Re: Is it possible for whales (and/or dolphins) to contract rabies?

You know, I never thought about this one before!  And unfortunately, 
the answer is that I that I really can't say for sure.
The rabies virus is a mammalian-specific virus.  It only infects mammals, 
but as best as I am aware it can infect all mammals, from bats to man.  
The exact mechanism or reason for this pattern of infectivity of is not 
totally clear, though.  There is simply a lot we do not understand about 
how the virus actually establishes an infection in an animal, and therefore 
why some might be susceptible and some not.  

It is clear that the virus propagates in muscle and then is transmitted 
from neuron to neuron until reaching and infecting the brain, and it is 
fairly well accepted that it does this at least in part by interacting with 
the acteylcholine receptor that is on these cell types.  But the story is 
clearly more complicated, since studies in the tissue culture dish do not
 accurately reflect the cell-specific nature of the rabies virus infection.  
In other words, the cell-specificity or "tropism" of the rabies virus seems 
to depend on factors only present in the whole animal, which makes them 
difficult to predict and/or study.

A further complication is that the outcome of infection is not the same 
for all species.  The infection is very aggressive in dogs, for example, 
while a person may have a latent (quiet) phase for years, while bats seem 
to live a normal life-span even with rabies infection.

Whales are most certainly mammals, since they bear live young, etc. etc.  
So, I would suppose that they would be infected by the rabies virus.  
But I know of no direct evidence to support or refute this.

You seem to suggest that seals and walruses are known to carry the 
rabies virus.  Is this conjecture, or has this been shown??  If you know of 
rabies infection of seals and walruses, you know more about this than I do!  
In my searches on this topic, the best I could find was a study that looked
 at viruses isolated from sea mammals (seals, I think).  They did find 
a rabies-like virus in the animals, but it was not rabies itself.

For both sea mammals (e.g. whales) and sea/land mammals (e.g. seals) we 
must finally consider how they might get infected.  The predominant way to 
be infected would be through the bite of a rabid animal.  The second way, 
and far less common, would be to eat an infected animal.  In any infection 
route, though, the virus must get into tissues to cause an infection - 
"casual contact" won’t do it.  Since the most common rabies reservoirs are 
dogs, bats, skunks, raccoons, coyotes, etc, I think it would be very unlikely 
that even a seal or walrus would ever get infected (but there may be something 
I don’t know about this!).  And even if they did, it is not at all clear to 
me how they would further transmit the virus to plankton-sucking whales.