The following Q&A is from a conversation with Henrik Christensen, PhD, DVSc, University of Copenhagen:

Q: Escherichia coli infection, or colibacillosis, is a major cause of first-week mortality in broilers. How do neonatal chicks contract and spread the infection?

HC: E. coli can be transmitted horizontally in the hatchery or vertically from parent to offspring. Genuine vertical infection happens when E. coli colonizes the egg-laying “machinery” of the bird, including the oviduct and cloaca, resulting in the embryos becoming infected. More often, however, it’s the surface of the egg that’s contaminated with E. coli, causing infection at hatch. This is what we call egg infection, but in a way, it’s also functioning as vertical transmission that can then spread horizontally to a very large number of chicks, increasing risk of first-week mortality.

Q: How is colibacillosis typically controlled in the hatchery setting?

HC: In the past, day-old chicks were sometimes treated with antibiotics to control E. coli infection, but this approach has fallen out of favor in many countries since antibiotic resistance is a major concern. Meanwhile we have also seen evidence of a high degree of vertical transfer from parent to offspring.¹ This means that new approaches are required, using all-in-all-out production methods, high levels of biosecurity, vaccination and competitive exclusion. And as it’s very difficult to control horizontal spread in the production setting, limiting vertical transmission is especially important.

Q: How does vaccination help limit the vertical transmission of E. coli?

HC: There are three indirect ways in which vaccination helps. First, vaccination of broiler parents should improve their immune response toward E. coli infection, thereby reducing the chance of transmitting E. coli to the embryo or eggshell. Furthermore, vaccination also supports maternally derived immunity in chicks, helping to further limit the risk of infection and severe disease.

Finally, research has shown that vaccination leads to changes in E. coli populations. If this were to reduce the pathogenic components, this could also affect vertical transfer.²

To read more of the interview, click here.