Oregon spotted frogs soaking in an anti-fungal bath. Photo: Josh Banta

When considering the biggest threats to endangered animals, the worst offenders are usually climate change, habitat loss or invasive species. A strange fungus likely wouldn’t be at the top of your list, but chytrid holds a significant role in the ongoing decline of amphibian populations.

In just one year we have learned so much about the treatment for this fungus and the early signs of detection. 

This is why our work is so important. Not only are we working to supplement the wild population of Oregon spotted frogs, and save this species, but we are also carrying out work that will benefit amphibians globally.

Oregon spotted frog. Photo by: Pourya Sardari

What is chytrid?

Chytrid fungi are a group of microorganisms belonging to the fungal kingdom. Affecting over 700 species globally, they have gained notoriety due to their parasitic nature and their ability to infect amphibians, particularly frogs and salamanders. The most prominent chytrid fungus responsible for the decline in amphibian populations is Batrachochytrium dendrobatidis (Bd). By infiltrating the keratinized skin of amphibians (the outer layer of skin), the fungus prevents frogs from being able to breathe through their skin, an incredible and critical process… especially during hibernation.

Infected amphibians might show symptoms like lethargy, loss of appetite, skin roughness or sloughing. It may even lead to death. This fungus presents a global issue and can be found in many wild populations around the world, including many in BC. Since this fungus can contribute to mass extinctions in amphibians, like the extinction of the golden toad of Costa Rica.

Although it is suspected that the spread of this disease could be due to the importing and exporting of amphibians around the world, we still have a lot more to learn, and the full impact on the endangered Oregon spotted frog is still not understood fully.

What we have learned

With the origin of the fungus remaining uncertain, information sharing is more important than ever. Although our work does not directly focus on the origin or causes of this fungus, each time the frogs in WPC’s breeding program are infected, we learn a little bit more about it.  Andrea Gielens, WPC’s lead biologist for our Fraser Valley Wetland Recovery Program, has experienced this fungal infection four times and has determined the most successful antifungal treatments for our population of Oregon spotted frogs.

In December 2022, when we first saw some of our frogs die practically overnight, we tore apart enclosures and saved the rest of the population by placing them in hibernating fridges until we could figure out what was going on. After swabbing both deceased and live animals, we quickly realized that we were dealing with chytrid.

Deciding whether we should wake the frogs, treat them and potentially lose our breeding season the following year, or if we should treat them in hibernation was a tough decision. We chose to treat them in hibernation, knowing this was uncharted territory, with only a handful of conservation organizations in the world having done this type of treatment for chytrid, and none of them with this species during hibernation.

The treatment included bathing the animals in an anti-fungal solution. After the first round of baths, chytrid was still present. This fungus wasn’t going down without a fight. After two rounds of treatment and over 100 baths, we finally received negative test results from the pathology lab.

Fast forward to the beginning of October 2023, we detected chytrid… again. Except this time we know what we are dealing with and what dosage works.

We will now follow a testing schedule, where we will be investigating the timeline for infection, if any, of our frogs to determine the best solution for husbandry and care of the colony. Right now our frogs are just finishing up their round of treatment. This will be followed by two rounds of testing. If they test negative both rounds then they are set to go back into their sterilized hibernation enclosures and if not, we will treat and test again!

Update: Round 1 of chytrid testing for the frogs came back negative! Now we wait a week and a half till second testing, fingers crossed.

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