7 mysterious diseases wiping out wildlife
By Jaymi Heimbuch, Mother Nature Network, 4 September 2015.
By Jaymi Heimbuch, Mother Nature Network, 4 September 2015.
Every so often an epidemic hits a species somewhere in the world. Sometimes it's just a way that nature helps populations stay in balance. However, some epidemics strike with such rapidity, in such a mysterious way, and has such a high death toll that it leaves scientists stumped on the causes of the spread of the illnesses as well as possible cures. For decades, researchers have been looking into some of the most alarming diseases striking species as diverse as frogs, Tasmanian devils and sea stars.
1. Bats: White-nose syndrome
Photo: U.S. Fish and Wildlife Service Headquarters/Wikimedia Commons
White-nose syndrome has been killing bats for the last decade, with more than 5.7 million dead in the eastern half of North America from this disease. The cause is Pseudogymnoascus destructans, a cold-loving European fungus that grows on the nose, mouth and wings of bats during hibernation. The fungus causes dehydration and causes the bats to wake up frequently and burn their stored fat reserves, which are supposed to last through the winter. The result is starvation. When the fungus infects a cave, it has the potential to wipe out every last bat. Bats play an important ecological role in insect control and pollination. They are vital to healthy habitats, so to lose them by the millions is alarming. Scientists have been looking for years for a solution to stop the spread and cure infected bats.
A new treatment for white nose syndrome was developed by U.S. Forest Service scientists Sybill Amelon and Dan Lindner, and Chris Cornelison of Georgia State University. The treatment uses the bacterium Rhodococcus rhodochrous, which is commonly found in North American soils. The bacterium is grown on cobalt where it creates volatile organic compounds that stop the fungus from growing. The bats need only be exposed to air containing the VOCs; the compounds don't have to be applied directly to the animals.
The U.S. Forest Service tested the treatment on 150 bats this summer and had positive results. "If they're treated early enough, the bacteria can kill off the fungus before it gains a foothold in the animal. But even bats already showing signs of white-nose syndrome show lower levels of the fungus in their wings after being treated," reports National Geographic. So the future is hopeful for curing bats of this devastating problem.
2. Snakes: Snake fungal disease
There have been reports of this strange disease for a few years, but since 2006, it has been on the rise. Snake fungal disease (SFD) is a fungal infection affecting wild snakes in the Eastern and Midwestern United States. And unfortunately it's taking a toll on the endangered timber rattlesnake and the endangered eastern massasauga as well as other species. Researchers are worried that it could be causing declines in snake populations and we don’t even yet know it.
“There’s not much known about the fungus that causes SFD, a species called Ophidiomyces ophiodiicola, or Oo…Oo survives by eating keratin, the substance out of which human fingernails, rhino horns, and snake scales are made,” reports Conservation Magazine. “According to [University of Illinois researcher Matthew C.] Allender and his colleagues, the fungus thrives just fine in soil and appears completely satisfied gobbling up dead animals and plants. What they don’t know is why it’s attacking living snakes, but they suspect it’s mostly opportunistic. After snakes emerge from hibernation, it takes some time for their immune systems to kick into high gear. That’s the perfect time for a fungus to move in and feast on their scales.”
The mortality rate is very high in timber rattlesnakes, and among massasaugas it has been fatal to every infected snake. This disease caused a 50 percent decline in timber rattlesnake populations between 2006 and 2007 alone. It isn’t quite known the effect it has on other snake species and it is really hard to track considering the solitary and hidden lives wild snakes generally lead. Researchers suspect that while it is known to exist in nine states, it may be more widespread than we think.
What’s worse is that climate change could speed along its spread, since the fungus prefers warmer weather. Without cold winters to slow the disease, scientists are racing against time to find out how to cure it as well as how to stop it from spreading.
3. Frogs: Chytridiomycosis
Photo: Forrest Brem/Wikimedia Commons
Save The Frogs puts it bluntly: “In terms of its effect on biodiversity, chytridiomycosis is quite possibly the worst disease in recorded history.”
Indeed, they have a point. The disease is responsible not only for dramatic declines in frog populations around the globe, but also for the extinction of many species of frog in the last few decades alone. About 30 percent of the world’s amphibian species have been affected by the disease.
