All You Need To Know About Marek’s Disease

All You Need To Know About Marek’s Disease Blog Cover

Marek’s disease is an insidious disease that catches many keepers by surprise. Its effect on your flock can be devastating.

We’ve discussed Marek’s in the past, however there is much mis-information out there, so this article will clarify matters for you and your birds.

Many keepers are lucky enough to go a lifetime and never see this disease, even though it is very widespread. To find out if it is endemic in your area, call your local extension office, they should be able to tell you if it is present near you.

I have written this article in a question and answer format as this is the easiest way to convey information about this complex disease.

I encourage you to read, read, read! There is a lot of information out there about Marek’s disease and with regard to vaccines it seems to be constantly changing. Remember, if in doubt; please contact your local veterinarian or extension office for help.

What is Marek’s Disease?

Marek’s disease is a viral disease of chickens that is caused by a herpes virus. Current research shows that there are six mutations of the virus that can cause the disease.

The virus can range from non-pathogenic (not causing disease) to highly pathogenic (causing disease and death), and this depends on the strain of Marek’s disease caught.

It was first noted by the brilliant Hungarian veterinarian, Jozsef Marek back in 1907. When he wrote his paper about it, it was likely that only one strain of virus existed- however since then other strains have mutated.

Reputable sources currently say that Marek’s is so widespread, that you already have it in your flock, or your flock has been exposed- don’t panic! Reading about the disease and understanding it will help to guide your decisions and treatment.

What Are The Signs of Marek’s Disease?

Some birds do not show any ‘symptoms’ of disease. They may simply be resistant to it, or the type of virus caught may be non-pathogenic (not causing disease).

It should be noted that there are four different presentations of Marek’s disease- Neurological, Visceral, Cutaneous and Ocular. The type of presentation will dictate the kind of signs that you will see.

Signs for each of these forms will vary- some birds display all signs, others not so many.

Neurological

The neurological form of the disease is the most notable and disturbing in its presentation.

The symptoms are mainly caused by lesions affecting the nervous system and several other problems usually follow.

Occasionally the affected bird will have a temporary paralysis which will resolve itself spontaneously.

  • The bird shows signs of progressive paralysis, usually in the legs or wings. Often the bird looks like it’s doing the splits.
  • Twisting of the head to one side or backwards.
  • Respiratory problems such as labored breathing.
  • Darkened or purple comb (lack of oxygen).
  • Diarrhea.

Marek's Disease

Ocular (Eye)

  • Graying of the eye color.
  • Misshapen iris.
  • Blindness.
  • Non-reactive pupil of eye.

Cutaneous (Skin)

  • Lesions around the feather follicles.
  • Ulcers and/or scabs around follicles.

Visceral (Internal)

Often the only diagnosis of visceral Marek’s is sadly, post mortem due to the nature of internal maladies.

  • Cancerous tumors grow inside the bird on the organs.
  • Weight loss.

It’s also very likely that your chickens will stop laying eggs during this time.

How Do Chickens Catch It?

The virus is primarily spread by infected dander (dead skin cells) from other birds. However, it can be transported in dirty hen carriers, on clothing and boots, wild birds, and by darkling beetles in the henhouse.

It can survive for up to 65 weeks in ambient temperature in coops and for years in soil.

The virus is spread horizontally- that is chicken to chicken, not from the hen to the egg. So the virus will spread quicker among hens in tight living conditions- make sure your hens have enough room!

The primary age for disease manifestation is between 5-25 weeks, but this does not mean that older birds will not suffer from it. It just means that younger birds are more susceptible.

How Can I Prevent It?

Vaccination of chicks will certainly help to lessen the severity of an outbreak if it should occur. However, the vaccine does not prevent the bird from getting Marek’s.

The vaccine simply allows the bird to build up a better immunity to the disease, reducing the likelihood of severe symptoms or death and and it also reduces the spread of disease if an outbreak occurs.

Part of the problem lies in the fact that the virus is constantly mutating, much as the human flu virus does, so your birds may be vaccinated against one strain of Marek’s but not the one that infects them.

Another way to prevent the spread of Marek’s is to not add any additional hens to your existing flock.

