The risk might be low, but the alternative is maybe months of debilitating diarrhea. It’s your choice. Photo Credit: Timothy Epp/Shutterstock
While we like to think of ourselves as rational creatures, there’s no doubt that human beings are actually quite awful at assessing risk. So I can understand why Ethan Linck thought to contextualize the risk of drinking from backcountry streams with data. “Life is triage, a constant series of negotiations between risks of varying severity,” he wrote. “And how we talk about those risks matters.”
Yes, it does—which is exactly why his piece in Slate last week was so damaging. It was anything but a careful, scientific evaluation of the risks. Wes Siler over at Outside Magazine already pointed out a myriad of issues with the article, but I want to zero in on the actual data, because Linck claimed to be looking at the matter scientifically. Instead, he cherry-picked sources to argue against doing one of the simplest things you can do to protect yourself from some truly awful diseases when you’re backpacking: treating your water.
— Outside Magazine (@outsidemagazine) February 7, 2018
Simply put: when you drink water straight from a stream, river, or lake, you have no idea what’s in it. And that’s bad, because, as epidemiologist Tara Smith, PhD, explained for SELF last month, it can be contaminated with all sorts of nasty things. “These include Giardia, a parasite found in streams and rivers that causes “beaver fever” in campers and hikers, and bacteria like Shigella and Campylobacter that can cause bloody diarrhea,” she wrote.
These organisms exist in waters because they exist in our digestive tracts and those of other animals. So anywhere that there’s poop near water, that water could contain pathogenic strains of Escherichia coli, Salmonella, Campylobacter, Aeromonas, Yersenia enterocolitica, Leptospirosis, Listeria, or Vibrio, in addition to a suite of viruses and protozoan parasites like Giardia and Cryptosporidium. Some of these bugs only cause short-term, if severe, gastrointestinal distress. Others can cause issues that last for weeks, months, or even years.
“Even water that appears pure or clear can be contaminated by people or animals,” explains Jonathan Yoder, MPH, who is deputy chief of CDC’s Waterborne Disease Prevention Branch. I asked Yoder and his colleague, epidemiologist Kathy Benedict, PhD, what their thoughts were on the bold claim that science doesn’t support backcountry water treatment (that “the scientific evidence shows that this mandate [to filter water] rests on a shaky foundation”). Needless to say, they disagreed.
Because appropriately assessing risk requires a clear understanding of what’s at stake, it’s important to point out that with many of these pathogens, we’re not just talking inconvenient cases of the runs. The gastrointestinal symptoms that can occur—intense diarrhea, vomiting—aren’t easily managed by hikers on long trips in the middle of nowhere. “If they have an acute situation, it can actually be quite scary,” says Benedict, “especially if they’re out there by themselves, because they can get themselves into a lot of trouble very quickly.” And people, even people with rapid access to medical care, do sometimes die.
A 3D rendering of Giardia lamblia a protozoan parasite that can set up shop in your intestines and get pretty comfortable there. Image Credit: fotovapl/Shutterstock
To his credit, Linck doesn’t exactly downplay the dangers of Giardia or other potential pathogens. But, he argues, that their dangers are not important. It’s totally ok to drink any water you might come across while backpacking (or as the title says, “You Don’t Need to Filter Your Stream Water”) because: “The idea that most wilderness water sources are inherently unsafe is baseless dogma, unsupported by any epidemiological evidence”.
It’s a lovely little straw man that he immediately sets to tearing apart. To paraphrase his argument: everyone says most water is chock full of terrible things. So as long as most water sources are safe, then you’re good to drink from any stream. And look! Here’s a study that says feces contamination was only found in a minority of the sites tested! And one by… a magazine… that says the same thing!
