S6 E7: It's Not Easy Being Green: The Story of Frog Fungal Disease

0:06 I'm Dawn and I'm Cole and Scottish Murders is a true crime podcast dedicated to people from or living in Scotland. Just like anywhere else in the world, these murders can be truly horrific and shocking and we want to shine more light upon them. Join us every two weeks on Scottish Murders. Where will bring you cases both solved and unsolved, giving you an insight into the other side of Bonnie Scotland. Find us wherever you stream your podcasts, as well as on social media. Join us there bye. What is Cause of Crime?

0:48 Because of Crime is a true crime podcast that focuses on the cause of each crime. We focus on the killers, we focus on the disappearances, We focus on them murderers, so we focus on parties that could be responsible, but dive into theories. We dive into different things that could have happened. But we also give our opinions and we banter and we talk about it and we give different points of view because we're different people. Our primary focus a Cause of crime is the focus on the victims and their stories and keep them alive, keep their stories going, keep their memories going. If they're long gone from this world or we just don't even know what happened to them.

1:30 We want to keep them talked about, and that is our singular goal. My name is Tracy and I'm the primary host and creator of Cause of Crime. I created this podcast for this reason and one reason only, to keep talking about people that need to be talked about, to keep doing this and using my voice to make sure I'm making some kind of difference. So if you'd like to join us and dissect each Cause a Crime with us, you aren't more than welcome to do so. My co hosts are Dan and Chris, and they alternate each week. You can check us out on all podcasting platforms at eleven am on every Wicked Wednesday, and you can join the abnormals.

2:15 It's fun here. Join us, won't you? Dark Cast Network, come on over to the dark Side. We're really nice people once you get past the true crime and scary science. Hello, and welcome to Cause of Death. One hundred seconds to midnight. I'm your host, Jackie Morante. Before we get started, I want to welcome my latest patron to the family. Welcome, Elizabeth. I'm so happy to have you here. I want to thank all of you for the get well messages that you sent while I was sick. For those of you who missed my messages, I had a little health mishap. What started as a sinus infection moved into bronchitis, and then quickly ended up as pneumonia. I'm feeling much better now and thank you for sticking with me. I apologize that this episode is late, but I had to sleep it off for a few days, so research wasn't happening.

3:30 We're almost finished with season six Who's Who Outside of the Zoo. After this there will be two more episodes. Then I'm going to take a short hiatus and be back with season seven. That season is going to be called Countdown. I have five or six one hundred seconds to Midnight episodes in mind for that one. For those of you who really like the one hundred seconds to midnight episodes, I hope you enjoy that. I know I will. I really like doing research on those episodes. It's interesting to explore the topics that could change the world as we know it. Today, we're talking about frog fungal disease. It's also known as amphibian citridiomycosis. There is nothing like going to the river in spring, the frogs are sending their mating calls back and forth. The males are trying to sing the best songs to attract females, and they're measuring up the other males to see if they really want to battle for the female they've chosen. When you think about it, frogs aren't only important to ecosystems. They're important to the natural rhythm of life. I thought that since we talked about white nose disease and bats last time, we could just hop on over to frog fungal disease this time. Let's begin with ideology and pathology. Batochochytrium dendrobades or B D is a chitridiomcata. BD has two

5:09 life stages, a motile zoospore and a spherical, reproductive sessile zoosporangium. The motile zoospore directs itself and attaches to the keratonized outer layers of its host. It will then absorb its flagella and bury itself below the surface of the skin. In about four days, it matures into a zoosporangia with rhizoids and produces and releases up to three hundred zoospores into the environment via a discharge tube. Then the cycle starts a lower again. The fungus may retain the same host, or it may choose a different one. Frog larvae is thought to be a reservoir for the fungus, since the fungus has been found in characterized mouth parts of frog tadpoles, but it doesn't kill the tadpoles. Many amphibian larvae can survive for as long as three years before metamorphosing. There's a lot we don't know about b D. It's surmised that there may also be a symbiotic relationship between the fungus and some species of salamanders and frogs, allowing them to be reservoirs of the disease. It has been suggested that the fungus may be able to survive in non amphibian hosts or feeding off of dead tissue until it can find a viable host. B D is a diploid and primarily reproduces asexually

