I haven't had problems with the horses.I have only found one on Okie. I'm still using the fly spray so I don't know if that helping. Poor Cindy, has to be dusted. We spray the yard but she still picks them up.
Even before we got chickens I didn't have too much trouble with them being on the horses, just on the dogs and us.
But I do know that Kristy and JEnny have terrible time with them being on the horses. We've stood and picked them off by the dozens before taking off on rides with them. It's terrible.
I'm surprised you don't have them so bad there. I thought the climate would be good for them. If you have trouble with them in your yard, get a couple of hens, I guarantee they are cheaper then sprays and dips and you get eggs too:). Hens wouldn't be a problem with the neighbors, they don't crow.
Becky