testing my horse for EPM?

I live in Michigan where EPM is common. Odd standing positions is one of the symptoms of the disease so it is likely that could be the cause. Even if you get another blood test or even a spinal tap it may not be definitive. The site I linked below has some good info and shows how to do the "carrot test" to keep an eye on her coordination and muscle control. The carrot test is also a great stretching exercise for the horse before riding.

I'd get her tested again with spring shots. Mostly because even though the test isn't always conclusive, if you get her treated before she has any bad neurological symptoms she can be "cured". Damage done my the protozoa is lasting so treatment may not get rid of the symptoms.

Was she tested with blood serum or csf? At any rate, there are myriad symptoms, and the parking out position, while unlike any that I've seen, could be a clinical sign of EPM. Did you treat her with Marquis? I know how frustrating an EPM diagnosis is . . . . None of the tests are conclusive, even the CSF tap. I guess the short answer to your question is that if it would make you feel better, you could have the CSF test, if you haven't already. It's just rather invasive and not totally conclusive, either. Best of luck with your horse.

I would to be on the safe side.

Isn't there a vaccine for it? I think it hasn't been properly approved though..

Good luck! ♥