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What is Marek's Disease?

Marek’s disease is a very common disease that may affect your chickens. It spreads quickly through a flock, affecting young birds between the ages of 8 and 20 weeks of age. If you raise chickens, it is vital to understand the signs of this virulent disease so that you can take action against it. There is no cure, with prevention being the most important course of action to take. The disease occurs most commonly as the nervous form, with progressive paralysis in one or both limbs, and sometimes showing in the neck or wings as one of the main symptoms.

Marek’s disease is highly contagious amongst chicken flocks and is caused by the herpesvirus. There is no cure and it brings a high mortality rate.

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Symptoms of Marek's Disease in Birds

  • Vision impairment, with a change in the eye colour showing a grey iris or irregular pupil 
  • Skin change in texture around the feather follicles, often appearing raised and bumpy 
  • Lameness and leg weakness without any visible signs of swelling or heat within the limb 
  • Partial or progressive paralysis of the limbs is a typical symptom of Marek’s disease 
  • The paralysis can also affect your chicken’s neck or wings causing your bird distress  
  • Loss of weight due to the inability to reach the water and their feed  
  • Difficulty in breathing 
  • Diarrhea 

Types  

Nervous Form

 The most common type of Marek’s disease begins as a progressive paralysis of the neck or wings, and limbs, affecting the sciatic nerve (main leg nerve). If your bird has this type of MD it may seem uncoordinated on its feet. Paralysis takes over very quickly and blindness can occur.

Visceral Form

This presents as tumors within the internal organs of your bird such as ovaries, spleen, liver and heart. Symptoms include depression, paralysis, loss of weight, anemia (pale combs) and sometimes diarrhea. Your bird may die suddenly without any sign of the disease.

Causes of Marek's Disease in Birds

  • Marek’s disease is caused by the herpesvirus or more specifically, it is a DNA virus 
  • This highly contagious disease (among your chickens) is spread by chicken dander (dust) through inhalation 
  • This condition increases the risk of other diseases as the immune system is compromised 
  • It can also spread rapidly through contact with other contaminated chickens in the flock 
  • Dander from other wild birds, the wind, human shoes can all spread the disease 
  • It can be spread through environmental factors such as an infected enclosure
  • MD can survive in the soil where chickens are kept for at least five months

Diagnosis of Marek's Disease in Birds

If your notice any of the symptoms of Marek’s disease within your bird population you will need veterinary assistance to diagnosis this condition. On examination, the symptoms will be a major factor, and if any of your flock have died, a post mortem will confirm your veterinarian’s analysis. With post mortem findings, the enlargement of the nerves such as the sciatic nerve will be obvious, and changes within the internal organs may be visible. 

There is a vaccination (for commercial poultry but small doses are not yet available to the backyard bird keeper) against MD that is advisable for your birds; it is not a cure, it only helps your bird to build up a resistance to the disease. In other words, just because your bird is vaccinated it is no guarantee that it will not catch this disease. Marek’s disease is a common virus that occurs where there a flock of chickens being raised. It can spread rapidly in unvaccinated birds, so that they become infected. They can carry the virus for life and can shed the virus through the feather follicles which then spreads rapidly in the dust and fluff in the environment. One thing to note, it is not spread from the hen to the chick through the egg, and the meat and eggs from infected birds are perfectly safe to eat.

Treatment of Marek's Disease in Birds

There is no cure or treatment for Marek’s disease. Those birds who are diseased should be removed from the others, and sadly humanely destroyed. Close monitoring of your remaining birds to see if they are infected is important. Although vaccinations are commonly used for those commercial poultry farmers, it is not available in small doses for the hobby poultry keeper. If you are buying new birds choose from a commercial source that has vaccinated its stock. Although it will not prevent your birds from getting this disease, it will make them more resistant to it.

Preventative measures are also important, such as ensuring chicks are separated and reared so that they don’t get the infected fluff and dust of older birds. A regular clean out of the shed or enclosure, and equipment such as feeding bowls is very important. Disinfecting these areas will help prevent MD. Superior quality feed and regular treatment from parasites is also good practice. By practicing good management, it will ensure your birds have the best chance to resist Marek’s disease. Consult your veterinarian regularly as to the annual care for members of your backyard flock.

Recovery of Marek's Disease in Birds

There is no cure for this disease. There is only prevention and management of your birds. Because MD is spread via chicken dander and dust, maintaining good conditions within enclosures is important. Sterilising of the utensils, perches and even relocating the birds to another enclosure while you turn over and treat the soil (if you have a dirt floor) is a good routine to get into. MD is not contagious to humans thankfully. But care with new breeding stock or chicks from reputable breeders who vaccinate their birds is important. Because this disease is so contagious it can travel through your flock of birds leaving them decimated within weeks. Prevention is an essential part of bird rearing management.

