Marek's disease; Causes, symptoms, treatment and prevention tips

 Marek's disease; Causes, symptoms, treatment and prevention tips

 If your bird is inactive or suffering from paralysis, they may develop Marek's disease.
This is a chronic disease that can destroy your poultry farm, so you need to prevent this from happening. In this article, you will learn how to recognize Marek's disease in your flock and what you can do to prevent it from spreading.
So, if you want to know more about this disease, its symptoms and how to treat sick birds, keep reading until the end. 

What is Marek's disease?
Marek's disease is a common disease in poultry farms that affects birds of all ages. It is a chronic disease commonly called fowl paralysis in backyard commercial farms.
 A variety of health problems occur when birds become infected and begin to show signs of contracting Marek's disease. 

The disease is named after Josef Marek, a Hungarian pathologist who described Marek's disease in 1907.
Sometimes the effect can be as small as weight loss due to extreme conditions and even cause the death of your herd. It depends on the degree of virulence of the virus, that is, how dangerous and cruel these viruses are.
Therefore, you must do everything in your power to prevent Marek's disease from entering your flock. Although this disease is fatal during an outbreak, it is easily prevented in the poultry house before an outbreak.
It is a highly infectious disease that spreads rapidly among unvaccinated birds. Although Marek's disease cannot affect humans, humans can be a carrier that spreads the virus on farms.

What causes Marek's disease and how does it spread? 

The cause of Marek's disease is an alpha virus known as Marek's disease virus (MDV) or Gallid alphaherpesvirus 2 (GaHV-2).
The virus has three known serotypes with different virulence.

 Serotype 1 virus is oncogenic and causes visceral tumors in birds.
Serotype 2 and 3 viruses are not as harmful as type 1 and are used to develop vaccines. 

The serotype 1 virus is also used to make vaccines but it needs to be well suppressed, having no force at all.

The visceral type usually occurs between weeks 16 and 35, moving into different parts of the body. 

You should know that the two main factors that determine the extent of damage caused by Marek's disease are:
The type of virus strain affects your flock and the type of chickens you raise on your farm.
Both indicate the damage Marek's disease will cause to your poultry. Some common breeds of chickens, such as silkies, leghorns, and egg breeds, are known to be susceptible to the disease.


How is Marek's disease transmitted? 

Marek's disease is an airbone disease that can be easily spread quickly in a flock.
It is spread through feces (contaminated litter), food, dust, fluffs, and contact with infected birds or objects. Often, the feathers and dead skin shed by the birds are highly laden with MDV.
Even workers on the farm are easily a carrier as it sticks to their clothes, shoes, skin and hair when they visit infected herds. In addition, dander (scaly white dead skin flake) from infected birds can fall anywhere and can be carried in the air around the coop, spreading the virus. and to transmit to others.
Since infected birds carry the virus throughout their lives, new or unvaccinated birds in the flock or environment will also carry the virus. It takes a period of 2 weeks for the disease to develop and develop in its new host and the signs of disease 3 to 6 weeks.
Remember that not all infected birds will show signs or symptoms of Marek's disease and become ill. Therefore, make sure that you know the history of diseases in your area, because this helps you prepare for possible outbreaks.
And arrange a good vaccination schedule for your laying and broiler chickens while maintaining good hygiene practices on the farm.

 What are the symptoms of Marek's disease?

 Possible signs that birds infected with Marek's disease (MDV) appear depending on the animal attacked.

 Here you have a list of symptoms that birds with MDV show

1. Immunosuppession in poultry birds:

 One of the first clinical signs of Marek's disease virus is to actively suppress the immune system of the affected birds. 

Viruses overcome their body's reaction to foreign substances and pathogens that want to invade.
They attack organs and tissues such as the spleen, thymus, lymph nodes and bone marrow, all of which produce antibodies against various diseases. Therefore, this weakens the immune system of chickens, giving way to other diseases.
Over time, affected chickens become more sensitive and begin to appear pale and weak. Poor poultry management practices and stress can also cause immunosuppression in chickens.

2. Paralysis of wings and legs:

 Marek's disease usually affects the nervous system of chickens within a few hours of their hatching time.
A virus that causes lameness and paralysis in flock birds. There is reduced or complete voluntary control of chicken wings and legs.
In other cases, the disease also causes the birds' necks to paralyse and their combs collapse.
Chicken paralysis is also a symptom of various diseases such as Newcastle disease, botulism (poisoning from improperly prepared food), etc. However, performing a necropsy on an infected bird will allow you to determine for sure whether the disease is MDV.
So if you suspect that your bird is carrying Marek's disease, contact your veterinarian immediately for advice on vaccination procedures.

 3. poor performance of bird:
Marek's disease also affects bird performance negatively. Affected broilers show a decrease in weight gain and are less likely to survive.
Layers affected with Marek's disease produce few eggs and sometimes eggs that are malformed, shellless, or empty. In addition, birds do not usually show interest in eating because they are always loss appetite for food.
They become weak and sick because they do not eat and carry the virus.

 4. Blindness in affected birds:
Chickens have very good vision, sensitive to small changes in light that we don't see. Their big eyes are monovision, which means they work independently and see more colors than us, but they have incredible night vision.
Unfortunately, blindness gradually appears as gray irises and regular pupils in birds with Marek's disease. Their eyesight begins to deteriorate and they lose their ability to see as the condition worsens.
5. Visceral tumors in the internal organs:
This symptom is unique to Marek's disease, and is caused by the highly virulent serotype 1 virus.
The internal organs of birds with this type of virus produce neoplastic tissue. This means that they develop abnormal new growths of irregular tissue that become tumors in the internal organs.
One of the hallmarks of Marek's disease is inflammation of the spinal cord and brain. Other internal organs and tissues affected by tumors are the liver, kidneys, ovaries, lungs, heart, nerves, gonads and skeletal muscles.
In some cases, you will find these tumors even on the skin of the affected birds.

 6. High mortality rate:
In flocks infected with the virus, the number of birds dying is higher than expected. A weakened immune system becomes more susceptible to viruses and other pathogens.
Also, the tumor can cause internal damage and is very serious. Therefore, MDV shortens the life of every bird it infects in your flock and increases the mortality rate.


What are the preventive measures against the spread of Marek's disease?

 Some of the things you can do to stop the spread of Marek's disease include improving biosecurity, maintaining good hygiene, and vaccinating birds.
Also, you must ensure that your chicken house is always clean even before the birds arrive at the farm. Likewise, you must ensure that you vaccinate the birds after they hatch or, better yet, inject the eggs right before they hatch.
Another method of vaccinating chickens is In Ovo vaccination which is the best method. This is because it does not require handling the chicks.
Everything about this vaccination process is automated and immunity starts within two weeks. Vaccination helps chicks develop resistance to Marek's disease.
Therefore, this reduces the chance of contracting the disease even though they can still contract the disease. Vaccination does not prevent infected birds from shedding the virus, even if their numbers are greatly reduced.
In addition, you should reduce the exposure of your bird to disease by using good stress management and proper hygiene.

In cases where there has already been an outbreak before vaccination, monitor the flock carefully to prevent further spread.
In addition, thoroughly clean and disinfect the chicken coop after removing the birds from the farm. 

What are the possible treatments for Marek's disease?
Simply put, there is no known cure for Marek's disease. Currently, there is no medicine for the specific treatment of Marek's disease.
But scientists are trying to breed birds that are resistant to viruses and genes. The use of vaccines and maintaining cleanliness in poultry farming helps to control the disease to some extent.he virus. 

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