Reducing avian colibacillosis in poultry farms through vaccination

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In poultry, colibacillosis manifests with an extraintestinal infection caused by avian pathogenic E. coli (APEC) that primarily or secondarily produces morbidity and mortality in broilers, turkeys and layers, among other birds. Dr Lisa Nolan considers an organism to be APEC when it contains more than 3 of the 9 virulence factors in its PCR panel.

• Escherichia coli (E. coli) is a gram negative bacterium that has been causing mortality in birds for many years. Not all strains are the same, and the different E. coli can be identified based on their genetic structure and correlated with their virulence in the field.

The disease is a syndrome that includes omphalitis and cellulitis and respiratory tract infections with aerosaculitis, pericarditis, perihepatitis, splenomegaly and swollen heads (it occurs in 95% of cases in laying birds between 18 and 30 weeks of age). In laying birds, the reproductive system is also affected, producing salpingitis or salpingoperitonitis syndrome (SPS).

• Certain highly pathogenic APEC serotypes such as 078 and 01 are most frequently associated with avian colibacillosis. (Wigley P. 2015)
• APEC infections appear as causes, especially when stress factors, such as other infectious agents, immunosuppression, lack of sanitation, poor air conditioning of the house, high density of animals or genetic predisposition act on the animals.
• Sometimes when small amounts of non-virulent strains are present in the yolk sac, they can grow and become pathogenic, causing septicemia (Horrox N. 2000).

There are other E. coli strains that make up the microbiota in the intestines of healthy birds where they can perform a number of beneficial functions, including vitamin K biosynthesis (Wigley P. 2015), but they can carry a variety of virulence factors that; at any given moment, can develop to a disease. (Johnson et al., 2010)

In laying birds, there are predisposing factors during the period of peak production that favor the action of E. coli (Beckman B., 2014):

• Complexes with multi-age birds
• Exposure to epidemic mycoplasma (M. gallisepticum or M. synoviae) and / or infectious bronchitis virus (IBV).
• Poor ventilation with high levels of dust and / or ammonia.
• Production stress in young developing birds.
• In 95% of cases, lesions appear in the respiratory tract due to dust in the air, pecking of litters or among the birds.
• High levels of endogenous hormones (especially oestrogen).

In laying birds there are some predisposing factors during the final period of production (Beckman B., 2014):

• Trauma to the cloaca, non-fatal cannibalism of the cloaca, and / or partial prolapse.
• Excess light intensity.
• Birds with a small skeleton.
• Eggs of an excessively large size.
• Excess fat pad.

In 2018, a study by the University of Copenhagen concluded that there was a trend towards a higher prevalence of E.coli associated with mortality in the first week in broilers from older breeders. It was also found that floor eggs should not be used, due to the risk of infection and the increased transmission in the incubator.