published on this subject ( Blooi et al , 2015a ; . 2015b ).

In summary:

  • It is safe, effective and cheap to treat the infected animals by exposing them to higher temperatures.
  • The animals should be kept at 25 °C for a period of 10 days.
  • Not all species can survive being exposed to 25˚C temperatures for long periods of time.
  • For those species, the procedure can be performed at 20˚C . Additionally, the animals will need to be treated with a combination of anti-fungal agents twice daily.