Thank you Lyn,
Based on Murphy's history (especially with his tongue out, drooling, and refusal to eat), I would be most concerned that his problem is based within his mouth. Notoriously, when a cat starts showing signs of a decrease of appetite, difficulty eating, drooling, and tongue displacement (with secondary lethargy, depression, and malaise) then this can be a red flag that there is an oral issue that needs to be addressed.
Most commonly, we see this associated with dental disease. This could be due a fractured tooth, gingivitis (inflammed sore gums), feline resorptive lesions (example), or tooth decay. Rotten teeth can cause pain and soreness which can contribute to a cat going off their food and showing these signs. A lot of cats with dental disease (or a rotten tooth) will initially appear to struggle to eat or seem to eat less but this can progress to the kitty's begging their owners for food (b/c they are hungry), only to look at it longingly before giving up. Where dogs will suffer through their pain, cats aren't daft and avoid it. (though not eating isn’t a great plan for dealing with dental disease either)
In this vein, any foreign material lodged between the teeth or injuries to the tongue (via rodent bites, etc). can also cause these signs. As well, since your kitty is older, we can't rule out oral tumours. We can see cats sometimes develop aggressive tumour types on or under their tongues or in oral mucosa. These can appear as ulcers and can have a secondary infection associated with them. As well, they can also present as growths in the mouth that can displace the tongue and make it stick out. These growths can be sinister but some may be polyps (which are benign). But in either case, any lesion can make a cat’s mouth uncomfortable, cause them to drool excessively and go off their food.
As well, another consideration is that we can see these signs associated with the pain of feline herpes virus induced oral ulcers. Herpes is a virus that causes lifelong infection, and often these cats are carrying it since kittenhood. It lies latent but can pop up and cause either signs of respiratory disease (ie cough, sneezing, ocular or nasal discharges) or it can cause oral disease (ie gingivitis, oral ulcers of the mouth and throat). In the latter, these are notorious painful and can be another reason why a cat could stop eating, stick out their tongue, and drool.
Finally, while you haven't noted a bad smelling breath, we do have to consider that in older cats we can see drooling and signs of this nature associated with kidney disease. The reason is because when kidneys struggle they are unable to filter out wastes as well as they used to. And one metabolic waste, called urea, can accumulate in the blood and cause a uremia. A side effect of uremia is the formation of oral ulcers and ammonia scented breath. And these ulcers (as well as associated nausea) can make the cats drool. As well the toxin is know to cause nausea for kitties and that as well factors into their lack of appetite.
Overall, these are the main things I would be considering in Murphy's case. Since he is already off his food and we don't want this to progress to a stage where he develops secondary health issues (ie fatty liver syndrome) that make it harder to get him eating again, I'd advise that you do want to consider having him seen by his vet soon. I would say that consider his signs and age, it would be an urgent visit but not an emergency one.
If you do need to wait to have him seen, we do want to try and facilitate his ability to eat and get nutrition in. To do this, you want to consider tempting him to eat, and consider feeding pate style food or even meat baby food (without garlic powder in the ingredients) for ease of eating with a compromised mouth.
Further to this, if tempting doesn’t work, then we do have to consider initiating syringe feeds to get food in. In that case, you may want to try Hill's A/D (LINK) from your local vet. This is a critical care diet that is comes as a soft, palatable pate. It is calorically dense, so a little goes a long way nutrition-wise and this could just help get some more calories into her even if we can’t get a huge volume of food in. As well, for syringing food, you can use the animal version of Ensure (balanced for animals dietary requirements) called Clinicare Canine/Feline Liquid Diet (LINK). It is actually by the same people who make Ensure, but is formulated to meet out pet's dietary needs. Your vet should be able to order it for you but it is available without a prescription. They also make one specifically for older cats with kidney troubles, and this could be an alternative for an older cat. This way it would a means of getting nutrition into him despite his sore mouth to ensure you avoid any complications of his self-starvation.
Once the vet does examine him, they will be able to help determine the primary condition that is causing his oral discomfort. The vet can do this via an oral exam (which cats in his situation don't tend to be particularly amenable to just letting anyone look). Depending in their findings, the vet will be able to access his mouth and address the root of the problem, and will also be able to provide long lasting injectable antibiotics and cat safe pain relief if necessary. And if they do find ulces in the mouth, then you might consider having a urine or blood sample checked to determine if these signs are actually due to underlying kidney troubles for poor wee Murphy.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
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