We had a German Shep that had heartworms. She did ok but that treatment is ruff on dogs (and their owners!) Spook stays on heartworm preventative year-round just to be safe. A friend missed 1 treatment and her dog ended up with them.
Spook has a "cough" more like a gag. She can't wear a collar, has to wear a harness. She will gag herself when she scratches her neck. Been checked out by the vet, nothing there, just sensitive in that area which makes her hack.
As you know Aussie are sniffers, nose in the air or on the ground, maybe she sucked up a feather or something. Glad to hear she is doing better.