Review of the Food-borne Zoonoses Research ... - ARCHIVE: Defra

Project code: OZ0326
Project title: Managing the challenges to the egg industry posed
by new SE PTs
Start date (dd/mm/yy): 01/04/06
End date (dd/mm/yy): 31/03/09
Total cost:
£403,472.00
Affiliation: University of Bristol
Sub-contractor(s): VLA
Abstract of research
Salmonella spp. are highly important zoonotic pathogens causing over one billion cases
of infection worldwide each year. One Salmonella serovar, in particular, is most
important. For the last 20 years there has been a pandemic of Salmonella Enteritidis
(SE) infection in almost all parts of the world, including Europe and this has largely been
egg-associated. The pandemic continues and SE remains a highly important zoonotic
pathogen. The longevity of the pandemic is unique and is associated with the invasive
behaviour of SE in chickens and the fact that infection in laying hens is largely subclinical.
The pandemic does have dynamic aspects, however, and the last few years the
UK, and some other EU member states, has seen a marked shift in phage types of SE
from human cases. Prior to this, one PT, PT4 dominated the epidemiological picture in
Western Europe. More outbreaks in the UK are now caused by PTs other than 4. For
example, PT 1 has risen from c.850 cases in 1999 to c.2000 in 2003. Similarly, cases
caused by PT 14b rose from c.150 to c.950 in the same period. The new PTs may
become established in the UK and it is important to establish the risk posed by these new
and potentially highly dangerous PTs, which threaten animal and public health in the UK.
Changes in Salmonella type, as manifested by PT alterations, occur with high frequency
and must challenge control measures put in place to deal with different strains.
The research is identifying how a range of relevant SE PTs differ in surface structures,
particularly LPS, and how these changes influence the growth and survival of the
bacteria in whole eggs and egg components. The work will also encompass interaction of
SE PTs with immune sera from vaccinated hens and infection biology in immunised (with
PT4) and non-immune hens. Identification of surface structures and how these affect
virulence will eventually enable improved vaccines to be produced. The investigators are
already interacting with vaccine companies.
Review Summary
Understanding differences between phage types of S. Enteriditis was considered
important, particularly if it shed light on understanding the risk to public health associated
with table eggs. Vaccination of poultry with a vaccine based on phage type 4 has been a
significant plank in the control of S. Enteritidis in the UK and it was important to establish
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