Foodborne infections in the Netherlands

Advisory report | 24-05-2000

Disease burden

Systematic and reliable information on the occurrence of diseases caused by foodborne infections in the Netherlands is only available in a fragmentary form. Furthermore, the proportion of infections that can be attributed to food remains unclear. It is therefore not possible to provide a suitably documented response to the question posed about the incidence of foodborne infections. However, the Committee is of the opinion that the available data are sufficient for a global assessment of the disease burden due to foodborne infections in the Netherlands. This assessment reveals annual figures of:

• A quarter of a million to one million cases of gastro-enteritis (inflammation of the gastro-intestinal tract, also known as ’gastric flu’) resulting from foodborne infections caused by known pathogenic micro-organisms. Several tens of thousands of these cases are so severe that they result in a visit to the general practitioner. A small proportion of the cases occur in the form of so-called outbreaks, involving two or more people. Most foodborne infections are caused by pathogenic bacteria. Small round structured viruses (SRSV) – recently designated as Norwalk-like viruses (NLV) – also play an important role. The significance of food in the transmission of other viral and parasitic causes of gastro-enteritis remains uncertain.
• Several hundred complications of bacterial foodborne infections. This includes several dozen cases of Guillain-Barré syndrome as a complication of campylobacter infection and several dozen cases of haemolytic-uraemic syndrome (HUS) as a complication of verocytotoxin-producing E. coli (VTEC) serotype O157 infection. 
• A couple of hundred cases of hepatitis A and several dozen cases of listeriosis.
• Several hundred cases of bacillary dysentery and several dozen cases of other notifiable infectious diseases that can be contracted – usually abroad – through food.

How many cases of some other food-related diseases, such as toxoplasmosis and taeniasis (tapeworm infection), occur annually in the Dutch population is also unknown.
Infectious diseases that can also be contracted through food result in several hundred hospital admissions per annum in the Netherlands. At the same time, a small number of deaths related to foodborne infections is recorded yearly. However, no reliable quantitative information is available.
Approximately three-quarters of the cases of food-related gastro-enteritis involve bacterial infections contracted from foods of animal origin. The previously mentioned complications, such as campylobacter-associated cases of Guillain-Barré syndrome and the cases of haemolytic-uraemic syndrome, are probably also largely attributable to infections contracted via foods of animal origin.

Risk groups and risk factors

People with a relatively low resistance to infections, such as young children, the elderly in a debilitated physical state, immuno-incompetent people and persons with a serious underlying disease may be considered persons at increased risk of disease due to foodborne infection. Pregnant women also constitute a risk group mainly because the unborn child is inadequately protected against certain foodborne infections*. In addition, travellers to countries with a relatively low standard of hygiene are at increased risk. Specific risk groups can be indicated for some pathogenic micro-organisms.
Furthermore, there are various factors and developments - mentioned below - in the area of primary food production, food processing and food preparation, as well as specific eating habits, that contribute to the risk of foodborne infection.
There is almost no quantitative information about the extent to which the different factors and developments contribute to the risk of foodborne infection in the Netherlands. To gain an understanding as to the relative importance of the various factors and developments, more quantitative risk analysis-oriented studies are required.

Animal production

The intensification of animal production has resulted in a reduced risk of the introduction of pathogenic micro-organisms onto farms. On the other hand, this development is associated with factors, such as a reduced resistance of the animals to infections, that contribute to the contamination of animal products and hence indirectly to the risk of foodborne infection.
There is currently a trend within animal husbandry towards greater extensification of the husbandry systems. The Committee does not exclude the possibility that this development will interfere with the control of pathogenic micro-organisms in animal husbandry, especially where the animals are given greater freedom to roam outside. This may also result in an increased risk of foodborne infection.
A number of measures have recently been taken that are directed towards limiting the use of antimicrobial growth promoters in animal husbandry. The available data give the Committee no cause to assume that there will be a resultant increase in the risk of foodborne infection.

