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Other Names: Escherichia Coli Infection, Avian Colibacillosis, Coliform Infection

Colibacillosis refers to any localized or systemic infection caused partly or entirely by avian pathogenic Escherichia coli (APEC), which include several clinical disease manifestations. Chickens of all ages are susceptible to colibacillosis, but young birds are more frequently and more severely affected, including developing embryos. Colibacillosis often occurs concurrently with other diseases, making it more difficult to diagnose.

The most common manifestations of E. coli infection in chickens include:
  • Cellulitis: Cellulitis is a bacterial skin infection resulting in inflammation of the subcutaneous tissue of birds, typically seen in the lower abdomen and upper legs.
  • Colisepticemia: Septicemia, also known as blood poisoning, occurs when an Escherichia coli infection has invaded the chicken's bloodstream. Once in the bloodstream, the infection quickly spreads throughout the body. It is a serious, life-threatening condition which is associated with acute onset of very generalized clinical signs of sickness, such as listlessness, depression, weakness, loss of appetite, and sudden death.
  • Omphalitis: Omphalitis, also known as yolk sac infection, is an infectious, non-contagious, common condition affecting the naval of newly hatched chicks. It is caused by invasion by several bacterial, with one of the most common being Escherichia coli.
  • Egg peritonitis: Egg peritonitis is considered to be an emergency condition for hens. It is the inflammation of the hen's peritoneum, which is the thin tissue lining the inner wall of the abdomen. It is usually the secondary result of hens silently suffering from salpingitis. Affected hens may have a history of egg binding, usually within the past six months.
  • Coligranuloma: A rare form of colibacillosis that occurs sporadically as a chronic infection in adult birds worldwide, resulting in decreased egg production, fertility, and hatchability.
E. coli infections often occur concurrently with other bacteria, fungi, protozoa, and viruses. The most common co-infections documented to occur with E. coli include:
  • Chronic respiratory disease (CRD): Chronic respiratory disease (CRD), also known collectively as mycoplasma gallisepticum (MG) infection, is considered to be one of the major pathogens that cause respiratory disease in poultry. It tends to develop slowly in flocks and associated with progressive and chronic respiratory signs. Chickens with chronic respiratory disease often show clinical signs associated with the respiratory system, which include mild tracheitis, sinusitis, airsacculitis and conjunctivitis.
  • Swollen head syndrome (SHS): Swollen head syndrome (SHS) is an acute, highly contagious upper respiratory tract infection of poultry. SHS is caused by infection with the avian metapneumovirus (AMPV), a type of pneumovirus which is classified into four subtypes (A, B, C, and D).

Clinical Signs

Clinical signs of colibacillosis are usually nonspecific and vary depending on the manifestation of the infection. The severity varies depending on the age of the bird, duration of infection, management conditions, and concurrent diseases present. E. coli strains are often resistant to many commonly sold antibiotics for chickens, including cephradine, tetracyclines, chloramphenicol, amino-glycosides, beta-lactam antibiotics, and sulfonamides.


E. coli is transmitted to chickens through ingestion, inhalation, or secondary to fecal contamination of eggs hatched in an incubator.

Clinical Signs

Reduced appetite
Poor growth
Pasted vent/diarrhea
Droopy head


  • History
  • Clinical signs
  • Bacterial culture
  • Necropsy


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
AntibioticsCephalosporin, Gentamicin, Apramycin
Clostridium butyricum probiotic2 × 10(7) cfu C. butyricum/kg of diet for 28 daysL Zhang et al., 2016
Mannan-oligosaccharides (MOS)0.05% MOS in dietR Jahanian et al., 2015
Pomegranate (Punica granatum)Showed potential benefit as an intestine astringent to relieve diarrhea and enteritis in chickens.Saeed M et al., 2018



  • Protect birds, especially young chicks from cold weather
  • Good husbandry practices
  • Feeding a diet high in antioxidants from fresh fruits and vegetables
  • Pomegranate (Punica granatum)- Showed potential benefit as an intestine astringent to relieve diarrhea and enteritis in chickens.

Scientific References

Good Overviews

Age Range

All ages are susceptible, but young birds are more commonly and severely affected.

Risk Factors

  • Mailing chicks from hatcheries--or from anywhere for that matter.
  • Cold weather periods
  • Placing dirty or feces contaminated eggs in the incubator to hatch
  • Dry, dusty conditions
  • Contaminated environment
  • Unsanitary living conditions
  • Overcrowding
  • Feed/water restriction
  • Abrupt feed changes
  • Poor ventilation
  • Temperature extremes
  • Concurrent secondary infection
  • History of previous trauma
  • Nutrient deficiency or unbalanced diet
  • Exposure to mycotoxins
  • Stress exposure