Marek's vaccine question

[chicknmania]

I've heard that birds vaccinated against Marek's can transmit the disease to unvaccinated birds. I assume that might be true, since Marek's vaccine is a live virus vaccine. But idk for sure. Anyone?

 

[coach723]

This is my understanding of the vaccine:
The vaccine does not cause them to transmit the virus. The vaccine doesn't prevent them from being infected with the virus either, it only prevents the formation of the tumors it causes, reducing mortality. So a vaccinated bird can still be infected with the virus and transmit it, they are just less likely to die of the disease. So if you know you have Marek's in your flock, whether you vaccinate or not, you have to assume that all the birds are carrying the virus. If you don't have Marek's and buy some vaccinated chicks, the vaccination itself isn't going to bring the disease into your flock. Many people have mixed vaccination status in their flocks, they may buy vaccinated chicks but if they hatch themselves those are most often not vaccinated (due to cost, large bottles of vaccine that has to be used up in hours once activated, and quarantine requirements to give the vaccine a chance). Vaccinated chicks have to not be exposed to the virus for at least 2 weeks following vaccination in order for it to have a chance to work, which is really difficult for backyard keepers to accomplish since it's so easily transmitted and carried on clothing, shoes, wind, equipment, etc. There are different schools of thought on the usefulness of the vaccine, much debate, strong feelings on both sides of the issue.
This is an interesting read, if you haven't seen it:
https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous

 

[Eggcessive]

Nope. I had vaccinated chicks from a hatchery, then got a few more not vaccinated, and they all lived fine. Never had Mareks in 11 years.

 

[azygous]

Yes, they can. But it's not from the vaccine being a live virus. It's the nature of the vaccine to merely provide resistance and not complete immunity. If a vaccinated chicken is exposed to the Marek's virus in the environment, that chicken can then pass the virus to other unvaccinated chickens.

 

[RoostersAreAwesome]

An infected vaccinated bird can pass on the disease just as well as an infected unvaccinated one, but they won’t automatically get the disease from the vaccine.

 

[Madhouse Pullet]

Another article on the subject.
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/

 

[chicknmania]

This is my understanding of the vaccine:
The vaccine does not cause them to transmit the virus. The vaccine doesn't prevent them from being infected with the virus either, it only prevents the formation of the tumors it causes, reducing mortality. So a vaccinated bird can still be infected with the virus and transmit it, they are just less likely to die of the disease. So if you know you have Marek's in your flock, whether you vaccinate or not, you have to assume that all the birds are carrying the virus. If you don't have Marek's and buy some vaccinated chicks, the vaccination itself isn't going to bring the disease into your flock. Many people have mixed vaccination status in their flocks, they may buy vaccinated chicks but if they hatch themselves those are most often not vaccinated (due to cost, large bottles of vaccine that has to be used up in hours once activated, and quarantine requirements to give the vaccine a chance). Vaccinated chicks have to not be exposed to the virus for at least 2 weeks following vaccination in order for it to have a chance to work, which is really difficult for backyard keepers to accomplish since it's so easily transmitted and carried on clothing, shoes, wind, equipment, etc. There are different schools of thought on the usefulness of the vaccine, much debate, strong feelings on both sides of the issue.
This is an interesting read, if you haven't seen it:
https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous

Thank you! All good information. And yes, that was us exactly as far as vaccination in our mixed flock. I was going to buy some vaccinated pullets from the hatchery because that's just the way they come, but as it turned out they sold out before I had a chance to grab any. Probably just as well. I'm getting unvaccinated chicks instead. And I always decline vaccinations for chicks because of the reasons you stated above.
.

 

[chicknmania]

This is a very well written article. The hatchery in fact referred me BYC and this article specifically when I spoke to them about my concerns about Marek's. Idk if my flock has had Marek's or not...as it's explained in this article, there are so many things that can cause neuro symptoms in chickens, it's really impossible to say without necropsy, which we choose not to do. It is expensive and not much fun in Ohio to get a necropsy. We've had chickens for a couple of decades and have had a few with neuro symptoms over the years, so who knows, really. I'm just thankful that so far, our flock overall has appeared to be very healthy.