But let’s take a quick look at those sources. The first study examined lakes and streams in Kings Canyon, Sequoia, and Yosemite National Parks looking for feces-associated bacteria (fecal coliform), because where there’s feces, there could be something dangerous in the water. And they found it at 22 of the 55 chosen sites. So yes, that’s a minority, but it’s 40%—and of those, ~16.3% (9) had “higher levels”. And that magazine one? Well, Linck didn’t directly link to it, but Google is a wonderful thing. They surveyed seven locations three times throughout the year for parasites, five of which had at least one test come up positive for either Giardia or Cryptosporidium—just over 71%. But, they claimed, only one had close to dangerous levels. That’s still 1/7—or a little over 14%. It’s a shame that Linck didn’t include the percentages in his article, because for all his talk about appropriately assessing risk, he doesn’t give the information needed to actually do that.
And those studies—if you can really call the magazine investigation that—were conducted in the early 2000s, each testing a miniscule fraction of the waters that are accessed by U.S. hikers every year on a handful of occasions. There is other research he could have cited—like this 2009 study from Georgia, which found 79% of water samples from rivers and streams in southern Georgia over a year tested positive for Salmonella. Or this 2011 one which found “Salmonella, Campylobacter, Staphylococcus aureus, Vibrio vulnificus, and V. parahaemolyticus were widespread—12 of 22 O’ahu streams had all five pathogens.” And even if he didn’t want to count Hawai’i (though it is a U.S. state), then he could have cited this 1987 study in Washington instead, which found Campylobacter at ~36% of sites tested (5 of 14), including a mountain stream. According to the authors, “Campylobacter spp. are widely distributed in central Washington and are present in a variety of aquatic habitats including ponds, lakes, and small mountain streams, which ranged in elevation from 1,460 to 5,400 feet above sea level.”
Even if he just looked at other papers by the same authors as his study, he’d have found this 2004 study, which found that out of 31 backcountry sites, 45% tested positive for fecal coliforms, and just over 25% had high levels. Or this 2006 study which found fecal coliform at 1/15 sites used by backpackers (~6.7%). Or this one from 2008, which found coliform bacteria in 18% of human day use areas, and 14% of backpacker sites. But really, they all tell the same story: one-in-five to one-in-ten sites test positive, which means they might get you sick if you drink their water untreated.
Even the cleanest water can harbor these pathogens. Photo Credit: michaeljung/Shutterstock
Of course, even counting every sample in every study I just mentioned, only a tiny fraction of potential hiker drinking sources have been tested, so a lot remains unknown. And because these pathogens are associated with human and animal activities, their presence can be as transient as the wildlife. None of these studies really explains just how variable the risks can be, which is actually something that was noted in that Backpacker article:
“Risk in this area is very hard to quantify,” explains Tod Schimelpfenig, curriculum director for the Wilderness Medicine Institute, of the Wyoming-based National Outdoor Leadership School. “Sample a creek at one point in time and you could have a flush of organisms from an animal that just defecated upstream. Sample it 20 feet upstream 2 hours later and you could find nothing. The risk of drinking untreated water in the wilderness depends entirely on when and where.”
If any conclusions can be drawn, it’s that not all areas carry the same risks, and that even remote streams can harbor dangers. Even if you could assume something like 10%-20% of water sources test positive for fecal contamination (and thus may get you sick)—then, yeah, technically, only a minority of sites are ‘unsafe’ (not that anyone was arguing that most of them were). But just imagine going to a buffet and seeing a sign that said “Nine out of ten of our menu items tested negative for fecal bacteria!”—would you want to eat?
Yoder wouldn’t. Of course, he’s had Giardia before, so he knows exactly what he’d be risking. “I think after you have a one of the more severe diarrheal infections—and I speak from my personal experience—I think you understand that even though you know ninety-nine times out of a hundred, if you drank from that water source, you’re not going to get infected, it’s worth it to protect yourself for that one percent chance.”
While Linck’s prevalence analysis is a straw man at best, he goes on to claim something that’s patently false: that “research to date has failed to demonstrate any significant link between wilderness water consumption and infection with these threats.”
