5 Times People Gave Animals Diseases | Reverse Zoonotics


This episode of SciShow is supported by NordVPN. Head over to nordVPN.com/SciShow to learn more about virtual private networks and internet security. [INTRO♪] We often hear about diseases we can get from animals, and for good reason. Many of these diseases, collectively called
zoonotics, are serious health threats. But illnesses are often two-way streets. Animals can get us sick, and we can pass pathogenic bacteria, viruses, fungi and parasites onto them. These reverse zoonoses are more common than you might realize. And they’re a big deal, because they can
harm animals we care a lot about, like the ones we eat, and the ones we’re desperately trying to save from extinction. In June 2009, an outbreak of metapneumovirus —a kind of respiratory disease— struck a group of mountain gorillas in Rwanda. Altogether, eleven of the twelve gorillas in the group got sick and two —an infant and its mother—died. And though that might not seem like a lot, it’s devastating to a species with just
600 or so individuals left, all of which are roughly in the same general area. In fact, infectious disease accounts for 20% of sudden deaths in mountain gorillas. 20%! But the worst part was that that outbreak was caused by people. You see, although researchers aren’t exactly
sure who passed the virus on to the gorillas, they know it was a person. Samples of the deceased gorillas’ lungs and throats contained genetic sequences from human viruses. Researchers also found pneumonia-causing bacteria in the mother, which turned out to be the
cause of death— basically, it moved in after her body had
been weakened by the virus. And that confirmed that the apes are catching human diseases—and those diseases can kill them. Which puts local scientists in a tricky spot. Conservation efforts rely on tourism money. But our devastating infections can pass more easily to gorillas than many other animals because we’re so similar to them. So the presence of potentially-ill tourists might do more harm than good. Right now, the plan is to restrict access to the gorillas and the area they live, and in some places, make people wear masks to help prevent the spread of infectious diseases like metapneumovirus. There’s also the possibility of developing a gorilla-specific vaccine for it. And that probably wouldn’t be that hard. Scientists have already successfully given vaccines to wild gorillas and apes to protect them from outbreaks of measles, tetanus, and
polio. But whether vaccine development actually happens ultimately depends on the cost and what governments, conservation groups, and tourists are willing
to do to save these animals. Unless you were living under a rock, you probably heard about the global influenza
A pandemic of 2009, better known as swine flu. Within six months of the World Health Organization’s official pandemic declaration, there had been
more than 414,000 confirmed cases in people and nearly 5,000 deaths worldwide. The first case was thought to have come from pigs in Mexico—hence the name
swine flu— and then spread among humans from there. But it turns out we actually started it by giving them the flu first. See, the whole reason swine flu was so contagious and all-around terrible was because its RNA
was a mix of human, pig, and bird influenzas. And that only happened because sometime around
1998, we passed our version of the flu onto some
pigs. Pigs can act like tubby genetic mixing bowls because they’re susceptible to viruses from different animals, and those viruses can all hang out together inside them. The pigs that got our 1998 flu were already
harboring their own pig flu, and then they also managed to catch a bird flu. These three viruses combined into what’s
called a triple reassortment—a mix of genetic material from three sources. Even then, the virus wasn’t so bad for us
at first— for about a decade, it mostly spread between
pigs and didn’t change much. Then, around 2008, the triple virus got even more genetic material from two other pig viruses. That’s when it became the pandemic version. And not only did we basically start this pandemic with our human virus, we also continued fueling the evolution of the virus by giving it back
to pigs. As of 2015 there were at least 49 cases from more than 30 countries where people spread swine flu back to swine. In fact, in general, we spread more influenza viruses to pigs than they do to
us. And that’s bad for the pigs who become infected, because they often are culled to stop the
spread. But it’s also really bad for us because
it can encourage the viruses to evolve into new strains which we don’t have vaccines for. Tuberculosis, or TB, is a disease where bacteria multiply in the body, usually
in the lungs, causing coughing, weight loss, fever, and
sometimes death. And though you’ve probably heard about it in the context of people, the bacteria involved — Mycobacterium tuberculosis and M. bovis— aren’t all that picky about which lungs
they set up shop in. And thanks in part to us, the disease has become a huge problem in elephants. Up to 25% of elephants have TB in some parts
of the world. Though, it’s hard to tell exactly how much
of that is our fault. It’s true that many modern cases involve zoo or circus elephants—basically, situations where animals and people are in close contact a lot of the time. But there are cases of elephant TB dating back 2000 years. And since it’s so contagious and can infect so many species, it’s sometimes difficult to know where the
disease comes from. Also, unlike some of the other diseases we’re talking about in this episode, the same strains of bacteria can be found in both people and other animals. So scientists aren’t always able to tell
if we gave it to an elephant or if it came from some other animal the elephant came in contact
with. But there have been several cases of wild elephants dying from TB infections where the evidence definitely points to a human
cause. For example, a 2017 study looked at the circumstances surrounding the TB deaths of 3 wild Asian
elephants in a wildlife sanctuary in India. In that case, there were no recent introductions of captive elephants, but lots of interaction
with native tribes and tourists who could have
carried the bacteria— and the story is similar for cases from other
parks in India as well as ones from Sri Lanka, Kenya
and South Africa. And elephant TB has become a really big issue
in Nepal, where there are many humans infected with
TB, and the elephants are often lead around private hotels to entertain tourists. The elephants don’t even have to come in direct contact with people. Wildlife veterinarians think that wild elephants might be getting TB from human-contaminated
