OK. So you’re sick with a nasty cold, or sinus infection, or whatever. You inadvertently cough in your dog’s/cat’s face. Presumably, a good amount of virus ends up in your pets nasal tract or mouth.
Of course, your pet won’t catch your illness. But what happens to those viruses that ends up in your pet’s system? What happens in the pet in the time between exposure to these viruses and whenever the viruses pass safely through the pet’s system?
I’m assuming that early on, the viruses “travel” across the mucous membranes in your pet’s nasal/oral cavities. Viruses, if I understand correctly, “look for” certain types of cells to latch on to. So the viruses are either latching on to canine/feline cells and can’t get anything going, or they never latch on to anything at all.
So what’s happening at the microbiotic level in cases such as this?
Most of them just dry & die (if you assume that virus is alive and can die, that is). Skin is great barrier against most infections.
Those few that manage to get inside will either:
a) be destroyed by immune system
b) remain inert, as there is no proper receptor to “latch” to, and eventually die/dissolve or leave organism by usual ways
c) there is possibility that there are receptors allowing viruses to infect pets cells after all. There are diseases that pets can catch from humans, and there is small but non-zero chance of virus mutating/being mutated into form that can infect pet.
Even if virus somehow infect pet, it doesn’t mean that said pet will automatically become sick. After all, there is still immune response and all that.
Is this known to occur/have occured with general upper-respiratory nastiness that people come down with from time to time? It’s just barely possible that a dog, say, can catch something akin to kennel cough from a human?
Missed edit window:
I forgot to add, that cats (and maybe dogs, I’m not sure) body temperature is higher than humans and some human viruses just can’t survive the heat
Don’t know about common cold and the like, but there are subtypes of flu virus that are endemic for dogs. Also inter-species transfer of some flu types is possible, although unlikely.
Most viruses are species specific. In order to infect a cell, the virus usually must bind to a receptor on the cells surface. These receptors are often altered in non-human animals (and vice versa). Not by much, but enough to prevent (or at least greatly hinder) infection.
In the case of colds, most human colds are caused by rhinoviruses. In order to infect, a rhinovirus must bind to a surface receptor called ICAM-1. Canine ICAM-1 is only ~62% similar to human, and that is enough to greatly reduce rhinovirus binding. I can’t find any data on cat homology, which leads me to believe cats don’t have that receptor. AS a comparison, chimp ICAM-1 is 97% identical to human.
Note that pets can get infected with viruses that mimic human cold symptoms, it is just highly unlikely that they will catch your cold.
According to teh Intarweb, ferrets are one of the few pets which can catch human colds. I don’t know if this is true, but it’s a claim which seems to be repeated everywhere (including by veterinarians), so I tend to avoid coughing on my ferret when I’m sick. For that matter, I avoid coughing on my ferret even when I’m not sick.
Species-jumping does happen. I know that parvovirus (B19/5th’s disease) that is deadly to puppies jumped from cats (who are not as affected) in ~1970s. And look how influenza jumps from pigs and birds to humans, or West Nile Virus. So there are many non-specific infections that you can give to your pets. I’d say that non-viral infections (bacteria, protozoa, yeast, helminths - anthrax, worms, giardia, etc) would transfer more easily as they are not as limited by specific receptors.
In “Guns, Germs, and Steel” by Jared Diamond, he discusses how almost every human disease evolved from livestock, and that the switch to an agrarian society greatly increased human diseases.
And that’s specifically because epidemic diseases need large host populations to survive in – when some hosts die or becoming immune, the virus or bacterium migrates to uninfected hosts and keeps going until new hosts are born. Small isolated populations (such as early, pre-agricultural humans) do not generally suffer from epidemic disease.
I wonder if mass-production of pets in high-density puppy mills enabled the parvovirus mutation described above to take root in dogs?