Again, he turns to decades-old data, citing a 1993 study where only 5.7% of backcountry travelers in California’s Sierra Nevada had Giardia, and none of them felt sick. Mind you, he failed to note that more than half of the travelers did purify their water, so they’d have been protected from the parasite. And he didn’t mention that 16.7% of them did return with gastrointestinal illnesses—they just weren’t that one. Then he cites a survey of health departments and a meta-analysis from the same researcher looking at Giardiasis in the US, both of which found that the majority of cases came from non-wilderness sources. But again, that’s a straw man—no one was arguing that backcountry streams were the main source of Giardia infections. That’s like saying most house fires aren’t started by deep-frying a frozen turkey, so by all means, it’s totally safe! And Giardia seems like a very specific hill to die on. What about the myriad of other possible disease agents? Nothing about Campylobacter, Leptosporosis, Shigella, Norovirus, E. coli—and the list goes on.
Heck, if we’re going back decades for our data, why not mention this 1984 study that found people who drank untreated water taken from a stream, river, or lake were about ten times as likely to have Campylobacter jejuni infections than their neighbors who didn’t? Or this 1983 one, which found both Campylobacter jejuni (23%) and Giardia lamblia (8%) in people who came back from Grand Teton National Park with diarrheal disease. They also found that Campylobacter occurred “most frequently in young adults who had been hiking in wilderness areas and was significantly associated with drinking untreated surface water in the week before illness” [emphasis mine]. They even isolated Campylobacter from one of the mountain streams suspected as a source.
You might not realize what has happened upstream. Photo Credit: Ruud Morijn Photographer/Shutterstock
Or, Linck could have looked at more recent data—like this 2016 study of Giardia outbreaks in the US from 1971-2011, which found six linked to rivers or streams. Or this 2017 study looking at waterborne illness outbreaks in the US in 2013 and 2014, which found another six outbreaks of Giardiasis affecting 91 people which were “caused by ingestion of water from a river, stream, or spring.” And these are just outbreaks where multiple people got infected and sought treatment—they don’t look at the countless individual cases, many of which are not reported to authorities because we don’t go to the doctor for diarrhea unless it’s really bad (diarrheal diseases are notoriously underreported). And it can take a week or more for signs to show in some cases, so you might not even connect your bowel troubles to your recent hiking experience.
Linck does mention a camping related outbreak of Giardia from 1976 which was thought to be waterborne. But he claims, citing a 2004 editorial, that the analysis was wrong. Instead, “the afflicted campers failed to properly wash their hands after using the bathroom.”
“I don’t disagree with the author that, in addition to water treatment, there are other very important things that people can do to stay safe in the backcountry,” says Yoder, “and those include the proper disposal of waste and using good hand-washing hand hygiene, particularly after using the bathroom and before eating before preparing food.”
By pointing to hand-washing, Linck is basically making the turkey argument again; the fact that poor hand-washing also causes outbreaks, maybe even more of them or worse ones, doesn’t mean that drinking untreated water never causes any.
In fact, the idea that every case reported from backpackers comes from poor hygiene instead of streams is not just hard to believe—it’s unsupported by the science. “We have data that there is a risk from backcountry water,” says Yoder. “There certainly are waterborne disease outbreaks—more than twenty that have been reported to CDC—where consumption of water in the backcountry has been linked to illness.”
The simple fact is, if you drink untreated water, you’re taking on a non-negligible amount of risk. The good news is that risk—however large or small it may be—can be mitigated. And no, not just with fancy filters.
Linck is quick to chastise the outdoors industry for “claiming the average hiker or camper needs a $99.95 microfilter pump to avoid illness and death.” Maybe expensive devices are talked up by their makers (are we really blaming companies for wanting to sell their products?), but luckily, the people that study waterborne diseases and pretty much everyone who has had any kind of training in wilderness survival will tell you that decent water treatment can be done a myriad of ways, many of which are dirt cheap. “Boiling water is one of the most effective ways to inactivate parasites, viruses, and bacteria,” Yoder notes. Or you could get chlorine dioxide tablets that treat a liter of water for about $0.50 each.
Boiling water goes a long way if you’re going to be off the grid for awhile. Photo Credit: AlisLuch/Shutterstock
Ultimately, the choice of what you drink is yours and yours alone. The point of this isn’t to shame you if you choose to drink untreated stream water—it’s to provide you with what is known from scientific research, rather than hyperbolic rhetoric. Now that you have the information, you can decide to trust in your ability to pick safe water sources, or to take precautions.
