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From: TSS ()
Subject: BSE waste water could slip through cracks, expert fears
Date: July 10, 2007 at 10:44 am PST

BSE waste water could slip through cracks, expert fears
U of A microbiologist says new rules not fool-proof
Margaret Munro, CanWest News Service
Published: 2:36 am
Brains, eyes, tonsils and other select tissues from older cattle -- even bone dust generated when their spines are split open -- will be diverted out of the food chain to meet new federal rules that go into effect Thursday in an effort to eradicate mad cow disease.

But the water that pours down the drains at slaughterhouses and rendering plants continues to be considered risk-free of mad cow, also called or bovine spongiform encephalopathy, or BSE.

"It's not contaminated," says Freeman Libby, an official with the Canadian Food Inspection Agency, who likens it to "normal waste water going down your sink drain."

Font: ****Mike Belosevic, a University of Alberta microbiologist, is not convinced, however.

"They are making a huge assumption," Belosevic says, noting there are "zero data" to back up claims that water from slaughterhouses and rendering plants is free of prions. "The point is no one has even looked."

He stresses the risk is "infinitesimally small," given that only 10 cases of mad cow disease have turned up so far in Canada. But the possibility of prions entering and persisting in waste water cannot be discounted, says Belosevic, who is leading a $2-million project to learn more about the water used in cattle-processing facilities.

Currently, saws, knives and other equipment are washed or hosed off after use to remove tissues that will be diverted into a special waste stream as part of a multimillion-dollar effort to eradicate mad cow disease in Canada.

The tissues, called "specified risk material," or SRM, are where infectious prions can concentrate. Prions are rogue proteins that induce abnormal folding of other proteins, leading to fatal brain-wasting diseases such as mad cow, scrapie in sheep and Creutzfeldt-Jakob disease in humans.

More than 100,000 tonnes of such SRM is generated in Canada every year, the bulk of it in Alberta. Until now it has been processed like other cattle waste, most of it ending up in pet food and feed for non-ruminant animals such as chickens, and as fertilizer and bone meal.

Once the new ban comes into effect, however, most of Canada's SRM will be taken to rendering plants in Calgary and reduced to dry meal. It will then be hauled to a Coronation, Alta., landfill and buried, according to officials at the rendering company that will be handling the material.

During rendering, the wastes are compressed and "dewatered."

"Along with that squeeze of water you may release prions," says Belosevic, who explains the proteins can persist for years and may be "bioaccumulating" in waste water ponds.

"Say you had a rendering plant and two or three infectious animals came through in a year," he says. "You may find it in leachates from that rendering plant."

Federal and Alberta research networks are

financing Belosevic's project, called "prion inactivation in the environment." Over the next two years, the researchers will look for prions in waste water from rendering plants and slaughterhouses. Belosevic says the team is working with industrial partners, but declined to identify the companies or plants involved.

BSE waste water could slip through cracks, expert fears
U of A microbiologist says new rules not fool-proof
Margaret Munro, CanWest News Service
Published: 2:36 am
He says hunting for the infectious particles is not easy. Interpreting the results of the tests could be even trickier, as it's unclear if prions in water can lead to the disease.

"That's a question for the risk assessors," says Belosevic.

His team is more interested in finding out if the prions are slipping through -- and if they are, in deactivating them.

Font: ****The only proven ways of destroying prions are with high-temperature incineration, or a combination of heat, chemicals and high pressure.

Composting is another option, although it isn't thought to completely destroy prions.

A Canadian Food Inspection Agency team in Ottawa recently reported that heat and microbial processes generated by burying infected material reduces the number of prions, but doesn't completely eliminate them.

"We don't anticipate composting is going to be so effective that it will totally destroy the prions, but it could decrease the infectivity," says Belosevic.

Even so, there is talk of composting SRM. Several small slaughterhouses in northwestern

Ontario are proposing to pool their waste at one compost site, says Libby, who is national director of the food inspection agency's feed ban task force.

