I'm sorry to hear Meanie has not been himself and is taking a long time to recover.
As he has now been vomiting for five or six days, I would begin to worry about dehydration in a cat of his age. This is particularly so as he has not been eating very much.
For most young cats, if they do pick up an infection or become unwell, this will only last 1-2 days, but poor Meanie does not seem to be improving. There are several reasons that this may be, but at this stage he should be re-assessed by a vet.
My main concerns would be a possible foreign body/blockage. This, for example, may have been caused by the chicken bones or may be something else entirely. Though he has had chicken bones before, this does not mean they cannot pose an issue, and bones have the potential to splinter, fragment and obstruct the gut. In a young cat, they can really eat anything, from Christmas decorations to cat toys, and even the most attentive owner can't keep them away from everything.
I am particularly worried about an obstruction as it has been so long since he has gone to the toilet and he is lethargic. To check for one, a vet will usually perform an x-ray or ultrasound of the abdomen.
There are other possibilities, such as a severe gastritis, pancreatitis, infection or a parasite burden, but we should really be ruling out a blockage first.
Other diagnostics, such as blood tests, may be useful to determine if there is an underlying infection or any other issues going on.
He may benefit from a fluid drip, some pain relief, anti-acids and some anti-nausea medicine.
I would suggest the sooner he is re-assessed the better as we can start with our diagnostics and get him better once again.
In the mean time, I would avoid milk or other dairy products which can upset his stomach. Instead, I would stick to boiled white chicken and rice, as well as water.
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