6:43 and clonally by producing aquatic, uniflagellated zoospores in a zoosporangium. Sexual reproduction of chytrid fungus has been associated with the production of resistant, thick walled resting spores, and this leads the hypothesis that the production of airborne spores could explain the widespread distribution of the fungus in relatively pristine areas. Other research shows that the population structure of the fungus is largely clonal, which would support the idea that the fungus lacks a sexual stage. This gives rise to the thought that humans or birds could disperse the fungus over long distances and bring that fungus into pristine settings. Citriteomycosis has been reported in thirty eight amphibian species in twelve families, including ranid and highlid frogs, bufanid toads, and plithontid salamanders. However, most of the population declines have been confined to the montane rainforests. This fungus prefers cooler temperatures and grows best at temperatures around twenty three degrees celsius, with slower growth occurring at around twenty eight degrees celsius and no growth at all at twenty nine degrees celsius. Amphibian keratin is used as a substrate for growth, and the fungus can grow for at least one generation on cleaned epidermal keratin or on amphibians that have died of the infection. A recent study by Voils and

8:20 his team found that BD causes such severe electrolyte imbalances in amphibians that it leads to an irregular heartbeat. Eventually, their hearts just stop. The skin of amphibians encourages proper osmotic balance inside the animal and regulates respiration. As the fungus takes over, the skin of infected animals is less adept at transporting sodium and chloride ions, thus causing an electrolyte imbalance. Sodium and potassium concentrations in the blood of infected frogs will drop and more so as the infect and intensifies.

9:03 Clinical signs of chitridiomycosis include acute death, anorexia, general malaise, and ventral edema. The skin may shed slaw become arithmetis, display epidermal hyperplasia and discoloration, or become depigmented. Hyperkeratosis is associated with diasdisis, and usually there will be evidence of secondary bacterial or fungal infections. Primary lesions are generally limited to keratonized epithelial cells. Acute infections are limited to the stratum corneum. In subacute and advanced stages, massive numbers of Thallie will be found in the retain layers of the epidermis. Acanthosis may also be present. This disease has very high mortality rate and has driven many amphibious species to near extinction. Research suggests that the disease has spread globally due to the importation of Xenopus species as pets.

10:15 This species was imported from Africa and many of these frogs were released in California. This introduced b D to naive California's species and has consequentially wrought havoc. This is the only chichred fungus known to infect vertebrates, and the host list is growing by the minute. Currently, it's considered an amphibian only disease, infecting both captive and wild animals. This is a global threat, so if you're thinking of adding a new frog tier, Amphibian habitat quarantine is important, as is disinfection of habitats and enclosures. Fungi as a rule love moist environments, so isolation of potentially contaminated animals, enclosures, and equipment is vital help is on the way, though researchers are working on cures, and of course, as we've learned in this season, logistics are a large part of that.

11:24 Wild animals are hard to treat, and when you have a severe zoonotic event, it's a big deal to get the cures to the animals, but it's a huge challenge to get the cures to the right animals, and this case is no different. Several antifungals work against b D, including voriconazole, but delivery and dosing are key. The use of amphoteraesin b and vericonozole was published in Medical Mycology. At the end of the study, it was found that amphoteraesin was toxic at the acute stage in tadpoles, but vericonozole was non toxic even at high dose levels. Vericonozole also remained stable in water, and after a seven day exposure period, domesticated elites sister nazii frogs that had been sprayed with the treatment for seven days were infection free. The experiment also included treatment of an infected colony of naturally infected poisoned dart frogs, and that experiment was also successful. Several other treatments have been suggested, but many of them would cause adverse reactions in the animals. Some of these treatments included soaking the animals in formaldehyde and malachite green, raising the temperature in the enclosure to thirty seven degrees celsius, and treatment with fluconazole and benzoiconium chloride. Any of these

