I wondered: If I get into the library and look into the medical section it is evident that there are thousands and thousands of different human physical diseases. But if I look into the section of animal diseases it is by no means as large as the human section. But humans are by no means the only beings with extraordinarily cell complexity. Many other animals have an equal amount of cell complexity. So shouldn't other animals have an comparative equal amount of diseases ?

Naturally as humans we are much more interested in human physiology which would explain the discrepancy. But is there any evidence that animals, especially mammals, have not an equal amount of (still unknown) different diseases ?

Remark: While a bit similar, this is not this question:

Why do humans seem so much more prone to disease than animals?

I am asking about the quantity of diseases, not if humans are especially prone for diseases.

ADDENDUM: The difference between the questions is like "Is building A more prone to fall in natural catastrophes than other buildings because it seems like it ?"

and "How many faults have building A in comparison to other buildings ?"

A correct answer to the first question is: "We made a statistical comparison and building A is more/less/equal prone to fall in a natural catastrophe. The impression is wrong/right."

A correct answer to the second question is: "Building A has in fact a mean approximately 13 000 faults while other buildings have only 5400 faults. But the reason can be that the other building are inspected with less care." Or "No, they both have very likely something like 9000 faults".

It is a completely different question. The second question does not ask for the severity of faults. It could even be that building A has more faults while being more secure because the faults itself are much less severe.

  • $\begingroup$ The problem is that it's very hard to quantitate diseases. Is each sickness caused by a different influenza serotype a different disease, or are they all "the flu"? What about the huge number of potential bacterial infections? Also, a number of human diseases today are diseases of affluence and longevity - cancer was quite rare when our lifespans were a lot shorter. We are the only species that have developed significant longevity without evolving it. Since we are self-cognizant beings, we have a number of psychoses and other mental illnesses that are not present in other animals, as well. $\endgroup$ – MattDMo Dec 20 '15 at 2:35
  • $\begingroup$ Just to add to MattDMo's point, we are able to bring many children into this world that would not have made it a century ago. Some genetic diseases are cured and many others treatable. That's unlikely to be as true for any other animal. So that would add to the thickness of the section on those diseases, whereas we might just add a line to an animal section that says, if this happens they die. $\endgroup$ – Nathan Dec 20 '15 at 2:49
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    $\begingroup$ This question has been asked before, several times at least. $\endgroup$ – anongoodnurse Dec 20 '15 at 16:26
  • $\begingroup$ @anongoodnurse If you would actually read the question instead of simply scanning the title, well.... $\endgroup$ – user10094 Dec 20 '15 at 16:28
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    $\begingroup$ Who said I didn't? It's not "a bit similar", it is exactly the same question. $\endgroup$ – anongoodnurse Dec 20 '15 at 16:28

There are two differences between humans and other animals that lead to humans apparently having more diseases. First, humans live longer than most other species, giving them more opportunities to encounter pathogens and for their bodies to wear out. Second, and more important, there is far more effort put into keeping humans alive than keeping animals alive. This leads to two effects: There's far more detail about human disease, and humans live through diseases and injuries that would lead to the prompt death of most animals. A rabbit with a small tumor on their leg will be eaten in a couple of days, and will never have a chance to develop al the myriad complications arising from the tumor that humans see; let alone to develop a second tumor.

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  • $\begingroup$ I suspected as such and it seems as the most reasonable assumption. I was interested if there are counterarguments which would give a reason that the number of diseases are really different because humans have some unique anatomical or physiological differences. $\endgroup$ – user10094 Dec 20 '15 at 16:55
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    $\begingroup$ Some references would be nice. $\endgroup$ – anongoodnurse Dec 20 '15 at 19:31
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    $\begingroup$ References for what? The fact that humans live longer than other species? That humans are more interested in keeping humans alive than animals? $\endgroup$ – iayork Dec 20 '15 at 20:29
  • $\begingroup$ There is also the fact that there are many more humans than any other species alive. This also means there are large amount of different/unique populations for diseases to crop up in. Usually leading to differences in which diseases are seen where in the world. $\endgroup$ – FrankyG Dec 21 '15 at 22:05
  • $\begingroup$ @FrankyG Humans are vastly outnumbered by many species. Even setting aside things like insects and rodents, there are some 19 billion chickens alive at any one time, for example. $\endgroup$ – iayork Dec 22 '15 at 1:31

The issue is more a matter of research focus than anything else. People care more about people than other organisms. Hence, more money is available for research and more money goes around in medical healthcare than in veterinary care. Research and drug development, in turn, focus on where the money is. The diseases of animals other than humans have simply not been investigated in such detail as in humans, because less effort has been done to document them as exhaustively as has been done for humans. Thus, when something is not in the literature, that doesn't mean it doesn't exist.

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