Frogs fight back against deadly bacteria

More than 30 years ago, amphibian researchers from around the world gathered in Canterbury, England, for the first World Congress on Herpetology, sharing the same horrifying stories over drinks.

Frogs disappeared from the wild, and no one could explain why.

“It was a scary time,” Australian veterinary scientist Lee Berger recalls. He was one of the first to identify the culprit in the 1990s. Batrachochytrium dendrobatidis, Or BD.

Scientists now know that this sneaky threat originated in East Asia and was probably accidentally spread by people to every continent except Antarctica.

This parasitic fungus is both deadly and contagious, wiping out some frog populations within weeks. And until recently, it turned out to be almost unstoppable. Despite more than 25 years of intense research, conservationists have not devised a panacea that can prevent Bd infections or save frog populations affected by the Bd-induced skin disease chytridiomycosis.

Bd is thought to be involved in the decline and possible extinction of approximately 200 species of frogs.

But now Berger and other researchers have found reason for optimism. There is evidence that some frogs. Naturally evolving resistance. Scientists are also trying to take advantage of the fungus’ temperature sensitivity by creating Bd-free habitats or moving frogs to areas where the fungus cannot survive. Additionally, some researchers are studying viruses that could be used to attack Bd and ultimately reduce its toxicity. These innovative strategies are emerging like slimy rays of hope in a dark landscape.

Chytridiomycosis is fatal, as the skin is an integral part of the frog’s cardiovascular system. When the chytrid fungus colonizes the skin, electrolytes are no longer absorbed. This disrupts the heart’s electrical rhythm and the animal dies of heart failure.

However, while effective at killing some frog species, the fungus is very sensitive to heat, and the disease progresses slowly at temperatures above 30 degrees Celsius (about 85 degrees Fahrenheit).

The yellow-spotted frog, which lives in the humid tropics of Queensland, Australia, appears to have adapted its habitat to take advantage of the fungus’ Achilles heel. The frog, thought to have become extinct about 20 years ago, no longer lives in shady areas near waterfalls in the mountains of the forest. However, populations persist in warm, sunny regions. Biologist Conrad Hoskin from James Cook University in Queensland says that’s probably because the frogs can rest on sun-baked rocks all night, increasing their body temperature and protecting against Bd. .

Since 2013, Hoskin has been transplanting yellow-bellied frogs from surviving populations to similarly sunny new habitats and closely monitoring the health of these new colonies.

In a larger effort, Hoskin and colleagues recently assessed the ranges of 55 frog species in eastern Australia, including 25 species affected by Bd. They found that even though this fungus has reduced the range of affected species, they are still present. persists in warm lowlands It’s raining more.

Other researchers are also trying to move populations of Bd-infected frogs to rescue dying frogs or spread the recovery. Of the 15 attempted migrations in Australia over the past 20-odd years, 7 populations are holding out And three are thriving.

Providing amenities to the frogs also helped. Anthony Waddle, a conservation biologist at Sydney’s Macquarie University, built an insulated shelter out of large bricks prefabricated with holes that happen to be the perfect size for the green-and-gold bell frog. The sick frogs that were hanging out in these “frog saunas” Reducing infection load Waddle et al. reported that patients recovered in the shade in 2024. nature.

As this gradual progress continues, scientists are racing to understand why some frog species are more susceptible to Bd than others. Conservation biologist Tiffany Kosh, who works with Berger in the One Health Research Group at the University of Melbourne’s School of Veterinary Medicine, is taking a genetic approach. Kosh recently sequenced the genome of the southern corroboree, a black, bright yellow frog of which fewer than 50 individuals remain in the wild. If scientists could learn which version of the gene is associated with Bd resistance; Breeding and releasing resistant frogsThe researchers also discovered a weaker strain of Bd, a fungal virus that appears to infect pathogens for pathogens. Although we have a long way to go to use such viruses to fight Bd, they may one day become another weapon. “In the science fiction version, you spray a virus in a field and all the frogs survive, and that’s the hope,” said Jason Starzic, a mycologist at the University of California, Riverside. Recent reports about viruses in current biology.Berger said, Latest information on Australian frogs and Bd in 2024 Annual Review of Animal Biosciencessays that despite losses, optimism is key to conservation efforts. “We have to choose to focus on the positive,” said Andrea Adams, an ecologist at the University of California, Santa Barbara. I am. “We cannot afford to take a hands-off approach.”

10.1146/knowable-110624-1

Martin J. Kernan is a science writer from central New York who became interested in slimy creatures as a child by spending hours, unsupervised, up to his elbows in pond mud. I think it’s because of what I’ve been through. This article was first published Magazines you should knowan independent journalism initiative from Annual Reviews. please read Click here for the original.