Few backyard keepers do this. We are drawn to getting new birds periodically, so it is very difficult to effectively keep Marek’s out of your flock.

If you are compelled to add additional hens to your flock though, ensure that new birds come from a reputable source which practices quarantine strictly. You should know that Marek’s does not always show in quarantine, so even with rigorous measures, it is possible to bring Marek’s home with you.

As always, good housekeeping , biosecurity and ventilation are essential tools in your fight against disease.

Marek’s virus is resistant to some disinfectants such as Phenol; however many keepers recommend the use of Oxine. This kills the virus and has a very low toxicity to the environment.

How Can I Treat Marek’s Disease?

Unfortunately there is currently no treatment/cure for Marek’s disease. Depending on the severity of the disease, some birds can be conservatively managed and do not require culling. However, they will remain carriers of the disease for the rest of their lives.

Are all birds affected?

If one bird in your flock gets Marek’s, it is likely that all will get it. However, not all will show symptoms or experience disease. Birds that have been vaccinated have a higher immunity, but birds that have a weak immune system or some other ongoing health issue will probably succumb.

In infected birds that have a strong immunity or resistance, the virus goes into a ‘sleeper’ mode. It will insert itself into the birds RNA sequence and lie dormant. If the bird becomes immune suppressed at a later time in life, the virus may emerge at that time causing symptoms.

Should I Vaccinate My Birds?

This is a very personal decision. If you want your flock to be entirely ‘organic’, or generally dislike vaccines you have to be aware that if Marek’s attacks your flock, there will likely be significant losses.

The birds that do not die from it, will be carriers for the rest of their lives, so you should not sell, give or loan your birds to other flock owners.

If you choose to vaccinate, you may still have losses. Some flock owners have had chicks vaccinated at the hatcheries only to have them die later from a different strain. The vaccine does not guarantee immunity.

If you show your birds, vaccination is highly recommended- as your girls will be in contact with other hens and the likelihood of them catching Marek’s is greatly increased.

Many keepers and poultry people recommend that you do vaccinate since Marek’s seems to be very pervasive. If it is endemic in your area, it would be prudent to vaccinate.

If you have older birds that have not been vaccinated, it is possible to vaccinate them at any time. However, this can become an expensive prospect, and as noted before, the vaccine will not guarantee immunity.

Marek’s Disease FAQ’s

Q: How do I know if it’s active in my area?

A: You can start by calling your local extension office- they should have the information. Also talk to chicken people in your area; they are always a mine of information! If they have been bothered by Marek’s, ask them where did they get the chicks from…

Q: Can I catch it?

A: No, Marek’s disease is not contagious to humans.

Q: Can I eat the eggs and meat from an infected bird?

A: The virus does not travel to the egg from the mother- eggs are safe. Just make sure to properly clean them.

Meat from an infected bird can be eaten as long as it is properly cooked- but we wouldn’t recommend it. However chances are you won’t be able to because infected birds should be incinerated to prevent the disease from spreading.

Q: How do I know if my hens have got Marek’s disease?

A: The only way to know for certain is to have a laboratory test and evaluation by a veterinarian. However if their symptoms match the symptoms mentioned earlier on in this article- it’s likely they have Marek’s.

Summary

Marek’s is a pervasive disease that is widespread amongst chickens. It is a cancer causing virus and as such is being researched constantly because of the implications for human treatment.

As a virus, it is constantly mutating and so presents an ever changing challenge.

The vaccinated bird is somewhat protected, but unvaccinated birds can be in danger of succumbing to a more contagious strain of the disease.

It is difficult, if not impossible for the average backyard chicken keeper to keep Marek’s out of their flock. Unfortunately, some experience devastating consequences when the disease emerges, but for most of us, the impact is minimal.

Keeping your flock healthy, practicing good house-keeping, strict quarantine practice will all help in the fight against this awful disease.



