A viral outbreak is killing amphibians, including frogs, toads and salamanders, in the Picos de Europa National Park in Spain. As if the imminent local extinction of amphibians wasn’t grim enough in itself, their disappearance, scientists fear, could also tip the ecological balance in favour of species amphibians feed on.

A team of researchers from Spain and the United Kingdom started monitoring amphibians in the national park in 2005 when they first noticed a die-off from viral infection. The team is now the first to report two related, highly infectious viruses – the ranaviruses – simultaneously infecting multiple amphibian species at several locations in Spain.

A diseased common midwife toad tadpole in Picos de Europa National Park. Image: Jaime Bosch

Ranavirus infection is often associated with severe disease and mass deaths of amphibians but previously decline of only one amphibian species had been [quantified]. Here, we show three amphibian species showing simultaneous population collapses in the Picos National Park,” says Stephen J. Price, researcher at University College London and an author of the study published today in the journal Current Biology.

Price and his fellow researchers found Ranavirus infection killing larvae, juveniles and adults of all the six common amphibian species resident in the park. However, three species – the common midwife toad, alpine newt and common toad – have suffered the most, with sharp population declines seen over 2007 to 2012.

The researchers also believe that similar viruses are emerging across Europe. “In the past five years, there have been sporadic reports of die-offs elsewhere in Europe, for instance, in France and Netherlands. This is obviously a worry considering the impacts we have seen in the Picos,” Price warns.

Price’s team also found a Ranavirus closely related to the one in the park killing a different set of amphibians at a site located 200km away.

“Amphibians do seem vulnerable right now; they are the most threatened vertebrate group on earth. But that they rely on land and freshwater to complete their life cycle probably exposes them to more risks and environmental impacts than other groups of animals,” Price explains.

K. V. Gururaja, amphibian expert at the Indian Institute of Science in Bangalore, who was not involved in the study, says the local extinction of amphibians will disturb the food chain and result in a spike in insect numbers.

According to Gururaja, “If we isolate the infected area and contain the spread of disease, amphibian populations might survive elsewhere.”

Image: Tero Laakso, Flickr