I’ll admit it – I don’t understand dogs. How is it that they have this incredibly well-developed sense of smell, but my dog feels it necessary to roll in the most disgusting smelling things he can find? I guess it’s not that he feels like he needs strong body odour, just that he has a poorly developed part of the brain that says “hey, that smells gross” (along with related parts of the brain that say “hey, that tastes gross,” “maybe I shouldn’t chase that skunk,” and “maybe body slamming the side of the bed to scratch my back at 4 AM doesn’t endear me to the people that feed me.”).
Anyway, that’s a pretty indirect introduction to a question of what animals can track back into the household and other unusual routes of zoonotic disease exposure. I won’t get into the whole issue, but I have had a rash of calls lately from people worried about indirect exposure to rabies virus. Questions have include:
- My dog was nosing raccoon roadkill. What if the raccoon had rabies?
- If I run over an animal and then touch the tire, could contract rabies?
- If someone who works removing bats from houses comes over, could they have rabies virus on their shoes and contaminate my house?
For someone to get rabies, the virus has to go from the infected animal’s body (saliva or nervous tissue) into the person’s body. Rabies virus isn’t airborne, it doesn’t survive long in the environment and it can’t infect through intact skin. Indirect transmission of rabies is exceedingly rare, with one of the only examples that comes to mind being rabies in a family of shepherds who cared for a sheep that was attacked by a rabid wolf. The attack occurred right before the people handled the sheep, and wolf saliva (containing rabies virus) was likely present on the sheep’s coat from the attack, and the handlers had cuts on their hands. Very rare.
That said, with infectious diseases we rarely say "never." That often causes angst because people want to hear “there’s absolutely, positively no way you could have gotten [insert disease here] from [insert event here].” Yet, there are situations that are so unlikely that we probably should take the plunge and just say "never."
For example, is there a theoretical chance that an animal run over by a car would be rabid, and that brain tissue would be splattered on the tire, and that it wouldn’t be killed right away by heat from the tire, and someone would touch the tire right after and that person touched a virus contaminated area of the tire and the virus had contact with an open wound?
Sure, I guess…
However, while rabies post-exposure treatment is very safe, the odds of an adverse effect of post-exposure treatment are probably infinitely higher than the odds of getting rabies in weird situations like those about which we are sometimes asked. Considering how well rabies cases are tracking in developed countries, and how many wild animals have rabies, if indirect exposure was a real concern, we’d know about.