eli5: Why do humans who drink contaminated water like from rivers get sick, while wild animals drinking from the same source don’t?
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Animals can and do get sick sometimes from simular things as humans do. They just don’t have any alternative and drink what they have to.
There are different ways for water to be contaminated. Some sources of water have really nasty pollutants, bacteria, and parasites in it – humans or animals drinking this water will get sick. Other sources of water aren’t contaminated by these very nasty things, but just somewhat dirty or populated with less-harmful-but-still-bad bacteria and parasites. Animals will also get also get sick from these but at a level that they can handle and build up some immune response to. Most people in developed countries have access to clean water most of the time and never get exposed to these pathogens, so if they did, they would get sick.
Because moving water is safe to drink while you shouldn’t drink from still water because still water like ponds and lakes are what contains the bacteria and all that contamination that gets you sick.
Animals do get sick from drinking contaminated water and they do die from it. But most water is not contaminated. It is just that we as humans do not want to take the risk of drinking from potentially contaminated waters while animals do not have a choice.
There are several reasons why humans may be more susceptible to getting sick from drinking contaminated water than wild animals. One reason is that humans have a weaker immune system than many wild animals, so we are more prone to getting sick from pathogens that may be present in the water.
Another reason is that wild animals are adapted to living in their particular environment and may be better able to handle the contaminants present in the water they drink. For example, they may have a higher tolerance for certain types of bacteria or parasites that can cause illness in humans.
In addition, wild animals may be more resistant to waterborne illnesses because they may be more likely to drink from moving water sources, which can help to dilute any contaminants that may be present. Humans, on the other hand, may be more likely to drink from stagnant water sources, which can increase the risk of illness.
It’s also worth noting that not all wild animals are equally resistant to waterborne illnesses. Some species may be more susceptible to certain types of contaminants than others.
Just wanted to add that even “clean” drinking water from municipal sources may have bacteria or micro-organisms in it that your body has not experienced before and therefore may not tolerate well the first time you drink it, especially when traveling in other countries. It might disrupt your gut microbiome enough to make you uneasy or “sick” but you will recover and should be good to continue drinking without consequence in the future.
I feed my dogs raw chicken and they’re never sick. If I ate it, I’d get campylobacter, salmonella and clostridium perfringens and probably be dead by now. Dogs can definitely deal with these bacteria better than humans.
Nature is not perfect, it’s just good enough.
So long as you live long enough to spawn then your purpose is served, any extra is a bonus.
As others have said, not everywhere is contaminated, but nature is not kind, animals die of something, old age is rarely it.
Who says the animals are not sick? Most wild animals have parasites for example. So they are not totally healthy. And way back when humans drank from those same sources and we survived. Back then humans had parasites too. That said some animals are more adapted to handling pathogens. Carnivores have shorter intestines. This allows them to poop out pathogens before they cause a problem. Vultures and other animals have very very acidic stomachs that help kill pathogens. But animals do get sick all the time. You don’t see them quite as much as they become targets of predators that take them out of the population. So you mostly see healthy animals, or in other words healthy enough to survive.
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