It does not describe symptoms of Marek's. However, you are working with a bantam breed, Sebrights, that worldwide seem unable to develop an immunity to Marek's. Most breeds can, over many generations, be bred for immunity. (??) How do you know?--Few Vets can test for it, even if it was not a great expense. Inbreeding and close breeding are the best way to obtain any trait that you want to be dominant, simply discarding any birds that show weakness for whatever trait you with to eliminate. It is too bad, but avoiding inbreeding is the slowest way to breed the dominant traits that you want! Keep for breeding, only the strong survivors in your breeding flock (which you may be doing) and breed those birds together, discarding any of their weaker or offspring that display the paralysis. While brother/sister is not first choice--once is OKAY-then breed to cousins, half brothers/sisters, sire or dam. 3 trios can give you breeding birds for YEARS, without obtaining ANY new birds EVER, becomes a personal strain of bantams with dominant traits for egg production, setting (which helps long life), whatever you choose--and good ones. New bloodlines, unrelated birds, send you back for YEARS, as you are bringing in unknown recessive traits that you DO NOT WANT. 3 trios can give birds that you can breed by "braiding" the offspring and not be straight inbreeding, but "linebreeding"--the best way to produce uniform birds with any trait you choose. This is why some Show bird breeders seem to always win with their birds-=-they have developed DOMINANCE with their birds--that are truly what their Standard requires. Cannot do it without inbreeding and line breeding! (And IF such breeders DO want "new blood", they will choose from a breeder with similar inbreeding that has discarded most recessive traits that they do not want! GOOD LUCK

And do check thoroughly for possible toxins that your birds may obtain as young birds. Feed storage, pasture, wood glues--anthing that your young birds could be ingesting. Scary when it keeps repeating with youngsters. Very sorry for your experiences. Breeding poultry can be such a great project, and yours can be very useful-- although I, personally, would not use the breeds you have chosen. Again, GOOD LUCK

Edited by CJR (09/18/16 09:04 PM)