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

Project code: OZ0135
Project title: Epidemiological studies of multiple-resistant
Salmonella Typhimurium DT104 in cattle
Start date (dd/mm/yy): 01/04/1997
End date (dd/mm/yy): 31/03/2002
£523,530
Total cost:
Affiliation: Veterinary Laboratories Agency
Abstract of research
This 5-year epidemiological project aimed to provide a better understanding of the
epidemiology of multiple-resistant (MR) Salmonella Typhimurium DT 104 and other
Salmonella infections in cattle herds. The project started during an epidemic of MR S.
Typhimurium DT 104 in cattle, and increasing numbers of human infections with this
organism, in the 1990s in Great Britain. The original proposal included an intervention
study to test the effectiveness of control measures in cattle herds, but this was replaced
with additional epidemiological studies because there was a marked decline in reported
cases of this organism in cattle during the study.
The studies demonstrated:
1. Salmonella infection of dairy herds in England and Wales was common but most
herds were infected with serotypes unusual in human cases.
2. Infection was clustered geographically and more common in large herds
3. Management risk factors were identified providing evidence for control
4. Herds with clinical outbreaks of S Typhimurium DT104 did not usually experience
further outbreaks but risk was higher than the general population
5. Biosecurity on dairy farms was generally poor and, at the time, it was considered
difficult to improve sufficiently to control Salmonella
6 The standardised environmental sampling protocol used had many advantages in
terms of cost and feasibility for the detection of Salmonella at the farm level and could be
adapted for other livestock systems and organisms
7. Many Salmonella infections in cattle herds will be unreported by routine surveillance
of laboratory submissions for clinical diagnoses.
It is unlikely that Salmonella will be eradicated from dairy farms in the short to medium
term, and therefore human exposure to this organism originating from dairy farms should
be minimised, for example by ensuring the proper pasteurisation of milk and provision of
advice to all farm workers and visitors.
There were numerous potential transmission routes for Salmonella, and other infections,
within the structure of G.B dairy farms (e.g., high number of animal movements) and the
industry (e.g., network of markets and dealers). Emerging serotypes (eg MR S. Newport)
are likely to spread rapidly after introduction and effective intervention to limit their spread
will be difficult. Emerging serotypes not associated with disease will not be readily
identified by current surveillance.
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