As for me, I’ll go with the instincts of the guy who studies these things. Yoder has analyzed the data, and his choice is simple: “I think that having that extra level of protection and making your water safer is worth it, because you’re trading that for more enjoyment out of the backcountry and not having to experience an illness that, at least temporarily, is pretty debilitating.”
It seems like the overwhelming majority of Slate’s twitter followers agree. (Ah, the ratio…)
— Slate (@Slate) February 1, 2018
Strange Drug Overdoses Are Mystifying Hospitals
A new wave of synthetic drugs is causing overdoses across the country. (Credit: busliq/shutterstock)
An explosion of strange new narcotics is hitting the streets, as clandestine chemists rush to produce drugs that exist outside the law.
One United Nations report tallied 644 new drugs discovered across 102 countries and territories between 2008 and 2015. And in an interview last year, a Drug Enforcement Administration spokesperson said they encounter previously unheard of drugs on an almost weekly basis.
Known as new psychoactive substances (NPS), these drugs appear faster than governments can ban them — not that banning does much. But the speed means drug users sometimes don’t know what they’re taking. And in cases of overdose, medical professionals are sometimes at a loss for how to treat patients.
A newly released study funded by the Office of National Drug Control Policy gives a small picture into just how bad the problem is. A team of researchers in Maryland wanted to see the prevalence of new drugs in hospital visits, especially synthetic cannabinoids (SC), drugs colloquially known as “Spice” or “K2” that can mimic some of the effects of marijuana.
Rashes of overdoses across the U.S. have been linked to synthetic cannabinoids, including last week when more than 100 people overdosed (but didn’t die) in New Haven, Connecticut, in just 48 hours. These new drugs have been implicated in “zombielike” behavior, psychosis, cardiac arrest and seizures, or have been laced with brodifacoum, a rat poison.
So there’s strong incentive for emergency rooms to know what they’re dealing with. Yet this group of researchers at the ONDCP found it was harder than they expected to figure out what specific drugs were causing these overdoses.
What’s In Your Urine?
In 2016, the researchers obtained nearly 200 urine samples from two hospital emergency departments in Maryland and screened for 169 different drugs, including 26 synthetic cannabinoids. They wanted to include more, but in some cases, these drugs are so new that reference standards for urine testing didn’t yet exist. Typically, the hospitals screen for less than nine drugs — but not any synthetic cannabinoids.
The 175 patients who provided their pee either showed up in the ER complaining of symptoms related to SC use, were caught with it by police or medical staff, or seemed to be agitated, hallucinating, or unresponsive thanks to an unknown drug.
Yet only one sample came back positive for SCs, which suggested that these overdoses were caused by drugs not included in the test panel. So a year later, the researchers retested the urine for an additional 20 synthetic cannabinoid metabolites.
Still, only about a quarter of the specimens returned with positive results, which was much lower than expected. The most commonly found synthetic cannabinoid was MDMB-FUBINACA, which is now illegal, but has been sold in vaporizer e-liquids and was linked to 25 deaths and hundreds of hospitalizations in Russia, according to the state-controlled news site RT.
“Even after we excluded the persons enrolled in the study for agitation from an unknown cause, we found that the percentage testing positive for SC only increased to about 24 percent in each hospital,” the researchers wrote. “On the other hand, these specimens were found to contain a variety of other drugs, many in combination with one another, that had likely caused their symptoms.”
Even with the 175 patients tested in this study, it’s a small sample size that may not represent the majority of people who use synthetic cannabinoids, especially given the high rate of multiple drug use in these cases. An average of 91 percent of those who tested positive for SC in this study had at least one other drug in their system.
And it’s not clear if the patients always knew what they were taking — they may not have even known they were taking SCs — but certain chemical combos can have different adverse effects.
“The continuously changing nature of the substances available make it difficult to develop urine tests for all of the new drugs as quickly as they are discovered,” the scientists wrote. “Even though we re-tested our specimens with a larger panel of SC metabolites, it is still possible that our results underdetected the SC that these patients might have used.”
