I have heard that a tick has to have been feeding for a few hours(possibly 24) to transmit Lyme Disease. So always check yourself and your dog straight away after a walk in an area where there are ticks. Taking them off immediately will most likely not result in transmission of disease. My dog has had ticks on her, I get them off immediately: with an alcohol-soaked cotton pad, grip the tick gently and turn anti-clockwise then pull off fairly firmly. This should pull out the entire tick and not leave the head embedded. If the head does remain embedded I find it 'dies' quickly if the alcohol pad is held on to it for a few minutes.
I once got 25 ticks on me!! All came off using the above method and I didn't get Lyme disease. Neither has my dog ever got it.
I've been thinking about this since I read the other post earlier today, and I was thinking the same thing with regard to the ticks. Since he is continuing to get worse, the first thing that came to mind was "tick paralysis". Other than that, I'm at a loss without some more symptoms.
Ghilly
I've just noticed, you are in the UK. Ticks are beginning to survive winters in the UK (though I think the recent below freezing temperatures will have got rid of any survivors!) But before Christmas it was quite mild in most of the UK. I've found ticks still alive in deep woodland in the South West during mild winters. They are pretty common in woods, heathland, grassland, more or less anywhere. You seem to get 'patches' of them (areas where they proliferate,and areas where they should be but aren't) Lyme disease is not as rare as you might think, and can take a while after being bitten to show symptoms.
I am not really sure. This is only a suggestion. Where do you live? Could he have had tick bites in the last few weeks? Could this be Lyme Disease? Lyme disease does affect dogs as well as people, causes malaise, fever, flu-like symptoms, and can cause arthritis-symptoms. Get your vet to do bloods for this if you think your dog was tick-bitten.
Antibiotics will help if it is.
Whatever, if he is not drinking, dehydration is a danger, and will affect him quickly. Get him back to the vet. At least he will need re-hydration support.