Comments

  1. Brian says

    Hopefully you can help. Thank you for all the info, it’s very helpful. I’m not sure what to do with my sebright though. She has the signs: paralysis, heavy breathing, dropped head, falling around when trying to move and looking like she’s going to die any minute. That said though, give her attention and she’s still perky and goes mad for her meal worms
    She also has a very hard disc shaped lump in her chest which is protruding. I’m close to culling her but she still has that sparkle in her eyes so here’s my question: you mentioned “temporary paralysis”, does that mean that she could pass this phase?
    She’s been like this for 2 days and progressively worsened. Thank you for any advice.
    Also, I’m giving water with vitamins by syringe and she only eats a little.

    • The Happy Chicken Coop says

      Hi Brian,

      So sorry to hear about your sebright 🙁

      In my experience the paralysis doesn’t ever get ‘cured’.

      By temporary I meant that it will come and go.

      Hope this helps clear it up for you Brian and sorry again for your sebright,

      Claire

    • Audrey says

      What you’re describing is exactly what my lovely buff orphington is doing now. She has almost no control over her neck but I hate to put her down since she’s still alert. She doesn’t appear to be in any pain.
      How did your sebright fare?

  2. Judy says

    This is my first & amazing experience with chickens & I am seeking some help. I have 9 hens & a rooster.. 25 weeks old. A few days ago, I noticed one of my Wyandotte hens turning her head sort of sideways to take food from my fingers, something I don’t remember her doing before. I spend a lot of time with them, so I did note this without really any concern. But today, I did notice one pupil a lot larger than the other & with watching her, I believe she is blind or partially blind in the eye with the larger pupil by the way she seems to be looking at things. She seems fine otherwise. Maybe I’m looking too hard for something, but she might be picked on a little bit by a couple of the other hens that I don’t recall before? She is my friendliest girl. Anyway, should I be concerned? I googled this & only came up with ocular Marek”s disease. Now I am worried. There seems to be clarity in her eye colouring but a very distinct difference in pupil size. I do not see it in the others. Can this be a natural fluke just for her & not this disease? Thank you for any reassurance or advice..

    • The Happy Chicken Coop says

      Hi Judy,

      Thank you for getting in touch with me 🙂

      The first thing to note is Mareks is a very aggressive and contagious disease- so I think it’s very unlikely that she has Mareks as the rest of the flock would have it too…

      In terms of it being a ‘fluke’, I have seen hens before that are blind in one eye and live perfectly normally lives.

      Have you tried examining her in more depth, covering each eye in turn and using treats to track her eyes?

      Claire

      • Christy says

        Hello, I am experiencing Marek’s in my flock. Their coop is in a very old barn with dirt floors, so I can’t truly disinfect the coop. It looks like I can expect to lost over half of them. Going forward, how can I try to get chicks that will hopefully have the vaccination to increase their survival rate? This is devastating to a flock.

        • The Happy Chicken Coop says

          Hi Christy,

          I’m so sorry to hear about your loss. Yes going forward you can actually buy chicks that have already been vaccinated, so that’s what I would recommend.

          Claire

      • Judy says

        Thank you kindly for your response Claire! 🙂

        Yes, I have examined her very closely & frequently. She is my friendliest girl so follows me around the most & is pretty easy to hold. I believe she is totally blind in her eye with the very large pupil. The pupil is non reactive to both movement & light & the gold iris is somewhat lighter on the blind eye.. but still coloured (not grey). Both eyes used to be the same.
        She turns her head one way all the time to see. It seems to be fairly sudden. What can cause this if it’s not Marek’s? 3 of my hens pick on her more than before like they know, but she still fits in on a bit lower order.

        I am not worried about the blindness so much, as it happens that I adopt special needs animals & comfortably deal with blindness. I am just worried about a contagious disease & my flock that I love. This is my first experience with my own chickens & want to do right by them.

        I appreciate any ideas or opinions you may offer.

        Thank you so much.. 🙂

        • The Happy Chicken Coop says

          Hi Judy,

          Ah ok I see- I thought she was born like this, but it is concerning that it’s only recently happened.

          It could be caused by many things, including Marek’s, an injury or an infection.

          Without seeing the hen it’s hard to say, but I would definitely take her to your vet sooner rather than later.

          Let me know how you get on,

          Claire

          • Melissa says

            Hi My name is Melissa, I have a chicken that from her symptoms seems like Mareks. She is now almost completely paralyzed which started with the splits as described. What should I do? wait? its been almost a few weeks. I read here that it is sometimes a temporary paralysis. Please advise! I feel so bad for her and void of what to do.