12:56 treatments would work, but they would have long term adverse effects on the frogs. Itraconazole treatment would be successful, but the animals would have to be soaked in the solution for at least five minutes over a period of several days. Itraconazole isn't something that's readily available, and this process would be very labor intensive and not easily delivered in the wild. For any of these treatment measures, the biggest problem is delivering these treatments in the wild without affecting other species in the environment. That's the biggest problem with any of the wildlife diseases that we've talked about this season. Treatment of one species doesn't mean that you don't end up dosing the whole stream and the fish don't need for a conozole. We all have bacteria that grows on our skin and in our gut, and this bacteria serves as a barrier between us and some of the pathogens that can invade our bodies. This is called a microbiome. Frogs have it too, and while BD is resistant to most of the bacteria that grows on frogs to protect them, there are a few that have been studied that could confer resistance to the fungus. I'm planning a whole season on the microbiome, but for now, I want to talk about two bacteria that exhibit antifungal properties. Genetho Bacterium

14:31 levidium in the family oxalo Bacteriasia and Ceratia marcises in the family your Sinia asia. Researchers studied these two bacteria and found that they produce antifungal metabolites biasin and protegeacin. Both comprimise the integrity of the fungal cell membrane, and protegiacin can also inhibit RNA and protein synthesis in bacteria. Several antifungal bacteria have been found in cold spots across the globe, and it seems that the frogs who live in regions where BD is imprevalent to have a higher degree of antifungal bacteria living on their bodies. This helps the animals in three ways. First of all, they produce antibed metabolites. Secondly, they produce a protective biofilm on the frog's skin surface, and lastly, there is a host mediated selection for the antibed metabolite producing bacteria on the animal's skin. Many of these bacteria live in the soil, so that can also be a protective measure by not allowing the fungus to proliferate in the environment. While research is ongoing, these studies offer some hope of a possibility of transferring some of these antifungal bacteria to frogs living in high spots. Okay, we're going to take a break to hear from

16:03 my sponsors. Then we'll be back. This some history. It's the dog days of summer and most of us are gathering the last of our corn and tomatoes from the garden. Soon we'll be gathering pumpkins and squash for fall. Since I live in an apartment, I have indoor garden beds and I grow greens and herbs all year round. This is why True Leaf Market is my go to when it comes to seeds, soil, and gardening supplies. I started twenty four herb plants this spring indoors, and now some of my plants are ready to harvest. I also planted some greens in my garden beds so I can have those all winter long. Trueleaf Market carries everything you need to keep your gardens growing and some things to get them ready for winter. Visit www dot true leafmarket dot com for all your gardening needs. Don't forget to check out their flowers and cover plants. Frogs, salamanders and bats are attracted to many plants, so help our keystone species. Visit Trueleaf Market at www dot trueleafmarket dot com today. Are you a truecrime advocate? Are you passionate about uncovering the truth and bringing justice to victims. Do you love the paranormal and spooky tales, Then you don't want to miss the True Crime and Paranormal

17:36 Podcast Festival in Austin, Texas. It'll be going on from August twenty fifth to the twenty seventh in twenty twenty three. This festival features panel discussions, workshops, live podcasts, all focusing on ethics and advocacy in the True Crime Sphere. Get your tickets now at www dot Truecrime Podcast Festival dot com and join us in Austin for an unforgettable experience. Don't miss out on the chance to connect with other advocates and take your passion for true crime and paranormal to the next level. Use Code Consequences at check out for fifteen percent off the ticket price. That's Truecrime Podcast Festival dot Com with promo Code Consequences at checkout for fifteen percent off the ticket price. Special guests will include Julie Murray, Teranewell and Call your Landry. I'll be there representing another podcast that I'm involved with, True Consequences. Come by and meet Eric Carter, Landein and I.

