What is egg yolk peritonitis?
Egg yolk peritonitis (also called coelomitis) occurs when yolk from a developing egg, an incompletely shelled egg, or a ruptured egg is deposited inside the body cavity (also called the abdominal coelom). Egg yolk peritonitis is commonly diagnosed in laying hens.
The normal egg development process is as follows:
- A yolk-filled follicle passes from the ovary (on the left side of the body) into the tube-like oviduct (salpinx), where albumin forms around the yolk.
- In the egg shell gland, calcium forms around the yolk and albumin.
- The fully formed egg is passed out the vent.
- Egg production generally takes 24 to 26 hours for a healthy bird, from yolk-filled follicle to laying.
With egg yolk peritonitis, yolk material is released into the abdominal coelom instead of the salpinx, causing inflammation of the peritoneum (the thin layer of tissue that lines the coelom and internal organs). It also typically causes fluid to develop in the coelom.
The reproductive tract and intestinal tract both empty through a common exit (the vent), so there are instances when bacteria may migrate up the salpinx to the ovary. In these cases, the yolk material can become infected with bacteria from the intestinal tract (most commonly Enterococcus or E. coli), causing a severe infection of the salpinx and ovary.
In rare cases, bacteria from the coelom may enter the bloodstream, causing sepsis — a secondary, life-threatening infection that can infect critical organs such as the kidneys, liver, and heart.
What causes egg yolk peritonitis?
Egg yolk peritonitis may occur when a single egg does not form properly or it may develop secondary to other underlying reproductive diseases, including inflammation of the oviduct (salpingitis), impaction of the oviduct with multiple abnormally formed eggs, ovarian cysts, ovarian cancer, or twist of the oviduct preventing normal passage of eggs through the reproductive tract.
Certain viral diseases, such as Marek’s disease virus or avian leukosis virus, may affect the reproductive tract directly or may cause an immune deficiency state that allows bacteria to infect the reproductive tract, leading to egg yolk peritonitis or coelomitis.
What are the signs my hen has egg yolk peritonitis?
Hens with egg yolk peritonitis will show the following signs:
- Stop laying eggs or lay only soft-shelled, thin-shelled, or misshapen eggs.
- Generally less active, choosing to sit in the nest box rather than walking around with other chickens.
- May eat less than normal.
- May have visibly distended abdomens due to the presence of fluid in the coelom.
- May have difficulty breathing due to pressure from the fluid on their respiratory tracts.
How is egg yolk peritonitis diagnosed?
If a chicken shows any signs of egg yolk peritonitis, have it examined by a veterinarian familiar with chickens as soon as possible.
Your veterinarian will perform a complete physical examination and may palpate (feel with fingertips) for fluid or soft-shelled eggs in the coelom. Your veterinarian will also notice if your bird is breathing quickly or with increased effort.
Typically, your veterinarian will perform blood tests, including a complete blood count (CBC), that may show an elevated white blood cell count, indicating inflammation or infection.
Your veterinarian may also perform coelomocentesis to draw off fluid from the abdomen. In this process, they insert a small needle through the abdominal skin and into the bird’s coelom, typically between the vent and the base of the breastbone. They will submit the fluid to a referral laboratory for microscopic analysis and/or a culture and sensitivity test to determine whether bacteria are present and, if so, which antibiotics will be most effective for treating the infection.
Your veterinarian may also take radiographs (X-rays) or perform an ultrasound to further assess the inside of your bird’s coelom and to confirm the presence of fluid and/or unshelled or partially shelled eggs. In some cases, they may detect an ectopic egg, which occurs when a fully formed egg is located in the coelom and not inside the salpinx.
How is egg yolk peritonitis treated?
While egg yolk peritonitis may be life-threatening, some chickens with this condition can be treated successfully. Mild cases of egg yolk peritonitis, in which there is no secondary bacterial infection or underlying reproductive disease, may require only supportive care, such as supplemental hand feeding and anti-inflammatory medication.
For more advanced cases of egg yolk peritonitis in which infection is present, your veterinarian may prescribe oral or injectable antibiotics along with anti-inflammatory medication. More aggressive supportive care may be required, such as hospitalization for fluids injected subcutaneously (under the skin) or intravenously (in a vein), oxygen therapy, and repeated drainage of coelomic fluid.
In the most advanced cases, surgery (called salpingohysterectomy) may be necessary to remove the offending egg(s) and oviduct. If a bird has reproductive disease with secondary egg yolk peritonitis caused by either Marek’s disease or avian leukosis virus, it is often fatal, even with treatment.
Many avian veterinarians treating egg yolk peritonitis will also administer a hormone, either through injection or as a slow-release implant under the skin. Hormone treatment may be beneficial to the chicken, but it is not a federally approved treatment option. This hormone temporarily prevents further egg laying that would worsen the hen’s already compromised condition.
It is critical to note that any time medications are administered to a chicken, there must be a withdrawal time before any eggs or meat from that bird can be consumed. These directives come from FARAD and your veterinarian can find the information at www.farad.org/eldu-and-withdrawal-time.
