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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 E. coli have 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, and loss of appetite.
  • 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 E. coli.
  • Egg peritonitis: Egg peritonitis, salpingitis, and oophoritis are frequently caused by E. coli, which ascended from the cloaca or by imprint metastases from infected air sacs. Affected hens may have a history of egg binding, usually within the past six months.
  • Coligranulomatosis: Also referred to as Hjaerre's disease, a rare form of colibacillosis that occurs sporadically. Coligranulomas are thought to occur secondary, following damage to the intestinal mucosa by other agents. It is thought that the galactans found in the E. coli capsule that stimulate the granulomatous reaction.
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.


Antibiotics that are administered orally or in the drinking water may be effective in treating mild E. coli infections of just the intestinal mucosa. Most E. coli infections require parenteral antibiotics for successful treatment. The drug selected needs to be able to penetrate the target tissues or granulomas.

Most E. coli strains are resistant to many commonly sold antibiotics for chickens, including cephradine, tetracyclines, chloramphenicol, amino-glycosides, beta-lactam antibiotics, and sulfonamides.

Clinical Signs

Reduced appetite
Poor growth
Pasted vent/diarrhea
Droopy head


  • History
  • Clinical signs
  • Bacterial culture
  • Necropsy

Reported Cases

  • Case 1: Impacted oviduct, colibacillosis and egg yolk peritonitis in a Chicken A 1-year-old golden comet hen was presented because of an enlarged abdomen, cessation in egg production, difficulty in ambulating, and difficulty roosting. Results of radiographs and ultrasound examination revealed a radiolucent oval area in the right coelom and fluid with flocculent debris throughout the coelomic cavity. Escherichia coli and Proteus species were cultured from a sample of the fluid. Antibiotic therapy was temporarily beneficial, but the problem persisted and the hen was euthanatized. At necropsy, the oviduct was impacted with yellow caseous material. The diagnosis was colibacillosis and egg yolk peritonitis, which may have originated from an impacted oviduct. Ref


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.
AntibioticsSelected based on the manifestation, and antimicrobial sensitivity testing
ProbioticsAdministered alongside antibiotics to help promote good intestinal tract flora.S Bai et al., 2013; Y Wu et al., 2018
Baicalin (Scutellaria baicalensis) extract100-200 mg/kg of dietX Cheng et al., 2022; Peng, Lu-Yuan, et al. 2019, 2021; F Yang et al., 2020; Z Wu et al.,2020; Y Zhou et al., 2019; B Yin et al., 2021; M Bao et al., 2022; Z Hu et al., 2022
Yucca (Yucca schidigera) extract120  mg/kg; reduced the proliferation of Escherichia coli in laying hens.J Wang et al., 2010
Schisandra chinensis1-2% of diet; Can be a potential agent to treat inflammation caused by avian colibacillosisM Yuan et al., 2020; Y Kim et al.,2013; D Ma et al., 2007
Neem (Azadirachta indica) leaf extract10% of diet;enhanced the humoral as well as cellular immune responses attributed to its immunomodulatory property in experimentally E. coli infected broiler chickens.V Sharma et al., 2019
Coneflower (Echinacea purpurea)5 mg/kg feed; improves hematological and serum biochemical adverse effects caused by E. coli infectionM Hashem et al., 2019
Oregano (Origanum vulgare)2 g/kg feed; Significantly reduced coliform and E. coli counts in broiler chickens.P Scocco et al., 2016; A Roofchaee et al., 2011



  • 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