Do Marek's vaccinated birds automatically become carriers?

[cicene mete]

I can't seem to get a straight answer on this one. Does anyone know for sure if the vaccine turns birds into Marek's carriers and therefore a risk to other birds?

Some here have said that the virus in the vaccination is the turkey version and therefore does not pose a risk to the vaccinated chicken or to other non-vaccinated birds. Others have said that the vaccination makes the birds a danger to non-vaccinated chickens and that the vaccination can even, on rare occasions, give the disease to the vaccinated bird.

I have some eggs in the incubator and before I decide whether to vaccinate them, I'd like to know for sure what the deal is. I hate for my vaccinated chicks ultimately pose a risk to the rest of my flock.

My thanks to anyone with information.

 

[Judy]

Marek's disease

Marek's disease vaccine is usually administered to chickens at the hatchery on the day of hatch. It is given subcutaneously (under the skin) at the back of the neck. It is best to order chicks already vaccinated at the hatchery.

It has been demonstrated that the vaccine only prevents the appearance of Marek's disease tumors and paralysis. It does not prevent the birds from becoming infected with and shedding the Marek's virus.

Chickens 2 to 16 weeks of age (prior to sexual maturity) are susceptible to Marek's disease. While Marek's disease can occasionally occur in pheasants, quail, game fowl, and turkeys, these poultry species do not normally receive Marek's vaccinations.

I pasted this from here:

http://dlhunicorn.conforums.com/index.cgi?board=vaccinationdisease&action=display&num=1158570032

Lots more info on this site.

 

[cicene mete]

Thanks for the info and the links.

According to the OIE manual "Vaccination greatly reduces clinical disease, but not persistent infection by MDV. The vaccine viruses are also carried throughout the life of the fowl and are continued to be shed, which results in the ubiquitous presence of MDV." (my emphasis)

So, if I'm reading this correctly, since the rest of my flock is not vaccinated, then vaccinating my new chicks might put everyone else at risk. Is that everyone else's understanding as well?

If vaccination results in "the ubiquitous presence of MDV," then by vaccinating aren't we just spreading the disease around?

 

[threehorses]

We aren't spreading the disease around because it's already very terribly prevalent in the environment. Every chicken will likely experience some exposure to mareks in their lifetime in my opinion.

It can be spread on the wind, in droppings, on the legs of a wild bird who ate at a neighbor's chicken place and picked up something that was shed, or from stuff on the feathers of a nest that sparrows build often using chicken feathers.

Basically the purpose of vaccinating is to give your birds a slight exposure in CONTROLLED circumstances so that they can (hopefully and more likely) develop an immunity. This will reduce chances of mareks becoming a problem in a flock. It will not stop it, just as most innoculations will not stop most diseases. It's a control measure.

And it does control.

The general rule with vaccinations and chickens is this: if you use a live or live-modifed vaccine of the chicken form of a disease, (such as Laryngeotracheitis), then your birds can become carriers. For some farms such as large industrial farms where all birds are kept up and a closed flock, this doesn't matter. For show birds or birds for sale it does.

Instead we use killed matter or a virus from a different species that causes the immune response to something to similar to the chicken version that the chicken becomes immune to the chicken version of the disease.

Incidentally, the vaccine used for chickens is a turkey strain. They cannot shed the turkey strain. Just the body can recognize some attribute that both the turkey and chicken strains have in common and creates an immune response to that.

Thereafter, when the bird is introduced to a small exposure of the chicken strain, the immune system goes against it to prevent paralysis and tumors. In a very large exposure, the effectiveness of the vaccine might be overcome. But generally it is not.

I hope this helps.

 

[cicene mete]

Thanks threehorses for the reply. So, are you saying that the commercially available vaccine made by Fort Dodge Animal products is the live turkey virus?

 

[threehorses]

If you're talking about MD-Vac CFL I would assume it is as it's a live virus vaccine.

You can contact Fort Dodge at 800-685-5656 if you want to make sure.

With all vaccinations, be sure to read and follow the instructions without flaw. Some vaccines are required to be used only in 1 day old chicks.

 

[AHappychick]

I spoke with the vet at fort Dodge and the vaccine is a turkey strain and can be given to any chicken at any age but is not as likely to be succesful since Mareks is everywhere and once they have encountered it the vaccine wont work.

They will not be carriers either way whether you vaccinate at 1 day old or later in life.

The ones that are not effected by Mareks are not carriers either, only those that have gotten it and survived or actively have it.

 

[cicene mete]

Thanks, AHappychick. I know you've had plenty of struggles with Marek's. I'm glad you spoke to their vet and can clear it up.

So, just to be clear, am I correct in saying that with the Fort Dodge vaccine, one day old chicks are given a modified form of the turkey virus. Because it is a live virus, they will shed the turkey version of Marek's, but not the chicken version, so they are not a risk to other, unvaccinated chickens or chicks?

 

[threehorses]

I read an article earlier saying that you can revaccinate with a booster of the shot if there's a risk of reinfection.

I have read in another article somewhere ( couldn't find it to reference today) that you should never vaccinate a bird that might actually have Marek's already. I don't know how that would effect the "booster" shot since sometimes birds can have Mareks and you'd never know...

But it seems the practice is to vaccinate day-old chicks. I've read to vaccinate any new incoming stock, but I personally haven't done that.

Here's a very interesting an dinformative article that discusses vaccination of older birds, etc:

http://www.firststatevetsupply.com/poultry-health/mareks-disease.html

 

[AHappychick]

Quote:
yea I've been there

i am not sure whether it is live or dead but I know it is kept in fridge in a freeze form and then re-constituted and is only good for 1 hour after making.

They will not shed either the turkey or the chicken strain after vaccination so vaccinated birds can be housed with turkeys with out causing risk to them. I asked exactly that to the vet. and I am willing to bet you will find many people who house their turkeys with chooks they got from hatchery and had vaccinated.