Introduction:
Avian colibacillosis is an infectious disease caused partly or completely by a group of pathogenic E. Coli bacteria, known collectively as Avian Pathogenic Escherichia coli, or APEC. It manifests as many different diseases, including:
Although avian colibacillosis has been found in all age groups, it is most commonly found in adult layers.
Structure of APEC
E. Coli is a rod shaped bacterium that is gram-negative and has 3 outer membranes. It has a tough cell wall, made mostly of peptidoglycan (a complex molecule made of sugars and ammino acids), which maintains the cell shape. It is usually are motile, so has a flagellum (a threadlike structure that allows ‘swimming’).
Above: Basic diagram on the structure of E. Coli.
Transmission
It can be spread either horizontally or vertically.
Horizontal transmission occurs via APEC contamination in the environment, for example: Faeces, feathers, directly from other birds and contaminated feed and water.
A laying hen with APEC colonising her reproductive tract may pass it on to her eggs, and therefore her chicks. This occurs in two main ways: The developing egg is contaminated before the egg shell has been formed or the egg is contaminated by fecal matter in the cloaca during laying. The latter is considered the most likely route of infection of the egg.
Aged layers are more likely to vertically transmit APEC to their chicks; an increase in age is associated with a decrease in eggshell thickness, resulting in a higher transmission rate than in younger layers.
It has been shown by some studies that beetles, wild birds, pigeons and rodents (especially rodent feces) are also methods of infection.
Above: Diagram of how APEC is transmitted between chickens.
Symptoms and overview of associated syndromes
Salpingitis:
Hens may suffer from salpingitis, which is an inflammation of the oviduct. This is the result of either an ascending infection from the cloaca, or an infection of the abdominal airsac (this has been shown to be a less likely route of infection than the former). This may result in egg peritonitis in laying hens.
Symptoms of salpingitis are: Laying fewer eggs; a swollen abdomen; weight loss; lethargy; difficulty walking; poor egg quality, including soft and thin shelled eggs.
Airsacculitis:
This is defined as inflammation of one or more airsacs. It is observed at all ages, and the chicken is usually infected by inhaling dust containing fecal matter.
Symptoms of Airsacculitis are: Laboured breathing; breathing with beak open; nasal discharge; weight loss; watery eyes; general respiratory distress.
Septicemia:
Again, this is observed at all ages. Several methods of infection have been observed: From lesions in the skin, from the respiratory system and from the reproductive system.
It is relatively rare, but mortality rates are high.
Symptoms are: depression; high mortality; feverish; huddling behaviour; pale combs and wattles; death; lameness; diarrhoea.
Cellulitis:
This typically occurs more commonly in broilers. Birds may not show any symptoms of cellulitis.
Symptoms are: Reddened, puffy skin; warm to the touch skin; yellowish discolouration.
Yolk sac infection (omphalitis):
As the name suggests, this is when the yolk sac becomes infected. It often occurs as a result of an unhealed navel. It only occurs in chicks.
Symptoms are: Depression; huddling; swollen abdomen; scab on the abdomen (the unhealed navel); listlessness; failure to gain weight; death.
Swollen head syndrome:
This is the visible swelling of the head, caused by inflammation under the skin. It most commonly occurs as a result of APEC, often due to a secondary infection of the upper respiratory tract.
The most obvious symptom is swelling of the head, however respiratory distress may also be seen.
Treatment
The Treatment for colibacillosis is antimicrobial drugs, however APEC has become resistant to many of these drugs, so treatment may not be successful. A veterinarian should prescribe the appropriate drug -This may be based on sensitivity tests, to avoid further antimicrobial resistance.
Prevention:
Prevention relies on the reduction of APEC in the environment.
As colibacillosis often occurs secondary to other infections such as Mycoplasma Gallisepticum (MG), limiting introduction of such diseases will reduce the prevalence of this disease.