Some patients were not included in the study because urine samples couldn’t be obtained. It’s also possible that some urine samples degraded before they could be detected.
This study demonstrates how difficult it is — and how ill-equipped most hospitals are — to detect and treat overdoses from new psychoactive substances. Even if your urine screen can expose hundreds of chemicals, it needs to be updated frequently, which is why some compare this issue to a game of Whac-a-Mole. As soon as one drug is made illegal, another, often more deadly drug, takes its place.
People Were Definitely High For the 2017 Solar Eclipse, Study Finds
Day turning to dusk in the span of minutes, sunsets all around, a jewel-bright ring in the sky where the sun once stood — an eclipse is an otherworldly experience. But, if there’s one thing we like to do with amazing experiences, it’s try to make them better. Though you may have already guessed, a new study provides the confirmation: Lots of people got high for the 2017 solar eclipse.
The new data comes courtesy of a study from a group of researchers from Murray State University in Kentucky looking at how celebratory events affect drug use. They compared two towns in Kentucky on a normal week and the Fourth of July, and looked at the solar eclipse in one town and the first week of a college semester in the other.
In the Water
Drug use being the kind of thing people don’t necessarily like to make public, the researchers turned to a clever, and increasingly common, method of assessing what and how much people were putting into their bodies: They simply analyzed the sewage water. What goes into our bodies must come back out, and most drugs show up in our urine wholesale or betray their presence through signature metabolites our bodies break them down into. It’s a much more accurate and timely method of measuring drug use than relying on self-reported surveys or estimates based on drug busts, and it’s been used all over the world, though not often in the U.S.
“We can utilize this technique to determine the level of drugs people are consuming yesterday, today,” says Bikram Subedi, an assistant professor at Murray State University and a co-author of the study. “Within 24 hours we can get all the results.”
The researchers took samples from wastewater treatment plants before, during and after big events and sampled them in the lab for the markers of drug use. Big celebrations, unsurprisingly, have a noticeable effect on drug use, they found, in research presented today at the 256th National Meeting & Exposition of the American Chemical Society. Both the Fourth of July and the solar eclipse produced significant spikes in levels of a range of drugs, from weed to cocaine to MDMA, when compared to a baseline reading.
Black Hole Sun
Compared to a more prosaic celebration like the Fourth of July, though, the eclipse seems to have encouraged a somewhat different kind of drug use. Marijuana, MDMA and amphetamine (a broad class of stimulants that includes drugs like Adderall and Vyvanse) use were all significantly higher during the eclipse than during the Fourth. More worryingly, though, drugs like morphine, cocaine and methamphetamine all spiked during the eclipse, though not as much as during the Fourth. The researchers didn’t look at other psychedelic drugs like LSD, psilocybin or DMT.
The one drawback to the work, however, is that they weren’t able to control for the massive influx of people the eclipse, and to a lesser extent events like the Fourth, brought. Some towns in the path of totality saw more than 10,000 people flood in for the event, so it’s impossible to say whether people did more drugs during the eclipse, or if there were simply more people around to do them.
The takeaway here is two-fold. One, we can prove that, yes, people did get high during the eclipse, using the stunning celestial alignment as a opportunity to try and expand their minds further under the influence of psychoactive substances. (No one seems to have gone blind while tripping on LSD , though, as one bit of 1960s anti-drug propaganda had it.)
On another level, however, it reveals that celebrations present an even greater danger for people addicted to already harmful drugs like meth and opioids. What’s more, that correlation holds whether it’s an established holiday like the Fourth of July or a more uncommon event like the eclipse. As the opioid crisis continues, the information could be helpful for everyone from police officers to hospital administrators who must deal with the the effects of addiction and overdose.
Their work, and similar analyses worldwide, are indicating that we may have underestimated howe many drugs are actually being consumed, something that has real implications for public health agencies. In the future, Subedi hopes that such wastewater monitoring can be carried out in larger cities and over extended periods of time. Such a project would track the ebb and flow of drug use to better inform the ways that we as a society deal with illicit substances.
And, with another eclipse set to blaze a path across the U.S. in 2024, the study offers a preview of what we might expect in terms of some people’s viewing plans.