Restrictions will, however, be put on the use of any compost made with SRM, he says, noting that it will not be allowed on grazing land or gardens, although it might be permitted on Christmas tree farms and golf courses.

To test their ideas in the lab, the researchers are busy rounding up a supply of prions. Earlier this year, for example, they infected 30 hamsters with scrapie at a secure federal laboratory in

Ottawa and hope to harvest billions of prions.

© The Edmonton Journal 2007

Prion White Paper
Issue: Can the potential presence of prions in land applied biosolids result in food chain contamination with the subsequent development of animal and human disease?

What are Prions and What are the Diseases Attributed to Exposure to Prions?
“Prion” refers to a particular kind of protein found in animal tissue. Most prions occur in a normal, harmless form, but there are abnormal or infectious forms. The normal, harmless form has the same sequence of amino acids as the abnormal form, but the abnormal, or infectious, form takes a different folded shape. (Epstein, 2005)1. In their normal, non-infectious state, it is believed that prions are involved in cell-to-cell communications and other important functions. Unlike bacteria and viruses, prions do not contain genetic material. However, like viruses and bacteria, prions are infectious and replicate in host tissues. Throughout this white paper the word “Prion” is used to indicate the abnormal, infectious form of prions. Prions cause normal celluar proteins to convert to the abnormal or prion form. In animals affected with prion-caused diseases, prions have been found mainly in the brain, spinal cord, lymph nodes, spleen, tonsils, eyes, pancreas, adrenal gland, and blood. In studies with mice, prions have been observed in muscle tissue. Prions have not been observed in manure or biosolids.

It is now commonly accepted that prions are responsible for a number of previously known but little-understood animal (including human) diseases generally classified under transmissible spongiform encephalopathy diseases (TSEs) (Wikipedia, 2005)2. These diseases affect the structure of brain tissue and are all fatal and untreatable. The TSE diseases that have received the most attention recently include chronic wasting disease (CWD) that affects deer and elk, bovine spongiform encephalopathy (BSE) that affects cattle (“Mad Cow Disease”)(Collinge, 2001)3, and Creutzfeldt-Jacob Disease (CJ Disease) that affects humans.

What Are the Sources of Prions That May be Relevant to Wastewater Treatment and Biosolids Production?

• Abattatoirs, Animal Rendering, and Meat Processing Operations - These operations, if they process BSE-contaminated cattle, can serve as a potential source of prions in wastewater treatment plants. However, preliminary calculations on a worst case scenario in which the entire prion-infected brain of a slaughtered cattle were released into a wastewater treatment plant over the span of a day indicate that the resulting concentration of prions in the treatment plant’s effluent would be significantly less than the prion concentration necessary to infect an individual (assuming that the individual was directly consuming the treatment plant’s effluent (Pederson, 2005)4). A recent effluent guideline (USEPA, 2004a)5 and general pretreatment standards promulgated by the United States Environmental Protection Agency (USEPA) for the Meat and Poultry Products Point Source Category, and the ability of local wastewater treatment authorities to impose these guidelines and standards on these discharging operations make it extremely unlikely that this assumed mass of prion-infected tissue would ever enter the sewer.

• Landfill Leachates - Leachates from landfills can act as a potential source of prions to a wastewater treatment plant if the landfill accepts for disposal carcasses from BSE-contaminated cattle or CWD-contaminated deer or elk. However, in areas where CWD is being actively managed, the disposal of contaminated deer or elk carcasses in municipal solid waste landfills appears to be an uncommon practice. CWD management approaches in the United States in areas of known prion infectivity typically involve incineration of infected materials. For example, the State of Wisconsin’s policy is to test potentially prion- infected deer and elk and to subsequently incinerate all prion positive deer and elk carcasses and landfill all prion negative carcasses (Kester, 2005)6. Because prions are positively charged, and have been described as being “sticky”, they are likely to strongly sorb to solids and soils both in the landfill and to the landfill liner (Taylor, 2005)7. Therefore, even if BSE-contaminated (prion) material were disposed in a municipal solid waste landfill that sent leachate to a wastewater treatment plant, the potential that significant concentrations of prions would be contained in the leachate is very low. This should be confirmed once analytical methodologies are developed to determine prions in leachate.

