Best to get the vet to diagnose, then disinfect everything, brushes, stable, tack, etc. basically anything that has come into contact with the horse. Keep in mind you can catch it as well. The vet should be able to recommend the bets products for all this.
Yes do be careful, I caught it once from a calf that came from market and was put in the stable next to my pony (only one patch on my leg thankfully). Keep an eye out for something that looks like an insect bite as it doesn't get the 'ring' shape straight away. It is treated with anti-fungal cream like Canesten. Don't know what they use as a horsey equivalent though as the pony was absolutely fine .
Yes. My horse had it when I bought her. I caught it off her (I groomed her, then scratched a gnat bite). Both cleared up pretty easily. None of my other horses / horses at the yard caught it but I have known a yard where every horse caught it
My pony got it from a calf too, then i ended up with it too. It was only a little bit and i treated it with normal athletes foot cream on both me and dpony, it cleared up easily. Nothing else (barring cows) got it - the hazards of having a pony who is friendly to farm stock!