Marek's disease killing vaccinated chicks?

[chickspea]

I had my GCM dying in just two days.
She manifested wry neck one morning, got worse by the evening, even worse by next morning, and in just a over a day she couldn't open her eyes. She had light green, paste like stool before she died.

She was dead in less than 48 hours after I noticed her symptoms.
I gave her E vitamin, B complex, Selenium and all that stuff for vitamin deficiency meanwhile, but didn't show any improvement.

At the same time I am "treating" another cockerel with "broken" leg, or so I thought for a week now, isolating him in a smaller box to prevent him fro moving excessively.
He, too, instead of improving got the second leg looking like paralyzed.

Now I am very concerned that it was actually Marek's symptom in the cockerel from the very beginning, as well as the GCM hen.

How can it happen if they were vaccinated?
Is it Marek's or something else can have the very same symptoms?

Any suggestions?

PS.
They got organic Scratch and Pack chick starter, Nutrena's NatureWise, as well as a third type of all natural chick starter..
Both chicken form the same flock, same breeder, same age, just different breed.
Very concerned for some of my other hens coming from the same breeder, same or different time..

 

[QueenMisha]

What age are your birds?

The Marek's I've seen rarely kills - usually just leaves perfectly healthy birds skinny and unable to walk for weeks - but it's not impossible that your (theoretical) strain is far more aggressive. Although certainly, I have never seen it kill them that fast.

Are you absolutely sure the cockerel does not have a physical injury? You should check over both legs very carefully, and take note of any abnormalities in the bone, joints, or muscle of the weakened leg. What, exactly, does the leg look like? How is he holding it? Kinda like he's doing the splits or half splits, with it way out, straight, to the front or back? Pics would be helpful.

The Marek's vaccine is tricky. It's usually useful, but you have two catches: The first is that there MUST be a period of time for the vaccine to take effect. This period is between 1 day of age (when immunization takes places) and 3 weeks of age. Therefore, if the bird is infected prior to 3 weeks old, the bird is usually either severely stunted, or the vaccine rendered useless. The second catch is that 5% of the time the vaccine fails for no reason at all.

The only disease I know of that resembles Marek's is Lymphoid Leukosis, except that Lymphoid Leukosis lacks the neurological symptoms of Marek's - wry neck, paralysis, etc., so you can rule that out.

I'd also like you to check your bird's necks. Even in birds which appear asymptomatic, I often find small, fatty, pancake-shaped tumors along the neck and spine. I can usually feel them easily beneath the skin. In naked necked breeds, you can see them at times.