• Urine, feces, and blood from CJ Disease patients - Several researchers (Gabizon, et. al. 20018; Reichl, et. al. 20029) have reported the presence of prions in the blood and urine of CJ Disease patients. Prions have not been reported in the feces of CJ Disease patients. It should be noted that the concentrations of prions in the blood and urine of CJ Disease patients would be relatively low and, after entry into the sewer with a vast amount of dilution available, even lower compared to the concentrations of prions in the neural tissue of these patients or in the neural tissue of BSE-infected meat that these patients may have consumed. This is important to consider since the risk assessment results presented below are based on these significantly higher prion contaminated materials than the levels of prion contamination in blood, urine, or untreated wastewaters.

Have Prions Been Detected in Wastewater or Biosolids?
There are no reports in the scientific literature of the presence of prions in municipal wastewater or in biosolids. Currently, no validated analytical methodologies are available for the determination of prions in municipal wastewater influent, treated municipal wastewater effluent, or in biosolids. Once these analytical methods are developed, prions might be detected and quantified in these media. However, based on the discussion above, their concentrations would be expected to be extremely low and not capable of causing subsequent infection either through direct contact or indirectly through food chain contamination. Analytical methodologies exist for the detection of prions in brain and other neurological tissue, mammalian lymphoid tissue, blood, and urine. Prions have been detected in each of these biological materials (Pederson, 2005)4.

What are the Methods of Prion Destruction?
Prions found in environmental media or in residuals such as biosolids appear to be extremely resistant to degradation and loss of infectivity. Current methods for denaturing prions and significantly reducing infectivity such as high temperatures and treatment with alkalis and bleach are applicable to prion-contaminated animal tissues but are not applicable to wastewater and biosolids treatment.

What Current Research and Measures Are Underway to Mitigate/Prevent Prion Entry Into Wastewater Treatment Plants?

• Abattatoirs, Animal Rendering, and Meat Processing Operations - The U.S. EPA in 2004 published an effluent guideline (regulatory standard) for the Meat and Poultry Products Point Source Category that will result in a dramatic reduction in the amount of animal tissue that can be discharged directly into the aquatic environment. (USEPA, 2004a)5. The technologies associated with this standard are designed to enhance ambient water quality by reducing the amount of solids such as animal tissues, biochemical oxygen demand (BOD), and ammonia that can be discharged into the aquatic environment. Although this regulation does not pertain nationally to operations that discharge into sanitary sewers (“indirect dischargers”), local wastewater treatment authorities are free to impose the standard’s technologies on these indirect dischargers through local pretreatment limits where the potential for the processing of infected animals exist. These operations are also subject to EPA’s General pretreatment regulations which will also reduce solids input to the sewer. The United Kingdom has promulgated guidance for their meat processing industry on practices that minimize the amount of neurological tissue lost to the sewer (Gale and Stanfield, 2001)10.

• Landfill Leachates - EPA has issued guidance on the operations of municipal solid waste landfills that accept prion-contaminated animal carcasses for disposal (USEPA, 2004b)11. This guidance discusses the importance of liners and leachate collection systems and recirculation of the leachate in the landfill rather than discharge of the leachate to the wastewater treatment plant for containment of prions at the landfill site.

• Urine, Feces, and Blood from CJ Disease Patients - There are no current regulations, at least at the Federal level, that prohibit pathology laboratories or mortuaries from disposing of prion-contaminated tissue and fluids of CJ Disease patients into the sanitary sewer. However, EPA has developed a draft strategy to reduce the prion contamination threat from the discharge of wastewater into the sanitary sewer from pathology/necropsy and research laboratories working with prion-contaminated tissues. (USEPA, 2005a)12.

• Research - Currently, there is at least one research effort (the University of Wisconsin/Madison funded by EPA) underway to characterize the potential presence and fate of prions in wastewater treatment plants. These studies will also determine the potential for prions to partition into and concentrate in biosolids (USEPA, 2005b)13.

