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Diagnosis And Prevention Of Mareks Disease In Chickens

Updated on October 3, 2016

Diseases In Chickens - Mareks Disease

Diseases in chickens are not that uncommon and Mareks Disease in flocks is very common but many times they go undiagnosed. Have you ever had a chicken or two die and just chalked it up to survival of the fittest? Unfortunately, there are diseases out there that can quickly wipe out an entire flock of chickens.

Chickens are normally pretty healthy animals but they, like any other animal, do get sick from time to time. When they do, time is of the essence if you intend to save your bird. Immediately separate the sick bird or birds and consult with a vet. You will need to provide a separate chicken house and run, waterer, feeder and medicine as recommended by your vet.

Mareks Disease In Chickens

If you own chickens, you should be aware of a very common illness called Mareks Disease that many chickens have.

What is Mareks Disease? It is a virus that causes tumors to grow on the internal organs of chickens and this disease kills more chickens than any other disease. Because it is such a common disease, it is almost a foregone conclusion that if you have chickens, it is present in your flock even if your birds don't act sick.

Mareks Disease is grouped with the herpesvirus category of viruses. Some people also refer to this disease as 'Range Paralysis'. It is easily spread from bird to bird and farm to farm by the wind. The affected birds don't even have to have contact with non-infected birds or people who have touched diseased birds. It is readily spread through feather dander that becomes airborne.


Symptoms Of Mareks Disease

Mareks Disease has been very exciting to researchers because it is used to study cancer in all species of animals as well as people. Researchers were actually able to create the very first vaccine for any species that was effective to prevent cancer.

Mareks disease can manifest in a different ways in chickens. Eyes and nerves are the most common areas of the body to grow tumors from this disease. When a chicken comes down with this disease in the nerves, the chicken can have mild to severe paralysis of any part of the body including wings, legs or the neck. Unfortunately, chickens that are afflicted in this manner are often trampled by their own flock and killed because they cannot get out of the way.

Sometimes an affected bird will only have intermittent or temporary paralysis but it will seem to resolve on its own in less than a week. If it develops in the eye area, the pupil may have a gray look to it or may be an odd shape. These birds will be very sensitive to light and will tend to try to hide in their chicken coop or another dark area. Birds that develop Mareks in the eyes will usually lose their vision. If you have a bird that looks like it is starving or just wasting away, Mareks should be strongly suspected to be the cause.

Mareks Disease Can Manifest In Three Different Ways.

* Classical Mareks Disease or neurolymphomatosis Symptoms include paralysis in one or more of the limbs of the affected chickens. Your chickens will have trouble breathing and their crop can swell up if the nerve is involved. Tumors will grow on the nerves and the internal organs including the spleen, the ovaries, the liver, kidneys, heart and lungs. Sometimes you will be able to see tumors growing on the skin and feel them on the muscles of the affected chickens.

* Acute Mareks Disease is defined as an epidemic or outbreak of this disease in a flock that didn't have it previously. Your chickens will start looking depressed, will experience paralysis and many of them will die. Epidemics will occur when your chicks are only between four to eight weeks of age.

* Ocular lymphomatosis is the form of the disease that causes the chickens eye to turn gray in color and eventually go blind.

* Cutaneous Marek's disease is the form of the disease where tumors begin to grow on the feather follicles.

Vaccinate Against Mareks Disease

Unfortunately, Mareks disease is very contagious and easily spreads from bird to bird. If the birds in your flock have contracted this disease but managed to survive, they will be carriers forever and will pass it on to any new chickens that you bring into the flock. The good thing is that it is not passed to the eggs and you can vaccinate day old chicks to prevent symptoms of the disease from occurring.

If you buy new chicks from a hatchery and you introduce them to your new flock of birds that carriers of Mareks disease, they are most likely to contract the disease between the ages of five and 24 weeks of age. If your birds start developing similar symptoms when they are older, it most likely isn't Mareks disease but another disease called Leukosis which is discusses in another article.

Because this disease is so highly contagious, the only way to prevent tumors from growing when they are infected is to vaccinate your birds against this disease. But the bad news is that it doesn't eradicate the disease. It just makes it much less likely to spread among your flock and others in the area. This vaccine has helped to stop huge loss of life in flocks across the country.

The vaccine should be administered to day old chicks but the closer to hatching that you give it, the better it is. Don't bother giving it to chicks once they are more than 24 hours old because it is a waste of time. But it requires some planning when chicks are hatched because the vaccine is only good for about thirty minutes after it is mixed. All chicks will need to be hatched together or several doses of the vaccine will need to be purchased. It can also be given by in-ovo vaccination which is what big hatcheries do. Chicks will become immune within two weeks of being vaccinated.

How To Raise Healthy Chickens

I have been raising chickens for quite a few years now and I love them. Diseases can occur in your chicken flock at any time. It is very important to provide proper care of your chicks and full grown chickens to help prevent diseases from cropping up and spreading rapidly. You need to be able to find the right information on how to properly care for these beautiful birds.


I designed this lens to provide general information on chickens and chicken care for anyone looking for it. But, you should know that I do this for a living and this website generates some revenue through affiliate marketing. If you click a link and purchase something from that link, I will make a percentage off that sale. Debbie Vornholt is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to


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