There is a terrible virus that you need to know about I have copied the text of some of the information so you can judge if your horse is at risk
"Several horses that attended the National Cutting Horse Association (NCHA) Western National Championships in Ogden, Utah from April 29-May 8 have been diagnosed with Equine Herpesvirus (EHV-1). Cases have since been reported in several western states and Canadian provinces.
According to the American Association of Equine Practitioners (AAEP), EHV-1 can cause respiratory disease, neurologic disease and abortion in pregnant mares."
There is lots of information on the web concerning this virus.