Sudden Death in Chickens

Sudden Death in Chickens
Reading Time: 4 minutes

There’s nothing more horrifying than having your seemingly healthy chickens suddenly die with no warning. What causes it? How can sudden death be prevented? 

Chickens can suddenly die for many reasons. Some causes exhibit pre-existing conditions; others don’t. Let’s examine a few. 

Heart attacks.

Yes, chickens can have heart attacks, and they most often afflict fast-growing birds. (I’m looking at you, Cornish Crosses.) Heart attacks may happen with any breed due to a sudden scare, such as a predator. It can also arise from obesity and lack of exercise, just like humans. 

Sudden Death Syndrome (SDS).

Sometimes called flip-over disease, this is a more catch-all term used to describe a metabolic condition found in fast-growing broiler breeds. As the name implies, the bird loses its balance, experiences strong muscular contractions, and violently flaps its wings. Death is swift. The cause of SDS is attributed to the excessive growth rate of broiler breeds and their high carbohydrate diets. 

Heart disease.

As in humans, poor diet and lack of exercise makes chickens more prone to heart disease. Some experts consider constant and artificial light also to be a causative factor. 

Yes, chickens can have heart attacks, and they most often afflict fast-growing birds.


Caused by the bacterium Mycoplasma gallisepticum, mycoplasma produces symptoms such as nasal discharge, coughing, decreased egg production, pink eye, gurgling sounds, facial swelling, and profuse tear secretion. 


This is the name of the disease caused by the bacterium Erysipelothrix rhusiopathiae. Chickens are infected mainly through wounds, though red poultry mites may be a potential vector. Symptoms of erysipelas include purplish or reddish skin blotches, weakness, listlessness, and a pale comb. 

Egg binding.

One of the more common causes of sudden death in hens, this is a life-threatening reproductive emergency. Essentially, an egg gets stuck. Causes can include low blood calcium levels, calcium tetany, poor or imbalanced diet, an excessively large egg, trauma, age, obesity, or mycotoxins in feed. Symptoms of egg binding include abdominal straining, depression, constant tail wagging, a “penguin” walk, abdominal distension, increased respiratory rate, and cyanosis (the comb changing to a crimson color, then to deep purple/blue). In cases where the egg is stuck in the pelvic canal, the compression of the ischiatic nerve may cause the hen to appear lame in one leg. If your hen is egg-bound, there are delicate ways to try and “lube” the egg out, but these actions risk breaking the egg inside the hen, which worsens things. The best thing is seeking veterinarian intervention. 

Fowl cholera.

Pasteurella multocida causes this highly contagious bacterial infection. Symptoms of infected birds include fever, ruffled feathers, lethargy, mucoid discharge from the mouth, anorexia, faster breathing, cyanosis, and diarrhea. Isolate sick birds. 

Injury, parasites, poison.

Within the dynamics of a flock, anything can happen. Chickens tend to eat anything, so ingesting something poisonous is not uncommon. Birds may be picked on, injured internally from a fall or trauma, trampled, wounded by a predator, or have an intolerable parasite load or any number of other things that can cause sudden death. 


Most frequently caused by bacterial infection ascending from the vent and cloaca, this inflammation can also be associated with respiratory and systemic diseases. The most visible symptom is the laying of a horrible “lash egg,” a roughly egg-shaped accumulation of pus and other sloughed-off internal tissue. The presence of a lash egg often (but not always) means the hen is doomed, though prompt veterinarian care may save her. 


While most people associate heatstroke with excessive ambient temperature and lack of shade, heatstroke in chickens is not uncommon on big industrial farms in broiler chickens due to “hot” feeds and dense populations. Inadequate ventilation, overcrowded conditions, lack of hydration, and high temperatures can cause heatstroke. Symptoms include severe lethargy, heavy panting, extreme body heat, staggering, disorientation, and seizures. 

Fortunately, sudden deaths — while you can never eliminate them — can be minimized through sensible husbandry.


The tiny protozoan parasite coccidia causes this attack on the intestinal lining. It is most often seen in chicks, though adults can also get it. The first sign is a lack of vigor and inactivity, followed by loose, watery diarrhea. This leads to dehydration and malnutrition, and eventually death if not caught and treated immediately. Coccidiosis can be prevented with good hygiene and medicated chick starter feed or an additive to their water. 

Marek’s disease.

The chicken herpes virus causes Marek’s disease, but it is not transmissible to humans. Birds become infected by inhaling virus-laden dander. Then the virus causes inflammation and tumors in the nerves, spinal column, and brain. Birds may become paralyzed in the legs or wings or develop head tremors. Not all chickens with this virus will get sick, but sick birds will suffer horribly and probably die. There is no treatment. Vaccination of day-old baby chicks is the most dependable way to prevent clinical disease, and they must get the vaccine before exposure to the virus. 


Endless things can cause stress in chickens — overcrowded conditions, predators, confinement, wide temperature swings, loud and continuous noise, etc. Chickens don’t adapt well to change; it stresses them out, and stress can cause death in chickens. 

After this incredibly depressing list, it’s worth adding there are many other fatal diseases not mentioned because they manifest obvious symptoms days or weeks ahead of time. This article focuses on sudden death. 

Fortunately, sudden deaths — while you can never eliminate them — can be minimized through sensible husbandry. Coops should be spacious and kept clean and do not overcrowd birds or constantly confine them. Provide them with “work” — the ability to scratch a compost pile or earn their food. Protect them from predators and provide abundant, clean water and a balanced diet. In other words, it’s up to us to practice sensible husbandry. 

But if your chickens are suddenly keeling over with no explanation, pay attention. 

Originally published in the June/July issue of Backyard Poultry and regularly vetted for accuracy.

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