What Are the Properties, Fate, and Transport of Prions in Wastewater Treatment and in the Land Application of Biosolids?
Very little data in this area is available. Based on the properties of prions, it is expected that prions initially in wastewater (most likely at very small concentrations- see above discussion) will survive and most likely be attached to and be transported by solid particulates in the wastewater entering the wastewater treatment plant. Once in the wastewater treatment process, no significant decrease in prion infectivity or prion degradation is expected to occur because of prions’ resistance to physical and chemical conditions encountered in wastewater treatment plants.

Whatever little concentration of prions in the incoming wastewater, they are expected to strongly partition to and concentrate in biosolids during wastewater treatment. Research in progress will provide a quantitative estimate of this partitioning (USEPA, 2005b)13. Based on the physical and chemical stability of prions, it is expected that prions will persist in biosolids, albeit at expectedly very low levels with respect to potential infectivity and the very limited number of potential environmental transport pathways available to infect animals or humans.

Prions and their infectivity related to an animal TSE have been demonstrated to persist in soils for several years (Brown, 1991)14. Because of their strong affinity with solid particulates and, therefore, very low concentrations in the aqueous phase, prions are not expected to threaten human-consumed or animal feed crops through root uptake in biosolids land application. For the same reason, transport of prions to groundwater or surface waters from biosolids land application is not anticipated. Prions have no volatility so ambient air transport can be ruled out. The only potential significant environmental transport mechanism available for prions with subsequent exposure and potential infectivity to animals and humans is biosolids/soil ingestion by grazing ruminants and, theoretically, biosolids/soil ingestion by toddlers in a home garden scenario. However, for these potential pathways of exposure, it is highly unlikely that prion concentration in the biosolids could ever approach an infectious dose for either animals or humans based on the extremely high dilution that occurs in wastewater treatment plants if prion-contaminated tissue were discharged to these plants and the prions subsequently partitioned to the biosolids (see discussions in previous sections and the section below).

What is the Risk to Human Health From BSE in Wastewater Treatment?
In 2001, Gale and Stanfield performed a quantitative risk assessment for BSE in biosolids for land application to cattle pasturing and vegetable crop production in the United Kingdom (UK)(Gale and Stanfield, 2001)10. Using a worse case set of scenarios, they concluded: The risks to humans through consumption of vegetable crops are extremely low (approaches zero). Although the risks to cattle are higher, because of their higher exposure to soil and greater susceptibility to prion infectivity, the risk assessment model demonstrates that biosolids containing trace quantities of prions alone cannot initiate or sustain a BSE epidemic in the UK cattle herd. The conclusions are consistent with the findings from epidemiological studies, which so far, have not detected horizontal transmission of BSE (including transmission from BSE-contaminated pastures) (Gale and Stanfield, 2001). The risk assessment demonstrates the importance of containment of neurological tissue from animal processing operations and absolutely minimizing or eliminating the amount of neurological tissue from BSE-infected animals that enter the sewer system.

Other “first order” risk assessments and estimates have demonstrated under worst-case scenarios extremely low risks to the theoretically highest exposed population, the farmer, from prions in land applied biosolids . It should be noted that these risk assessments are performed on subpopulations that are at “bounded” maximum exposures. In reality, compared to these subpopulations that are used for risk estimation purposes, almost all people living in countries with mature and regulated agricultural industries are exposed orders of magnitude less to prions or for that matter to any other chemical or biological agent that can be found in trace quantities in biosolids or in background soils. This in turn results in orders of magnitude less risk to the general population from theoretical or actual exposure to these substances.

The information presented in this fact sheet strongly suggests that the risk of prion transmission directly to ruminants and indirectly to humans with subsequent infection from biosolids land application is extremely low and indeed is practically zero. Prion transmission via biosolids land application seems less likely than other potential food chain pathways such as the consumption of prion-contaminated feed in animal raising operations and prion transmission to or between humans via contaminated surgical instruments and blood products, all of which are relatively rare, and compared to which, biosolids transmission of prions is even rarer.