Marek's Disease Questions and Advice from Veterinary Professionals

Cookie
chicken
8 Days
Serious condition
1 found helpful
Serious condition

Has Symptoms

Eating good but pooing very little
Wings limp
Falling Over

Does my chick have this?? I just got some baby chicks and just yesterday one of them has been walking them falling over she is only 8 days old and when we got her she was 1.30 is them her weight has been fluctuating through out the few days she is now 1.45 and the others have gained 3x as much as her. We have seen the other chicks push her when she trys to stand up or peck at her. We have picked her up out of the cage and her wing was limp and hanging down. We have been feeding her hard boiled egg, and sugar probiotics water for the past 3 hours and no improment has happend we have separated her from the other chicks, still in the same cage but in a small box in the corner and she can't stand still and is kicking her legs from under her and scraping the bottom of the box all at the Same time laying down.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
Whilst there are similarities with Marek’s Disease and Newcastle Disease, it is unlikely that one bird would be showing symptoms whilst the others aren’t; numerous conditions may lead to similar symptoms including developmental disorders, slipped tendons, nutritional deficiency among other disorders. If Cookie isn’t gaining weight and is unable to move it may be best to cull, but this would be your choice. Regards Dr Callum Turner DVM

Can Mareks be spread to pet parrots and ducks.

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Milk and Oreo
Bird
6 Months
Critical condition
0 found helpful
Critical condition

Has Symptoms

Leg paralysis won’t eat or drink

We had 9 chickens about 6 months old. We went on vacation and my parents kept an eye on them. When we got home one chicken would not get up. My parents said she was acting weird for a few days. We brought her inside and it was as if her legs were paralyzed. She died that night. Two others we noticed could not hop up onto their roosting bars and one layed down at the back of the coop. The next day she hadn’t moved. Her legs are paralyzed and she won’t eat or drink. We separated these two chickens and the one has not been able to use her legs since Thursday. We are giving her water with electrolytes with a syringe. We don’t think she will make it. The other chicken is still able to walk and eats and drinks fine. She’s just moving slowly and not herself. Could this be Marek’s disease? Please help!

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Group of chickens
Plymouth Rocks
7 Months
Moderate condition
1 found helpful
Moderate condition

Has Symptoms

Mareks

I have some Plymouth Rock one pullet died very suddenly another very unwell stumbling took her the vet did a necropsy came back not Mareks but a very rare tumour. Then 2 day's ago my rooster he was about 8 months ago started limping then could not walk. Went to the vet he was euthenized had a necropsy done by that vet he had tumours in his liver consistent with Mareks. I have 3 remaining pullets and 3 hens and one young rooster the brother of the one that died. Do you think I could lose the whole flock none are symptomatic. The other chickens it all happened over the last 6 weeks. Thanks Judy

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
It is possible that all may be lost over time, however you may want to think of culling and repopulation since you have a small number of chickens; you should discuss with your Veterinarian. Regards Dr Callum Turner DVM

Thank you for advice regards Judy

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Goldie Hen
buff
Eight Months
Moderate condition
1 found helpful
Moderate condition

Has Symptoms

not laying

Our chicken less (than 1 yr presented with one wing hanging down 3 days ago so treated as broken wing and isolated her for observation. Now she seems to have neck tortion (torticolis) and blindness in one eye with general uncoordination. Otherwise eating and drinking well and vocalizing and breathing normally with normal poop- All hens (16) have been laying poorly for 2 wks. They are free range 1/2 day and have large pen and roosting area. Is this Marek's?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
Without examining Goldie Hen and (I don’t want to say) perform a necropsy (if necessary) I cannot say whether or not she has Marek’s Disease or another condition, given the symptoms I would recommend that you visit an Avian Veterinarian for an examination to diagnose the cause of the symptoms (the torticollis and asymmetric wings are concerning). Regards Dr Callum Turner DVM

I have a new born pheasent poult... He has disease of leg weakness and mouth opening.... Please suggest me how to treat this kind of disease

SHE SEEMS BETTER TODAY! ALL OTHER HENS NON-SYMPTOMATIC SO WILL CONTINUE TO OBSERVE- NO VETS IN OUR AREA TREAT POULTRY... WOULD HAVE TO TAKE HER TO DAVIS- 1HR AWAY. IS IT IMPORTANT TO DX THIS FOR THE HEALTH OF THE FLOCK? TRYING TO FIND OUT FROM SOURCE IF SHE WAS VACCINATED... THANX FOR YOUR RESPONSE- MELANIE

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Bok Bok
chicken
2 Years
Serious condition
4 found helpful
Serious condition

Has Symptoms

Immobility

Our chicken appeared fine last night, but when we woke up this morning she was laying on her breasts with her left leg sticking out behind her. I picked her up and she is unable to maintain weight on the left leg. She is also gurgling when she breathes, and vomited once. Because she is unable to put weight on her leg, she cannot eat or get water.