The coop should have adequate ventilation. Dust and ammonia build up should be limited as much as is possible. This is because high ammonia and dust levels will damage the respiratory tract, increasing the likelihood of a respiratory infection.
Other environmental stressors, such as temperatures, humidity and bad air quality, should also be limited.
Overcrowding should be avoided, to reduce stress.
Many animals, such as rodents, are sources of APEC. Good biosecurity should therefore be maintained.
Reducing wild birds, houseflies and rodents access to waterers, feeders, coops, runs and nest-boxes is also incredibly important in the prevention of colibaccilosis.
Above: Pigeons have been shown in some studies to be sources of APEC. Preventing their access to feeders and waterers is therefore an important prevention measure.
Although vaccination is possible, the diversity of APEC strains limits its effectiveness. However, vaccinating the chickens against other diseases, particularly immunosuppressive and viral diseases, is an effective control measure.
Good nutrition that supports a healthy, strong immune system helps reduce the prevalence of colibacillosis.
Feed, water and bedding materials should regularly be changed and cleaned.
To avoid fecal contamination of eggs, they should be collected regularly, and nest-boxes should be cleaned thoroughly.
Above: Egg should be cleaned if there is any fecal matter on them.
Useful Links
Controlling rats:
https://www.backyardchickens.com/ar...how-to-protect-your-chickens-from-rats.47714/
Some useful info on salpingitis and egg peritonitis:
https://www.backyardchickens.com/articles/reproductive-health-in-chickens.79238/
Yolk sac infection:
https://www.backyardchickens.com/articles/mushy-chick-disease-yolk-sack-infection-omphalitis.64686/
Coop ventilation:
https://www.backyardchickens.com/ar...-there-and-cut-more-holes-in-your-coop.47774/
Disclaimer
All pictures, diagrams and drawings in the article are my own. Please do not use or share them without asking my permission first.
Thanks for reading!
Avian colibacillosis is an infectious disease caused partly or completely by a group of pathogenic E. Coli bacteria, known collectively as Avian Pathogenic Escherichia coli, or APEC. It manifests as many different diseases, including:
- Acute fatal septicaemia
- Airsacculitis
- Egg Peritonitis (in laying hens)
- Salpingitis (in hens)
- Cellulitis
- Yolk sac infection (in chicks)
- Swollen head syndrome
Although avian colibacillosis has been found in all age groups, it is most commonly found in adult layers.
Structure of APEC
E. Coli is a rod shaped bacterium that is gram-negative and has 3 outer membranes. It has a tough cell wall, made mostly of peptidoglycan (a complex molecule made of sugars and ammino acids), which maintains the cell shape. It is usually are motile, so has a flagellum (a threadlike structure that allows ‘swimming’).
Above: Basic diagram on the structure of E. Coli.
Transmission
It can be spread either horizontally or vertically.
Horizontal transmission occurs via APEC contamination in the environment, for example: Faeces, feathers, directly from other birds and contaminated feed and water.
A laying hen with APEC colonising her reproductive tract may pass it on to her eggs, and therefore her chicks. This occurs in two main ways: The developing egg is contaminated before the egg shell has been formed or the egg is contaminated by fecal matter in the cloaca during laying. The latter is considered the most likely route of infection of the egg.
Aged layers are more likely to vertically transmit APEC to their chicks; an increase in age is associated with a decrease in eggshell thickness, resulting in a higher transmission rate than in younger layers.
It has been shown by some studies that beetles, wild birds, pigeons and rodents (especially rodent feces) are also methods of infection.
Above: Diagram of how APEC is transmitted between chickens.
Symptoms and overview of associated syndromes
Salpingitis:
Hens may suffer from salpingitis, which is an inflammation of the oviduct. This is the result of either an ascending infection from the cloaca, or an infection of the abdominal airsac (this has been shown to be a less likely route of infection than the former). This may result in egg peritonitis in laying hens.
