According to a report in the journal Scientific Reports, a new strain of ranavirus* is wreaking havoc in Portugal's amphibian populations.
The infectious agent that causes the epidemic is highly virulent and in addition to amphibians, it now is affecting fish and reptiles.
Jaime Bosch, a researcher at the National Museum of Natural Sciences in Madrid, the author of the study, explained that "ranavirus has long been known, although in recent years globalisation is triggering massive mortalities around the world. In addition, new strains continue to arrive, probably, from Asia."
The fact is that Spain is not immune to this infectious agent and runs the risk of "ending up like Portugal."
According to Bosch, "we have had infected Spanish amphibian populations probably for several decades. In 1992 we discovered what would be the first case known in Spain but at that time we did not know exactly which organism was the cause of the problem.”
Gonçalo M. Rosa, of the Center for Ecology, Evolution and Environmental Changes in Lisbon adds that "viruses of this genus are found all over the world and can infect several groups of animals."
But different strains have different degrees of virulence and in the Serra da Estrela national park, one is circulating that belongs to a hypervirulent group called CMTV-Ranavirus. This new strain has been associated with the annual mass mortality of several species of amphibians, similar to that recorded in the north of Spain.
In 2009 hundreds of midwife toads (Alytes obstetricans) were found dead in one of the ponds in the Serra da Estrela park.
One of the best known cases in Spain is the one that occurred in the Picos de Europa national park, where several populations of amphibians were wiped out. The problem is that there is no effective treatment.
Another case is being investigated in Pontevedra, Galicia and "three episodes of massive mortalities related to these viruses have been detected and there are cases in other areas of Spain that have not yet been published."
This situation is a challenge for wildlife managers, and raises an urgent need to concentrate conservation strategies for amphibians.
While it is currently possible to clear up certain cases of infection back in the laboratory, little is known about this new ranavirus group, “We do not know how to treat individuals with ranavirosis nor how to mitigate the problem in the field,” warned Gonçalo Rosa, as research contines.
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*Ranavirus is a genus of viruses, in the family Iridoviridae. There are four other genera of viruses within the family Iridoviridae, but Ranavirus is the only one that includes viruses that are infectious to amphibians and reptiles.
