Researchers at Oregon State University and the University of Pittsburgh have found that bullfrogs are not just the carriers of amphibian fungus but are also susceptible to it.
Contrary to popular belief that bullfrogs have over time become immune to the fatal amphibian fungus, which they are responsible for carrying and spreading, researchers at Oregon State University and the University of Pittsburgh have found that bullfrogs too die from diseases caused by this fungus.
A two-year study shows that the pathogen has led to a significant amphibian decline around the world. A previous research revealed that the African clawed frogs carried the same virus, which led to the extinction of many amphibian species around the world. These frogs were found immune to the fungus, but it severely affected other species of frogs and salamanders.
Now researchers have found a strain of the fungus named Batrachochytrium dendrobatidis, or Bd, in bullfrogs grown in controlled experimental conditions, and discovered that some juveniles were susceptible to this strain.
Nearly 40 per cent of all amphibian species are either extinct or on the brink of it due to various factors including infection from this fungus. Habitat loss, climate change, pollution, insidious species, increased UV-B light exposure are some other reasons for their decline.
The Bd fungus leads to the thickening of skin by up to 40 percent than normal and causes heart attacks in just weeks after infection, said a conservation biologist at San Francisco State University, Vance Vredenburg, who was not involved in this study.
Stephanie Gervasi, a zoology researcher in the OSU College of Science, says that the bullfrogs are not the sole culprits for the decline of amphibian population around the world, but they are also the victims of the infection just like other species of amphibians.
Despite researchers finding the host for the pathogen, it is still a cause of concern and as to how Bd has spread so quickly in several parts of the world.
"One possibility for the fungal increase is climate change, which can also compromise the immune systems of amphibians," Andrew Blaustein, a distinguished professor of zoology at OSU and international leader in the study of amphibian declines, said in a statement. "There are a lot of possible ways the fungus can spread. People can even carry it on their shoes."
Although the bullfrogs are hosts to the deadly fungus, they cannot be blamed solely for the spread of the infection. The bullfrogs have the ability to reduce the infection and even eject it out of their system over time, say researchers. A rapid spread of the fungus into different parts of the world may have been caused by the international trade of other fungus-carrying amphibian species, researchers suspect.
The study is published in an online professional journal EcoHealth.