For almost two decades, research about chytridiomycosis has been increasing worldwide, becoming one of the major concerns for the conservation of global biodiversity. However, until now we have not been able to eliminate the pathogen from the natural environment, and all of the efforts against the disease was limited to trying to prevent its spread and establish captive colonies if the species went extinct in nature.
Although the global eradication of chytridiomycosis is impossible, it is important to count on the possibility of eradicating pathogenic fungi from the natural environment, even though it would be locally and only under specific environmental conditions. To develop a methodology to eradicate fungi from the environment has been a great challenge, and, finally, after a lot of effort, we have succeeded on the island of Mallorca. In the last issue of the prestigious journal Biology Letters, we described the first case in the world to eradicate the pathogen from the environment. It has been 7 years of work in Mallorca collaborating with the Balearic Government’s Ministry of Environment to arrive at eliminating the fungi from Balearic midwife toad populations or ferreret (Alytes muletensis).
Unfortunately, some ferreret populations were accidentally infected through a recovery program for the species in the 1980s, when the scientific community was unaware of the existence of pathogenic fungi. Fortunately, the infection was very localized and only affected small populations, but there was an enormous risk of it dispersing into the nearby streams that host more than half of the species. The Balearic government responded bravely, prohibiting public entrance into the infected areas, and establishing standards to minimize the risk of canyoneers dispersing the fungi.
The analysis of the adult specimens indicated to us that all of the infected carriers were found in larvae. In addition, the mathematical models by other colleagues pointed out that, in order to end the fungal population, it would be sufficient to eliminate only a substantial part of the infection. So, we decided to treat all of the larvae in the laboratory with fungicide and completely dry the pools in order to destroy the fungal spores. It was a tremendous effort, walking for hours through steep ravines, using climbing equipment to reach the most inaccessible areas, and carrying thousands of larvae back in water bottles. The Balearic government helped us with helicopters to move the larvae and took care of the animals for months until they could be freed. However, after all of this effort, and after releasing the animals in clean pools of water once they were filled anew with rain, we checked with frustration that the larvae had returned to being infected.
The situation worsened by the minute, and one of the infected population torrents, which once numbered with more than 2500 larvae, was already at the point of disappearing. So, we decided to repeat the process, but this time applying a potent disinfectant around the bedrock of the pools after removing the water and all of the specimens we could capture. It was a longshot, but we thought that the conservation of the ferreret was the priority.
And this time it worked! Two years after the disinfection, the majority of the treated sites remain free of fungi, and the pools have returned to life, without any appreciable impact on the ecosystem.
We are very close to completely eliminating the damn fungi from Mallorca, and this experience has driven us to continue in other infected areas, where we are already planning similar actions.
Many thanks to all of those we have helped us, and especially to our friends from the Majorcan Ministry of Environment for their courageous commitment towards the conservation of the ferreret (Joan Mayol, Joan Oliver, Eva Moragues, Gloria Fernández, Samuel Pigna, Xavier Manzano, etc., etc.)