Hi. My Polish pullet (8weeks) is still standing around with her eyes closed. My other one is up here on the patio.
I've had one cockerel floundering on the ground for 3 days, paralysis, and then got better and acted like nothing happened. He stayed normal for about 3 weeks. Then he wasted away.
Flock History:
I've traced all but one death to one silkie pullet I bought 2 years ago. The rest of my flock were all hatched here. The first one to get sick was a 1+ year old silkie roo who was in the same coop. Classic by the book symptoms. Vet office necropsy showed no tumors, so vet said it was equine encephalitis. But now I know it was not. The other 3 in that coop survived and there own chick hatches produced resistant chicks, (antibodies passed on)
A few months later, after the roo died, the purchased pullet died. Wasted away. Last year, a blue Orp died 8 months old, wasted away. Then a JG blue roo, 8 months old, died a few months later, wasted away. ** From June 2011 on>>> A blue laced red wyandotte, a year old, wasted away. Then a Polish mix, 2 years old, was found floundering and paralyzed, I thought she broke her leg. She was wasting and I put her down. Right after that, My silkies had hatched 8 Polish chicks for me. One gets a broken leg, 8 weeks old. I splint the leg. A week later, another gets a broken leg, now I know they're not broken legs. Every week, one gets paralysis or wastes away, or both, some eating, some not. Now I've lost all the chicks. Then a silkie, one year old, wastes away, then can't walk. She was put down. That's 15 over 2 years. All hatched at home cept "Typhoid Mary". They all varied in age from 8 weeks old to 2 years old, the most being under 8 months old.
The other 8 silkies did well. They were all hatched here. I think any silkie chick hatched under my silkies were resistant because they were all from one of my resistant hens. Maybe alot of my hatches from purchase eggs did well because their mom was resistant and passed that on. I had one die from each hatch in the last 2 years.
There is not much known about Marek's because different strains develop. I think that some strains do not respond to the vaccine. The genetics, and concentration of the present virus makes a big difference. Researchers also suggest that it's been bad because they are always finding new strains of Marek's that the vaccines have not been manufactured yet. I think these strains are the cause of the vaccine not working, and chickens getting a strain later in life, but most under a year. It's referred to as "Latent Marek's"
Still, most of those are 6-25 weeks. Most of the written stuff about Marek's has not caught up yet about chickens dying older , and lesser known symptoms , such as no symptoms at all, wasting (most common). It depends on the nerves that are attacked. All most people know is symptoms of paralysis, one leg forward one leg back, dying early in life, and cloudy eye. Most people don't realize that the symptoms can be other than those. Paralysis being the easiest to see and know, but wasting is the most common.
As the large chicken companies got their situations under control by vaccinating, and all-in-all-out, sanitizing, they now have very little problem. But backyarders have not been practicing those important methods, and the problem is now running rampant thru our backyard flocks with very little people educated passed the paralysis symptom or tumors, or classic one leg back on leg forward sign-all easy signs to diagnose. But very few are educated to the fact that it's more common to waste away. And they can look perfectly normal until one realizes how skinny they are whether eating or not., or just die.
Vaccinated chicks can get and spread Marek's (not from the vaccine). The vaccine only prevents the paralysis and tumors, it does not prevent carrying Marek's. Marek's is spread by dander and dust. The dander is produced in larger amounts when a bird is symptomatic
We need to practice with vaccination, keeping younger chicks away from the flock for as long as possible, and not adding random chickens to a healthy flock. Disinfecting and cleaning lessen the available virus and may help develop resistant chickens. Professional necropsy is the only way to know for sure. Symptoms and a good flock history is the only other thing , but just an educated guess.
This info is from "Diseases of Poultry" Editor in chief (of hundreds of research scientists) W.M. Saif. Appears to be a 1,000 page reference book from a University. Or scientific research online. Other info was found on the web, but most of that was missing important points or not including recent research. But a good place to start, but realize that this information is not including everything known. And there is no cure. If a chicken is treated and survives, it's probably not Marek's.