Cat with fever responding to anti inflammatories

[Odee77]

Our one year old cat has had 39.8 fever and slight limping on his back leg since a week. We`ve been to the vet twice with him. First visit he got a shot of anti-inflammatory and antibiotics. The vet said he could not find any physical marks like bite wounds or anything. He was good until the anti inflammatory wore off, then back on the couch sleeping with 39.9 fever. We went back to the vet next day and he got an oral anti inflammatory and checked by a different vet, who also was unable to find the cause of the fever. That put him back on his feet and he was acting normal until next day he had 39.9 fever again and as before, after giving him the anti inflammatory today he has been fine to now again. He has been eating normal throughout the whole ordeal. When the anti-inflammatory works he jumps around and behaves just normal.
If anyone knows what could be causing this please let us know. Thank You.

[AnnieBrooke]

Sometimes bites on a cat are very hard to locate, because a cat's skin can heal over them very fast and they aren't visually discernible, even though infected. You might not see one until it begins to abscess. Is he exposed to other cats with whom he might fight? Does he hiss at you if you touch him anywhere on his hip or leg? It does sound like a bite to me, and if so, the trick is to locate it and lance the abscess. Antibiotics, not anti-inflammatories, would be called for after cleaning out the wound.

[AnnieBrooke]

Also, here is info about fevers with no known cause in cats.
https://vcahospitals.com/know-your-pet/fever-of-unknown-origin-for-cats

[Odee77]

Thank you, I appreciate your advise. He is getting better so very happy about that.