Dr. Michele King, DVM
Dr. Michele King, DVM
1604 Recommendations
Since I cannot examine BokBok, or provide much assistance over an email, she should see a veterinarian. They will be able to examine her, determine what might be going on, and give her any treatments that she may need.

I had the same with one of my chicks at 10wks old, she died later that day but none of my others have shown similar symptoms.

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Philly
Buff Orpington/Red Sussex
1 Year
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Multiple symptoms above
Bloody vent, eye discoloration

I cannot tell what is wrong with my rooster, Philly, who I’ve hatched over a year ago. He has had several symptoms at different times. The first morning I had noticed he was bleeding from his vent and was often complaining. He did not poo much. The next days on I noticed that he looked pale and sick in the face, his eyes were irregularly shaped and discolored. His eyes were originally orange. I have been feeding him plain yogurt, corn, bread and fresh water. He was eating okay but he had lost a lot of weight. He stands around a lot like he is the most saddest chicken on Earth. He has not crowed in the past 2 weeks. I have 11 healthy chickens.(2 roosters; the rest are hens)I regularly clean out their coop refresh their water and give them plenty of food. I was not aware about Mareks disease at the time I hatched him so there was no prevention. This has been going on for a week.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
Apart from the ocular changes there is little else tying in with Marek’s Disease; however if you do suspect that Philly has Marek’s Disease you should visit an Avian Veterinarian to be on the safe side, but generally a definitive diagnosis can only be made at necropsy. Regards Dr Callum Turner DVM www.msdvetmanual.com/poultry/neoplasms/marek’s-disease-in-poultry

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Rocco
Venda
4 Years
Fair condition
1 found helpful
Fair condition

Has Symptoms

Loss of Balance

In all my years of having chickens, I've never seen this. WHY would my rooster be losing his balance and falling over? He's a youngish Venda boy of about 4 years old. When he falls over, he struggles to get back up but he does. He waits at the back door at night so he can sleep inside in his box with some wood shavings. I'm worried about him, he's an amazing rooster, gentle and even plays with my one dog. He's eating, drinking, crowing as normal. he runs around, crows, covers my hens, eats drinks normally, poop is fine, just gets dizzy spells and falls over. i have checked his ears they are clean and clear. my chickens dont have mites or lice or anything. generally a healthy flock.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
From what you have described it doesn’t sound like the transient paralysis syndrome associated with Marek’s Disease; but if Rocco is otherwise in good health and is behaving normally apart from these episodes I cannot think of anything specific which may be causing these episodes. You should try to consult with an Avian Veterinarian for an examination to get to the bottom of this. Regards Dr Callum Turner DVM

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Rooster
Japanese Bantam
6 Months
Critical condition
0 found helpful
Critical condition

Has Symptoms

Paralysis
Lethargy
Lame

Hello, we had 6 point of lay bantam chickens until 3 weeks ago one got sick and died. Then 2 weeks later another one became lethargic and then paralyzed until within 5 days it also died, even with a lot of care and nursing. Now the rooster of the brood has become paralyzed and lying on his side. Comb and wattles are good color. Legs appear in good condition, yellow in color. Head movement good, alert. Eats and drinks well when food/water is right in front of him but otherwise immobilized. No signs of blood in poo. No signs of anything coming from beak/mouth. Is this likely to be Marek's disease? Is there anything that can be done to help recovery and prevent spread to other 3 birds left?

Dr. Michele King, DVM
Dr. Michele King, DVM
1604 Recommendations
It is possibly Marek's disease, and there is a vaccine that could protect the rest of the flock. I'm not sure if the rooster will recover from this, and it may be a good idea to have them seen by a veterinarian to see if any nursing care is needed.

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Tanner, sweetie
Appenzeller
5 Months
Serious condition
1 found helpful
Serious condition

Has Symptoms

puffed up uncoordinated

I got some 3 month old chickens 2 months ago. after about 1 month 1 was acting ill, fluffed up feathers diarrhea. Her wings would droop the she was walking uncoordinated. She died in a day, then a cockel died. a few days later another became ill and I syringe fed her but she died after three days same fluffing up, not eating, uncoordinated. I thought they were okay and then a month later another became ill closing her eyes laying around puffed up uncoordinated and she died after two days. I have 5 left in that group. Do you think it is Marek's? I have other chickens but have kept them separated. Thank you.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
A diagnosis of Marek’s Disease is based on a necropsy examination of dead birds which would indicate characteristic lesions of infection including lymphoid tumours, enlarged nerves, bursa atrophy among other signs; ante-mortem symptoms are indicative but not conclusive. Regards Dr Callum Turner DVM www.msdvetmanual.com/poultry/neoplasms/marek’s-disease-in-poultry

Thank you. If I have another loss I will get a necropsy.