This infectious disease is caused by chytrid Batrachochytrium dendrobatidis, a nonhyphal zoosporic fungus. It affects the outer layers of skin, which is particularly lethal for frogs considering they breathe, drink and take in electrolytes. By impairing these functions, the disease can easily and rapidly kill a frog through cardiac arrest, hyperkeratosis, skin infections and other problems.
The mystery behind the disease is that it occurs anywhere - but not everywhere - the fungus is located. Sometimes populations are spared an outbreak while others suffer a 100 percent mortality. Discovering exactly why and how it strikes, which would lead to predicting and preventing new outbreaks, is currently being researched. What is also being researched is exactly how the fungus spreads through the environment once it is there. But there is a good deal of evidence that it ends up in new locations through human actions, including the international pet trade, through exported amphibians for human consumption, the bait trade, and yes, even the scientific trade.
There is no effective measure for controlling the disease in wild populations as of yet, at least nothing that can be scaled up to protect an entire population of frogs. There are some options being tested for controlling the fungus, but it is so time- and labour-intensive that it is not feasible to scale up.
4. Starfish: Sea star wasting syndrome
Photo: Brocken Inaglory/Wikimedia Commons
Sea star wasting syndrome is a disease that has popped up as epidemics in the 1970s, '80s and '90s. However, the last plague that started in 2013 took scientists by surprise because of how rapidly and how far it spread. All along the Pacific Coast from Mexico to Alaska, the wasting disease affected 19 species of sea star, including wiping out three species from some locations. By the summer of 2014, 87 percent of the sites surveyed by scientists had been affected. It is the largest marine disease outbreak ever recorded.
The wasting disease is spread by physical contact, and attacks the immune system. The sea stars then suffer from bacterial infections which lead to lesions, and then to arms falling off, and then turning into piles of mush. Death can happen within a few days of the lesions appearing. Scientists spent months researching what was going on and finally identified the culprit, a virus they named “sea star associated densovirus.”
“When researchers tried to figure out where the virus may have come from, they learned that West Coast starfish have been living with the virus for decades. They detected the densovirus in preserved starfish specimens from as far back as the 1940s,” reported PBS.
Scientists still don’t know why there is suddenly such a significant outbreak if the sea stars have been dealing with the virus for so long. Warming water temperatures or acidification are potential culprits. As for cures, the scientists note that it could be possible to potentially grow resistant stocks of sea stars in aquariums which could provide a backup should species drop in number enough to become threatened. That is where scientists are focusing their attention: on how sea stars can develop a resistance to the densovirus to protect future generations of these ecologically important animals. Interestingly, the bat star and leather star seem to be resistant to the disease, so may be of interest for researchers looking for clues.
Unfortunately, the wasting disease now also seems to be affecting sea urchins, the prey of starfish. “In scattered southern seashore pockets from Santa Barbara to Baja California, urchins' spines are falling out, leaving a circular patch that loses more spines and enlarges with time, marine scientists say. No one is sure what is causing it, although the symptoms are hallmarks of a disease.” reported National Geographic.
5. Tasmanian devils: Contagious facial cancer
Photo: Menna Jones/Wikimedia Commons
A devastating facial cancer has been decimating populations of Tasmanian devils for the last 20 years. The cancer forms tumours around the face and neck, making it difficult for the devils to eat, and usually they die within months of the cancer becoming visible. But the part that makes it particularly worrying is that this cancer is contagious. Called devil facial tumour disease (DFTD), the disease was first observed in 1996. It wasn’t until 2003 that research began to find out exactly what the facial tumours are and how to cure them. By 2009, the Tasmanian devil was listed as endangered.
"DFTD is extremely unusual: it is one of only four known naturally occurring transmissible cancers. It is transmitted like a contagious disease between individuals through biting and other close contact," writes Save The Tasmanian Devil. Researchers are still trying to figure out exactly how the cancer spreads between devils, and any possible cures. There are at least four strains of the cancer that have been discovered, which means it is evolving and could potentially become more deadly.
The Conversation points out that perhaps a contagious cancer isn’t even the cause. "It is true that Tasmanian devils bite each other in ritual fights, but their teeth are not sharp and not an obvious mechanism for spreading cancer. Furthermore, various complications soon emerged from the biological research…a role for pesticides and poisons seems plausible, because the devil disease is found only in parts of Tasmania where there are extensive forest plantations. Furthermore, because devils, as carnivores, are at the top of the food chain, toxic chemicals in the environment are concentrated in their diet."