          • The Happy Chicken Coop says

            Hi Melissa,

            If you think it is Marek’s then I would contact your vet ASAP.

            Claire

    • Kat says

      Hello Judy,
      How is your hen doing now?
      I have the same thing happining to me right now. My hen in from spring of 2016 and she is a black and white laced wyandotte.
      Iam now wondering is this could be related to the genes as I saw another case with the same breed of chicken and color. I went wild thinking it was mareks myself. How is everything now? What state are you in? I am in north east washington.

      • Cindy Frantz says

        Hi Kat. Are you in Spokane? I have never had any problems with my chickens but suddenly may have Marek’s in one pullet. I have been so careful…very disheartening. C.

  3. Rosie says

    I have a 4 month old cockerel who suddenly can’t stand up . Hes been like this a week and 3 days. The vet couldn’t see any injury and put him on metacam. He said if no better this week probably best to call it a day. He is eating and seems ok in himself. I booked an appointment at the vet to do the dead when suddenly he was standing up again and managed to walk over to a treat. Greta I thought hes getting better so cancelled the appointment. Next morning can’t walk again, in the evening he could again this morning all over the place again. He is still eating and cockadoodling. Do you think this is mareks? So far all the other chickens are ok . I did buy in 3 new girls at the beginning of October. Any suggestions about this boy? Could he get better? Thanks for any advice

    • The Happy Chicken Coop says

      Hi Rosie,

      Sorry to hear about your cockerel.

      Without seeing him I can’t really say whether it is Marek’s disease or not sorry.

      Claire

  4. Shane shults says

    We had a four day and a one day old silkie chick. Last night our four day chick died from what seems to be Marek’s disease. We haven’t vaccinated the other one yet but if were able to vaccinated it will that help for it to survive. I can’t stand to see another baby die like that.

    • The Happy Chicken Coop says

      Hi Shane,

      If your four chicks had Marek’s, I would get a vet to check your surviver ASAP. If they haven’t caught it already then they could be vacinated to protect them.

      Sorry to hear about your loss,

      Claire

  5. Debbe says

    Hi Claire,
    I’m thinking our little girl has Mareks. She has been paralyzed for 4 days now. Her little body doesn’t move but she will drink and eat. Her little head moves and she seems in great spirits. I feel so bad that she just lays there. Is it best to put them down when they get this? We only have 6 chickens. The other 5 seem fine. We quarantined her the first day. Any advice is greatly appreciated?

    • The Happy Chicken Coop says

      Hi Debbe,

      Sorry to hear about your little girl 🙁

      Without seeing her in person it’s hard for me to say. I would get a local vet to see her ASAP.

      Claire

    • mitzi says

      Did anymore of your chicks get sick? I think I am dealing with mareks. Second chick in a week that has lost use of one leg. This is my first time owning chicks, I am so sad.

    • Ellen says

      My 24 week old pullet got Marek’s. she has been sick for a week and is dying. I quarantined her as soon as I noticed the symptom. My other chickens look fine so far. I hope they have built up resistance. I have been doing everything I could to make her comfortable.

  6. Frankie says

    Lost one hen just got droopy and wouldn’t eat. The rooster laid with her found them both dead 2 days later. Have one Welsummer now just sitting but can move around but doesn’t want to eat much one eye has been cloudy for months thought it was an injury. How do I protect the rest of the flock

  7. Veronika says

    I have a 6 week old pekin frizzle bantam and yesterday he suddenly became really lethargic. Yesterday he just stood with his eye closed, not eating or drinking. I have been giving him warm molasses water with a spoon. This morning he is even less active. He is now laying down and seems unbalanced if he tries to walk. He just seems really weak. I took him to an emergency vet centre last night and the vet said he could feel a bit of hardness in his chest and mentioned Marek’s disease but couldn’t confirm anything without further testing. I am really worried about him as he is not eating anything and cant drink on his own. I have two chicks and they are best friends and the other would be devastated if he didn’t make it. Is there anything i can do to help him/ boost his immune system? I don’t know where he might have caught Marek’s from and it all happened really suddenly.

