Agriculture Reference
In-Depth Information
faster during storage at 15°C in manure from cows, the more grass and less concentrate was
used in the their diet (three different treatments); second, when mixed with (a conventional)
soil, pathogen numbers were quickly reduced in all treatments except in sterilised soil, and
pathogen numbers fell faster when the soil was mixed with organic manure than when the
same amount of conventional manure was added.
Whereas neither of these studies definitively rules out that pathogens can enter the organic
food chain through animal or plant products, they support the observations made by organic
farmers of relatively good resilience to infections. Together, this shows an imminent need for
well-designed studies to determine the efficacy of various procedures and their combinations
as used in organic farming to eliminate pathogens introduced at various levels of the food
chain. If the concept of suppressive soils can control not only plant pathogens (see
Chapter
4
),
but also zoonotic pathogens, the concept of a healthy soil will gain a completely new angle.
However, this effect may depend on special conditions that may not be present on all organic
farms, and it is therefore very important to understand the process in greater depth before it
can be used as an effective safety provision.
One study (Tschape
et
al
. 1995) reported a foodborne infection by the verotoxinogenic bac-
terium
Citrobacter
freundii
in a nursery school in Germany caused by contaminated parsley
from an organic garden in which manure of pig origin was used. The bacterium produced
symptoms of gastroenteritis and Haemolytic Uremic Syndrome (HUS) in about 15 people, one
dying of HUS (Lund 2002). This seems to be the most recent case recorded, and predates the
establishment of defined standards and regular certification visits for organic farming. Although
most organic certification schemes are not meant to regulate general good practice in terms of
food safety, inspectors observing violations of general safety guidelines should still advise pro-
ducers to meet those standards as well as the special requirements for organic certification.
Additionally several surveys show that the restricted use of antibiotics in organic agricul-
ture reduces the problems of antibiotic resistance, a theme that is very important in relation to
zoonotic pathogens. These studies demonstrate that isolates of relevant bacteria from organic
dairy herds were significantly more susceptible to antimicrobials than those from conven-
tional herds in the USA, Denmark and Scotland (Tikofsky
et
al
. 2003, Sato
et
al
. 2004, Hoyle
et
al
. 2004).
Another disease, bovine spongiform encephalopathy (BSE, 'mad cow disease'), arises when
animals are fed contaminated tissues from other animals with the disease. Organic regula-
tions have never allowed the use of animal residues as feed for animals of the same species, and
although at least one cow raised in a conventional herd that was later converted into organic
did develop BSE, until now BSE has not been detected in any cattle born in organic herds
(Kouba 2003, BMVEL 2003). Technically these data represent a significantly lower statistical
risk from organic than from conventional meat, but since the overall risk is very small this dif-
ference does not have any measurable effect on consumer health.
Overall, while organic production methods may superficially appear to comprise more
risks for pathogen transmission from farm animals to humans than conventional farms, the
evidence indicates the opposite trend, although not complete safety. And if bad luck strikes,
pathogens from organic animals are more susceptible to antibiotics and are thus easier to
eliminate from patients.
Safety from toxic substances
Synthetic toxins intentionally applied to the food
Many consumers are concerned about the use of synthetic pesticides, food additives and veter-
inary medicines, which they perceive as possible health risks (O'Doherty Jensen
et
al
. 2001).
