Colibacillosis is the disease caused by infection with the Escherichia coli (E. Coli) bacterium. It can result in systemic (generalised) or local infection. Colibacillosis is one of the most commonly occurring infections in poultry farming in the Netherlands, but also in the rest of the world. GD research in 2013 estimated the economic damage at 3.7 million euros per year in laying and breeding farms alone.
E. coli can be present in the intestines as part of the common microflora, but can also take the form of a pathogenic bacterium causing serious illness. It can either result in secondary problems, after another trigger has opened up the door, or be a primary issue, which means that the bacterium requires no further assistance to cause disease. Infection with E. coli can manifest itself in a variety of ways, depending on the affected organs, the age of the animal, any comorbidities and the strain of the bacterium. In young animals, we often see an acute, systemic infection in which the animal quickly becomes very ill and can eventually die. Animals surviving the acute phase often suffer residual symptoms caused by inflammatory processes in the body, including the air sacs and peritoneum (which covers the important organs).
Inflammation of the air sacs expresses itself in respiratory difficulties. Air sacs are pockets in the body of the chicken, which are part of the respiratory system. E. coli can cause inflammation there, hindering the oxygen exchange. Inflammation of the peritoneum can result in adhesions, which will hinder the animal’s normal functioning for the rest of its life. In hens, we also see damage to the reproductive tract (i.e. the ovaries, oviducts and uterus of the hen) caused by the bacterium.
Infection with E. coli can be diagnosed by culturing the bacterium from affected organs. Biochemical tests or other techniques can subsequently determine whether this concerns an E. coli bacterium. Supplementary diagnostics can provide additional information on the strain of bacterium, including its susceptibility to antibiotics or relationships between various strains.
The E. coli bacterium is resident in the intestines, and only actually leads to infections outside the intestines. Many years ago, GD conducted research that included studying a number of infection models which showed the bacteria to be mainly inhaled. Only a very small volume of bacteria needs to be inhaled to make the animal sick. Another routes can via damage to the quality of the intestine, allowing the bacteria to penetrate the intestinal wall. Routes, including via the egg yolk and via skin scratches can also result in infection with E. coli.
Once the infection route has been identified, the risk factors can be tackled. Good hygiene and biosecurity can reduce the number of pathogens coming from outside the animal, from entering the animals’ surroundings, thus lowering the risk of infection. By making changes in the management, for example optimisation of air ventilation and belt ventilation, the housing conditions of the animals can be improved, giving E. coli less chance of causing illness.
Infections with E. coli can be treated using antibiotics. An antibiotic susceptibility test will show which treatment has the best chance of cure (or reduction of the clinical signs). However, prevention of the problems is most definitely better than treatment. Alternatives for antibiotics can be used, but often with varying success.
Besides working at reducing the risk factors, there is also the option of vaccinating against E. coli. Vaccines can help boost the chickens’ immune system and prepare them for the possible introduction of the E. coli bacterium. Upon infection, the immune system reacts more quickly, giving the bacterium less opportunity to cause an infection. The effective use of vaccines is a challenge. We not only want to protect our chickens against the E. coli bacterium, but also against other pathogens. Vaccinations therefore need to be accurately scheduled within the vaccination programme. The great diversity of E. coli bacteria also makes vaccination very tricky. Which strain of bacteria should the vaccine protect against? There are commercial vaccines available on the market, which have proven effective, but vaccines can also be custom-made. In practice, their effectiveness may disappoint. This will mainly be due to the great diversity of E. coli strains, whereby vaccination with one strain will not always provide sufficient protection against another. There is extensive research into vaccination and advice aimed at providing protection against multiple or even all E. coli strains.
The clinical signs are known to worsen in the event of combined infections with, for example, IB virus or Mycoplasma gallisepticum. Tackling and preventing other pathogens is therefore also important to reduce problems caused by E. coli.
Escherichia coli peritonitis syndrome (EPS) is a form of colibacillosis.