There is an ongoing need for additional research in the areas described in this fact sheet to better quantify the information presented herein. Results of this research should further expand the scientific knowledge based on the subject of prions.

1. Epstein E. and N. Beecher. 2005. Mad Cow Disease, Creutzfeld-Jakob Disease, other TSEs and Biosolids. J. Residuals Science and Technology. 2(3): 181-187.

2. Wikipedia. 2005. The Free Encyclopedia. “Transmissible spongiform encephalopathy”. Available on the Internet.

3. Collinge J. 2001. Prion diseases of humans and animals: Their causes and molecular basis. Ann. Rev. Neurosci. 24: 519-550.

4. Pedersen J. 2005. Personal communication from Joel Pedersen, University of Wisconsin/Madison, to Alan B. Rubin.

5. USEPA. 2004a. Effluent Limitations Guidelines and New Source Performance Standards for the Meat and Poultry Products Point Source Category. 69 Federal Register (173):54475-54555. September 8, 2004.

6. Kester G. 2005. Personal communication from Greg Kester, Wisconsin Department of Natural Resources, to Alan B. Rubin.

7. Taylor D. 2005. Personal communication from David Taylor, Madison (WI) Metropolitan Sewerage District, to Alan B. Rubin.

8. Gabizon R., Shaked G.M., Shaked Y., Karn-Inbal Z., Halami M., and I. Avraham. 2001. A protease resistant prion protein isoform is present in urine of animals and humans affected with prion diseases. J. Biol. Chem. 276(34): 31479-31482.

9. Reichl H., Balen A., and C.A. Jansen. 2002. Prion transmission in blood and urine: What are the implications for recombinant and urinary-derived gonadotropins? Human Reprod. (10): 2501-2508.

10. Gale P. and G. Stanfield. 2001. Towards a quantitative risk assessment for BSE in sewage sludge. Journal of Applied Microbiology. 91:563-569.

11. USEPA. 2004b. Recommended Interim Practices for Disposal of Potentially Contaminated Chronic Wasting Disease Carcasses and Wastes. Memorandum from: Robert Springer, Director, Office of Solid Waste to: RCRA Division Directors (Regions I-X), Superfund Division Directors (Regions I-X), OSWER Office Director. April 6, 2004.

12. USEPA. 2005a. EPA Draft Strategy Addendum to the Region 8 Local Limits Strategy. Discharges of Wastewater to Publicly-Owned Treatment Works (POTWs) from Pathology/Necropsy and Research Laboratories Working with Prion-Contaminated Tissue. Industrial Pretreatment Program (8P-W-P). May 9, 2005.

13. USEPA. 2005b. Preliminary Results from the First Phase of a Two Phase Study Examining the Fate of Prions in Wastewater Treatment. Poster presentation. USEPA Science Forum, Washington, DC. May 17, 2005.

14. Brown P. and D.C. Gajdusek. 1991. Survival of scrapie virus after 3 years internment. The Lancet. 337:269-270.

We establish that prions bound to
Mte are orally bioavailable, and that, unexpectedly, binding to Mte
significantly enhances disease penetrance and reduces the incubation period
relative to unbound agent. Cox proportional hazards modeling revealed that
across the doses of TSE agent tested, Mte increased the effective infectious
titer by a factor of 680 relative to unbound agent. Oral exposure to
Mte-associated prions led to TSE development in experimental animals even at
doses too low to produce clinical symptoms in the absence of the mineral. We
tested the oral infectivity of prions bound to three whole soils differing
in texture, mineralogy, and organic carbon content and found soil-bound
prions to be orally infectious. Two of the three soils increased oral
transmission of disease, and the infectivity of agent bound to the third
organic carbon-rich soil was equivalent to that of unbound agent. Enhanced
transmissibility of soil-bound prions may explain the environmental spread
of some TSEs despite the presumably low levels shed into the environment.