18:41 We would love to meet you. This disease existed for centuries in the Korean Peninsula, where it grew and prospered on its own. Then sometime in the nineteen fifties during the Korean War, humans brought it to the rest of the world. Mass die offs were noted in the nineteen seventies in the French Pyrenees, where the midwife frogs would climb out of their birth legs and barely make it to shore before dying. Biologist Matt Fisher described these events as quote, they'll do one last hop, then they'll expire in your hands. You can walk the lakes. It's just carpets of dead frogs end quote. Researchers didn't realize these dieoffs were related to BD until nineteen ninety seven, when the connection was made. From two thousand and four to two thousand and eight, a site in Panama lost forty one percent of their amphibian species to b D.

19:44 In two and seventeen, Jennifer Shelton began exploring the mountains of Taiwan. She was looking for infected salamanders. When anyone on her team found a sick amphibian, they snipped off one of the animal's toes brought it back to the lab. Okay, before anyone gets upset about the toe snipping. Snipping off a toe is a non lethal way to get a skin sample, so after the toe was removed, the animal could be released back into the wild. Researchers would then bring the toe back into the lab and put it in a petrie dish to see what grew. As the fungus grew, the researchers were able to sequence its DNA one hundred and seventy seven b D genomes from around the world were combined with fifty seven previously published ones. Two hundred and thirty four genomes revealed that there were four distinct lineages in the family tree. The samples from the Korean Peninsula showed the greatest genetic diversity of any of the other samples taken, and this is what told them exactly what they needed to know.

21:00 The Korean Peninsula is where it all began. That was ground zero for b D. They then calculated the mutation rate for the fungus and this told them that the ancestor of today's BD line emerged out of Asia in the early twentieth century. This lineage is referred to as the global panzootic lineage. A lethal strain called BD GPL. Human activity is largely the blame for the global spread of BD. Shipping, live frog pregnancy tests, the amphibian meat, and pet industries. They all gave rise to a global zoonotic event. During the Korean War, frogs would hitch rides on equipment being moved from one place to another, even if the fungus couldn't survive without a host. A sister species of BD, known as B. Salamandra four ends, killed ninety nine percent of the Dutch fire salamanders from two thousand and nine to two thousand and twelve. This spurred US Wildlife officials to ban the importation of two hundred and one salamander species into the US in an effort to keep B. Sal out of the country, but during a US Court of Appeals ruling, it was decided that if the animals were already in the country, their sales couldn't be banned, so they could and still can, be transported anywhere in the US.

22:37 Now, researchers are studying the inevitability that less virulent strains of BD could come together and make a super virulent strain of BD. This has already begun to happen a Brazilian strain of BD mixed with the current virulent BDGPL, and the results were disastrous. It's been considered that all amphibian trades should be banned globally, and wildlife conservationists are particularly arguing this in the US. Currently, US Fish and Wildlife are monitoring the spread of B D across the States, but they argue that since the disease is already here. There is little that a ban would do to stop the spread. Matt Fisher disagrees he would love to see a global ban on the amphibian pet trade. Quote. Do we really need to be mining our environments for organisms and selling them around the world for financial profit, just so we can keep them in terrariums in our living rooms and say, hey, that's cool. It seems like a fairly innocent pastime. But we are putting entire ecosystems at risk. End quote. We are indeed putting entire ecosystems at Frogs are a very important part of the world around us. Like bats, several habitats depend on frogs for survival. Frogs

24:10 are both a keystone species and an indicator species in their environments. If we lose a keystone species, the entire ecosystem will fail. Frogs provide food for several species, including birds, fish, monkeys, and snakes. As tadpoles, they eat algae, which helps regulate blooms and reduce the risk of algal contamination. As they metamorphose from tadpoles into frogs, they become more carnivorous, and this means that they eat a lot of bugs. They can eat up to one hundred insects in a day. Okay, so this isn't quite as impressive as the bat, but still that's a lot of bugs. The larger the frog, the larger the prey. Some species can eat animals as big as snakes and birds. Okay, so maybe you didn't want to hear that part, but it does show that frogs are an important part of the food chain as predator and prey. Frogs are also an indicator species. If you listen to the Greed and Avarice episode on chemical spills and the Environment, I talked a bit about researchers walking the stream where the train derailment occurred in Ohio.