Agriculture, horticulture and fisheries

The Committee believes that, in particular, agricultural and horticultural products obtained from exotic areas constitute an increased risk of foodborne infection. In the case of fisheries products, it is chiefly shellfish from faecally contaminated coastal waters that might be infected with pathogenic micro-organisms.
In both agriculture and horticulture alternative farming methods, such as mild methods for crop protection, are increasingly used. The Committe is of the opinion that this development may affect the risk of foodborne infection.

International trade

According to the Committee, the increasing international trade in production animals, raw materials and food may bring about the introduction of pathogenic micro-organisms, including exotic pathogens, and thus make it difficult to control the risk of foodborne infection. An example cited by the Committee is the risk of listeria infection through imported soft cheeses made from raw milk.

Food processing and professional food preparation

The food processing industry is cashing in on the increasing preference of the consumer for a ’fresh’ product, associated with convenience. This trend requires ’mildly’ preserved foodstuffs. The the introduction of new mild preservation technologies could result in new microbial hazards. The increasing demand for convenience foods, such as cold fresh food and food ingredients, results in a greater volume of microbiologically vulnerable foods. The vulnerability of this sort of product requires strict storage conditions in the logistics chains. At present, the effect of this development on the risk of foodborne infection cannot be determined.
Mistakes resulting in foodborne infections can also be made in professional food preparation, such as in hotels and restaurants, the catering trade and institutional kitchens. The consequences may be particularly serious where the preparation of food is for groups of people with relatively low resistance (for example in a nursing home).

Household food preparation and eating habits

Incorrect methods of food preparation and preservation in the consumer’s home kitchen, still play a significant role in the occurrence of foodborne infections. Well-known risk factors are cross-contamination, insufficient heating, insufficient cooling and storing food for too long a period. In the case of cold fresh food and food ingredients, failures to observe the expiry date or specified storage conditions are particularly critical. Conversely, the Committee believes that the limited household processing and preparation of this sort of food is probably associated with a lower risk than the traditional preparation of meals*.
Specific eating habits, such as the frequent consumption of raw shell fish or steak tartare, can also contribute to the risk of foodborne infection. Furthermore, there is an increased risk whenever the normal method of storage and preparation of food is not followed, as is the case with barbecues, grills and camping.

Opportunities for risk control

Opportunities exist for reducing the risk of foodborne infection in both the successive phases of the food production process and amongst consumers. Based on the important role of contaminated food of animal origin in the occurrence of foodborne infections, the Committee recommends that measures to protect the consumer against foodborne infections, should primarily be aimed at reducing the contamination of these (raw) foods. The main opportunities for risk control are:

Animal production

The present approach to salmonella and campylobacter in the poultry meat sector has, to date, only had a limited effect. This calls for a thorough analysis of the available data and a careful evaluation of the measures taken. Furthermore, measures should also be taken in other animal production sectors to prevent animals and animal products from being contaminated with micro-organisms that are pathogenic to human beings. Tackling salmonella in the pig sector should be the first priority. Consideration must also be given to preventing the contamination of cattle and beef with verocytotoxin-producing Escherichia coli (VTEC) serotype O157.
There are various possibilities of (further) risk control in animal husbandry, such as the administration of probiotics and vaccination. However, the efficacy of these measures has yet to be evaluated.
Measures to control micro-organisms in animal production which are pathogenic to human beings must form part of an integrated quality control system within the production chain. Accordingly, the meat inspection legislation should be amended so as to incorporate meat inspection within such a quality system.
In fact, the hazard analysis critical control points (HACCP) concept can be effectively used in the animal slaughtering phase, provided that a decontamination step, such as irradiation or the use of decontaminants, is permitted within the production process as an additional measure within a quality control system.

Processing phase

In the industrial processing of raw (animal and plant) foodstuffs, greater risk control is possible through the practical implementation and validation of HACCP. The degree of risk control in the traditional production of foodstuffs must be no less than that in industrial production processes. The development of new preservation technologies that guarantee the desired microbiological quality should be encouraged. The reliability of irradiation as a method of decontamination in the processing of food must also be promoted. Careful risk analyses should guarantee the microbiological safety of novel foods and new preservation concepts.

