Marek’s Disease

Vaccinating for Marek’s

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Marek’s vaccine does not prevent Marek’s disease, it prevents the malignant tumors caused by Marek’s disease.

 

 

 

SINCE I ORIGINALLY  WROTE THIS PAGE THERE HAS BEEN MORE INFORMATION COME TO LIGHT ABOUT THE MAREK’S VACCINE.  PLEASE TAKE THE TIME TO READ THE ARTICLES ABOUT THE MAREK’S VACCINE BEFORE YOU LEAVE OUR BLOG  http://www.pbs.org/newshour/updates/tthis-chicken-vaccine-makes-virus-dangerous/

http://phenomena.nationalgeographic.com/2015/07/27/leaky-vaccines-enhance-spread-of-deadlier-chicken-viruses/

http://www.livescience.com/51682-vaccines-evolve-deadlier-viruses.html

Marek’s Disease in Chickens

Marek’s Disease is a viral tumor-causing disease of chickens.  Marek’s is seen worldwide and is so common that if you have birds, they have been exposed to Marek’s, regardless of whether they show symptoms or not.


There are 4 different forms of Marek’s:

  • Cutaneous (skin Form)
  • Neural (nerve form – causing paralysis)
  • Ocular (eye form)
  • Visceral (internal-organ form)

CAUSE

Marek’s is caused by herpes virus primarily affecting young birds.   It is believed that most  birds are immune by the time they reach maturity or 5-6 months old.  Marek’s is often characterized by  abnormal cell growth in the peripheral nerves and central nervous system causing paralysis, commonly in one or both legs: It used to be known to old timers as range paralysis. In addition the disease also may cause lesions on internal organs and other tissues, including feather follicles of the skin. The most prominent lesions may be tumors on vital organs such as liver, kidneys, testes, ova, spleen and lungs.  Some birds may also exhibit the ocular form causing blindness and gray eyes in one or both eyes.

How Marek’s Disease is Spread

Marek’s is highly contagious and spreads by bird to bird contact, by contact with infected dust and dander, and by darkling beetles and mealworms that may live in the chicken house, although the virus has no affect on the beetles or mealworms.  Chickens are most commonly exposed to Marek’s by contact with residual dust and dander in  preciously infected houses, by air contamination from a nearby house, or by virus particles carried by personal  equipment and clothing.

Mareks disease is not transmitted by mites, mosquitoes and coccidia.  The virus does not survive the egg incubation process and is not spread by hatching eggs.  Marek’s
diaease-causing virus particles can survive for months to years in chicken house dust and litter.

Signs

The signs and symptoms of Marek’s disease vary depending on the form of the disease.

Cutaneous form:  

Enlarged reddened feather follicles and white bumps on the skin that form brown crusty
scabs.

Neural form:

Characterized by one, all or none of the following symptoms;

  • Progressive paralysis, usually of the leg or wing, a typical leg-paralysis victim will have one leg extended  forward and one leg extended back.  A swelling of the sciatic nerve is the cause.
  • Weight loss
  • Labored breathing
  • Diarrhea
  • Starvation and death due to an inability to reach feed and water and to trampling by pen mates.

 Ocular form:

  • Grey eye color
  • Misshapen iris
  • Weight loss
  • Blindness
  • Death

 Visceral Form:

Tumors on internal organs including heart, ovary, liver and lung.  This form can not be readily seen while the bird is alive.  It can cause unexplained death until a necropsy is done.  If  you have chickens processed for the freezer you should ask the processor to let you know if they see anything  unusual when butchering.  They will make a note and let you know if tumors were found.  Generally this information is not offered but they will tell you if you ask.  No one knows the inside of your chickens like your butcher.

 

Prevention

As always, first and foremost practice good biosecurity !  (yes I say that a lot 😉  )

  • Breed for resistance – we have noticed that the imported birds are more susceptible to USA Marek‘s Disease, it is slightly different than Marek’s in the UK
  • Good sanitation and ventilation
  • Brood chicks separately from adults until 5 months of age (very important!)
  • Keep turkeys with chicks (the vaccine is made from turkey herpes virus  and raising turkey poults with chicks has shown to provide additional immunity to chicken mareks -( however could lead to black head disease in turkeys)  In my own unprofessional study, this, along with vaccination, has worked nearly 100%.  Chance?


Tumor formation from Marek’s disease can be prevented through vaccination.
Vaccination at one day of age usually protects birds through their lifetime.  Again, in my own personal study, multiple vaccines at day old, and 3 weeks did not increase immunity.  There is no treatment for Marek’s  disease.  Birds that contract Marek’s should be culled.  Infected birds that recover can become carriers for life.

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