food or waste at rest stops close to where the animals live. Overall, this is a huge problem because all elephant species are considered vulnerable
to extinction. Not only is TB probably contributing to that, but increased contact with people from ecotourism or even breeding programs could lead to more sick elephants. Again, it’s a case of us wanting to help, but that help could be posing a risk to the
animals. So to keep everyone healthy, we need to address the human illness, too. Scientists also want to follow up on cases where TB is found in the wild to figure out
if there are other animals acting as disease reservoirs by carrying the bacteria, or whether it’s basically just us. This year, we’ve seen a spike in the number of human measles outbreaks around the world. And that’s concerning for our species and our primate cousins. Measles is a highly transmissible disease because it spreads through the air. And there have been a lot of cases of measles
in monkeys —some from other infected monkeys, and some
from people. One of those human-caused outbreaks happened in 1999 in a primate research facility at the National Institutes of Health in the
US. In that outbreak, 94 monkeys from several
species became infected with measles. That’s a lot of rash-covered, coughing, stuffy-nosed monkeys. And the thing is, every new monkey brought in to the facility had undergone a
medical exam which ensured they were measles-free. That alone is not enough to guarantee that the initial spread went from person to monkey,
though. So, researchers analyzed samples of the measles
virus taken from the monkeys, and found it was really
similar to the strain going around humans at the time. And when they tested the people in the facility, there was one worker who tested positive for measles antibodies in their blood, which indicates they had recently fought off
the virus. All and all, the epidemic spread across two
buildings; it lasted 16 days in one and more than a month
in the other. Then many of the monkeys had to spend two additional months in quarantine. Though this incident was pretty bad, it taught scientists a lot about how to prevent and control measles in primates. For example, like in humans, vaccinating the monkeys stopped the outbreak sooner. You see, the whole scenario served as a kind
of natural experiment because the monkeys in
one building couldn’t be vaccinated because they were already part of an experiment. And that’s building where the epidemic lasted
twice as long. Of course, the best way to prevent monkeys getting measles is to prevent the people they come in contact with from getting measles— like, by requiring vaccinations for people
who work with the animals. But the danger extends beyond captive monkeys. Like with the gorillas, measles can also spread to wild populations—in fact, is has, at
least four times, in places like wildlife sanctuaries and temples where monkeys often get close to tourists. Such places do have some options if the situation gets really bad. Like, in addition to handing out disposable facemasks and getting tourists to wash their
shoes in disinfectant, these places could decide
to refuse entry to people who aren’t immune to measles or other contagious illnesses. Which is another reason to get vaccinated! As we’ve seen, our germs can have an impact on species all over the world. But up until 2018, scientists thought there
were at least some areas that were untouched by reverse zoonoses. Like, the continent of Antarctica. That all changed when paper in Science of the Total Environment revealed
that Antarctic bird poop contains bacteria from
humans. The researchers found that 24 bird species from all over Antarctica, including rockhopper
penguins, Atlantic yellow-nosed albatrosses, giant petrels
and skuas, had all been exposed to some kind of bug from tourists or visiting scientists. Specifically, they found evidence of what doctors call enteric bacteria— ones that live in our guts and sometimes cause things like diarrhea and food poisoning. The birds’ feces contained DNA from known human pathogens like Campylobacter jejuni, an antibiotic-resistant type of Campylobacter
lari, and several strains of Salmonella. And while it’s possible some of these were passed along from their feathered kin, C. jejuni is almost never seen in wild birds— just humans and domestic animals. Now, the Antarctic birds in this study didn’t appear to be sick, but it’s hard to say what effects these
bacteria might have in the ecosystem because this is
likely the first time Antarctic animals have been exposed to them. Both the Campylobacter and strains of Salmonella found in the study can give us raging food
poisoning. But they’re mostly harmless in animals like chickens and cattle, minus the occasional case of the runs. Even if these strains aren’t dangerous to Antarctic animals directly, they indicate
that our pathogens are reaching the most remote
corners of the planet—though, exactly how they’re
getting there remains an open question. They might be coming from researchers who come in direct contact with wildlife, or, scavenging birds might be picking them
up from human waste that’s left near remote
research stations. They could also be coming from inhabited areas close to Antarctica, like Patagonia, where
wild birds can waddle in places where livestock are kept. And scientists think that once some Antarctic
wildlife are infected, they could be spreading it between themselves. One thing seems clear: as more research stations and tourist operations pop up in the area, there’s an increased risk of native animals getting these bacteria as well as other, potentially nastier human pathogens. So the paper’s authors are now urging governments to do more to protect them, like requiring stations carry out human waste when researchers leave. It’s no secret that our species has conquered
the globe, but now, we’re realizing our pathogens have
also infiltrated the furthest reaches of this planet. And as human populations grow, cases of reverse zoonoses are expected to
increase. That means to keep animals healthy, we have to keep ourselves healthy, too. And we should be especially mindful of what
we leave behind when we visit natural areas— from footprints to feces. Really, we should be mindful of what we’re
putting out into the world wherever we go. I mean, your computer or phone might be telling others a lot more about you than you’d
like whenever you connect to a public wifi network. But that’s something that a virtual private
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100 thoughts on “5 Times People Gave Animals Diseases | Reverse Zoonotics”

