This is a question Gail asked in a comment. She is a well known figure in the cat world ;). She couldn’t find a clear answer on the internet. I searched myself and had similar problems. This is an attempt to clarify the situation. Right away I can tell you that despite extensive searching I have failed to find a definitive answer from a sound source. Nonetheless here is my answer.
Whether conjunctivitis is contagious from cat to dog depends on the cause. There are various causes of conjunctivitis. This is one reason for confusion. The two main causes of conjunctivitis are viruses and bacteria. These are two different sorts of organism.
Conjunctivitis is sometimes referred to as “pink eye“. It describes inflammation of the membrane covering the back of the eyelids and the surface of the eyeball. When inflamed it looks pink.
A veterinarian website, vetinfo.com says in relation to conjunctivitis:
“The transmission from cats to humans can also be made by direct contact…”
That implies the same could occur between cat and dog because it implies that the bacteria can be transmitted between different species. One of the causes of conjunctivitis is a secondary bacterial infection on the back of the primary infection, which most commonly is the feline herpes virus. There might be pus and mucus (thick yellow to green discharge) forming a crust. This is purulent conjunctivitis. This suggests a secondary bacterial infection as the cause.
Bacterial infections are contagious, but only when the animal with the bacterial infection is in direct contact with the animal which is healthy. That is my understanding of the way bacteria is transmitted.
So a dog would have to make direct contact with a cat with conjunctivitis. Could a dog licking an infected cat over the eyes get the disease? It seems the answer is yes, it is possible.
The feline herpes virus is not zoonotic. “Zoonotic” means a disease that can be transmitted between different species of animal including animal to human and vice-versa. So if the cause of the conjunctivitis is entirely due to the feline herpes virus, it could not be transmitted to a dog.
Accordingly, if a cat has a feline herpes virus infection and conjunctivitis as a result (as a secondary bacterial infection) this condition could be contagious to a dog, if the dog is in direct contact with the cat in some way or other.
The direct contact may be indirect in fact. What if a person touched the cat’s eyes, trying to clean them and then touched the dog’s eyes? That would seem to be possible and it could transfer the bacteria.
Another form of conjunctivitis is “serous conjunctivitis”. This is caused by irritants such as pollen and wind. This condition is obviously non-contagious.
Conclusion
This is a difficult subject. Answers are hard to come by, or unavailable even in good books. I think it is correct to say that transmission of viruses between different animal species is rare, while transmission of bacterial infections between different species is less rare. But viruses can be transmitted through the air and in other ways, while for bacteria there has to be direct contact. Another example of bacterial transmission between species (cat to human) is toxoplasmosis.
OK, the answer to the question in the title is yes, possibly if the conjunctivitis is caused by bacteria.
Associated: Feline conjunctivitis
Thanks for the article and advice. The question came up last weekend when one kitten with conjunctivitis spread it like wildfire to the rest of the litter. They’re on meds now, but the question came up since one of the infected kittens is about to be adopted along with a Maltese mix dog. Shelter personnel are divided. Personally, I told the adopter that the kitten would have to be on meds for a few days before being adopted to be safe. I figure, why take chances?
I totaly agree – if it’s not a problem to wait a few days, then why not. You may as well. Funny how nobody really knows for sure.
Pleasure to try and help a fellow cat lover. It was a bit of a struggle producing this post! That tells you the information is not out there, which is surprising. Neither is it in the books I have.
Well, don’t feel bad. I’ve gotten conflicting answers from vets too! The general consensus seems to be to quarantine to err on the side of caution. Thanks everyone for your input. BTW – I totally convinced the adopters to wait when I told them that any sickness would be on their pocketbook since they’d have total disclosure. Considering vet costs these days, they opted to wait.
I find it a bit odd that more isn’t known about this. There are lots of families with cats and dogs. Herpes virus is common and so therefore will conjunctivitis. So where is the veterinary advice on transmission from cat to dog?
Therein lies the question, doesn’t it? The best I can find is that, generally speaking, the virus shouldn’t jump from cat to dog. The fine line seems to be if bodily fluids are exchanged (rough-house play/fight) causing cuts/scratches, etc.), there may be a chance of passing the virus. I’ve also been told it depends on the type of virus. In other words, I really don’t know anymore than when I started, but I think I’ll still err on the side of caution.
Couldn’t agree more. I think we can conclude that there is a chance of transmission either bacterially or as you say in the virus. Even a small chance means we should take steps to prevent transmission.
It’s unusual for a cat to rub up against or cuddle a big dog – Marvin sounds like such a great boy – friendly 🙂 I wonder if Daisy is much taller so it just doesn’t reach her eyes? I wonder if it just happens that afterward Daisy didn’t happen to giver herself a clean or somehow get the bacteria up to her eye through some motion. Maybe even sleeping with her head on her leg where Marvin rubbed against.
Oh, Marvin is a cuddlier with Daisy. Nose to nose when Daisy is laying down. I’ll ask Michael to add a couple pictures here if he can. It was the nose rubs I was worried about, but no problems so far. Marvin is certainly unusual in this regard. It is as if they were old friends.
Oh….I must see these photos, dw. They are like old buddies. They really do like each other. This gives us an insight into the emotions of cats and dogs. They have more emotions than we recognise, I believe.
Marvin’s first mis-adventure trip to the vet was mainly for conjunctivitis and his symptoms were as you discribed, a thick mucus yellow discharge from his eyes. The vet diagnosed feline herpes. Marvin rubs up against ‘his’ dog Daisy often. Fortunately she hasn’t shown any signs of problems. His episode lasted a week and he’s been fine since. I understand it can show up again at any time. Bummer.
Nice to hear that. First hand experience. On the basis that a bacterial infection causing conjunctivitis can be transmitted from cat to dog and human, it is still rare and difficult. There has to be direct contact and the infection has to get inside the individual. There are a few obstacles/barrriers there.