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  • From: <clearviewfarm AT bluefrog.com>
  • To: "Market Farming" <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] manures/GAP training
  • Date: Wed, 3 Mar 2010 12:03:01 -0800

Rivka,

Is Cornell not within easy reach of you?  I will be down there in a week and a half for a poultry meeting and can look up the article then, as long as my short memory allows me to!

Kurt Forman
Clearview Farm
Palmyra, NY 14522

--- organic87 AT frontiernet.net wrote:

From: Road's End Farm <organic87 AT frontiernet.net>
To: Market Farming <market-farming AT lists.ibiblio.org>
Subject: Re: [Market-farming] manures/GAP training
Date: Wed, 3 Mar 2010 14:54:14 -0500


On Mar 3, 2010, at 1:35 PM, KAKerby AT aol.com wrote:

Here is a link to the paper they cited in class:
 
 
Here is the title of that same paper, in case the above link gets butchered:
Survival of Escherichia coli O157:H7 in soil and on carrots and onions grown in fields treated with contaminated manure composts or irrigation water, by Mahbub Islam, Michael P Doyle, Sharad C Phatak, Patricia Millner, and Xiuping Jiang, Food Microbiology 22 (2005) 63-70
 
 

Thanks. The link does work, but only gets me to an abstract. The page has a tab to click to get the actual article; but it would cost me $31.50 to do so, and I'm not feeling rich enough right now. I don't think any library I have easy access to gets Food Microbiology.

Merely searching Google on "survival of escherichia coli soil" came back with a bunch of different studies, so there's quite a few to choose from.
 
As to your point about 'not all E coli are dangerous, and in fact most are beneficial', yes that is absolutely correct and that was discussed in class.  The general point is that, soil does NOT naturally carry E coli as part of the normal microbiological flora.  Only soils which have been pooped on (or irrigated with contaminated water) within the last 200 days, will carry E coli of any variety.  If Farmer Joe's production systems allow for E coli of any variety to get into his soil, then by definition at least some of his fields could have been contaminated by E coli from the more dangerous strains.  In other words, if Farmer Joe's fields can be contaminated by poo, then it's only the luck of the draw whether that poo will have come from an animal which carried the most dangerous strains. 

Well, yes. And if Farmer Joe is breathing, then he might be inhaling marijuana, or H1N1 flu virus. Maybe we'd better stop him from breathing, to make sure that he can't breathe the wrong thing.

Any field can be, and in practice will be, at least occasionally contaminated by "poo"; unless the crops are grown entirely indoors under sterile conditions; and it would have to be the kind of sterile conditions that involve sealed rooms with workers sticking their hands into gloves through ports. (After which I suppose each individual item would have to be sealed in sterile packaging, not to be opened until it reaches the final consumer.)

Birds fly through the sky, last I noticed. Mice get into an astonishing number of places, including many indoor places. And as you note, human workers also produce e coli, and while hygiene really needs to be and should be encouraged, there's no practical way to guarantee that absolutely everybody's hands and clothes are sterile every time they come into the field.

The issue really can't be, "is there some theoretical possibility that pathogenic E coli can get into this system", let alone "is there some theoretical possibility that non-pathogenic e coli can get into the system". The issue has to be, "What overall systems significantly decrease or increase the chances of pathogenic E coli, and other pathogenic organisms, being in the crop at harvest time?" The survival time of non-pathogenic strains, or even of pathogenic strains, while it's useful information, is only one of many factors to consider in overall management systems, and such survival itself is extremely likely to be affected by all sorts of other factors.

Again, we were told at the FDA meeting that there are strong indications that the use of "indicator organisms" techniques, at least as currently used, is not effective. Would you have major surgery based on the results of a medical test that gave massively more false positives than accurate results, possibly by factors of thousands or millions?

The whole point of the class was to show us how that contamination can occur, how long that contamination can last,

If they didn't test specifically for pathogens, then the study tells us nothing about how long the pathogenic strains can last; only how long at least one non-pathogenic strain can last. And if they didn't somehow absolutely guarantee that there was no later source of contamination, it doesn't even show that. And even if it did show those things, then unless or until results are available in a large number of studies done in different farming systems, soils, climates, etc. we don't know how any of those affect survival time.

It is certainly possible that pathogenic e coli can survive, for instance, in Kim's specific farming system for 210 days, or even for 2100 days. But that study is unlikely to prove it. It's also possible that specifically pathogenic strains can only survive in Kim's particular system for two and a half days before something beneficial in that farm's manure eats them. None of us knows the answer. It would be a good idea to find out. 

and what we can do to minimize it.  

We do indeed need to minimize it. The question is how we can actually do so. 

I did just read the abstract of the study, and it leaves most of my questions open (some of them may be answered in the full study.) It does state that they used "an avirulent strain of E. coli O157:H7"    and implies that that particular strain survived, though as I don't have the whole study it's not clear to me whether they did test for the specific strain or only inoculated with the specific strain (possibly along with whatever else was in the manure) and then tested for e coli in general. I also read "avirulent" to mean "nonpathogenic", so either this was only a nonpathogenic relative of the dangerous strain, or it had been modified in some way to make it safe; either of these might affect survival rates.

I also note that in order to get the strain they used into their manure composts, they inoculated the composts with the strain: presumably because they thought there was no pathogen in the material before they inoculated it. A large part of the question is, of course, how often manure from given species, living in particular ways, in particular areas, is actually infected with pathogenic strains; and how we can reduce the chances of its so being infected.

Pasture-raised animals and ruminant wildlife, even with no grain whatsoever, have been positively ID'ed as being sources of dangerous strains of E coli.

Yes, this I'm aware of. I don't know, however, whether they have been so ID'd only in circumstances in which they have been in contact with strains emanating from feedlots (for instance, because the strains got into their drinking water from runoff from feedlots); or whether the pathogen is as common in grass-fed animals and wildlife as it is in feedlots (if, say, 10% of feedlot livestock have it, but only 1% of livestock raised in small operations with some grain and some pasture and 0.1% of entirely grass-fed livestock have the pathogen, then the pathogen could still be massively reduced by getting rid of the feedlot technique-- please note I just made those figures up as examples! and that may not be what's actually happening). 

One of the nasty things about problematic living organisms produced by modern (or non-modern, for that matter) techniques is that they often don't stay where they started out. Decreasing the use of the techniques that caused them in the first place may still be a good idea.


-- Rivka; Finger Lakes NY, Zone 5 mostly
Fresh-market organic produce, small scale



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