  1. Beastiality, beastialitu everywhere. Proof? Man with monkey fetish, took away mercury.
    But too be honest free love movement didn't help things either. Dam hippies, spreading STDs like wild fire.

  2. I can't tell if his t-shirt is green like the green screen, or if it's really that color.

    Why is this the thing my brain focused on?

  3. I think you should have noted the reason why there are so many diseases in livestock. By keeping basically billions of animals in confined places, with abuse, poor conditions and epidemics. Perfect environments for breeding the next pandemic.

  4. You could have added Bovine spongiform encephalopathy (BSE). In the 1980’s, farmers fed cattle, well, cattle and it was legal. It was all about getting the most from each cow. It wasn’t until cows started to exhibit strange behaviours such as the inability to stand or walk. Inevitably, cows with BSE died horrible deaths. This triggered scientists to investigate. Low and behold they found it’s never a great idea to feed cows with cows. Thousands of cattle were subsequently slaughtered. Then it jumped the species barrier to humans and caused vCJD. Totally preventable and tragic story. It went full circle sadly

  5. I guess now I'll have to start making sure my penguin eggs are thoroughly cooked before eating them. Is nothing safe from salmonella?!

  6. AYYY LMAO THE THUMBNAIL is me as a kid! My uncle is a photographer and he took that picture of me when I was at my grandmothers house, and he caught me LEGITIMATELY mid sneeze. he’s been proud of it forever lmao.

  7. “Reverse zoonoses” is incorrect, it’s actually “anthroponoses” (anthro=Human, noses=disease) Edit: I’m a Master of Public Health student who spent a year specializing in infectious diseases, including zoonoses

  8. Why can the phrase "human waste left near remote research stations" even be uttered as a thing that happens? Aren't these the people who ought to know better than to be leaving garbage around their site? It's honestly completely absurd to me that this happens, it seems like one of the most obvious and easy things to no do, not to forget one of the most important.

  9. So antivaxxers not only endanger themselves, they're children, and people around them, they also endanger the environment. Way to go idiots

  10. I’m not gonna lie all of this was important information but I think that I’m going to start calling people I don’t like “disease reservoirs”

  11. "Don't vaccinate the gorillas! They'll get autism!"