Oral Transmissibility of Prion Disease Is Enhanced by Binding to Soil

"There was an enhancement of infectivity and we're estimating roughly a 700-fold enhancement of infectivity."

WHAT about the watersheds, aquifers and springs, that flows through layers of sand, clay, rock, and or gravel, and the content thereof (i.e. SRMs), filtering down on the fields of crops and animals grazing ???

5. What is the scope of the provisions on material collected from wastewater
The animal material covered by the provisions in Articles 4(1)(d) and 5(1)(b) is only animal
material collected from primary treatment, namely animal material retained in the filters and
skimming of solids such as sludge from the primary physico-chemical treatment process
onsite. It is believed that this material can easily be collected and disposed of in accordance
with the Regulation, but if necessary, the Commission is ready to clarify further by defining
the scope of the provisions in Annex I.
The Regulation requires that all materials collected when treating wastewater from rendering
plants processing category 1 material – such as cadavers of potentially BSE infected animals
and slaughterhouses in which BSE specified risk material is removed – must be disposed of
by incineration, co-incineration or landfill following sterilisation. The only exception to this
rule is where such wastewater contains no specified risk material or part of such material.
This is in line with current opinions of the Scientific Steering Committee.
Bearing in mind that the existing EU legislation including the TSE Regulation does not deal
with the issue of disposal of material collected from wastewater, the new rules on wastewater
from facilities handling category 1 materials are necessary as this type of material may be
contaminated with the BSE agent. Its disposal in urban wastewater treatment plants should
be prevented to avoid possible dissemination of the BSE agent into the environment. Since
sewage sludge from urban waste water treatment plants is commonly used on agricultural
land as organic fertiliser without having undergone any effective sterilisation, there may be a
potential risk of spreading BSE this way. Lord Phillips (2000) highlighted the potential risk
of spreading BSE in the UK through this practice in the BSE Inquiry report.

Evaluation of Bovine Spongiform Encephalopathy (BSE) Infection Risk of Cattle via Sewage Sludge
from Wastewater Treatment Facilities in Slaughterhouses in Japan

Takehisa YAMAMOTO1), Sota KOBAYASHI1), Akiko NISHIGUCHI1), Takashi NONAKA1) and Toshiyuki TSUTSUI1)

1) Applied Epidemiology Section, National Institute of Animal Health

(Received 21-Jul-2005)
(Accepted 24-Oct-2005)

ABSTRACT. Scattered SRM residues from BSE-infected cattle are possible to contaminate sewage during the slaughtering process in slaughterhouses. A proportion of the sludge discharged from wastewater treatment facilities at slaughterhouses has historically been processed into fertilizer. We therefore investigated the associated risk of BSE infection to cattle via sludge-derived fertilizer. Each stage of the process associated with BSE exposure was qualitatively evaluated and quantitative evaluations were subsequently performed using infectious dose as a unit of concern. Results of these qualitative evaluations indicated that installation of filter(s) at the drains to the wastewater treatment facilities has been undertaken by many slaughterhouses and has decreased the likelihood of SRM contamination of sewage. The level of sludge-derived fertilizer ingested by cattle was considered to be very low since the fertilizer is mixed with the ground soil, and the amount of soil ingested by cattle is likely to be small. Results from the quantitative analysis indicated the total infectious dose ingested by cattle in Japan from an infected cow has been estimated to be 5.5 × 10-3 ID50. Preventing scattering of SRM during the slaughtering process, installing filters to the drains with the removal of residues from the drain water and preventing the application of sludge-derived fertilizer to pasturelands would be effective to reduce the risk. Although the limited extent of available information, this study should provide useful indication for the development of an inclusive risk assessment for slaughterhouse sludge in the future.

To cite this article:
Takehisa YAMAMOTO, Sota KOBAYASHI, Akiko NISHIGUCHI, Takashi NONAKA and Toshiyuki TSUTSUI “Evaluation of Bovine Spongiform Encephalopathy (BSE) Infection Risk of Cattle via Sewage Sludge from Wastewater Treatment Facilities in Slaughterhouses in Japan”. J. Vet. Med. Sci.. Vol. 68: 137-142. (2006) .

