DETECTION OF CONTAMINATION OF BABY MILKAN
INTERNATIONAL INCIDENT AND COLLABORATION
Food-borne disease is a major public health
problem. Modern food distribution and manufacturing practice is
that foodstuffs are now produced or harvested in one country and
distributed internationally. This presents the opportunity for
infections to emerge far from the source of contamination. A responsive
surveillance system that can recognise and react to international
outbreak of food-borne disease is essential. Enter-netthe
international surveillance system for salmonella and Escherichia
coli is such a system, and has been co-ordinated by the PHLS
at the Communicable Disease Surveillance Centre in Colindale since
its inception (as Salm-Net) in 1992.
The threat of food poisoning from contaminated
products is ever present, and successful surveillance depends
on a partnership between microbiological and epidemiological experts.
Surveillance is even more critical when vulnerable groups are
affected. An example of this partnership is a recent outbreak
of Salmonella anatum associated with consumption of infant
milk formula. In late January 1997, 12 cases of S.anatum
in babies under the age of one year were identified, eight in
England and four in Scotland. The Communicable Disease Surveillance
Centre and the Scottish Centre for Infection and Environmental
Health under took a joint case-control study, which was completed
within 48 hours. Results of the study implicated a particular
brand of infant milk formula. International investigations through
Enter-net revealed other associated cases in France and Ireland.
Strains of S.anatum were subjected to an in-depth microbiological
analysis. The analysis of strains from England, France and Scotland
by pulsed-field gel electrophoresis (PFGE) showed that all the
cases were the outbreak strain. A sample from an unopened packet
of the implicated product was positive for S.anatum that
had the same PFGE pattern.
As a result of the epidemiological investigation,
confirmed by the microbiological testing, the product was withdrawn
from sale in both France and the UK. If these investigations had
not been done so rapidly and efficiently the contaminated product
would have been available for consumption for a considerable while
longer. This would have exposed many more babies to the possibility
The public health benefits of international
surveillance networks such as Enter-net have been demonstrated
many times. One of the strengths of these networks is that of
the hub being based within the PHLS. This brings the benefit of
epidemiological experience in outbreak investigation, microbiological
expertise and contact with colleagues in sister institutes in
other countries all working in harmony.
The development of Enter-net needs to be ensured,
and improved, by increasing the capacity of all participating
countries to be able to sub-type food-borne pathogens using phenotypic
and genotypic methods. This can be resolved by ensuring that appropriate
submissions to the European Commission are made at the correct
time. Development of new, rapid typing techniques is a key area
of the future.
The PHLS has identified that international surveillance
for the benefit of public health is important and it has successfully
fulfilled its role as a key player in this field. Public health
requires a multi-disciplinary approach. By combining epidemiological
and microbiological expertise, and fostering international collaboration,
the PHLS is ideally placed to develop the surveillance of food-borne
Ian Fisher on behalf of the Enter-net participants.
The Enter-net international surveillance networkhow it
works. Eurosurveillance 1999; 4: 52-5.
Prepared by Dr Ian Fisher (PHLS) on behalf of
the Enter-net participants.