    Yeah, this is gonna be a fun time indeed. Thanks for giving us a new power move against antivaxxers. This will be absolutely hilarious! x'D

  12. We also spread diseases that only infect animals. Chytrid for example is decimating the worlds populations of amphibians and it is being spread by humans as they travel. It started in South America and now has been detected on nearly every continent minus Antarctica. I found one of the only cases in Kentucky 2 years ago as it infected a population of America Toads. It's horrible to see the skin just falling off of these animals and knowing that you can't do anything about it. The disease was confirmed by an independent lab after I took samples and shipped them to be tested. All because of people and their need to travel. I carry around a bottle of ammonia solution (ammonium hydroxide, 3%) to spray my shoes, hands and all of my equipment when I go herping (searching for reptiles and amphibians. Herping is a slang term derived from herpetology, the study of reptiles and amphibians.) Snake fungal disease is another disease that we keep spreading that doesn't affect us. There's nothing like finding a snake with its head covered in scabs to the point that it can no longer feed. Resulting in higher rodent populations, and there is no cure for either of these diseases. Scientists are pulling out all the stops to find cures for them, Though by the time it is found it may be too late and most of these beautiful animals who hold many secrets and possible cures for hundreds if not thousands of diseases like breast cancer, diabetes, ace inhibitors, etc. It also seems that most people do not care, which is a damn shame. 😞

  13. The "swine flu" almost killed me. It, directly and indirectly, caused so much damage to my body that it took over two years to mostly fully recover. I never did fully recover to my previous self. The typical flu virus only makes me slightly sick for maybe 2-4 days tops. The swine flu was something my body just couldn't handle apparently. I was sick for three weeks. Couldn't eat. Couldn't walk (too weak). Ran a rather high fever the entire time.

  14. Great. So unvaccinated ppl can spread their germs on animals who can graciously return the gift virulent and deadly.
    I'd seriously consider making antivaxers criminals.

  15. For the last one, cargo ships dumping wastewater tanks and carrying water from region to region as ballast would pretty much explain it.

  16. the part he doesn't mention is half the monkeys take 2x aslong but now have a natural way to fight the measles not a way to modify it making it a issue later

  17. I wonder if that's how the Spanish Flu got so bad, we started it and animals kicked it up a few notches before it made it back to us.

  18. clearly no corner of the planet has been untouched by humanity. people need to think more carefully now about our impact on the planet. I don't have much I can afford to do because I'm poor. But I do grow a garden, I don't spray pesticide on it, and I make sure to give some of that space over to insectiary plants. The bumblebees are actually the least spectacular creature in my garden. I get hoverflies, aphidius wasps, this year I got a yellow swallowtail and a dragonfly, and every year I get baby orb weaver spiders. The plants and the pits in the brick of my apartment building draw in these gorgeous green and teal metallic wasps, so tiny they could fit on my index finger, as well as these beautiful black and white jumping spiders.

  19. Anti-vaxxers are already willing to let their own offspring be at risk of dying from easily preventable diseases. I doubt they would care about wild animals.

  20. Triple reassortment. That must have what happened to my cousin when he got bit by a vampire, a werewolf, and a zombie at the same time.

  21. I'm surprised he didn't discuss the case of koalas getting chlamydia. Then again I really don't think I want to know how the heck that happened

  22. Hank, is using "the runs" in place of "diarrhea" an Indiana saying? Because I've never heard a non-Hoosier say it. Lol my father says it, and it totally grosses me out.

  23. all these people blaming people who dont want to be vaccinated yet virus' live everywhere in the ground chilling in animals, people not affect them even shall fish can hold measles. plus with travel theses days how are you going to vaccinate all 7.5 billion people maybe some natural selection will help control the population which will help with global warming and resource strain….

  24. I gave my guinea pig a uri when i had one.. it wasnt pretty.. we both got treated.. but he died from old age a month later

  25. One of the lowest viewed videos. Speaks volumes about the real human capacity for compassion to those without as much agency.

  26. Except they are not OUR pathogens. They are living beings (debatable), that want to reproduce and spread out. These microorganisms might be more successful at infecting humans, but that doesn't make them part of us or ours. If they adapt/evolve to infect other species, well… Survival of the fittest.

  27. I was exposed to marine TB from my fishtank, and attempting to explain my situation to the advice nurse hotline was… Embarrassing

  28. i skip and end the video whenever you put ads directly in the script. and thumbs down. put ads that are skippable after a few seconds like everyone else

  29. sooo…..basically all it takes is an anti-vaxxer who takes his/her love for animals a bit too far and the poor creatures get infected with e.g. Influenza and HIV?….poor animals

  30. We’re glad that Lyme disease is getting more national attention (we’ve been talking about it for a while now!), and that actual progress is being made in terms of diagnosing and treating the condition. It remains to be seen how effective this new process is in practice, but we’re cautiously optimistic.

  31. Another reason why herd immunity is important is, it doesn't usually happen, but it does happen that sometimes time immunity you got from your vaccine stops. They thought a friend of mine had mumps for that reason, that's how i learned about it, but it turns out she had a different, less severe, strain of mumps.

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