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Hey, Everybody! I hope you are doing amazingly well and your chickens are too! I want to discuss infectious bursal disease in this article. Chiefly, what is infectious bursal disease, and what can you do about it?


Infectious Bursal Disease (IBD), also known as Gumboro disease, is a highly contagious disease that affects young chickens, typically between the ages of 3 and 6 weeks, although it can affect chickens at other ages as well. It is caused by the infectious bursal disease virus (IBDV), a type of Birnavirus.

The disease primarily targets the cloacal bursa, an immune system organ in birds, leading to immunosuppression. 

What is a Bursa?

A bursa is a fluid-filled sac that cushions the friction between body tissues. Of course, there are many in a chicken, but the main one affected is in the cloacal bursa, or just above the vent area. Keep that in mind.

The cloacal bursa is the area above the cloaca that primarily controls antibody production and immunity in chicks.

The cloaca is the chamber at the lower end of the digestive tract where the reproductive, digestive, and urinary tracts meet.


What Does Infectious Bursa Disease Do To a Chick?

I’m glad you asked because it invades the lymph system of young chickens, attacking most notably the cloacal bursa. It also invades the thymus and the spleen. 

By attacking and destroying immature lymphocytes, the young chickens’ immunity system becomes depressed, and the chicks will be more susceptible to other diseases like laryngotracheitis, avian flu, Marek’s disease, and more.

Wait a minute! What is a limpasight?

Lymphocytes are white blood cells that are central to the immune response. They are produced in the bone marrow and found in the blood and lymphatic system. There are several types of lymphocytes, including:

  1. B cells: These cells are responsible for the production of antibodies. When they encounter a pathogen, they can differentiate into plasma cells that produce antibodies specific to that pathogen.
  2. T cells: These cells do not produce antibodies. Instead, they have other functions in the immune system, such as helping B cells to produce antibodies (helper T cells) or directly attacking infected cells (cytotoxic T cells).
  3. Natural Killer (NK) cells: These cells play a role in the innate immune response and can attack infected or cancerous cells without prior exposure to the pathogen.

Hoo boy — I didn’t know this would be a science lesson.

What Happens To Chicks That Get Infectious Bursal Disease?

Chicks infected before they are three weeks old are generally protected by antibodies passed on by the mother hen. They can still be infected, but the symptoms are generally mild or unnoticeable.

Chicks that get IBD between 3 and 6 weeks after hatching become suddenly acutely ill, showing various symptoms:

  • Depression and lethargy
  • Ruffled feathers
  • Diarrhea, which is often white and watery
  • Pasty or wet vent
  • Dehydration
  • Swelling and inflammation of the cloaca (the common chamber into which the intestinal, urinary, and reproductive tracts open)
  • Inability to stand or wobbling
  • Slight trembling

In severe cases, death can occur, but the mortality rate is about 20%.

Are Chickens Healthy After Surviving Infectious Bursal Disease?

Chickens that survive IBD will bounce back well enough. Once cured, they will not be carriers. The disease, however, does remain stubbornly in the environment, so consistent cleaning and disinfecting of living areas are essential.

Chicks infected before three weeks after hatching will develop a natural immunity to the disease. When they grow up and have their own chicks, the immunity will be passed along.

Let’s Close The Barn Door On This

Viral diseases are more common in large flocks than in backyard situations, but you still need to pay attention. Early detection of any odd behavior amongst your flock is a good reason to pay close attention and act fast if you think something is amiss.

I wish you well in your journey to raise wonderful chickens and collect wonderful eggs. I’m glad you are part of the backyard chicken community.


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