Pie is apparently the most immunilogically sensitive of my horses - while both Dawn and Red also had EPM last year - Dawn phenotype 1 and Red phenotype 5 - Pie had both, in sequence. Pie was also the only horse to test positive for Lyme, even though all three horses were living in the same conditions.
EPM horses can be subject to inflammatory flare-ups that mimic their EPM symptoms. Various things can trigger this, including vaccinations - the immune response to the vaccination can cause inflammation that can produce neurological effects in a horse who has had EPM. With my three horses, I spread vaccinations out - I never use the 5-way or 7-way vaccines any more, and do the 3-way, West Nile and rabies with at least a two-week break between each vaccination.
My three horses were all vaccinated for EHV-1 on March 6. Only Red got a small fever in the first 24 hours - otherwise no problems. All three horses had their Eastern and Western encephalitis and tetanus (three-way) vaccination a week ago Friday - March 29. Pie was the only horse to get a small fever 24 hours later, but was otherwise fine. Yesterday, when I was picking his feet, I noticed that he wasn't as comfortable with this as usual, and when I picked up his right front, he at one point buckled a bit behind and put his full weight on me. This was something that used to happen when he had EPM, so I was suspicious. Difficulties with hoof picking were one of the earliest indicators of EPM with all three horses. I did a few neuro tests - backing was fine, turning in tight circles was fine - he was stepping across with both hinds - but on the foot placement test, I was able to place his right hind behind the left hind and he just left it there - this is not normal. I consulted with the vet who advises me on EPM matters, and I gave him a 1,000 lb. dose of banamine to reduce any inflammation.
She said it was fine to ride him at the walk and trot, so long as he felt OK - which he did - we had a very nice ride. We didn't canter, because of the risk of a trip or wrenching of the hind leg if he placed it wrong.
Tonight, foot picking was normal, and he resisted slightly when I tried to place the right hind in the wrong position - he moved it away once and left it once, although not in as extreme a position. I gave him another 1,000 lb. dose of banamine - no riding today as it's his day off. I think he's improving - he's certainly not any worse. We'll see how he is tomorrow, and if he continues to improve, I'll tail him down to a 500 lb. dose of banamine.
I'm very fortunate that my horses all recovered so well from their EPM and in Pie's case, Lyme, episodes, but there are some follow-on effects I have to be careful about.