Uncertain Hope Blooms for Tasmanian Devils
Using remote camera traps, photographer Heath Holden captured rare images like this one of wild Tasmanian devils (Sarcophilus harrisii) in their natural habitat. The animals’ bright red ears and eerie, raucous scuffles earned the scrappy marsupials their haunting common name. (Credit: Heath Holden)
On a misty summer morning in 2015, Manuel Ruiz ditched his pickup truck along a dusty two-track road in northwest Tasmania and trod into a grove of eucalyptus. He was searching for a devil. “If I were a devil, this would be a nice place to spend the night,” thought Ruiz, a wildlife veterinarian and doctoral candidate at the University of Tasmania.
The Tasmanian devil (Sarcophilus harrisii) is the world’s largest carnivorous marsupial. Despite that distinction, the animal is only about the size of a raccoon. But what the species lacks in heft, it makes up for with tenacity. At night, devils hunt and scavenge wallabies, possums, and other small mammals under the cover of their black fur. During the day, they retreat to underground dens and sleep off the rigors of their nighttime exploits.
As picturesque and wild as northwest Tasmania’s landscape may be, it is also a battleground for disease, and in 2015, Ruiz was patrolling the epidemic front lines. It didn’t take him long to find evidence of the fight. A few dozen paces into the undergrowth, he knelt to inspect a white cylindrical trap nestled amidst a lush cluster of ferns. Inside, a female devil peered down her pointed, whiskered snout at Ruiz. He had seen this individual, nicknamed Leesa, once before. A raw, oozing tumor as large as a ping-pong ball gaped behind the right corner of her mouth—the mark of a debilitating cancer.
Leesa and thousands of other devils suffer from what’s known as devil facial tumor disease. The cancer was first detected in 1996 in eastern Tasmania. Since then, it has spread rapidly across the island state, causing an overall species decline of 80 percent, with localized declines of more than 90 percent. A decade ago, scientists predicted imminent extinction for the critically endangered species.
Since then, some wild devils have begun to show signs of resistance, offering new hope for the species’ survival. And while the quickly spreading cancer has wrought great devastation, it has also offered scientists a rare window into the progression of cancer at large. Researchers are monitoring the disease as it runs its course, searching for clues that will help them derail it. They’re hopeful that their findings might soon be applied to combatting cancers in other species—maybe even in humans someday.
A Tasmanian devil with two large facial tumors walks along a fire trail at night. These tumors, caused by a form of cancer, can grow so large that they ultimately prevent the animal from feeding. (Credit: Heath Holden)
no matter what species it’s in,” says Greg Woods, an immunologist who recently retired from the Menzies Institute for Medical Research at the University of Tasmania after two decades studying the devils. Genetic mutations trigger runaway tissue growth, which leads to detectable tumors in most forms of cancer. “It’s the same mechanism,” says Woods, “just in the devils’ case it’s transmissible.”
Most cancers arise within their hosts and die along with them. But some are infectious, shuttled by agents like viruses (as in California sea lions), bacteria, or other microscopic vehicles. In devil facial tumor disease, the cancer cells themselves are the infectious agents—making the tumors transmissible from one individual to another. Transmissible cancers are not well understood, partly because they only recently landed on researchers’ radar screens. Of the eight known transmissible cancers identified so far in devils, dogs, and marine invertebrates, seven were detected within the past three decades.
A devil is captured with a visible DFTD (Devil Facial Tumour Disease) near the upper canine and is checked out and a biopsy is taken for further study. (Credit: Heath Holden)
Devil facial tumor disease is passed from devil to devil through physical contact. Individuals brawl, bite, and scratch one another in competition for food and throughout the breeding season. (Early European settlers likened the haunting hisses and growls of their scuffles to the sounds of the Devil, and the name stuck.) During these clashes, an infected individual can transfer live tumor cells from its open wounds to a healthy devil’s face. The cells then grow into disfiguring, puffy blights that bloom in and around the animal’s mouth, face, and neck. Once contracted, the cancer is almost always the kiss of death.