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Chicken
Battery
2 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

see above

In a year and a half had 3 hens display similar signs of illness. Wondering if it’s merricks. All lost weight, slowed down, slept or closed eyes , comb went black/ or pale puffed up their feathers , lost use of legs. Other hens seem fine and long periods between each bird getting symptoms ( a year from 1st to 3rd) . Any ideas. Vets here in Wales are very unhelpful when It comes to hens.

Dr. Michele King, DVM
Dr. Michele King, DVM
1604 Recommendations
Thank you for your email. It is possible that your chickens are showing signs of Merrick's disease. There is a vaccination for that disease, and you may have more luck consulting with a large animal veterinarian, or a bird specialist who will know more about chicken health concerns and preventive care.

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Giselle
Maran
2 Days
Fair condition
0 found helpful
Fair condition

Has Symptoms

none

Is Mareks disease transmissible to parrots? I ask because we just acquired a 2 day old Maran chick from a reputable feed store and it's housed in the house for now. We also share our home with 3 healthy parrots and want to make sure everyone is safe and healthy. They are all housed separately.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
Marek’s Disease affects chickens and turkeys with other species of birds not being affected; however you should ensure that you are keeping good biosecurity practices which bringing in a new bird into your home or environment as other diseases may be found. Regards Dr Callum Turner DVM www.merckvetmanual.com/poultry/neoplasms/marek’s-disease-in-poultry

I have a question based on this answer about if Merek's is transmittable to parrots. I've had several (maybe 6-8) birds die in the last 9 months or so with very similar symptoms. Chickens, ducks, turkey & goose. All were juveniles (about 4 mo ths old) they were all fine 1 day & the next stumbling around like a drunken sailor! Most developed a problem with their necks, they asted as if it wes broken! Fell over & eventually couldn't walk would tip over on their backs not being able to get up. Some took only 1 day to die & others have been longer. I have a 4-5 month old Gosling thats been like this a week now! My vet ( general large & small animal vet, no avian vets within 5 to 6 hours of where I live) sais it sounded like Merek's to her. So it it correct that you said only chickens & turkeys can get it? If so then whst do you thinkay be going on in my flock? I have over 100 birds so its not a huge percentage of the flock but still concerning, especially since i sell them & their chicks locally

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Hop
Silkie hen
4 Months
Moderate condition
1 found helpful
Moderate condition

Has Symptoms

Weakness

Hi, my hen is alert and has a good appetite, but unable to stand. This began three days ago where she was not able to put weight on one leg, now she can't stand at all. Can you please help? Thanks

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3314 Recommendations
Most issues with chickens not putting weight on their feet occur under the age of six weeks and is normally attributable to perosis; some dietary deficiencies may also cause issues but most likely some trauma to the affected leg is the cause. For the time being, if there are no other symptoms ensure that Hop is on a sufficient diet and all rest; if there is no improvement over the next week or so I would drop in to your Veterinarian. Regards Dr Callum Turner DVM

I just got some baby chicks and just yesterday one of them has been walking them falling over she is only 8 days old and when we got her she was 1.30 is them her weight has been fluctuating through out the few days she is now 1.45 and the others have gained 3x as much as her. We have seen the other chicks push her when she trys to stand up or peck at her. We have picked her up out of the cage and her wing was limp and hanging down. We have been feeding her hard boiled egg, and sugar probiotics water for the past 3 hours and no improment has happend we have separated her from the other chicks, still in the same cage but in a small box in the corner and she can't stand still and is kicking her legs from under her and scraping the bottom of the box all at the Same time laying down.

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Jon jon
Toyogamatsu
2 Months
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Unable to balane

We got 7 chickens. They're about 2 months old. All are doin well except for Jon Jon. He can't stand or walk. He falls forward and just pushes himself on his breast and face.and afterward he shakes a little. I just wanna help him. He's still the same size and weight of his siblings too.

Dr. Michele King, DVM
Dr. Michele King, DVM
1604 Recommendations
JonJon may have an inherited problem, or an infectious disease. Since the other 6 chickens are okay, it seems that there may be a problem that he was born with that is affecting his balance or mobility. It would be best to have him seen by an avian veterinarian to have an examination and see if there is a treatment that might help him.

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