Contamination Aliments
29/03/2013 3 min

Microbiological risks in food: vigilance remains necessary, especially with regard to emerging pathogens

Foods can be contaminated at several stages of production and preparation by a variety of pathogens (viruses, bacteria, moulds, parasites) whose effects may be benign, or on the contrary quite serious or even fatal. For the publication of two expert reports on potential emerging pathogens (hepatitis E virus and the Vibrio parahaemolyticus bacteria), ANSES reviews the issues faced when assessing microbiological food risks while reiterating its recommendations on the subject. 

Foods can be contaminated at several stages of production and preparation (plant cultivation, animal farming, harvesting, slaughtering, processing, distribution and home use) by a variety of pathogens (viruses, bacteria, moulds and parasites). While these effects may be benign, some are however quite serious, and others even fatal. 

These pathogens can be grouped into three main types: 

  • agents responsible for the majority of cases of foodborne infections (from mild to average severity, although certain complications can occur);
  • more rarely incriminated pathogens, but with serious consequences (E. coli, Listeria); 
  • "emerging" pathogens, that have only recently been discovered, or whose presence in foodstuffs is promoted by new conditions (global warming which modifies the zones where a pathogen is found, warming of coastal waters which promotes proliferation of a pathogen, etc.);
  • major pathogens (type 1 and 2) which are subject to stringent surveillance and management measures. Their presence in foodstuffs and the surveillance methods used are regulated by European or country-based laws. However, vigilance should also apply to emerging food pathogens. 

In 2012, the Agency pursued its efforts regarding two of these pathogens, the hepatitis E virus and bacteria of the genus Vibrio, excluding the Vibrio reponsible for cholera (choleragenic Vibrio cholerae). Along with the publication of this work, ANSES is also issuing a reminder of its microbiological food risk recommendations.

Hepatitis E, the importance of improved information campaigns 

The hepatitis E virus is the primary agent of acute hepatitis. The cases identified in France are generally known for being contracted in countries with poor levels of hygiene. However, in 2004, the first cases of hepatitis E contracted by French patients who had not travelled to other countries were described. Several clustered cases of hepatitis E which occurred in France in 2008 and 2009 established a link between consumption of raw pork liver products and the disease, making it possible to clearly identify pork as the virus vector. The Agency has issued a number of assessments regarding this risk and has contributed to the development of detection methods. 

The most recent ANSES Opinion, published today, reviews the possibilities for providing optimal management measures at various stages of production and preparation and emphasises the necessity of providing effective information for consumers and healthcare professionals (especially in areas of high prevalence) on the risks associated with the consumption of products made with raw pork liver (figatelli, etc.).

Vibrio parahaemolyticus, a bacterium to be carefully monitored 

Another unregulated pathogen, Vibrio parahaemolyticus, is of interest to the public health authorities.  This micro-organism, found specifically in marine environments, causes gastro-enteritis through the ingestion of raw or undercooked fish or shellfish. The bacterium has a curved, rod-like shape and has a wide distribution in coastal marine areas.  It is considered to be normal flora in bivalve molluscs, crustaceans and fish. Most infections with the pathogen cause gastro-enteritis, or more rarely septic shock.

In order to more effectively evaluate the risk related to this pathogen via shellfish, the Agency had just issued its conclusions in a major report. 

The report reveals the inadequacy of current data and recommends that authorities collect additional information on Vibrio prevalence in oysters and mussels. 

With regard to seafood in general, the Agency also reminds consumers of the following precautions:  

  • place seafood in a thermal bag, especially in the summer ;
  • eat shellfish within 2 hours of taking it out of the refrigerator ;
  • avoid raw seafood if you are pregnant, elderly or immunocompromised.

Find out more: Foodborne illness outbreaks in France

In France, foodborne illness outbreaks (FIOs) as well as certain other food-based diseases (listeriosis, etc.) are subject to mandatory declaration by physicians. However it is still difficult to evaluate the actual number of cases due to food. For this reason, a report by the Institut de veille sanitaire [French Institute for Public Health Surveillance] on the morbidity and mortality due to foodborne infectious diseases in France (for the years 2000 to 2002) shows that the actual number of cases is greatly under-estimated. (The actual number of cases is estimated to be 230 000, while only 12 000 cases are declared.) 

In France, in 2009, 1 255 foodborne illness outbreaks (FIO) were declared, affecting approximately 14 000 individuals, including 9 deaths. The most frequently incriminated or suspected agent was found to be the toxin produced by the bacteria Staphyloccocus aureus (staphylococcal enterotoxin) (31% of outbreaks), followed by bacteria of the salmonella group (20% of outbreaks). In 42% of reported cases, no known agent could be found or suspected. 

These figures emphasise the considerable health impact of FIOs, whose economic and financial repercussions have not yet been precisely evaluated in France. However, in many English-speaking countries such estimations do exist. For example, the United States have evaluated the annual cost of FIOs at 75 billion dollars for the 14 main pathogens involved (1) ; New Zealand has estimated the cost of the six main foodborne pathogens (Salmonella, Yersinia, Listeria, Campylobacter, Norovirus and shiga-producing E. coli) at 162 million dollars (2) ; and the approximate cost in Great Britain came to 1.5 billion pounds.

(1) S. Hoffmann et al. (2012)
(2) D. Gadiel and P. Abelson (2010)