Food and Environmental Safety

The Food and Environmental Safety Programme, often in collaboration with the Health Protection Agency (HPA) provides consultancy, research and surveillance on food safety issues on farms and their environment, in support of both public and animal health.

Surveillance and Epidemiology of Food borne Pathogens

An example of antimicrobial resistance to Tylosin in S.suis and Actinobacillus pleuropneumoniae recovered from pigs

An abattoir survey was undertaken in 2003 with the Meat and Livestock Commission to determine the prevalence of food borne zoonotic organisms in cattle, sheep and pigs at slaughter in Great Britain.

The results, presented at two public meetings showed that the prevalence of Escherichia coli O157 faecal carriage was unchanged in cattle since 1999/2000 but was significantly less in both sheep and pigs. Salmonella carriage was low in cattle and sheep but, as in the previous survey it was frequently isolated from pigs.

VLA is supporting a British Pig Executive control programme to reduce the prevalence of Salmonella infection in slaughter pigs. Meat juice samples from batches of slaughter pigs are tested for antibodies to Salmonella and, if a high prevalence is found, further support is provided in the form of advisory farm visits and microbiological testing. Thermophylic Campylobacter spp. were frequently isolated from all species. However, the incidence of Yersinia enterocolitica was reduced in all animals and the incidence of Cryptosporidia, monitored for the first time was very low in both cattle and sheep.

At the request of the HPA, VLA investigated seven outbreaks of Verocytotoxigenic E.coli (VTEC) O157 in humans and two for cryptosporidiosis. As a consequence of these requests, new guidelines have been written for the investigation of human cryptosporidiosis, where there is a link to animal contact. Enhancements have also been made to the E.coli surveillance procedures to include standardised submission and testing criteria and the use of a new PCR-based diagnostic test.

To support EU legislation on zoonoses, VLA is working with Defra and other organisations to deliver a series of surveys to establish baseline levels of various food borne pathogens in farm animals. The first of these, looking for Salmonella in egg laying flocks is underway.

A joint pilot study with the Universities of Reading and Liverpool, examined three intervention packages to help reduce VTEC O157 in young cattle. The introduction of biosecurity measures at farm-level together with keeping bedding dry, using enclosure-specific boot dip and overcoat and keeping other animals away from cattle enclosures, reduced the risk. Interestingly, enclosure hygiene also reduced the prevalence of Eimeria spp. but the interventions had no effect on Campylobacter.

Other projects on VTEC O157 have been very successful in collaboration with the Universities of Liverpool, Edinburgh, Bristol and Imperial College and with the Silsoe, Institute of Food Research, Moredun and Sanger Institutes.
Of particular note is the finding that non-O157 Attaching and Effacing E.coli (AEEC) interfere with VTEC O157 colonisation in ruminants and that predisposing factors such as cryptosporidial infections enhance VTEC O157 colonisation.

Antimicrobial Resistance

Measurement of inhibition zones to bacteria

An extended-spectrum beta-lactamase (ESBL) enzyme was detected in E.coli isolated from scouring calves. It seems unlikely that the E.coli was causing the calves any disease problems but, the presence of this enzyme is of concern as it confers resistance to a wide range of beta-lactam (penicillin and cephalosporin) compounds. This is the first detection of an ESBL enzyme from food producing animals in GB.

Zoonotic organisms, commensal E.coli and Enterococcus faecium, isolated from animals sampled in the 2003 abattoir survey were examined for antimicrobial resistance. A higher prevalence of resistance to antimicrobials was found in bacteria isolated from pigs rather than ruminants.

Biology and Control of Food borne Pathogens

A project comparing genotypic and phenotypic features of virulent Yersinia enterocolitica from humans and animals was undertaken in collaboration with the HPA and the London School of Hygiene and Tropical Medicine. Findings have challenged the perceived understanding of the classification of subtypes as virulent and avirulent.

Novel Salmonella vaccine design and the development of probiotics is an area of interest in the commercial sector of the animal health industry and as part of a consortium approach with the Institute of Food Research (IFR), Reading University and others, VLA is working on ‘The Healthy Gut in Animal Health and Welfare’.

Chemical Food Safety

Contaminated water courses can be a potential source of animal disease

VLA has provided advice on the risk of increased incidence of suspected cattle botulism. Many incidents are circumstantially associated with the spreading of poultry litter on grazing land or inadvertent exposure to poultry carcases. Lead poisoning was also regularly diagnosed and many cases were associated with exposure to known risk factors such as lead paint, batteries and lead mine workings.

Radiochemical analyses of food and environmental samples were carried out for the Food Standards Agency (FSA) to assess human exposure to radionuclides and to increase their level of information on risk management. In addition, VLA mounted a rapid response to nine incidents of suspected excess release of radioactivity from a nuclear site by collecting and analysing environmental samples.

Examples of other collaborative projects include:

University of Liverpool, Leahurst campus

University of Liverpool and IAH

Study of the immune response in cattle to endemic and epidemic strains of Salmonella

HPA

New approaches to detect and differentiate resistance genes by PCR and microarray

University of Glasgow, ADAS and Direct Laboratories Ltd

Studies on the risk of transfer of antibiotic resistance genes between bacteria

University of Liverpool, HPA, Scottish Centre for Infection and Environmental Health and IFR

A project to assess the contribution made by the food chain, relative to other pathways, to the problem of quinolone resistance in Campylobacter causing human disease. Foreign travel was the top risk pathway.

Silsoe Research Institute, University of Liverpool, HPA

Studies of VTEC in farm wastes concluded that the risk of human infection, due to contact with farm waste is low.

University of Bristol, Imperial College at Wye

Studies of Campylobacter infection in broiler flocks resulted in the development of a LightCycler Biprobe Assay to detect environmental sources of Campylobacter jejuni strains.

Cryptosporidium parvum

Cryptosporidium Reference Unit, Swansea

Studies to investigate the relationship between isolates of Cryptosporidium in human disease and in animal and environmental contacts. Also to establish the host range of Cryptosporidium species and genotypes extraction procedures.