  8. Jaime says

    Thank you for this article. We believe ours became infected with Mareks disease when we brought home some new ones to our flock. We are devastated. Going forward we would like to know how to begin again? Do we need to do anything special for cleaning coop/new feeders?? Thoughts? We had 25 chickens we are down to 10 in a very short amount of time. Neurological seems to be the issue. Thank you.

  9. Matt says

    I had three Legbar pullets in an old coop that had not been used in a while in order to transition to the flock in the larger coop.

    Two of them died of Marek’s and the third never showed symptoms. It has been a month since the two pullets died.

    Can I move the remaining pullet into the main coop safely? Will my 1-2 year old chickens be in danger of Marek’s?

    Thanks!

    • The Happy Chicken Coop says

      Hi Matt,

      As mentioned in the article it can last up to 65 weeks so personally I wouldn’t risk it unless your other hens have been vacianted…

      Claire

  10. Karolina says

    Hi,

    it’s me again. I did some research yesterday and went through photos present in internet related to the symptoms of the Marek’s Disease. Unfortunately I am 100% sure that I am experiencing Marek’s Disease in my flock of silkies 🙁
    My question is, knowing that this virus can survive 65 weeks, is there any chance to clean somehow the place where my ill chickens are. Does this virus stay deep in the ground? (My silkies are in a wooden aviary, not a building with floor). Is it possible to get rid of the virus by exporting few cm layer out of the aviary, or to powder the ground with some cleaning powder?
    And what about the rest of silkies, those without symptoms, shoud I put them down? If I decide to have them, will I be at risk to pass the virus on my shoes or clothes to other birds I have in different aviaries?

    Thank you for your time and reply.

    I hope my description of the symptoms I experienced in my flock will help others to understand what is going in their flocks when they happen to, unfortunately, meet the disease.

    Best regards,
    Karo

  11. Dei says

    So I have lost two to Mareks. I have one girl left. All three were vaccinated. Going forward what should I clean with and if I wait 65 weeks can I safely restart my flock?

    • The Happy Chicken Coop says

      H Dei,

      This number is provided as a general figure to give you a rough indication.

      If possible, I would recommend raising chickens in a different location to be sure. How much land do you have, is this possible?

      Claire

  12. Rene says

    Hi,
    I got chicks last spring and was told that they were “flock vaccinated” – I bought them at my local farmer’s union, ordered from a hatchery. I got 21 chickens, and of those original 21 I now have 6 left. I did send one for necropsy and it was indeed Mareks. The remaining birds seem to have survived the disease and are laying eggs regularly, but although acting healthy in all ways they seem to have diarrhea most of the time. No weight loss or other symptoms. I’m wondering if I can add vaccinated chicks to this flock? I’ve considered just building a new coop an acre or two away on another part of my property. Any suggestions? Thanks!

    • The Happy Chicken Coop says

      Hi Rene,

      The important thing is the vaccination doesn’t give them immunity to Marek’s- it just gives them a better chance of surviving if they catch Marek’s.

      Hope this helps,

      Claire

  13. Anna says

    Hi I think my flock is infected. I lost 3 hens to what I think is mareks before October and now I have another hen who is experiencing the same symptoms. I did notice in her that she has one dilated pupil. Is it normal that there will be a lull in them showing symptoms? They are now about 40wks.

    • The Happy Chicken Coop says

      Hi Anna,

      It’s not normal but certainly possible.

      Did you get a post-mortem on your other hens to identify the cause of death?

