Dysautonomia in a six-year-old mule in the United States.

Equine dysautonomia, also known as equine grass sickness (EGS), is a well documented disease in several countries. To the authors' knowledge, EGS has not been reported previously in North America. This report describes EGS in a 6-year-old female mule in the USA. Failure initially to consider EGS resulted in a delayed diagnosis. EGS should be considered as a differential diagnosis and appropriate diagnostic tests performed in similar cases in North America.