Thanks
@Wyorp Rock for the tag.
@Annalyse I'm so sorry to hear about your Silkie. Yeah, I have the same thoughts about the test BUT, Silkies are #1 with a bullet when it comes to Marek's disease. That being said, it's chances of being positive are probably higher than it being negative. Of course a post mortem necropsy is the only true diagnosis testing for Marek's.
Unfortunately, if it is Marek's the Genie is out of the bottle and your whole flock is carrying the disease. And yes, I've heard of remissions only for the disease to come back later when the bird reaches POL or sexual maturity. Mine all died at a year to a year and a half average, but showed no signs of the initial infection with the exception of a few birds.
Until you get it figured out 100% my best advice is to lock your flock down. No birds out, no birds in unless they are vaccinated and even that isn't a 100% guarantee that you won't suffer losses. Keeping her separated from the flock isn't necessary. They already have been exposed to her.
I invite you to read my article about dealing with Marek's in your flock:
https://www.backyardchickens.com/ar...-i-learned-to-deal-with-mareks-disease.76944/
And take heart. You aren't alone here.