Tumors may take down their host in a number of ways: by acquiring deadly bacterial infections; by growing so large they physically prevent the devil from feeding; or by metastasizing to other systems in the body and eventually causing organ failure. Once facial tumors appear, the cancer typically kills its host within six months to a year.
Scientists from government agencies and research institutions across Tasmania are tracking how devil populations fare in the wake of the cancer’s swift spread. Monitoring teams routinely visit sites across the island, staggering their data collection geographically to complement one another. Ruiz, who is a member of the University of Tasmania team, tracks the devil’s physiological response at several sites stricken by cancer in the northwest region. Out in the field, he and his colleagues snap mugshots of all individual devils they capture, which, when viewed as a collection, are reminiscent of a Most Wanted poster. Along with tissue samples, these photos allow the team to assess tumor growth over time.
Visitors observea captiveTasmanian devilat Trowunna Wildlife Sanctuary, one of the first facilities to successfully breed devils in captivity and now a recognized authority on devil husbandry. (Credit: Heath Holden)
The scientists also analyze blood samples to chart the devils’ immune response as the cancer progresses. “We can be collecting blood samples, and the devils are just snoring away without a care in the world,” says Ruiz, who has trapped, micro-chipped, and tracked more than 400 devils. “They seem like a little teddy bear when they’re asleep—but with big jaws that can chop your finger off at any time.”
Even perfectly healthy devils are short-lived: Most individuals live just six years. Since the cancer’s outbreak two decades ago, several generations of devils have come and gone, and that short generation time may confer a selective advantage. People often think of evolution as happening over thousands or millions of years, but, according to Ruiz, it’s happening right now in Tasmanian devils and their cancer. “This is one of the most interesting systems in the world for understanding the evolution of pathogens and their hosts,” Ruiz says.
Once it emerged, devil facial tumor disease moved swiftly. Its progression through Tasmania was so alarming that the government launched the multi-stakeholder Save the Tasmanian Devil Program a mere seven years later. As an insurance measure, the program established a disease-free population of devils on an island off the Tasmanian coast. Nearly two-dozen zoos and wildlife parks across mainland Australia and Tasmania also pitched in to help maintain genetic diversity in captive populations. By 2013, the program had raised more than 500 captive, healthy devils. But officials were reluctant to re-introduce these individuals into the wild; odds were too high that the animals would contract the cancer and die.
An expectant mother will lay down a trail of saliva for newborn pups to follow as they wriggle from the birth canal to her pouch. There they find warmth, protection, and nourishment. (Credit: Heath Holden)
That same year, scientists discovered that devil facial tumor disease had the capacity to hide markers on its cell surfaces. These molecules are what typically signal to the immune system that an intruder is present. With this discovery in mind, a team led by Woods at the Menzies Institute set out to develop a vaccine that could direct the devil’s immune system to recognize and target the cancer cells despite the inherent absence of more obvious signals. They first treated dead cancer cells with cytokines, special molecules that force the disease cells to express their surface markers. This makes the cancer recognizable to the body’s immune defenses. The team then injected these modified cancer cells into healthy devils. By delivering two types of immune-activating molecules known as antigens and adjuvants at the same time, the devils’ immune systems sprang into action—flagging the injected cells and producing antibodies to fight back. “We’re fighting cancer with cancer,” says Woods.
The scientific community was buoyed by the promise of this finding. But the trials had their limitations. Sample sizes were small, and vaccinated individuals released into the wild were sometimes difficult to catch again, making it a challenge to measure the vaccine’s effectiveness. Additionally, most of the animals that were eventually recaptured came back with malignant growths, indicating that while the vaccine could stimulate the immune system to produce tumor-fighting antibodies, it wasn’t protecting the devils from contracting cancer in the wild.
A year later, just as vaccine research was gaining momentum, researchers detected a new transmissible facial cancer in devils—a genetically distinct cell line that also causes tumorous boils across the face. So far, scientists have diagnosed only about a dozen devils with the new cancer. But they already know that it’s possible for an individual to contract both types simultaneously.
