Adding vaccinated juveniles to marek's positive flock

Just a question - have you had confirmation of Marek's through testing/necropsy?

Hopefully @rebrascora or others that have experience with Marek's will chime in.

I'm so sorry that you are having to deal with this. I wish I had better answers, but here is my opinion:
There is really no way to know how well your new pullets will do. Since they are a bit older than day old chicks, they will have had time for the vaccine to "take", but the vaccine only prevents the formation of tumors from the virus, but does not prevent symptoms. Meaning, that they still could develop paralysis, wasting, etc.

I do hope that the vaccine provides some level of protection. Marek's is one of those illnesses that seems to be ever so slightly changing. Do the best you can, I can't imagine what it's like to have to deal with this.

The best I can do is give you links to the information I have. @Nambroth has one of the best articles I have found https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq you may want to pm them, to see if they have thoughts about your question.

Please do keep us posted on how well the vaccinated chickens do, it will be educational for us all.

Here's a snippet from the MerckVetManual online
Transmission and Epidemiology: (source http://www.merckvetmanual.com/poultry/neoplasms/marek’s-disease-in-poultry)

The disease is highly contagious and readily transmitted among chickens. The virus matures into a fully infective, enveloped form in the epithelium of the feather follicle, from which it is released into the environment. It may survive for months in poultry house litter or dust. Dust or dander from infected chickens is particularly effective in transmission. Once the virus is introduced into a chicken flock, regardless of vaccination status, infection spreads quickly from bird to bird. Infected chickens continue to be carriers for long periods and act as sources of infectious virus. Shedding of infectious virus can be reduced, but not prevented, by prior vaccination. Unlike virulent strains of Marek's disease virus, which are highly contagious, turkey herpesvirus is not readily transmissible among chickens (although it is easily transmitted among turkeys, its natural host). Attenuated Marek's disease virus strains vary greatly in their transmissibility among chickens; the most highly attenuated are not transmitted. Marek’s disease virus is not vertically transmitted.

Marek's
http://extension.usu.edu/files/publications/publication/AG_Poultry_2013-01pr.pdf


Common Poultry Diseases:
http://edis.ifas.ufl.edu/ps044

 

Quote: "It takes ten days to two weeks for the vaccine to develop antibodies in the chick, vaccinating on Day One is the safest policy.
The vaccine given to day-old chicks isn’t as effective as the one given to eggs. Vaccines are available against all strains of virus, and are sometimes given in combination."

Found this on the link above.

 

Hi

Apologies for the delay in responding to this post (Wyorp Rock PM'd me). I've been having problems with my broadband connection.

Firstly I will say that I do not have personal experience of vaccinated chicks, but I do have Marek's and this is my third year with it. My broodies hatched and raised 56 chicks last year within my Marek's infected flock and I only lost 3, all of which displayed Marek's symptoms....mostly paralysis. Whilst it would be nice not to lose any and of course there is heartbreak when you have been giving them supportive care and they don't make it, I feel that this is an acceptable level of loss. I don't isolate sick birds but give supportive care within the flock whenever possible and I've had some completely recover after limping or even flailing around on their side for a couple of days, others that deteriorate despite my best efforts and I had one that I spent 3 months intensively nursing and after twice setting a date to euthanize if she was no better, she kept fighting and eventually recovered to the point that she could free range with the others again, albeit with a limp. My flock has been exposed to it, so I see no point in isolating birds with Marek's symptoms and since I have had some recover, I don't euthanize unless they stop showing an interest in food and no longer have the will to fight.

I think being broody reared within the flock, exposes chicks from day one and perhaps enables their immune system to build some resistance. Also there is no integration stress, which can be a trigger for the virus. I am also breeding these chicks from birds that have been exposed and may therefore have some natural resistance to the virus.

There is some research which suggests that the vaccine may actually be causing the virus to mutate into more aggressive/hotter strains and therefore long term, it may be more harmful that beneficial. Here in the UK the virus seems to be milder/less virulent and that might be a reflection on the fact that most back yard flocks are not vaccinated. We don't have large hatcheries that chicks can be mail ordered from like you do in the US, so most obtain their birds from local breeders who don't vaccinate and many are broody reared which generally makes for a more robust immune system.

I'm sorry that I am unable to address your main question about introducing vaccinated older chicks to your flock as that is beyond my experience. As you know the vaccine is imperfect. My experience is that the stress of introduction to your flock may make them vulnerable to the virus. Do you have any hens left that have a broody tendency. If so, I might be inclined to get some hatching eggs from a local source when next she is inclined to set and try that route for restocking. Of course you would need to be prepared to deal with the cockerels that hatched and having a Marek's flock that would mean butchering yourself or selling/giving to someone else to butcher.

So sorry that you find yourself in this situation. I know how heart breaking it is, but I can offer hope from my experience of it.

Regards

Barbara