25:30 They were looking for dead fish and frogs. Frogs need clean habitats to survive. They need clean water and clean soil. Anything that affects their environment will kill them. If the pH goes too high or too low, frogs can't survive. This is what happened immediately after the train derailment. There were many many frogs and fish found dead after the event, and it told researchers and clean up crews that the water was contaminated. People can't survive without clean water either. Go back to the episode on the global water crisis, I talk a lot about how pollutants can affect a water supply. If the frogs are gone, the water isn't safe for anyone. That's what indicator species do.

26:26 They tell us if our environment is safe. Okay, we're going to go on to some trivia. Now. Back in the nineteen twenties, African clod frogs were used to see if a woman was pregnant. The frog would be injected with urine from a woman, and if the frog produced eggs within twenty four hours, the woman was pregnant. Today, the African cloud frog is still used in vertebrate embryology research. The females are prolific egg layers, and their eggs are transparent, so it's easy to observe the growth patterns of the larvae. Epibatadine is a pain killer that's two hundred times more potent than morphine. It's also the venom of some poisoned dart frogs. People can't take ebibedodine for pain right now because it's toxic to humans even in small doses, but research is ongoing to see if there is a way to use it as a compound for pain killers. It's a possibility that ebabatadine could be used topically when combined with another substance to relieve pain. I'm going to take you back to middle school for just a minute. Remember when you were stuck in a biology class and the first thing they made you do is dissect a frog.

27:48 I know many of you got pretty grossed out, but my biology teacher was pretty good. I remember looking at the parts and pieces and trying to figure out how the body worked, especially the muscles of the legs. That's what frog dissection was really about for me, learning how muscles worked, learning the attachments and what propelled the frog through life. I learned a lot about muscle structure from frogs, and it was my first look at a complex organ system. The dissection of frogs also gives us insight into evolution. How does an organism go from living in water to living on land? Frogs teach us that.

28:36 Now. I'm not going to tell you to go out and find a frog to dissect. Most of you don't want to know how complex organ systems work. You just want to know that they do work, and that's just fine. Leave the dissection to me. So I can figure out how to keep your organ systems working the way they should. Thank you again for listening to Cause of Death one hundred seconds to Midnight. We have two more episodes in season six, Who's Who Outside of the Zoo. When this season ends, I'm going to take a month off to get ahead. That means I'm going to be putting up more bonus content. Also, I really didn't want to take a break, but that's the only way I can get a few episodes ahead after having so much weird life stuff that got me way behind.

29:29 If you'd like to support the show, please take a look at the show notes for links to my Patreon page and my cofi account. You can also sign up on Apple subscriptions for bonus content and add free episodes. The show notes are a great way to look at some of the research I do for each episode. If you're really into white papers, or if you just want to get your sleep schedule on track, go check out some of the links. There's so much information on frog fungal disease, medical search involving frogs, and ways that you can help frogs survive. Check out my sponsor for this month, True Leaf Market. There's a link to their website where you can find gardening supplies and every manner of seed. Summer is quickly coming to an end, so now is the time to think about growing indoors. I have my indoor garden beds all set up and I'm looking forward to a winter of fresh greens and amazing herbs. True Leaf Market is my go to for all of my gardening needs. Go check them out. The link is in the show notes. I also want to let you know that my daughter Jessica and I are going to be launching a new show in early October. It's called Diving into Unsolved History. We're going to look at some mysteries from the past that are still unsolved, the Alien More incident, the Ditluff Pass incident,

31:00 the Marie Celeste. We're going to talk about famous treasures that could still be out there, like Alaric's Treasure, the Dresden Green Vault, Burglary, and Thomas Beale's ciphers. We're going to tell you the story behind the mystery, look into the facts, and look at some of the crazy theories that really just don't make a lot of sense. It'll be a lot of fun and I hope you join us, join me next time when we look at human encroachment on wildlife and the negative effects it has on species. Thanks again for listening, and have a great week.