by Dr. Robert D. Lucas
Special to Barbados Free Press
In the 5th.of June Edition of the ‘Nation” newspaper, there was an article by Mr. Matthew Farley entitled: “Spain blamed.” Farley seemed to be concerned about the use of human feces in the growth of agricultural produce by the Chinese, while conceding the fact that, animal manures are used locally in agricultural production.
Nowhere in his article is it stated whether or not human feces were used in the cultivation of vegetables for salads in the current outbreak of food-borne illnesses in Europe. In the final paragraph of his article Farley urges Caribbean peoples to be cautious when growing vegetables using non-traditional methods. I have some comments to make on the above, but before I do so, I will review some aspects of food microbiology and food safety.
According to the Institute of Food Technologists’ Scientific Status Summary: Food Borne Disease Significance of Escherichia coli O157:H7 and other Enterohemorrhagic E. coli. 1997.51:69-76 : “E.coli has been used since 1890 as a non-pathogenic indicator of enteric pathogens such as Salmonella”.
Most E. coli bacteria are harmless
While most E. coli bacteria are harmless, the enterohemorrhagic E.coli (EHEC) group can produce toxins. Since the 1980’s, strains of E.coli which have acquired virulence characteristics have been isolated; the most common one implicated in food-borne illnesses being E.coli O157:H7 (designated by its somatic or cell wall, O, and flagellar, H antigens). Other E.coli which are pathogenic to humans and animals are referred to as non-O157:H7 stx E.coli. where stx refers to shiga toxins one or two.
It should be pointed out here, that all enterohemorrhagic E.coli (EHEC) produces shiga toxins, also referred to as verocytoxins. Bacteria can acquire virulence traits either by the transfer of genetic material within species and between species (ie.by plasmids or bacteriophages as well as by sexual means). In the case of O157:H7, the shiga toxin was acquired from Shigella spp. via a bacteriophage. The present causative agent of the outbreak in Europe is designated O104:H4. Previously, the serotype O104 was of minor importance to food microbiologists.
From a food safety aspect, it is obvious that, the hazard analysis critical control point (HACCP) program in Germany at the point of concern has malfunctioned. With vegetables which are normally consumed raw, it is necessary that good agricultural and manufacturing practices (GAP and GMP) be observed. HACCP guidelines must be observed from the field to the table. Critical control points in this process are as follows; the quality of the irrigation and rinse water used; manure whether human or animal should be properly treated.
“Animal manure and human fecal matter represent a significant source of human pathogens. A particularly dangerous pathogen, Escherichia coli O157:H7, is known to originate primarily from ruminants such as cattle, sheep and deer, which shed it through their feces. In addition, animal and human fecal matter is known to harbor Salmonella, Cryptosporidium, and other pathogens. Therefore, the use of biosolids and manures, including solid manure, manure slurries, and manure, must be closely managed to limit the potential for pathogen contamination.”
… 1998. Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables. Food and Drug Administration.
Wash those hands!
Additionally, hand-washing after the use of toilets must be enforced. At one of these critical control points, corrective action was not taken, resulting in the outbreak of food borne illness. The ability to pin-point the food which actually caused the problem is not going to be easy, since the contaminated food may have already been discarded. One point, which I find interesting, is the fact that Spanish cucumbers were blame initially. It appears that, the DNA profile of E.coli found on Spanish cucumbers was not compared with the DNA profile of E.coli isolated from the sick people initially. I would hope that, the scientists on the scene did not give into political pressure, to come with the initial finding. In any event, confusion seems to be the order of the day.
As can be seem, Farley need not be unduly worried by the use of human manure in the production of agricultural produce. The Chinese have been using it and their civilization extends back over five thousand years and China has a population of over 1.3 billion. Other countries use the sludge from sewer treatment plants. What I do find amusing, is what Farley means by cautious and non-traditional methods. You cannot get more traditional when manure, either human or animal is used.
Robert D. Lucas, PH.D.