Symptoms of salpingitis are: Laying fewer eggs; a swollen abdomen; weight loss; lethargy; difficulty walking; poor egg quality, including soft and thin shelled eggs.
Airsacculitis:
This is defined as inflammation of one or more airsacs. It is observed at all ages, and the chicken is usually infected by inhaling dust containing fecal matter.
Symptoms of Airsacculitis are: Laboured breathing; breathing with beak open; nasal discharge; weight loss; watery eyes; general respiratory distress.
Septicemia:
Again, this is observed at all ages. Several methods of infection have been observed: From lesions in the skin, from the respiratory system and from the reproductive system.
It is relatively rare, but mortality rates are high.
Symptoms are: depression; high mortality; feverish; huddling behaviour; pale combs and wattles; death; lameness; diarrhoea.
Cellulitis:
This typically occurs more commonly in broilers. Birds may not show any symptoms of cellulitis.
Symptoms are: Reddened, puffy skin; warm to the touch skin; yellowish discolouration.
Yolk sac infection (omphalitis):
As the name suggests, this is when the yolk sac becomes infected. It often occurs as a result of an unhealed navel. It only occurs in chicks.
Symptoms are: Depression; huddling; swollen abdomen; scab on the abdomen (the unhealed navel); listlessness; failure to gain weight; death.
Swollen head syndrome:
This is the visible swelling of the head, caused by inflammation under the skin. It most commonly occurs as a result of APEC, often due to a secondary infection of the upper respiratory tract.
The most obvious symptom is swelling of the head, however respiratory distress may also be seen.
Treatment
The Treatment for colibacillosis is antimicrobial drugs, however APEC has become resistant to many of these drugs, so treatment may not be successful. A veterinarian should prescribe the appropriate drug -This may be based on sensitivity tests, to avoid further antimicrobial resistance.
Prevention:
Prevention relies on the reduction of APEC in the environment.
As colibacillosis often occurs secondary to other infections such as Mycoplasma Gallisepticum (MG), limiting introduction of such diseases will reduce the prevalence of this disease.
The coop should have adequate ventilation. Dust and ammonia build up should be limited as much as is possible. This is because high ammonia and dust levels will damage the respiratory tract, increasing the likelihood of a respiratory infection.
Other environmental stressors, such as temperatures, humidity and bad air quality, should also be limited.
Overcrowding should be avoided, to reduce stress.
Many animals, such as rodents, are sources of APEC. Good biosecurity should therefore be maintained.
Reducing wild birds, houseflies and rodents access to waterers, feeders, coops, runs and nest-boxes is also incredibly important in the prevention of colibaccilosis.
Above: Pigeons have been shown in some studies to be sources of APEC. Preventing their access to feeders and waterers is therefore an important prevention measure.
Although vaccination is possible, the diversity of APEC strains limits its effectiveness. However, vaccinating the chickens against other diseases, particularly immunosuppressive and viral diseases, is an effective control measure.
Good nutrition that supports a healthy, strong immune system helps reduce the prevalence of colibacillosis.
Feed, water and bedding materials should regularly be changed and cleaned.
To avoid fecal contamination of eggs, they should be collected regularly, and nest-boxes should be cleaned thoroughly.
Above: Egg should be cleaned if there is any fecal matter on them.
Useful Links
Controlling rats:
https://www.backyardchickens.com/ar...how-to-protect-your-chickens-from-rats.47714/
Some useful info on salpingitis and egg peritonitis:
https://www.backyardchickens.com/articles/reproductive-health-in-chickens.79238/
Yolk sac infection:
https://www.backyardchickens.com/articles/mushy-chick-disease-yolk-sack-infection-omphalitis.64686/
Coop ventilation:
https://www.backyardchickens.com/ar...-there-and-cut-more-holes-in-your-coop.47774/
Disclaimer
All pictures, diagrams and drawings in the article are my own. Please do not use or share them without asking my permission first.
Thanks for reading!