While researchers struggle to find the cause of the disease, conservationists are struggling to keep the Tasmanian devil alive as a species. The disease might even cooperate a little bit. New research shows that the disease might be transforming to allow infected Tasmanian devils to live longer in order to find more hosts. "Animals and their diseases evolve and what we expect to happen...is that the host, in this case the devil, will evolve resistance and tolerance to the disease, and the disease will evolve so that it doesn't kill its host quite so fast," Associate Professor Menna Jones told ABC News.
It isn’t exactly the brightest ray of hope, but both conservationists and scientists alike will take what they can get right now. "The best hope to save the devils from extinction is to make, at some stage in the future, the devils and the tumours co-exist,” says Rodrigo Hamede of the the University of Tasmania.
6. Saiga: Hemorrhagic septicemia
Photo: Saiga Conservation Alliance
Well, maybe it is hemorrhagic septicemia. This is the preliminary findings of a crew of scientists trying to figure out what killed 134,000 critically endangered saiga antelope - about one-third of the global population - within two weeks earlier this year. This is a huge blow to the species which has already declined by 95 percent in just 15 years due to poaching, habitat loss and other factors. To have a mysterious disease take out so many of the remaining population is devastating. The disease hit during calving season, and mothers and calves died by the thousands.
At first, scientists thought that the cause of death was Pasteurellosis, which caused a mass death of saiga in 2012. However, Steffen Zuther thought there may be more to this mystery. He and his team collected samples of water, soil and grass and had them analyzed in laboratories in the United Kingdom and Germany. In his preliminary results, the cause of death was believed to be hemorrhagic septicemia, a bacteria spread by ticks that produces various toxins.
This cause of death is yet to be completely confirmed, but scientists are working as quickly as possible to make sure they know exactly what the cause is, and most importantly, prevent such a mass die-off from happening again. Meanwhile, the Saiga Conservation Alliance is doing its best to help protect remaining individuals.
7. Bees: Colony collapse disorder
A natural beehive of Apis dorsata, the giant honey bee. Photo: Muhammad Mahdi Karim/Wikimedia Commons.
The mysterious disease that has gathered the most media attention is probably colony collapse disorder, and rightly so. Without bees pollinating plants, we don't have food, so it is in our own best interest to understand as soon as possible exactly why whole colonies of healthy bees seem to suddenly drop dead or disappear.
"Over the past decade, billions of bees have been lost to Colony Collapse Disorder (CCD), an umbrella term for a host of factors thought to be killing honeybees in droves and threatening the nation's food supply," reported The Ledger last month. "Bees are still dying at unacceptable rates, especially in Florida, Oklahoma and several states bordering the Great Lakes, according to the Bee Informed Partnership, a research collaborative supported by the USDA."
Even after years of intensive research, it still is unclear exactly what is going on. One culprit seems to be a cocktail of pesticides, particularly neonicotinoids, a class of pesticide that has been implicated in multiple colony deaths. A recent study from Harvard showed that over 70 percent of pollen and honey samples gathered in 2013 in Massachusetts contain at least one neonicotinoid. Other causes of CCD may be an invasive parasitic mite called varroa destructor, poor nutrition resources due to monocrops and a loss of wildflowers, and a virus that attacks bees' immune systems. And of course it may also be a varying combination of these and other factors.
With pesticides known to be a factor in, if not directly causing CCD then weakening bees enough that other factors kill them off, that leaves a big question: Why aren't the pesticides being banned? This becomes one complex can of wriggling worms, that contains corporate interests and an utterly inefficient Environmental Protection Agency. A recent article in Rolling Stone pushes the questions farther, "Despite these limitations, many feel that the body of evidence against neonics is strong enough that the EPA should be taking a stand. Which raises certain questions. 'Why did the Europeans put a hold on the use of neonicotinoids?' [Ramon Seidler, a former senior research scientist in charge of the GMO Biosafety Research Program at the EPA] asks. 'And why did the EPA look at that and stare it right in the face and say, 'No'?"' Why is the EPA not restricting neonics when another government agency, the Fish and Wildlife Service, announced that it would phase them out on national wildlife refuges by 2016?"
The exact cure-all solution to CCD is not yet known, but a way to slow the die-offs seems rather obvious to many researchers and bee keepers focused on preventing CCD. No bees, no food, so a solution needs to happen in short order. If you want to help, check out 5 ways to help our disappearing bees.
[Source: Mother Nature Network. Edited. Some images added.]