Scientists today know that when rescuing amphibians from a chytrid-tainted environment, it’s important not to accidentally let the fungus hitch a ride on the soles of their boots. Clorox signed up as the first corporate sponsor of Amphibian Ark’s rescue mission because its bleach is used to remove the fungus from gloves and boots and equipment. Dwindling amphibian populations are being placed into the protective custody of zoos and other conservation organizations for captive breeding — with the goal of eventually reintroducing them into the wild.

People didn’t know about chytrid back in the early 1990s — at least they didn’t know what it does to most amphibian species. And now, we’re learning of a case in which a captive breeding program for Mallorcan midwife toads resulted in chytrid-carrying toads being released into the wild. Here’s an excerpt from the story in Science Daily:

The new study suggests that an endangered species of frog from South Africa, Xenopus gilli, which was housed in the same room as the Mallorcan midwife toads, was responsible for spreading the infection to them.

The captive breeding and reintroduction programme for the Mallorcan midwife toad has been highly successful in increasing the numbers of the rare toad on the island. Over half of all the current populations on Mallorca are derived from reintroductions.

Although the chytrid fungus can be deadly, toads appear to be doing well in three out of the four populations in Mallorca infected with the chytrid fungus. This finding suggests that there are unidentified factors that are preventing these populations from extinction. The situation is being closely monitored by the Mallorcan conservation authorities.

Global efforts to save amphibians from extinction hinge on species being taken into captivity and bred until they can be reintroduced to the wild. The researchers behind the new study say their findings reveal the risks of reintroducing species into the wild even when health screening is carried out, and highlight the need to ensure that species bred in captivity do not become infected with pathogens from other species.

As soon as Bd was discovered in the late 1990s, screening for the disease was incorporated into amphibian conservation plans. Zoos are now moving towards breeding threatened frogs in strictly quarantined, biosecure facilities in an effort to prevent the disease spreading in captivity.

The chytrid fungus has also been added to a list of diseases that need to be quarantined compiled by the World Organisation for Animal Health. It is hoped that these quarantine measures will help those involved in conservation efforts to stop Bd from spreading further, by controlling the international trade in infected animals.

Dr Mat Fisher, one of the authors of the study from the Department of Infectious Disease Epidemiology at Imperial College London, said: “Our study has shown that species reintroduction programs can have unpredicted and unintended effects. However in this case we believe that the toads are going to survive the infection. The global conservation community is united in its goal of saving species from the effects of Bd and we now have international legislation which should prevent this disease being accidentally introduced into the wild.”

The researchers reached their conclusions after comparing the specific genotype of Bd from infected wild toads from across Mallorca, and infected toads from mainland Spain, the UK and the rest of the world. They found that the disease in all Mallorcan toads was of the same genotype, and that this was a different genotype from those on mainland Europe and elsewhere.

Bd infects amphibians’ skin and is thought to interfere with their ability to absorb water. Over 257 amphibian species are known to be affected by Bd. Some species are very susceptible and die quickly while others, which are more resistant, are carriers of the pathogen.

Background on the Mallorcan Midwife Toad

Mallorcan midwife toads had been known only from fossils and were thought to be extinct until 1978, when they were ‘discovered’ hiding in inaccessible gorges in the northern Mallorcan mountains.

The Mallorcan midwife toad is on the list of the 800 species most likely to go extinct in the near future unless they receive special protection. They are ranked 55 on a list of the 100 species most threatened with extinction according to the Zoological Society of London EDGE ratings.

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