Hello! I fear I am long belated to this post, however I have a pony with similar symptoms. Did you ever find out what your horse was suffering from?
My particular pony in question- 14.1 welsh/TB had a 104 fever and cough back in November. The vet Diagnosed him with anaplasma but the cough lasted for weeks and he wasn’t the same Under saddle. The vets put him on Spectus to rid the cough. It somewhat went away but pony who was normally forward and happy to work wants to stop and baulk even at the walk. And still occasionally coughs- a dry cough no mucous. LOTS of head tossing at trot and canter with any sort of light contact, and can’t even do more than one line of jumps without stopping to seeming catch his breath? He does puff too way too much for the small bit of work. Sweats more too clearly his body is working hard to trot for 30 seconds.
so I had him scoped and teeth done.
upon scope vet said it looked like AID as there was mucous in his trachea and top of his lungs.
however it’s been over 3 weeks now of treating h like an AID patient (no straw or dusty bedding) mostly outside turnout, no hay (wet beet pulp and alfaca cubes only) Zyrtec for the allergy (20 pills per day) and fatty acids added to his feed.
after 3 weeks there has been zero improvement under saddle. To be noted- no fever and seems happy in the field. Otherwise happy pony.
my mom sent me up meds she used on a pony with an airway disorder (ventipulin syrup and hydrochloride maybe) Also zero improvement.
its breaking my heart to see this pony not enjoy his saddle time- he used to be such a spitfire and one that loved a job. The vets have spent thousands of my dollars and I can’t keep paying them to find nothing.
Thank you to anyone who has an input! I just started him on Dex to see if there’s any improvement here (also one of the meds that helped my moms pony with failed tie back surgery)