Two friends in France, both English, have experience. One horse died the other recovered. They are on holiday at the moment. Where are you? If it is not too late I will try and find out for you.
My horse in Spain got it back in June. Luckily my friend who looks after him has lost a horse to piro in the past and spotted the symptoms immediately - the vet was there within 30 minutes and treated him. She spotted it as:
- He didn't eat his breakfast - VERY unusual for him
- His gums were very pale (sign of anemia)
- Temp was 42
By the following day on the meds his temp dropped right back down, I'm afraid I don't know what the meds were but I can find out if you like. I saw him 4 days later and you wouldn't know he'd been sick, and I took him for a short ride 3 days after that where he was great but quickly got tired, similar to a human after a bout of flu (he'd have had longer off but I was only there for a few days and wanted to check how he was - he subsequently had a couple of easy weeks just to give him a full chance to recover).
It is very common in southern Spain and commonly treated by vets there, early treatment seems to be the key factor in survival rates.