“There’s something that might make devils more susceptible to disease,” says Rodrigo Hamede, a research fellow at the University of Tasmania, and one of Ruiz’s advisors, who studies the ecology of transmissible cancer. According to Hamede, the emergence of a second transmissible cancer in the same species is rare and raises many questions about the perfect storm of factors that has targeted devils twice in just 20 years. He hopes to identify what makes devils susceptible; his findings may shed light on whether we could see a transmissible cancer emerge in humans someday.
A curious Tasmanian devil peeks through a window at Trowunna Wildlife Sanctuary.In the wild, devils roam highly diverse habitats, from sandy beaches to lush rainforests and the high alpine. (Credit: Heath Holden)
When Ruiz first trapped Leesa in the summer of 2015, four of her teats were engorged, a sign that she had nursing pups awaiting her return to the den. Despite the gaping wound on her face, she was docile and calm when he interacted with her, which is typical of wild devils. (Captive devils often show more aggression toward humans.) When Leesa showed up in one of his traps a third time, five months later, Ruiz was happy to see that she had survived the disease long enough to raise and wean her pups. And to his delight, her tumor had taken an unexpected turn.
Once raw and red, the lump on her right cheek now gleamed with healthy tissue. Ruiz thumbed through Leesa’s previous datasheets in excitement to confirm before phoning Hamede from the field: Leesa’s tumor had naturally regressed. Somehow, she had developed antibodies to fight the disease.
Leesa was not the first wild devil to show spontaneous tumor regression. The University of Tasmania team had detected six other individuals with naturally regressing tumors before Leesa’s case was documented. Since then, eight more animals—a total of 15 devils at northwest monitoring sites—have shown signs of regression. And other individuals are simply living longer with their tumors; although transmission rates have remained high in northwest Tasmania, mortality rates and the overall devil population in the region have stabilized.
Adult female devil, Leesa is released from the scientist, Manuel Ruiz’s mesh bag after her checkup. Leesa is one of very few devils who has been recored to have tumour regression in the wild. (Credit: Heath Holden)
Armed with this information, scientists have been working to understand why some individuals are responding differently to the disease. Two years ago, a team that included Hamede looked at whether the species could be evolving natural mechanisms to combat devil facial tumor disease. They compared individuals from three sites across Tasmania, all born four to six generations after the cancer’s outbreak, and detected rapid changes in their genomes; two regions of genetic code in particular looked different. These regions contain genes that are known to influence cancer risk and immune function in humans—suggesting that devils could be evolving resistance. If scientists can firmly establish that certain devils have evolved resistance to the cancer, they may be able to accelerate the recovery of the species by introducing immune individuals into populations that currently lack genes for resistance.
Devils aren’t the only species benefitting from this research. Hamede hopes that what we learn from devils will inform immunotherapy—harnessing the body’s immune system to combat cancer—when treating other cancers, even those in humans. He and his colleagues are investigating differences in immune profiles in wild devils and the role they might have in the animals’ ability to resist tumors. By analyzing facial tumor disease and human cancer side by side, scientists can learn more about the fundamental role the immune system plays in combatting disease. “We have a more holistic view of cancer now that we wouldn’t have had without devils,” says Hamede.
Meanwhile, Woods’s team continues working to develop a vaccine that can prevent devils from contracting facial tumor disease. In the most recent trials, the team vaccinated more than 50 disease-free individuals from insurance populations and released them into the wild. Some animals were fitted with GPS collars to allow for higher recapture success and follow-up immunizations. The study found that 95 percent of vaccinated individuals produced antibodies that combat the disease.
The next step is seeing whether the vaccine can be strengthened in a way that would lead to tumor regression and keep devils from contracting facial tumor disease in the first place. The team remains optimistic that in the not-too-distant future, captive devils destined for the wild might be released with full immunity to the disease. These introductions will bolster wild populations that are still hanging on, despite the dire predictions issued a decade ago.
Ruiz last trapped and released Leesa in August of 2016, when she was an elderly 7 years old. While he assumes she no longer patrols the eucalyptus forests of northwest Tasmania, he feels strongly that Leesa likely died of old age or another natural cause—not from cancer.
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