1. Enteric Pathogens in the Vegetable Production Chain: Is the risk higher in the organic than in the conventional chain?
Prof. Ariena H.C. van Bruggen
Organic Farming Systems
Wageningen UR
Marijkeweg 22
6709 PG Wageningen

2. Health problems with food-borne pathogens1
Health problems with food-borne pathogens
Six-fold increase in gastro-enteritis and food
poisoning in the last 20 years (Nicholson et al., 2000)
Water and food contaminated with pathogens from
human and animal manure
Animal products and plant products, especially raw meat,
eggs, but also fresh vegetables and fruits
Pathogens: various bacteria
a.o. Salmonella spp. in pig and poultry manure
Escherichia coli O157:H7 in cow manure
Source: Nicholson et al., 2000

3. Markets grow for organic produce1
Markets grow for organic produce
Fresh vegetables in Italy FAO/N.Scialabba
Packaged vegetables in Brazil

4. Concerns about pathogen spread in the media
Food safety issues
- Residues of synthetic pesticides
- Inherent components (organic, mineral)
- Toxic compounds (mycotoxins, plant derived toxins)
- Disease germs
Concerns about pathogen spread in the media
Manure contains human pathogens
Spread from manure via soil to roots and plant products
- Organic food more risky than conventional food

5. Counter-arguments which deserve investigation1
Counter-arguments which deserve investigation
Microbial compositions and pathogen contents of
ORG and CONV manure differ
- Manure handling differs on ORG and CONV farms
Microbial compositions and resistance against
pathogen invasion of ORG and CONV soil differ
root environment differs (exudation and N content)
plant physiology and endophytes differ (N content)

6. 1
Differences between conventional and Organic animal and vegetable production
Conventional
fertilizer (and liquid manure)
high N-concentrates in feed
low-fiber diet for cows
antibiotics in feed
Organic
composted and liquid manure
limited organic concentrates
high-fiber diet for cows
no antibiotics in feed

7. 1
Cow dung varies in: consistency, decomposition rate, microbial diversity, pathogen content
Low-fiber, high-N feed High-fiber, low-N feed

8. 1
Survival of E. coli gfp introduced in manure and then with manure to soil
Cells, CFU/g. d.m.
Semenov, unpublished

9. Survival of Escherichia coli O157:H7 gfp in manure
Franz et al., unpublished

10. Survival of Escherichia coli O157:H7 gfp manure- amended soil
Franz et al., unpublished

11. 1
Risk analysis
Based on
HACCP (Hazard Analysis and Critical Control Point) system
I. Risk Assessment
1. Hazard identification
2. Hazard characterisation
(evaluation health effects  dose-response relation)
3. Exposure assessment (evaluation likely intake)
4. Risk characterization (final risk expressed as a probability)
II. Risk management
III. Risk communication

12. Possible human factors affecting risk analysis1
Possible human factors affecting risk analysis
Societal: - perceived risk of consumers and their reaction
- food production and processing infrastructure
- knowledge of food producers, processors,
traders, and consumers
- scientific and healthcare infrastructure
Biological: - ability to quantify data (bias and precision)
- abiotic versus biotic approach
- medical versus ecological approach (exposure
and dose-response assessment versus microbial
cycles in ecosystems)

13. Conclusions The general public is concerned about food safety;
use of manure is perceived as risk
Conditions in organic production systems are different from conventional systems (a.o. animal feed and microbial communities)
Real risks need to be determined scientifically and
need to be distinguished from perceived risks
4. Complacency and conceit are dangerous and must be avoided!!

14. Acknowledgements - Alexander V. Semenov (jr.), MSc student1
Acknowledgements
- Alexander V. Semenov (jr.), MSc student
Experiment with P. fluorescens 32 gfp
- Eelco Franz, PhD student
Literature review and survival of E. coli O157:H7
in manure and soil
- Dr. Anne van Diepeningen
Literature review, microbial diversity in soils,
survival of E. coli O157:H7 in manure and soil