Prions in soil can be detected below 1ppb
Methods for detecting prions remaining in soil have been developed by French
researchers, who say they can now identify the presence of prions at levels as low
as 0.2 parts per billion.8
Prions have been reported to persist in soil for years after contamination. The
adsorption and desorption of a recombinant prion protein was studied by the
research team using natural soil samples and a clay mineral (montmorillonite)
which is known to be a strong adsorbent for organic molecules, including proteins.
An original electro-elution method was developed to extract prion protein from
both montmorillonite and natural soil samples, allowing quantification when
coupled with rapid prion detection tests. The method produced concentrated prion
protein extracts and allowed detection of prions at levels as low as 0.2 ppb in
natural soils.
The montmorillonite was found to have a large and selective adsorption capacity
for both the normal and the aggregated prion protein. Adsorption occurred mainly
via the N-terminal domain of the protein, say the researchers. Incubation with
standard buffers and detergents did not desorb the full length protein from
montmorillonite, emphasizing a largely irreversible trapping of prion protein by this
soil constituent.


Slaughterhouse waste needs risk assessment
Japanese researchers have investigated the need to control the spread of
potentially contaminated slaughterhouse waste containing residues of specified risk
material (SRM), especially when these are recycled as fertilizer for agricultural
SRM residues from BSE-infected cattle can contaminate slaughterhouse sewage
during the slaughtering process, and a proportion of the sludge discharged has
historically been processed into fertilizer. The researchers investigated the
associated risk of BSE infection to cattle via sludge-derived fertilizer applied to
pastureland. Results of their qualitative evaluations indicated that the level of
sludge-derived fertilizer ingested by cattle was considered to be very low since the
fertilizer is mixed with the ground soil, and the amount of soil ingested by cattle is
likely to be small. The total infectious dose ingested by cattle in Japan from an
infected cow was estimated to be 5.5 x 10(-3) ID(50). Preventing the scattering of
SRM during the slaughtering process, installing filters to the drains with the
removal of residues from the drain water and preventing the application of sludgederived
fertilizer to pasturelands would be effective to reduce the risk. The
researchers call for the development of a more comprehensive risk assessment for
slaughterhouse sludge.


US finds 3rd case of BSE
The United States Department of Agriculture (USDA) confirmed on March 13 the
country’s third case of BSE.19 The animal tested ‘inconclusive’ on rapid tests
conducted the previous week. USDA Chief Vet John Clifford stated "The samples
were taken from a non-ambulatory animal on a farm in Alabama. A local private
veterinarian euthanized and sampled the animal and sent the samples for further
testing, which was conducted at one of our contract diagnostic laboratories at the
University of Georgia. The animal was buried on the farm and it did not enter the
animal or human food chains.”
Under USDA testing protocols, surveillance samples are sent to contract
laboratories for screening tests. If the sample is found to be inconclusive on the
screening test, it is then shipped to the National Veterinary Services Laboratories in
Ames, Iowa, for an additional rapid test and two confirmatory tests: the
immunohistochemistry test and the Western blot test. An animal is deemed
positive for BSE if either of the two confirmatory tests returns a positive result.
The animal was believed to be a dairy cow over 10 years of age, and hence likely to
have been born prior to the 1997 feed ban. The USDA will attempt to locate
animals from the cow’s birth cohort and any offspring, and to determine any feed
history that may be relevant. Tracing its cohort may prove difficult as the case was
reportedly found without ear tags, tattoos or brands, and spent less than a year on
the farm where she died. The only record appears to be her sale at an auction last
year. The problem highlights the slow progress being made in the USA towards a
full tracking scheme for cattle, which has been promised for 2009.

