Marek's Vaccines.... in older chickens.

[LTygress]

Most of my flock has had their Marek's Vaccine. All of the chickens I have gotten were given the vaccine before I got them. And the purebreds that have hatched out were given the vaccine, along with mixed breeds that were sold. But all of these were done by another person, not myself. If I hatched them out, I took them to someone who gave them the vaccines for me. If I bought them, I made sure I ordered them with the vaccine already.

There ARE some exceptions, probably including the three chicks I bought last spring from a horrible breeder. And about two months ago, I lost my first chicken - a 7-month old mixed-breed bantam hen - to Marek's. So I've decided to start doing it myself, for ALL of my chicks.

After a delayed shipment because of the freezing weather, my 1,000-dose bottle of Marek's Vaccine is due to arrive on Friday. And that's just in time, because I've got one pipped right now.


My question is, the "exceptions" - should I go ahead and vaccinate all of my flock that either has not received the vaccine, or that I'm not sure about? I read plenty of things about the problems with vaccinating older chickens. But if you were to "play it safe" would that mean giving them the vaccine.... or not?

I know at least one other hen that is about two years old now, and never been vaccinated. She was given to me. And her mixed-breed offspring was the one I lost to Marek's a couple of months ago.


So it if were you, and you were getting 1,000 doses of the vaccine (thanks to my diabetic mom who visits the doctor a lot more than most - I have access to that many syringes, too), and you KNEW some of your older chickens probably had not received the vaccine, would you give it to them? Or would you let them go and just hope they were past any possibility of developing the disease's symptoms?

 

[Michael Apple]

No. If you try to vaccinate older birds for Marek's and they've already been exposed, the virus is already in them. The vaccine will do no good and the bird will eventually come down with the disease. All manufacturers of the vaccine state it must be done with chicks at one day of age. Many birds often show symptoms at 6 to 9 months of age. Here is some info on vaccinating for Marek's. I hope everything works out well for you: http://www.shagbarkbantams.com/mdvac.htm

 

[LTygress]

But if the chicken already has the virus in them, then they have already built immunity to the virus. So how does giving them the vaccine - with a virus they are already immune to - make them come down with the diease and die?

The whole purpose of a vaccine is to teach the chick's body to become immune to the virus with a strain that won't kill them, before they are infected. The 5% that still die from Marek's even after immunization, merely didn't "learn" how to kill the virus before actually being infected.

More importantly, the vaccine is made from a turkey-based strain of the virus - one that does not actually infect chickens, which is why we use it. We are trying to teach their bodies how to deal with the virus with something that won't ACTUALLY infect them, in hopes that their body learns enough to deal with the strains that do.

So what I guess I am failing to see here is the "why" for older chickens. If there is a chance that the chicken has not even come into contact with the virus at all, the vaccine would be helpful. And if it has, then the vaccine would just be useless, right? Their body's immune system would just attack it like any other germ, and be on its way, right?

 

[Michael Apple]

Yes, the Marek's vaccine is derived from the Turkey. There are some details to this though. Some years ago, it was discovered that the turkey does not get Marek's. The reason is that the turkey harbors a virus that in simple terms, blocks the Marek's virus from entering it's cells as well as the cells of a chicken. The turkey virus is a non-infectious type, so when the vaccine derived from this is injected into the chicken, it won't put a case of Marek's disease in the chicken. Some vaccines put a minute sample of the disease into a bird so it can build up resistance to the disease. The Marek's vaccine does not put a case of any disease into the chicken.

The biggest obstacle with the Marek's vaccine is that the turkey virus must get into the chicken before the Marek's virus does. This is why the younger the bird is, the better chance of the vaccine's effectiveness. This is why manufacturers of the vaccine suggest it must be used at 1 day old. If you have additional questions about that, I can only suggest you contact the vaccine manufacturer.

More recent discoveries found that there are 6 viruses that cause Marek's disease. The vaccine on the market today covers 3-4 of these strains. This was talked about in another thread where this subject came up, but don't remember the name of it. The FDA has developed a new vaccine called B-1 that when used with the current vaccine, will supposedly cover all 6 strains. Last I heard it was available only in a liquid nitrogen. That's not on the market as far as I know and it needs to be put in a freeze dried form like the current vaccine. If anyone knows of any new research performed about B-1 vaccine, post away.

 

[LTygress]

Okay, so the vaccine itself won't get them sick. It either helps them build immunity, or it simply doesn't - regardless of what age the chicken is.

That would mean giving them the vaccine later in life is not really any different than not giving it to them at all. The only possible benefit, is if the chicken was somehow raised in "sterile conditions" and really hasn't ever been exposed to the virus, prior to receiving the vaccine.

IN WHICH CASE, I'm going to go ahead and give all of my chickens the vaccine when I get it. Because simply put, it can't HURT. With 1,000 doses possible, I've got plenty to spare.

 

[Michael Apple]

A truth to realize is that Marek's is everywhere in the environment. The only difference in age of vaccinating is that every day the bird lives, the greater the chance of exposure to the virus, making the vaccination ineffective. You asked the questions, I answered. Do what you want.

 

[Farmer Viola]

So it if were you, and you were getting 1,000 doses of the vaccine (thanks to my diabetic mom who visits the doctor a lot more than most - I have access to that many syringes, too), and you KNEW some of your older chickens probably had not received the vaccine, would you give it to them? Or would you let them go and just hope they were past any possibility of developing the disease's symptoms?

Personally - yes, I would.

Quote: source: https://www.backyardchickens.com/t/263563/should-chickens-be-vaccinated/10#post_4222402

 

[LTygress]

No. If you try to vaccinate older birds for Marek's and they've already been exposed, the virus is already in them. The vaccine will do no good and the bird will eventually come down with the disease.

This is what I didn't get. This sounds like you're saying that the vaccination itself will kill them.

 

[Scribbles]

One of my chickens just died in December from complications due to Marek's (what the autopsy report said) and she was about...probably close to two years old, maybe a little under? If I'd known she wasn't vaccinated I would have done it. Was a sweet and docile hen (and a really great egg-layer). Now I have to learn how to do it for the other chicken who was her 'flock sister' (I got them as a pair from another backyard owner) and I guess as a safeguard I should probably do it for the rest...live and learn. RIP Pearl.