The name we give to the problem your cat has is "Fever of Unknown Origin." Basically, this is a catch-all phrase to indicate that we have not yet diagnosed the underlying problem.
Before I go over the things that might be causing this fever, I want to mention that there are no human pain killers or fever reducers that you would have at home that are safe to give a cat. Aspirin, acetaminophen (paracetamol) and ibuprofen are all very toxic to cats and should never be given! You can read more about them here:
Now, if your cat were on his way in to see me, the things that I would be checking him for would be:
1. A cat bite wound
This is by far the most common cause of a fever in cats!
What happens with a cat bite wound is that there are 2 puncture holes - one caused by the upper and one by the lower canine tooth. The cat's teeth have a lot of bacteria on them, and these bacteria get placed deep below the skin when the bite occurs.
The hole is small and quickly scabs over, leaving the bacteria below there.
The most common type of bacteria in the cat mouth is Pasteurella multocida - and it loves to grow in a warm, moist environment that has no oxygen present. And that is exactly what you have with a bite wound!
So, the bacteria multiply, and the body sends in white blood cells to fight the infection, and soon you have a big pocket of pus and bacteria: an abscess! The abscess grows bigger until it ruptures and the pus pours out. This relieves the pressure and allows the hole to close over which then allows the process to start again.
If your boy were bitten, he might be very sore, and would have a high fever. It can be very hard to find the bite wounds if they are covered by fur. This should respond to antibiotics.
Here is more information:
2. Feline Leukemia
Feline leukaemia (FeLV) is a devastating virus for which there is no cure once cats are exposed.
If your boy is vaccinated for this, then do not worry any further about it!
Transmission occurs through infected saliva, bites or sharing bowls with infected cats may infect other cats within the household. Symptoms are numerous including fever, frequent infections, weight loss, depression, decreased appetite, and swollen lymph nodes.
Prevalence of the disease is worldwide with locally high numbers of incidence possible in infected groups of feral cats.
Blood tests can identify infection. Supportive care is the only option for treating cats positive for feline leukaemia. Prevention is therefore the best solution. Cats should be tested and vaccinated if owners intend to allow them outside.
If owners are intending to keep cats indoors with no potential for exposure to cats outside of the household, cats need not be vaccinated against feline leukaemia.
However, an initial blood test upon bringing a new kitten or cat into the household is recommended to identify whether the cat is carrying the virus.
3. Feline infectious peritonitis (FIP) is another serious and destructive virus.
The disease is most commonly seen in facilities housing large numbers cats, such as catteries and animal shelters. Transmission occurs when a cat comes into contact with an infected cat's bodily secretions, primarily saliva and faeces. Unfortunately, the virus can survive a long time outside of the body and can remain a source of infection on a dirty food bowl or litter pan. Initial symptoms include upper respiratory problems, depression, and weight loss. Two types of the disease are recognized. "Wet" type FIP-infected cats appear with large "pot-bellied" abdomens that are actually filled with fluid, eventually leaving the cat struggling to breathe. "Dry" type FIP-infected cats have minimal fluid accumulation and exhibit weight loss, depression, anaemia and fever.
Unfortunately, FIP is hard to diagnose as test results are unreliable. By the time symptoms are identified as likely resulting from FIP, the disease has already significantly progressed. The only way to care for an FIP-positive cat is to provide supportive care based upon the symptoms. A vaccine does exist for this virus but is quite controversial and is not frequently used. The best prevention is to minimize a cat's possibilities of exposure.
4. Feline immunodeficiency virus (FIV) is yet again, a seriously destructive and fatal virus for which there is no cure.
FIV exists throughout the country and is transmitted through bite wounds. There is no standard vaccine to prevent FIV. Once the virus infects a cat, the cat may live a relatively normal life for many years. Since the virus affects the immune system of the cat, the cat is less able to fight off infections of any sort and will require supportive care as needed. Symptoms include fever, recurring infections and illnesses, weakness, depression, and weight loss. Prevention is best achieved through minimizing potential exposure to potential carriers. FIV-positive cats hospitalized should be treated similarly as cats carrying FeLV or FIP. Never allow direct contact with other cats and practice good hygiene and disinfecting practices. There is currently no known correlation between FIV and human immunodeficiency virus (HIV).
5. Infection elsewhere in the body-Your boy could have an infection in the area of his pancreas or bile ducts, which can occur for no known reason.
He may start showing signs of nausea or vomiting if this is the case. Blood work and x-rays aid in diagnosis. It sounds like your vet has already looked for this.
6. Toxoplasmosis - This is caused by a parasite that cats can get from their mother, or from eating mice or birds. The common symptoms are fever, depression and loss of appetite. It responds to antibiotics.
For more information, see:
7. Hemobartonella - this is a parasite that affects the red blood cells and causes fever and weakness. It can be diagnosed on a blood sample and responds to antibiotics.
Here is more information:
Now, I don't want to make you panic! A lot of the things that I have listed are very serious . However, the most likely thing to be causing his fever is a bite wound that is getting infected.
Here is more about fever in cats:
The most helpful thing would be to really encourage him to drink. This will help to bring down the fever and to keep him hydrated.
What you can do is try to get some calories into him in liquid form. That way he is getting nutrition at the same time as fluids.
I suggest opening a can of tuna *in water* and offering him the liquid, diluted 50:50 or more with water.
Also, you can pick up Clam Juice in most grocery stores (sold in with the V8 or with the canned tuna in 'my grocery store') and mix that with some water.
You could try Lactose Free milk (Lactaid is the Canadian brand).
Offer him some canned cat food, and mix it with water to make a slurry if he won't eat it.
Things you can do to encourage a cat to drink are:
- Offer water from a very wide flat bowl as cats don't like their whiskers to touch the edges when they drink (which is why lots of cats like the toilet bowl).
- If he likes dripping water, leave a tap dripping for him.
- Offer bottled water and see if he prefers it.
- Offer onion free chicken or beef broth, diluted 50:50.
- See if he likes water with an ice cube in it.
- See if he likes it out of a cup or martini glass.
- Offer Whiskas CAt Milk http://www.whiskas.ca/catmilk.html
- Offer him canned food as the first ingredient in water
- You could try getting some human baby food in meat flavours (check that there are no onions or garlic in the ingredients) and mix that with warm water and offer that, or syringe it in little bits into your cat's mouth. Beech Nut makes a line of baby food that has nothing but meat (beef, chicken, turkey or veal) in it.
Here's a link:
If you cannot find this, you could find another meat baby food. Just read the label carefully to be sure there are no onions, onion powder, garlic, or garlic powder in it. Try to get him to drink small amounts frequently. If you can, try syringe 1 teaspoon (5 mL) or liquids per half hour into his mouth.
It sounds like your boy is going to need to see his vet when they open and will likely need some antibiotics. However, until you can see your vet, I hope that this helps you to help your cat!