Should I Have My Chicks Vaccinated for Marek's Disease?

By orrpeople · Dec 6, 2017 · ·
  1. orrpeople
    th (1).jpeg There's that question!! It's at the end of every order for chicks purchased from a hatchery, and even from some small hobby farms. The Marek's vaccination? Should I get it? What, exactly, is it? Do my chicks really need it? Will it harm them? Why do I have to decide before I get my chicks?

    The first time I ordered chicks from a hatchery, I was already so astounded by the fact that I had to order so many chicks and pay so much for shipping, that the idea of tacking on even one more cent was just inconceivable. Granted, I was fairly new to raising chickens and didn't really even know what types of chicken diseases were "out there" in the first place! Marek's seemed like something foreign, distant, and rare. I had no idea how common and prevalent it is.

    The purpose of this article is two-fold. But first, I will tell you what it is not. It is not an in-depth article about Marek's disease. Others have done beautiful, extensive work with this topic. It is also not a "pro" or "anti" vaccinations discussion. We all must make our best, educated decisions regarding the health and well-being of our birds.

    My first goal is to shed some light on the vaccine itself; why and how it came into existence, and what makes it effective/ineffective.

    My second goal is to explain the process for administering the vaccine, as well as why it is only given to chicks.

    I would also like to achieve both of these goals using layman's terms. In other words, although the science involved is extensive and intricate, it is vitally important that anyone with a backyard flock be able to understand the topic and make an educated choice for their birds.

    In the 1920's, the poultry industry hit a large "bump" in the road...a virulent disease began to destroy large quantities of birds. It killed in a variety of different methods - but always leaving its tell-tale visceral tumors (tumors on internal organs) as a calling card. The disease, which came to be known as Marek's disease (after the man who identified it), rapidly spread world-wide on the dander (tiny skin cells) of infected birds.

    Between the 1930's and 1960's, attempts were made to breed chickens for resistance to the virus. This proved to be quite complicated due to genetic chromosome issues (inbreeding). It also opened doorways for other viruses by creating too many birds that were genetically similar.

    In the 1960's, the first vaccination for Marek's was created. Made from a Herpesvirus from turkeys, it was a groundbreaking discovery. It was the first time a vaccine effectively stemmed the development of tumors - in any species! Widely successful, it eliminated the drastic losses associated with the disease for roughly ten years.


    But viruses are living organisms that adapt to their environment in order to survive. So, despite good vaccination protocols, more Marek's cases began to occur. New vaccines were introduced; and combining vaccines was also practiced. Over the last 40+ years, the use of vaccines managed to reduce Marek's mortality by almost 99%, but the disease could not be eradicated completely.

    One of the reasons the virus continued to create complications was that the vaccine functioned not to eradicate the disease itself, but to keep the virus from killing its host. It prevented the growth of the lethal tumors formed by the Marek's virus, but did not keep chickens from "catching" the disease. Therefore, inoculated birds were still able to carry the virus, thus continuing its spread. They were, however, not dying, and the poultry industry was kept afloat as a result.

    As backyard chicken owners in 2017 (almost 2018!), we are the beneficiaries of historical vaccination protocols. Even though vaccination did not address the underlying cause of the disease, it did allow birds to live out their lives, producing offspring, and many of the vast variety of colorful breeds we know and love today.

    But, should today's backyard hobbyist have their chicks vaccinated for the disease?

    First, in order for the vaccine to have any effect on the bird's system, it must be administered before the bird is 24 hours old. Often hatcheries have the capability to give the "shot" at day 18 of incubation - while the chick is still developing in the egg. Others innoculate just-hatched chicks. The reason for this early vaccination protocol is to -effectively- "beat" the deadly virus to the punch. Once a chick is exposed to outside elements, it is, quite literally, a race as to which will take hold in their system first; the vaccine, or the virus. Chicks who have been given the vaccine must then be free from any possible exposure to the Marek's virus for 7-10 days, giving the vaccination an opportunity to bond with the bird's genome.


    As stated earlier, the Marek's vaccine is derived from the turkey form of the same type of virus (they are both Herpes viruses). It is not a chemical or artificially created substance. The vaccine has never been shown to cause Marek's in chickens, therefore, vaccinating a bird cannot infect that bird or those with whom it comes into contact. Only the Marek's virus, itself, can cause an infection. It is, however, as possible to contract the disease from a vaccinated bird as a non-vaccinated bird, as both can contract the virus.

    As other extensive articles have stated, the Marek's virus is likely found in all poultry environments. It has an extraordinary capability for dormancy. Environmental flock management factors like good hygiene and health maintenance programs; proper coop size and space; and limits on stress, prove to greatly reduce the virus' impact on backyard flocks. Therefore, it is entirely possible for a backyard hobbyist to never encounter the manifestation of the disease, and vaccination may not be necessary.

    However, poultry populations such as show stock, new imports, or birds kept in high population density conditions, will likely maintain a much higher risk for succumbing to the disease. These factors may indicate the need for vaccination.

    It is vitally important to note that poultry owners must assume their chickens carry the virus, whether vaccinated or not. Therefore, they must always endeavor to limit factors that may trigger an outbreak. The vaccine is not a foolproof "cure-all" - in fact, as the virus continues to adapt and mutate, it may become increasingly more difficult to address with the current vaccination protocol.

    Making educated choices is one of the primary duties of all backyard chicken keepers. We really do love our birds, and want only the best for them. Whether or not to have your chicks vaccinated is your choice, but unlike me - when I bought that first batch of chicks - hopefully you will know why you are - or are not - checking that Marek's vaccine box!

    "Marek's Disease: History, Actual, and Future Perspectives" (Dr. Frank Fehler)’s-disease-in-poultry

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  1. ForrestGump
    Thank you for writing up the facts about Marek's vaccine. Many of us get so tired of people thinking the vaccine gives birds the disease. It does not as the vaccine is a Turkey virus that creates antibodies for the chicken form of the virus. Again, great job.
      orrpeople likes this.
    1. orrpeople
      I think the majority of the confusion arises because the term "leaky" has mistakingly been applied (even by some very well meaning and educated folks) to this vaccine when they try to describe its efficacy in eliminating the virus.
      The vaccine doesn't eliminate the virus (the cause for the commonality of the virus' presence); resulting only in the suppression of tumor growth. The term "leaky" implies "Infectious" and should not be used in connection with the MDV vaccine.
      ForrestGump likes this.
  2. CapricornFarm
    Excellent information, well written.
      orrpeople likes this.

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