Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Again I do apologize that my colleagues could not aid you sooner, but I wanted to touch base with you about Theodore.
Now you have noted an interesting fact about his having had cat flu before but that these signs are more mild here. The reason is because that is very common to see. Many cats end up carriers of the viruses causing respiratory infection signs and they can reappear through life often with stress. But when they do, since adult cats have stronger immune systems, they tend to have more mild signs. So, this is likely what we are seeing here.
Now as long as those discharges aren't snotty, we can try some supportive care as his immune system fights this off. For that we can start with steam treatment. To do so, you can take him in the bathroom while you run a hot shower. The steam will help loosen and clear discharge from the airway. You can also use a baby nebulizer, but often they don’t like things held up to their faces. So, if you find that to be an issue, you can make a little ‘steam tent’ with him in a carrier, the nebulizer next to that, and a bed sheet over both.
Furthermore, if he is building up mucus that the steam isn't shifting, use a cotton ball moistened with warm water to wipe away crust and mucus. As well, non-medicated saline nasal drops (ie Ocean Mist or Little Noses) can be used. To do so, just tilt the head back and drop 2-3 drops in one nostril. Not a favorite, but it helps. After the drops go down, you can let the head up and wipe away any discharge that gets loosened. Then repeat with the other nostril. Similarly eye safe sterile saline can be used to flush his eye. This can be purchased over the counter as first aid eye wash or plain contact lens solution.
Making sure he is getting food and water is important, as congested cats who can’t smell their food often won’t eat as well as they should. Therefore, if need be, try offering smelly wet foods (since they are high in water). It may help to warm it up a bit in the microwave to help him smell it.
Furthermore, since feline herpes virus is a suspect, we can also start OTC L-lysine. This is a nutritional supplement that can help them recover quicker. This is available over the counter at vets, pet stores, and even online. They come as gels, powders, and as crushable tablets that can be mixed into food. An average cat dose is 500mg a day.
Overall, this does sound highly suspicious of an upper respiratory based infection and its likely he is a carrier of the agent causing this. Therefore, you can try the above to help give him some relief. Of course, if these signs linger or are severe, then we'd want the local vet involved. They can confirm our concerns and dispense cat safe decongestants (since human ones are toxic for kitties) +/- antibiotics to help us nip this in the bud.
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