Todayโs path rounds are on ๐๐ก๐ฒ๐ญ๐ซ๐ข๐๐ข๐จ๐ฆ๐ฒ๐๐จ๐ฌ๐ข๐ฌ!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐ก๐ฒ๐ญ๐ซ๐ข๐๐ข๐จ๐ฆ๐ฒ๐๐จ๐ฌ๐ข๐ฌ is a fungal infection of the skin of amphibians. Unfortunately, this disease has caused population declines in many wild amphibian species. Sometimes, it can even occur as outbreaks leading to a massive mortality event.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
This disease affects any amphibian, but we most commonly think of it in frogs and salamanders.
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
The main cause of chytridiomyocosis are fungal species called ๐๐๐ญ๐ซ๐๐๐ก๐จ๐๐ก๐ฒ๐ญ๐ข๐ฎ๐ฆ. This fungus infects the skin of the amphibians. Its life cycle begins with fungal bodies in the skin maturing to form ๐ณ๐จ๐จ๐ฌ๐ฉ๐จ๐ซ๐๐ง๐ ๐ข๐ containing many infected ๐ณ๐จ๐จ๐ฌ๐ฉ๐จ๐ซ๐๐ฌ that have a flagella, allowing them to swim through water. These zoospores will infect other amphibians continuing the life cycle.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
These fungi interrupt the normal function of the amphibian skin. This produces a rough skin texture, ulcers and a brownish or reddish skin discolouration. The skin of these amphibians also sheds incorrectly, called ๐๐ฒ๐ฌ๐๐๐๐ฒ๐ฌ๐ข๐ฌ. With this condition, the shedding skin comes off in small flakes rather than the typical large sheets.
The major consequence of this poor skin function is an inability to regulate their electrolytes, like sodium. These animals become ๐ก๐ฒ๐ฉ๐จ๐ง๐๐ญ๐ซ๐๐ฆ๐ข๐ (low sodium), ๐ก๐ฒ๐ฉ๐จ๐ค๐๐ฅ๐๐ฆ๐ข๐ (low potassium) and ๐ก๐ฒ๐ฉ๐จ๐๐ก๐ฅ๐จ๐ซ๐ข๐๐๐ฆ๐ข๐ (low chloride), and ultimately die from cardiac arrest.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
The best way to diagnosis this disease is a skin biopsy, in order to visualize the fungi directly. Within the skin, a pathologist would be able to see ๐ก๐ฒ๐ฉ๐๐ซ๐ค๐๐ซ๐๐ญ๐จ๐ฌ๐ข๐ฌ (thickening of the skin layers) with many ๐๐ก๐ฒ๐ญ๐ซ๐ข๐ ๐ญ๐ก๐๐ฅ๐ฅ๐ข (the skin-living form of the fungus). Often you can also see ulceration and ๐ง๐๐๐ซ๐จ๐ฌ๐ข๐ฌ (cell death) of the skin cells.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
The main treatment options being explored are temperature therapy and antifungal therapy. With temperature therapy, the amphibians are heated beyond the normal living temperature of the fungus. Antifungal therapy involves applying drugs toxic to the fungus to the amphibian, however this can be risky due to the highly absorptive nature of amphibian skin. Because of the high risks of treatment, these treatment protocols need to be completed under the supervision of a qualified veterinarian.
๐๐ก๐จ๐ญ๐จ๐ฌ
1-4) Sad frogs with chytridiomycosis, showing reddish brown skin and poor skin shedding.
5) A salamander showing black to brown dots of chytridiomycosis.
6-7) Absolutely beautiful microphotos of chytrid thalli in the skin of a frog!
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Terio, KA, McAloose, D, St. Leger, J. Pathology of Wildlife and Zoo Animals. 2018.
Photos 1-2, 6-7 ยฉ Noahโs Arkive contributors Terrell, Rech licensed under CC BY-SA 4.0.
Photo 3 ยฉ Wikimedia Commons contributor Gratwicke licensed under CC BY 2.0.
Photo 4 ยฉ Wikimedia Commons contributor Voyles licensed under CC BY 2.5.
Photo 5 ยฉ Wikimedia Commons contributor van Rooij licensed under CC BY 4.0.