Professional food preparation

In addition to the existing codes of hygiene for professional groups involved in the professional preparation of food, further risk control is possible by means of a more thorough inspection of kitchen facilities and a more stringent control of kitchen hygiene. Furthermore, it is recommended that persons such as nurses, nursing auxiliaries and home care providers who distribute food as part of their duties should receive even more education on food hygiene during their training.

Consumer phase

Risk control among consumers should mainly be concerned with increasing consumer awareness as to their own responsibility for the hygienic preparation and handling of food. The Committee stresses the importance of providing good information with the product, for example, by labelling, and targeted education and advice. In this respect, the recently issued ’Code of hygiene for private households’ is a step in the right direction. Specific information is required for population groups at a higher risk of foodborne infection, particularly the elderly (over 75 years of age), pregnant women and travellers abroad.

Health benefit

The maximum health benefit that can be expected from making food of animal origin pathogen-free is, in principle, the prevention of all cases of illness and death arising from infections contracted through products of this kind. However, the exact relationship between contamination of the end products of animal production and exposure of the population to pathogenic micro-organisms through food of animal origin remains unclear. The same applies also to the link between exposure and the occurrence of disease. Therefore, the question as to the health benefit that can be obtained from making food of animal origin pathogen-free cannot yet be answered. The health benefits of various scenarios for risk control can only be estimated once the necessary quantitative risk-analysis research has been carried out.

Recommendations

The Committee makes the following recommendations:

• The risk of infections through food, particularly of salmonella and campylobacter infections through raw food of animal origin, should be limited by government regulations on food safety objectives, based on adequate risk analyses.
• Failure to achieve the stipulated food safety objectives should lead to consequences for the producer.
• The further development and implementation of integrated, chain-oriented strategies for risk control of specific pathogenic micro-organisms in animal production chains is of major importance. In addition to an integrated quality system in the raw meat production process, a decontamination step, such as irradiation or use of decontaminants, should be permitted.
• Products that are possibly contaminated with pathogenic micro-organisms, especially raw food of animal origin, must be provided with a warning aimed at the consumer and contain information about correct storage and preparation.

Based on the information currently available, the Committee concludes that it is only able to respond in a very limited manner, to the questions raised by the ministers in their request for an advisory report. If these questions are to be answered properly in the future then appropriately conducted risk analyses are, in the Committee’s opinion, necessary. These risk analyses are also required as the scientific basis for food safety objectives. In this respect, the risk analyses should initially concentrate on salmonella in poultry meat and pork, S. Enteritidis in eggs, campylobacter in poultry meat and VTEC serotype O157 in beef. A systematic collection of the necessary data is required for these risk analyses to be undertaken. The Committee envisages in the first place:

• In addition to the existing continuous laboratory surveillance systems, a regular (for example every five years) general practice sentinel study combined with a population based study. This would provide insights into trends in the incidence of gastro-enteritis and in the occurrence of the causitive agents of this illness, as well as the effect of the control measures taken.
• Epidemiological studies, such as case-control studies, to obtain a better estimate of the food-related fraction of cases of disease due to certain pathogenic micro-organisms.
• Quantitative and modelling studies on the occurrence of certain pathogenic micro-organisms in the whole food production chain and in the consumption phase. This will enable the exposure of the population to pathogenic micro-organisms through food to be determined. In addition, the effects of measures taken in production sectors can be established. At the same time, the systematic collection of data on the occurrence of pathogenic micro-organisms in farm animals and products is necessary to gauge the effects of extensification in animal husbandry systems, alternative farming methods and the liberalisation of international trade.
• Experimental and modelling studies of the relationship between exposure of the consumer to certain pathogenic micro-organisms and the occurrence of adverse effects on health.
• Further identification and quantification of risk factors in the area of food production and household food preparation in order to gain an insight into the relative importance of the different factors and on this basis to select the most appropriate opportunities for reducing the risk.
• Evaluation of the possibilities of risk control of specific pathogens in the food production chain.

• * Committee member Prof. J.A.A. Hoogkamp-Korstanje has made it known that she cannot support this statement because as she considers the scientific basis to be inadequate.