Treatment and control of Marek's disease.

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I started my first poultry farm last two years. As a newbie who doesn't know much about poultry farming aside feeding, giving water and all those basic stuff. I couldn't reap the fruit of my labour, all thanks to Marek's disease.
I lost about fifteen of my broiler birds to Marek's diseases. What a gruesome loss. Isn't it?

At a point, I discovered that my birds were getting paralysed and emaciated. The birds go off feed and after some time they die. Marek's disease struck fear in my heart and even made me think poultry farming as risky and unprofitable.

Today, I would like to provide you with the following information about Marek's disease and it's control.

Causes of Marek’s disease

The disease is caused by two strains of herpes virus which both approach towards lymphoid tissue (lymphoid tissue is spread throughout a chicken, unlike a mammal where it is confined mostly to lymph nodes) and also causes demyelination of peripheral nerves (leg and wing). There are two strains of the virus; one which lives in the cell and one which is cell-free and lives in the feather follicle. The virus was discovered in 1907 by Jozsef Marek, a Hungarian veterinarian.

 Life cycle of the herpes virus

The virus replicates in the host chicken’s lymphoid tissue and is shed in feather dander. The virus can remain viable for at least one year in feather dander and hen-house dust.

 Females are more susceptible than males. Chickens from 6 weeks of age are affected, symptoms are most frequently seen 12-24 weeks of age with the hormonal stress of point of lay being a prime time for the signs to appear. Older birds might be affected if stress (changes in weather, food, handling, environment) are not minimised.

 Symptoms


  • Mortality:  Mortality is variable and depends on which of the peripheral nerves is affected.
  • Paralysis of the legs and wings.
  • If the neck nerves are affected, the neck can twist around.
  • In the acute form, birds may die suddenly with no symptoms and tumours may be found in the liver, gonads, spleen, kidneys, lungs, proventriculus, heart, muscle and skin.

The virus is common in poultry worldwide. Infection in chicks occurs by inhalation and two weeks later, the virus is shed by the infected chick in feather dander and by oral and nasal secretions. The virus is NOT passed on through the egg.


 Prevention of the disease

  •  Proper hygiene and management practices are necessary to the control of this infectious disease.
  • Quarantine any new stock for 4 weeks.
  •  Rear chicks for 2-3 months away from adult feather dander if adult birds have shown symptoms.
  •  Vaccinate birds if the vendors have not done so.
  • Select genetically resistant breeds of bird.

Treatment  and Control

There is no proven treatment yet, the birds appear to return to normal, but frequently die from internal tumors after a short time. 
The following measures might be of help. 
  •  Cull any affected birds. This increases the resistance to the disease in the surviving birds.
  •   Vaccination is feasible, especially if Silkies or Sebrights are kept. These are very susceptible to clinical signs of Marek’s and there would be few of these breeds seen at exhibitions if vaccination was not used. The vaccine is administered twice, once in the water (live vaccine) and once by injection when chicks are slightly older. In other breeds, using vaccine can hide the virus and so the whole stock gets progressively more susceptible (weaker) without any symptoms and if birds are sold without the recipient being told of the vaccination, the birds can pass on the virus to unvaccinated chicks, thereby bringing the disease to a flock which may have been free of it before.

 Diagnosis

 Clinical signs include paralysis and postmortem lesions.

Do you have any experiences with Marek's disease please tell us in the comment section. And don't forget to share this post.


 

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