Are the thumps the same as heat stroke?
Just in visible symptoms...heat stroke is caused by dehydration or anhydrosis and is due to failure in thermoregulation. SDF is more of an electrolyte deficiency....low blood calcium. Horses suffering from both may heave as they breathe, sweat and appear exhausted....but usually because both are brought on by exercise.
A long, long time ago, horsemen would inject quinine under the skin and give drenches of sulfuric ether and beer.