      Claire

  14. Paul Beesley says

    Hi my name is Paul and I live in France, a year or so ago see dicided to get a few chickens and a couple of geese.
    One day thee make goose developed a limp, after a day or so it became difficult to walk, the next day I found him in the coup laying on his back with his neck twisted back, the next day he died.
    A while after I noticed one of the chickens limping luckily this only lasted a couple of days and she was ok after. Then later that week I found 3 chickens hobbling about 2 began to shed thier feathers and later died the other recovered. We also had 2 pantards ( very effective a keeping foxes away) again the developed the same symptoms, one died and one recovered.
    I have no idea as to the cause until last week, last summer we brought a young peacock, he has grown and eventually got his wonderful tail feathers. He has lived in a separately but in the same vacinity as the chickens. Yes you guessed it he caught the same symptoms, I called the vet and he immediately diagnosed Marek’s Disease which ultimately lead me to your sight which I have found very helpful and informative.
    Thank you
    Paul

  15. Alex says

    Hi
    I noticed one of my 4 month old chicks struggling to walk after I came home.
    The other chickens all seem to be fine and can walk normally.
    I am keeping her seperate from the others but I’m not sure what to do. I’ve been reading on what it could be but all I seem to find is that it’s possibly mareks.
    Do I have mareks in my flock?

    • The Happy Chicken Coop says

      Hi Alex,

      It’s certainly a possibility.

      However, without being there in person it’s hard to say. The only way to know for sure is to bring a vet in to test her.

      Best of luck,

      Claire

  16. Karen says

    We have an 11 month old Serama that started with some diarrhea and just not herself a few weeks ago. We brought her in the house and are keeping her separated from the others in a dog crate. We noticed that she can’t use her one leg now. Our rooster has been really rough with her lately (we only have 2 hens and a rooster) Her original mate passed in December from what we are not sure but could be the same thing. She is eating and drinking. We had her on a 5 day regime of Corid. I am not ready to give up on her. I have read that B12 can help. My husband thinks she is not going to get better. We don’t really have any poultry vets in our area. She is a sweet little thing and I hate to give up on her already. Any thoughts? Thanks.

    • The Happy Chicken Coop says

      Hi Karen,

      I’m really sorry to hear about your Serama.

      The main thing is making sure she isn’t in any pain. As long as her condition isn’t continuing to deteriorate then you have nothing to lose.

      Make sure to read our 2 articles on caring for sick/disabled hens.

      I have my fingers crossed for you,

      Claire

  17. Pam Beatty says

    I see you had requested someone to email you on the proper way to sanitize after a Mereks disease out break. Could you please do the same for me PLEASE!

  18. Aldwin Jumaquio says

    Hi and thank you for this article you shared. It’s very helpful.

    My first and favorite broodcock, I think, caught Marek’s and his left eye has gone blind with its pupil turning smaller.

    My question is – would his left eye see again if he survive the disease? I didn’t put him down. I pity him a lot as he’s a favorite of mine. I also understand that probably all my flock has the Marek’s, I intend to stregthen the immunity of my flock by breeding Marek’s survivors. So I’m really hoping my favorite broodcock will survive and will also get his left eye vision back.

    • The Happy Chicken Coop says

      Hi Aldwin,

      If I’m being honest I’m not entirely certain. I would contact your local avian vet who will be able to advise you 🙂

      Claire

  19. Briana says

    I have a small backyard flock. 7 hens ranging from 1-4 years old. Over the past month I lost 2 of my 4 year old hens. Based on their symptoms it sounds like Mareks. Is that likely since they were much older than when it typically manifests?

    • The Happy Chicken Coop says

      Hi Briana,

      It’s certainly possible. Did you get a postmortem on your hens to identify the cause of death?

      Claire

  20. Lauren says

    Hi! We have 35 chickens and 2 have died so far from mareks. They are in an old barn with a makeshift run right now. Would it be of any benefit to move them all to a different coop/ area?? Trying to think of any way to lesson the chances of losing them all. Thank you!

  21. Naomi says

    Hello! We had brought home some day old (hatchery) chicks.. We didn’t realize that they had been vaccinated for marek’s, until I noticed a dot on the back of one of the chicks necks. They were added to a brooder that had 1 week old chicks in it. They were together for 1.5 hours. The brooder is INSIDE our house, I seperated all the new chicks from the 1 week olds. How likely are these 1 week old chicks to become infected, as they are NOT vaccinated.

    • The Happy Chicken Coop says

      Hi Naomi,

      It’s very hard to say without knowing exactly what the hatchery chicks were injected with. If you are concerned I would contact your local vet who will be able to check for you.

      Failing this, you can closely observe your chicks as they develop and look for any symptoms which are mentioned within this article.

      Best of luck,

      Claire

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