I'm pleased to update with some positive news too.
My welsummer has picked up without treatment. I really thought she was a gonner, as she had stopped eating for 3 days and looked very unhappy. I'm now wondering if it wasn't Marek's related and she just had some sort of slow crop or blockage. Anyway, she is happily foraging with the flock again and even laid an egg yesterday.
My two definite Marek's girls are still holding their own. Hoppity who has been the same for 6 months is very light weight but I suppose, since she is carrying all her weight on one leg, that at least helps her mobility and she is very bright eyed. The other one whose paralysis is worst, has actually stood up this afternoon and walked rather than crawl. That's the first time I have seen both her hocks up off the ground and her standing upright for at least 4 weeks. I do think that having made them an enclosure which is allowing them to enjoy the fine weather and sunshine, is benefitting their wellbeing. enormously.
I had thought only one of them was laying, but I got an egg from each of them the day before yesterday in the outdoor cage, so I have had to give them a little nest area now and I got another egg this morning, so that's 6 this week. I let Hoppity make her own way out to the cage on a morning and she even stopped and squatted for the cockerel on the way out! Previously she would have fled screaming, so I take all this as positive signs.
None of the other young pullets are showing signs and they are about 9-10 months now, so discounting the Welsummer, who never really ticked the boxes for Marek's anyway, I've not had a new case since October.
I'm going to confess now that I have allowed my broody to hatch some eggs within the flock from pullets that have been exposed and not shown signs. Three hatched, 2 Maran's and a CCLxRIR but I'm not sure which cockerel will have sired these chicks. Anyway, they will not be vaccinated as there was no way I could isolate them from exposure or justify the expense of buying the vaccine for so few, They are being raised by the broody in a rabbit hutch within the hen house at the moment, so will have maximum exposure to the virus from the beginning. I appreciate that you may think I am being irresponsible but since they are going to be exposed to it anyway, then in my view, the sooner their system is challenged by it, the sooner it either learns to deal with it or succumbs. I also hav peace of mind that the hen house is more secure from predators than any other option, being a stone building. If all the chicks suffer from it then I will not try to raise chicks like this again, but I need to get an understanding of how this works on a practical level within my flock. The chicks will be a week old tomorrow. It is done now, so please wish me luck.