Why doesn't rabies like squirrels?

Once, a long while ago, I saw someone rescue a baby squirrel from the middle of the highway. Someone in the car with me remarked “I hope it doesn’t have rabies.” I replied that so far as I knew, it’s pretty unusual for squirrels to carry rabies. . . but then I wondered “Why?”

I’m guessing either a) something about squirrel (and their allies) biology is inhospitable to the rabies virus, or b) anything with rabies that chomps on a squirrel is likely to kill it then and there.



My guess would be that:

  1. Small rodents are most likely going to be killed by any sort of attack by an animal with rabies.
  2. Small rodents, having survived that attack, are probably going to die pretty quickly from the illness.
  3. Small rodents are unlikely to be able to communicate the disease to others since they are neither large nor fierce.

I doubt they have any particular resistance to the illness, but I guess we’ll find out when Colibri pops by.

I looked into this a little while ago, and the answer I got was that small mammals such as squirrels tend not to survive attacks from other rabid animals.

Here’s one site, specifically about squirrels:

edit: well that’s what I get for taking too long to get a site

I know for opossums, their body heat is too low for the rabies virus to survive - maybe it’s the same for squirrels?

And bats are small mammals, but they’re wonderful carriers of rabies. So some critters can and do survive rabid attacks, no?

Rats and mice don’t really carry rabies either. It supposedly can happen but hardly ever does due to the reasons listed above.

Yup, it’s not that squirrels are particularly resistant to rabies, it’s that squirrels generally don’t survive an attack from a rabid animal (or a non-rabid animal, for that matter).

At least that’s what the state Animal Control said when we had a squirrel-bite incident.

And they finally confirmed that bats carry Marburg virus (related to Ebola). What is it with these bats? :slight_smile:

I never thought of this before! They survive by freaking out their attacker with their bat vibes* but what the hell is attacking bats in the first place?!

*Or, maybe because they have the advantage of being able to fly. Nah, it’s the bat freakiness that does it.

Rabies can be acquired by inhaling bat guano, that’s why spelunkers are told to take precautions. I imagine that since bats like to hang about in caves infested with other bats and their guano that would be the most likely route of infection along with bat on bat violence since one bat biting another is not likely to be fatal … except for the rabies part.

Many, many years ago I had read that rodents (not talking about bats anymore, I know they’re not rodents) did not “readily transmit rabies” something to do with their salivary glands. I have since been unable to find this information so it’s possible that it has since been thrown out, debunked, pooh-poohed or whatever.

[vet hat on] Mice can experimentally acquire rabies. Heck, the lab down the hallway does more of their experiments in rabies with mice. That said, I doubt they can acquire the disease naturally, for reasons mentioned above. At least to get it for long enough time to pose serious danger to humans.

Rabies virus survives in opossums.
[vet hat offf]

I’m not that sure on squirrels’ poor survivability. They are incredibly tough critters for their size, as any squirrel hunter can attest. Squirrels fight each other frequently, biting off pieces of tail, tearing ears etc with their razor-sharp front teeth. I once hit a squirrel with a blunt arrow that has taken pheasants and mallards cleanly at longer distances. The arrow tore the squirrel’s forelimb clean off at the shoulder. I assumed a quick drop, but the bushtail clung onto the tree for a long while as I looked at the gaping wound. Many bullet-hit squirrels will quickly climb a tree and not come down. Some take several .22s to dispatch. I’d suspect many squirrels survive rabid predator attacks, even though most surely die from the immediate injuries.

After researching the cases of supposed aerosol rabies transmission, I doubt in the extreme that it happens. It essentially came down to two cases. In one, the man may have handled bats barehanded. In the other, the man was in a cave with a phenomenally high concentration of bats (such that avoiding physical contact was impossible) and likely had open sores on his face and neck.

That being said, it’s still a bad idea to breathe in the air from a heavily batted cave as you can get toxohistoplasmosis and other fun things.

The CDC says that “terrestrial carnivores” are the commonest carriers and transmitters of rabies. In re squirrels, the following:

From here

They do not speculate on the “why” question. No definitive answer appears to exist, as all rodent species do seem able to support the rabies virus. The extremely low incidence in wild populations is known, but not explained. Some worthy candidates for possible explanation appear above. Add to them the fact that individually squirrels are not only tough, but highly skilled at avoiding predation in the first place. A “terrestrial carnivore” like a fox or raccoon that is suffering from rabies is unlikely to be an active or effective predator. Squirrels will likely be better able to avoid contacts with such an animal than with an unimpaired predator.

The CDC does though go on to caution that local health departments be consulted in the event of an exposure. It is theoretically possible for there to be a local outbreak of rabies in some species not commonly seen as a carrier, and local authorities would be expected to have some insight. Our county’s health department has a “Rabies Task Force” (I’m a consulting member) and one of its duties is to review all possible exposures. If, say, an upsurge in squirrel bites on humans or some other indicator caused suspicion, the health department would ask the local animal control agency to trap some for testing. If necessary, special public advisories could be issued, and/or control programs initiated. This has never occurred here with squirrels, but it does repeat locally at about 5 year intervals with raccoons.

While all carnivores are suspect, bats (as well as raccoons and skunks) are a case apart. These species have the potential to act as “asymptomatic carriers”-- meaning that they may harbor and even transmit rabies while never showing symptoms or succumbing to the disease. That makes human exposures to these animals especially problematic, as even normal-appearing individuals must be treated as carriers. No quarantine period or history of captivity is sufficient to guarantee safety. The only definitive test remains microscopic examination of brain tissue. Just one more reason not to get bitten by your friend’s “pet” raccoon.

Well, yeah, that’s the point. They have to survive several weeks of incubation before rabies is actually symptomatic and/or infectious. It doesn’t really matter if thy die in the actual attack, die a couple of hours later from blood loss, or get eaten the next day because they’re injured.