Causes and symptoms of Marek's disease in chickens, treatment methods

Causes and symptoms of Marek's disease in chickens, treatment methods

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It is possible to determine in a timely manner that chickens have developed Marek's disease by regularly examining the birds. To do this, chickens must often go for a walk, since often the first symptoms are mild. The disease can proceed in stages and in a short time affect the entire chicken coop. Symptoms may vary depending on the age of the bird.

General information about the disease

Infection with the disease occurs as a result of the activation of a virus in the body of a bird. The virus often affects the nerve cells and internal organs of layers. When examining the affected areas, you can notice swelling of the soft tissues and the presence of formations.

The types of the disease are distinguished:

  1. Neural - this type affects nerve cells. The result is paralysis in chickens.
  2. Ocular - the virus infects the visual organs. The bird begins to see poorly, as a result it becomes blind.
  3. Visceral - internal organs are affected. Soft tissues are destroyed, as a result of which the organs do not perform their functions.

Often the disease appears in complex forms that lead to the death of layers. In order to timely identify the type of disease, it is necessary to consult a veterinarian.

Causes of Marek's disease

The disease occurs as a result of improper care of the chicken coop and birds. The virus spreads through the air and can remain indoors. Pests, flies, beetles or food can carry the disease. The cause of the disease is reduced immunity. Most often, the disease affects chicks up to 2 weeks. The reason is unsanitary conditions and a poorly processed incubator. However, adults can be infected.

Infection routes

Disease carriers can be sick birds. The virus can be spread by airborne droplets over long distances. The virus can also be transmitted through droppings, feed and feathers.

The carrier of the disease is cleaning equipment. The virus also persists in feeders and drinkers. After infection, the chicken does not show symptoms, so further damage to the chicken coop occurs.

Important. After infection, the bird does not show any symptoms for 10-15 days. The virus can be in an inactive form, after a decrease in immunity, it quickly progresses.

How is the incubation period going?

If young individuals are infected, the virus adapts in the body within 2 weeks. After this period has elapsed, the chick can infect other chickens without showing symptoms of the disease. The acute period of infection occurs in the first 5 weeks after the virus enters the bird's body.

Often, the disease begins to manifest itself only on the 5th week after infection.

In adult chickens, the incubation period is positive. The first signs of the disease are noticeable only after 6-7 weeks. The acute form of the virus infects the entire chicken coop within 2 days.

Symptoms of the disease

Marek's disease can have symptoms depending on the stage of development and age of the bird. The first signs of illness can be noticed during daily walks or after careful observation of the layers.

Acute form

This type of viral infection can resemble other types of diseases. Has the following symptoms:

  • limbs in chickens do not move or are subject to paralysis;
  • the chicken does not move well, often the coordination of movements is impaired;
  • wheezing and shortness of breath;
  • lack of appetite, diarrhea, vomiting;
  • the wings are spread out, not symmetrically located;
  • loss of vision.

This type can occur with additional symptoms that appear in each case of infection.

Classic form

This species is often ignored by poultry farmers. The disease manifests itself with mild symptoms and is often confused with other types of infection. Symptoms in classic Marek's pathology are as follows:

  • the chicken is weak, lies for most of the day;
  • poorly coordinated in movement;
  • limbs are paralyzed;
  • the wings sag.

Also, you often notice a lack of appetite and the appearance of fleas. Such additional symptoms appear as a result of a weakened immune system.

Diagnosing the problem

In order to identify the stage of the disease, you need to contact a veterinarian who will diagnose. The following methods are used in diagnostics:

  • external examination of the bird during a walk;
  • inspection of poultry in quarantine conditions;
  • analysis of the feathers of a sick bird;
  • bacteriological culture study;
  • detection of the virus by the method of samples.

Examination of healthy and sick layers is being carried out. If the laying hen has died, it is necessary to make an examination of the internal organs.

Treatment activities

Treatment methods depend on the age of the bird. Sick birds in an acute form are not treated, since the virus has already spread throughout the body and has affected all internal organs.


When the disease develops in chickens before the 2nd week, it is not advisable to carry out treatment. Most often, these chicks do not have immunity. In rare cases, a special vaccine may be used.

In adult chickens

Treatment in adults should be carried out in the early stages of the onset of unpleasant symptoms. For treatment, special antiviral drugs are used, for example, "Acyclovir". The action of the drug is aimed at suppressing the virus and blocking its further spread throughout the bird's body. In order for the bird to endure the negative effects of the drug, it is necessary to use additional probiotics. The action of probiotics is aimed at protecting the lining of the stomach from destruction. Duration of treatment is at least 5 days.

Important. When the first symptoms of paralysis appear, treatment is not performed. The bird dies.


Broilers belong to the meat breed of chickens. The use of special preparations does not give the desired result. Since birds raised in artificial conditions, as a rule, do not have immunity to diseases and viruses. Therefore, on the third day after hatching, broilers are recommended to carry out a special vaccination, which will reduce the risk of disease.

After infection, birds die and can infect healthy individuals within a week. After each batch of chicks, the incubator and adjacent premises must be thoroughly disinfected.

Vaccination against disease

The use of a special vaccine does not give a 100% result, but the risk of a virus is reduced. It is used for vaccination with a live virus that promotes the development of immunity. Once injected, the vaccine begins to produce antibodies, which, once infected, suppress the virus. The following form can be used:

  • M 22/72;
  • "Interve".

The vaccine is purchased from a veterinary pharmacy. The drug is stored in a cool place. Before use, check the expiration date and perform a trial introduction into the chicken.

Is it okay to eat meat and eggs from infected birds?

Marek's virus is not dangerous to human health. It should also be noted that symptoms appear late in adults. Therefore, a person often eats eggs that are laid by affected layers, however, veterinarians do not recommend eating contaminated meat and eggs. Since pathology often provokes the appearance of other infectious diseases that can negatively affect human health.

It is forbidden to use meat products that have a yellow tint or signs of muscle damage.

General preventive measures

The virus is difficult to treat, so veterinarians recommend taking preventive measures that will preserve the health of the birds. Among the preventive measures, it is necessary to highlight:

  1. When buying young animals, carefully examine the chicks. Do not buy chicks from unverified organizations.
  2. Use a veterinary first-aid kit, where there are drugs to prevent the appearance of viral diseases from the first days of chicks' life.
  3. Vaccinate chickens.
  4. Eliminate sick chickens in a timely manner.
  5. Clean the coop and drinkers regularly.
  6. Timely removal of droppings, which can act as a carrier of diseases.
  7. The coop should have a flat floor without cracks and holes. This prevents pests and insects from entering.
  8. After death, the affected chicken must be removed from the chicken coop within 24 hours and the room must be treated.
  9. Strengthen the immunity of birds with vitamins and minerals that are added to food.
  10. Treat equipment used in the cleaning process with antiseptics.
  11. Walk chickens regularly to identify an infected individual.

When an individual appears that has suspicious symptoms, it is necessary to separate the chicken from the livestock. Observe under quarantine until the type of infection is fully identified.


Marek's virus can kill birds in a chicken coop in a short period of time. Both adult and young chickens can be infected, and the virus often infects ducks and geese. When the first symptoms of the virus are detected, it is necessary to isolate the bird and take treatment measures. Birds that were treated in the early stages of the appearance of the virus are cured, but such individuals lose their immunity and are exposed to other types of infection. Therefore, veterinarians recommend taking timely preventive measures against the disease.

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