I'm no expert but did have a dog that was coughing once - took it to the vet and they pulled out a long blade of grass which I wouldn't have seen - if he is anything like Maggie she runs around at full pelt occasionally snatching at blades of grass.  Maybe too he could have scratched it - do you give him hide chews or bone- because maybe this could have scratched his throat.  Worth checking with your vet - if he is trying to be sick it would suggest to me that there maybe something stuck in his throat. 
I hate ticks - horrible things.  I have never found one on Maggie but Tilly has had them a couple of times.  I pull them out with tweezers very slowly and very carefully - just keeping a slight pressue until they let go - but got told off by the vet for doing this because of the risk of leaving the mouth part in. 
Had a lovely walk again this afternoon with Maggie and her friend Nelly.  Nellie (a whippet) flushed a pheasant right under Maggie's nose, my mother praised Nellie and said what a clever girl she was - After that Maggie was determined to find one herself - so busy running back and forth - she eventually flushed one up and then looked accross to me as if to say 'did you see?' - and then ran back to me to get a treat - so funny.  She does make me laugh.