Probably not Marek's... at least, not an active infection/symptoms of it, as it would be much more easily detected in his blood.
This actually brings up more questions than it answers, but for now, I'll roll with it in case we can figure this out.
My theory, as someone that is hardly an expert, is that he has Marek's... all of my birds do, as they have all been exposed... but he is not actively symptomatic and thus it is not in his blood stream, but instead is latent in other cells in his body. If he had active, raging Marek's causing paralysis and an immune response (as guessed via his bloodwork), we should have found Marek's virus markers in his PCR testing.
Of note, lead toxicity can cause the same elevated white blood count that we observed....
Again I am just a layperson, trying to puzzle this out. Hardly an expert.
Hmmm.
At least he is still doing okay! This morning he launched himself across the basement while I had stepped out to take care of the girls... I found him near the couch, with a trail of gross cecal poops between him and his chair! Thanks for those special presents, Baron Rufflerump!!
So I guess he is feeling pretty spunky!