Marek’s Disease Vaccinations

We vaccinate all chicks for Marek’s disease. This page is to explain what it is and why you should care.

What is Marek’s Disease ?

Marek’s is a herpes virus that primarily infects chickens. It can cause cancerous tumors that weaken and eventually kill the bird. It is usually associated with lameness and wasting away, and there is no cure. Many, probably most, chickens are infected with at least 1 type of Marek’s as it is extremely contagious. Not all, or even most, of the affected chickens will show symptoms.

Here are some great articles that everyone with chickens should read: 

Why buy vaccinated chicks ?

The idea with vaccinating chicks for Marek’s is that they get infected early with a benign form of the disease, which acts to prevent the development of symptoms. They can still be infected with the disease-causing type, and can even act as carriers, infecting other birds, but they are far less likely (but not guaranteed) to ever exhibit symptoms or die.

Can vaccinated chicks harm my existing flock ?

Rumors abound of Marek’s vaccinated birds bringing the disease into a flock and ending up as the only birds that survive. This is not caused by the vaccine, but the vaccine could enable it to happen. Here is what is going on, remember I said that a vaccinated chick could later be infected with the disease causing type of Marek’s and not show symptoms? Imagine that infected, but vaccinated, bird moving to a flock that does not have any Marek’s. The vaccinated bird would show no symptoms during any quarantine period, but would transmit the virus to the unvaccinated flock, with nasty consequences. It is also quite possible for an unvaccinated chicken to be infected with Marek’s and never show any symptoms. The vaccination status of the chicken makes no difference here, either bird will bring the Marek’s viruses they are infected with into their new flock.

Makes you want to never bring new birds into your flock, doesn’t it? Keep in mind that every chick is hatched free of any Marek’s virus, it does not pass from mother to chick via the egg. The point of the vaccine is to get the non-symtomatic type of Marek’s well established in the chicks before they are exposed to the disease inducing type of Marek’s. It is far, FAR, safer to always buy chicks rather than older birds. You will not be able to determine the Marek’s status of an older bird, but if the chicks are handled in a bio-secure way, they are carrying only the vaccine type of Marek’s. If that should get passed to your flock, it will have the effect of helping them to become immune to the disease.

How to care for vaccinated chicks ?

There are no special handling for these chicks, but it is essential that you keep them isolated from the disease-causing form of the virus for at least 3 weeks. That means practicing strict biosecurity if you also have older chickens. Change clothes and don’t share equipment. This is temporary and for the best health of your young chicks. Note that this is for the protection of your new chicks, not your existing flock. The vaccine does not contain any of the virulent type of Marek’s, but rather a benign type that typically infects turkeys, but with no symptoms. Your vaccinated chicks can still get infected with the virulent type, but the chances of them developing any symptoms is greatly reduced once this 3 week period is past.

Is there ever a reason to not vaccinate ?

For years, I have avoid vaccinating, preferring instead to breed for resistance. Some of my birds have shown very high resistance to Marek’s, but I lose some birds to lameness and wasting every year, part of the “price” for breeding for resistance. I plan to vaccinate my replacement breeders from now on. There are concerns about the overuse of vaccines that are “leaky” as the Marek’s vaccine is. To understand the concerns here, I refer you to yet another article to read:

Can I get unvaccinated chicks from you ?

It is too much special effort to keep unvaccinated chicks separate, so I cannot accomodate requests for unvaccinated chicks.

Would you vaccinate chicks for me that I hatched or bought somewhere else ?

I cannot do this. I haven’t looked into the legality, but it seems like I would be providing a service that only licensed veterinarians would be permitted to do. In addition, administering the vaccine is time-critical and mixing a dose for a few chicks is quite costly in terms of time and supplies.