6.6 Members noted that a large number of pathways had been examined in
the original assessment including sewage sludge and waste water from
abattoirs. Although it was not in DNV’s remit to examine all potential pathways
affecting prions, Members suggested other potential environmental pathways
that could assessed, including the disposal of human blood and cadavers from
CJD victims. It was also suggested that because of the many scientific
uncertainties relating to the propagation and degradation of BSE infectivity in
the environment, it was important to test the sensitivity of the risk assessment to
different assumptions.

Proposal for an Order controlling the disposal of waste waters from rendering plants processing ruminant material

January 2001

Section VII
Prevention and control of
waterborne zoonoses

Canada spreads scrapie sludge
Thu, 04 Jan 2001 By A.J. BLAUER, Ottawa Sun
The grass might be greener on the other side of the fence, but how safe is that crud it's growing in?
An environmental researcher is questioning the practice of spreading municipal "biosolids" on agricultural land after some diseased sheep tissue found its way into the local mix.

"Biosolids is just a designed name to make the mind go numb," said Maureen Reilly, founder of Sludge Watch. "We're really turning our farms into landfills."

Between February and July 2000, tissues and fluids infected with scrapie, the sheep equivalent of Mad Cow Disease, were released into Ottawa's sewage treatment stream after being disinfected at a lower-than-ideal temperature by the Animal Disease Research Institute (ADRI) on Fallowfield Rd.

The sewage was then "stabilized" by the region's wastewater treatment plant and some of it spread on local farmland as a cheap source of nitrogen and other nutrients.

Dave Robertson, manager of the region's wastewater treatment branch at the time, said an investigation raised no contamination concerns. About 1,000 metric tonnes of water-separated sludge was spread over 125 hectares of local farm land during the period in question.

According to the Canadian Food Inspection Agency, the diseased material would have been rendered 99.9999% sterile [based on what study? -- webmaster] when the ADRI inadvertently "cooked" it 13 degrees cooler than the target temperature of 134C.

"There's no 100% guarantee -- scientists won't go there -- but we don't believe there's a problem," said CFIA spokesman Andrew Adams.

But that incident doesn't put an end to the controversy of using sewage for fertilizer. Even after treatment, Ottawa's spreadable biosolids contain some viruses, bacteria and toxins. Better cleaning equipment would cost $50 million, plus millions more in operating costs.

But even in its current form, some argue that biosolid spreading saves the city money and provides a free source of soil nutrient for cash-strapped farmers.

Paul Cooper, a director at the Ottawa-Carleton Regional Federation of Agriculture, said there's no evidence of health problems after seven years of biosolid spreading in the region. A public meeting on the issue is slated for Jan. 16 at the Manotick Legion Hall.

Comment (Maureen Reilly): "Here's what happened: The Animal Disease Research Institute in Ottawa Ontario is researching a live test for scrapie and is waiting for the sheep in their pen to show signs of scrapie then killing and performing disection. There were 6 infected sheep in the 5 month period. It is not certain to me how much of the infected blood and tissue was placed in the autoclave and treated at suboptimal temperatures.

However for 5 months the temperature was lowered to 121 rather than 134 degrees and the tissues released into the sewage treatment plant. The sewage treatment sludge (including the tissues) is agriculturally applied. However, the scrapie specialists at the lab were never told that the sludge with the tissues was placed on farmland. Therefore, when the lab issued their press release they thought the sludge went to landfil or incineration.

The municipal officials and the ministry of Evironment officials failed to consider the possible infectivity of any unprocessed prions that went to land application. The quality of the 'biosolids' was not considered at any point.

Now, in this instance, the amount of infective prion tissue may indeed have been relatively minimal and relatively diluted by the sludge, but the problem remains that the provincial and municipal officials failed to inform the scrapie researchers of the final fate of the tissues on farmland. The farmers have not been informed. The agriculture Ministry and the provincial scrapie expert for the provincial ministry of agriculture were not informed, the Ministry of Natural Resouces (wildlife) was not informed.

We know so little about the incubation period and infectivity of prions that a prudent course of action would be to determine which farms received suspect sludge and to monitor those farm animals and nearby wildlife for effects for the next few years. Greater accountablilty and transparency is required."


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