Sludge Watch ==> Prions can accumulate in the soil - where ammended with prion containing sludges

[maureen.reilly at sympatico.ca]

The UK Spongiform Encephalopathy Advisory Committee (SEAC) forwarded a new
research article  this past week:

"Interactions of prion proteins with soil", Liviana Leita, et al, Soil 
Biology &
Biochemistry, (Elsevier) accepted November 7, 2005"
Excerpts:
"Results clearly demonstrate that both the no infectious (PrPc) and 
infectious
(PrPsc) forms are absorbed by all soils. . . . . The strong interaction of 
PrPsc
with soil favors the accumulation of prions in soils, especially if amended 
with
prion-containing organic fertilizers and/or whenever TSE-affected animal
carcasses, placenta, and excreta in general are buried or laid at the soil
surface."

"In conclusion, although these results cannot precisely define the nature of 
the
bonds between prions and soil components, especially if they are reversible
under conditions other than those tested in the present study, the apparent
strength of such interactions suggests that prions can be retained, and
accumulate in soil, especially if amended with prion-containing organic
fertilizers and/or whenever TSE-affected animal carcasses, placenta, and 
excreta
in general are buried or laid at the soil surface (Miller et al, 2004). If 
the
adsorbed prions also retain their pathological activity (Brown and Gajdusek,
1991; Leita et al., unpublished results), they could represent a hazardous
environmental source of infectivity, and provide a further explanation for 
the
horizontal transmissibility of TSE forms, such as scrapie and CWD."

Please note these Italian researchers specifically identify  "organic
fertilizer" and "excreta" as potential sources of prions.   This  European 
study
parallels and reinforces the recent conclusions of University of Wisconsin
scientists (Johnson, Pedersen, et al 2006) that prions in soil survive for 
long
periods and may contribute to horizontal transmission of TSEs (transmissible
spongiform encephalopathies) in animals.

The US Composting Council is a wide-reaching, well read forum for 
discussion.
Last week, in response to a posting,  I had a call from an oral surgeon  who 
was
concerned about dealing with medical instruments used on elderly patients 
who
may potentially be infected with sporadic Creutzfeldt Jakob Disease (sCJD).
His concerns are well founded since between 2 and 25% of Alzheimer's 
patients
are actually infected with sCJD, and standard autoclaving does not 
inactivate
infectious prions.    Some experts advise discarding medical instruments 
used on
patients who turn out to be infected with sCJD -- obviously an expensive
proposition.

I also received a call from a Southern California composter who questioned 
the
accuracy of my statement that  EPA approved sewage sludge pathogen reduction
methods do not inactivate prions.   He was concerned about top dressing his
Class A sewage sludge biosolids compost on playgrounds and childrens' ball
fields.   His caution is noteworthy and well justified because children with
their undeveloped immune systems and hand-to-mouth (eat dirt) behavior are 
most
at risk of infection from any pathogens, including human and animal prions,
which may survive in Class A sludge biosolids.  He was quite interested to 
learn
that in June 2004, the US EPA  made a $100,000 grant to University of 
Wisconsin
researchers (Judd Aiken, Trina McMahon,  Joel Pedersen, Craig Benson) to
investigate the fate of prions discharged to wastewater treatment plants.  
In
2002, the Wisconsin Dept. of Natural Resources  concluded the infectious 
prions
pass through the sewage treatment plant and are reconcentr
ated in the sludge biosolids.

The US EPA recently committed to upgrading the Process Design Manual  for 
Sludge
Treatment and Disposal..    The original 26 year old document doesn't even
mention prions as a potential sludge pathogen.       If the US EPA is going 
to
continue promoting land application and top dressing of both Class B and 
Class A
sewage sludge biosolids on hay fields, grazing lands, dairy pastures,
ballfields, playgrounds and home flower and vegetable gardens, the  
potential
risks of human and animal prions in both Class B and Class A sludge 
biosolids
should be fully evaluated without delay.



Helane Shields, PO Box 1133, Alton, NH 03809   603-875-3842