22 VTEC and Agriculture

The European Chilled Food Federation (ECFF, www.ecff.net/) established a VTEC Working Group in 1997 to gather information on the occurrence and control of VTEC (verosytotoksinen Escherichia coli) and make recommendations as to any changes required to be made to the ECFF Guidelines for Good Hygienic Practice in the Manufacture of Chilled Foods.
This summary gives key information and recommendations arising from the Group.

Chain of Infection

While contamination with VTEC usually occurs at the primary production level, the significant health problems that result are manifested downstream at the consumption level. Food processors, in the middle of the food chain, are clearly interested, therefore, in the development of effective means for the control of VTEC and the prevention of their resulting infections.
Cattle and other ruminants are the main reservoir for VTEC in Europe. However, VTEC has also been isolated in fruit and vegetable materials. The main food sources of VTEC infection include undercooked beef, contaminated/unpasteurised milk, and raw vegetables, due to contamination from animal waste.
Seeds can harbour VTEC. The germination of contaminated seeds in a warm, moist environment allows the growth of pathogens, leading, for example, to the development of mature sprouts contaminated with VTEC.
Produce contamination by VTEC is primarily via agricultural practices and the use of organic materials, i.e. animal or human waste, as fertiliser.
Various potential transmission vehicles include:

1. Human sewage sludge: In the UK the use of untreated sludge is banned from land used to produce all food crops, and harvest intervals are specified between the application of digested and “enhanced treated” sludges (ADAS Safe Sludge Matrix).

2. “Exempt wastes”
-Blood and gut contents from slaughtered animals.
-Waste food, drink or materials used in, or resulting from the preparation of food and drink.
-Septic tank sludge.
-Sludge from biological treatment plants.

3. Farmyard manure: proper composting is critical

4. Organic farming methods.

5. Irrigation and processing water.

6. Direct contamination by animals.
VTEC has been shown to be more persistent in the environment than salmonellas in certain cases. Research has demonstrated the high survival rate of E. coli O157 in soil, faeces, and water under laboratory conditions (Maule, 1997). In one study, it was shown that E. coli O157 was able to survive for 21 months in a manure pile collected from experimentally infected sheep (Kudva, 1998).

Recommendations to Minimise the Risk

Minimising the risk of VTEC infection, both in foods of animal and vegetable origin, is of importance. Control of production is key, with the aim of eliminating sources of contamination as far as possible. Microbiological testing is of limited value since methodology is time consuming, sampling low numbers has little statistical significance and there is no accepted satisfactory indicator organism.
Although heat is effective in controlling VTEC, many produce products cannot be “decontaminated” through the application of heat (e.g. it is not practical to apply heat treatment to lettuce). Measures must therefore be taken to minimise contamination in the field and during handling. However, there is very little guidance on the controls to be applied in the field.

Research Requirements

ECFF’s VTEC Working Group recommended that further work should be conducted at EU level on the following priority areas:

1. Agriculture
-The microbiological quality of wastes — both animal and human-derived — and their use in agriculture and the effects of various treatments and application.
-Strategies to reduce carriage of VTEC in cattle.
-Practices to minimise cross contamination on the farm, during transport and slaughter.

-The relative importance of different serotypes of VTEC.
-Terminology, surveillance systems and case identification.
-The survival of VTEC and other emerging pathogens at low temperatures.

3. Food
-The correct storage of various raw materials (e.g., relative humidity, temperature).
-Effective decontamination methods for produce.
-Control of VTEC through manipulation of pH in products.

Working Group’s Strategic Recommendations

I. The EU should assume clear responsibility for implementing and enforcing measures to effectively control VTEC.

II. ECFF believes that first priority should be given to phasing out the use of untreated sewage sludge. ECFF supports a requirement of 30 months delay between application of treated sludge on land before planting a crop that can be eaten raw (ADAS Safe Sludge Matrix).

III. Voluntary industry guidelines should be modified to appropriately reflect the measures needed for the control of VTEC. The UK Chilled Food Association is finalising such guidance for suppliers to chilled food manufacturers, which is to be published shortly.

IV. EU legislation for agriculture and hygiene should be modified to appropriately address issues related to VTEC. Within this context, ECFF recommends the development of European Good Agricultural Practice standards based on HACCP principles, and relating to the general food hygiene Directive, 93/43/EEC, and its successive legislation. Such a document should address both human and animal waste-treatment standards and guidelines for the use of waste in agriculture.
ECFF recommends that it be developed as a joint project between the authorities, primary producers and the food processing industry. Good Agricultural Practice standards need to be supported by:

1. A programme of education and monitoring at the production level.
2. The development of practical and effective decontamination methods in processing plants.
3. Full implementation in processing plants of measures to prevent cross contamination (see ECFF Guidelines).
4. A distribution system that ensures the continued safety of food products.

V. The EU and its Member States should work in unison to implement changes in Codex Alimentarius guidelines for the effective control of VTEC.

VI. Safe food-handling guidelines should be developed for in-home, restaurant and catered food preparation. These guidelines should be distributed through a wide communication network to ensure the effective control of VTEC and other forms of pathogenic exposure in these situations.
It should be noted that measures developed to control VTEC are expected to also be important in relation to the control of other foodborne pathogens including Salmonella spp. and Listeria spp.

Current Status

The ECFF Report was presented to the EC in 2000 and a special sub committee of the Scientific Committee for Food was formed to carry out a risk assessment on the microbial safety of produce. The Opinion of the full Committee is awaited.
Much research has been carried out on this general area, but several key questions remain to be answered definitively.
The legislative and political environment has developed since the Report was published, but many of the strategic requirements remain valid. The awaited finalisation of new hygiene Regulations presents an opportunity for key points to be taken into account, particularly regarding the role of HACCP in agriculture.
January’s EU Regulation (EC/178/2002) represents a major step forward in addressing food chain issues, rather than focusing on the point of usage of raw materials by manufacturers.

Kaarin Goodburn
MSc BSc (Hons)
kaarin.goodburn (at) pinebridge.co.uk

Kaarin Goodburn on konsultti ja UK:n Chilled Food -yhdistyksen (CFA) toiminnanjohtaja. Hän on ollut perustamassa ECFF:ää vuonna 1991 ja toiminut useaan otteeseen sen pääsihteerinä. Hänen yhteytensä suomalaisiin elintarvikealan edustajiin ovat vilkkaat mm. suomalaisten sukujuurten ja suomen kielen taitamisen ansiosta.

References/Further Reading:
ADAS “Safe Sludge Matrix”, www.adas.co.uk/matrix
CFA “Microbiological Guidance for Produce Suppliers to Chilled Food Manufacturers”, 2002, CFA, PO Box 14811 London NW10 9ZR, cfa@chilledfood.org, ISBN 1 901798 03 8
ECFF “Guidelines for Good Hygienic Practice in the Manufacture of Chilled Foods”, 1996, www.ecff.net
ECFF “VTEC & Agriculture”, ECFF, 2000, www.ecff.net
Kudva Appl Env Microbiol, 1998, Vol. 64, No. 9, p. 3166—3174
Maule “Survival in the Environment” in “Coliforms and E. coli: Problem or Solution?”, 1997, Eds Kay & Fricker, Royal Society of Chemistry, ISBN 0 85404 771 9