Sybille Wildlife Research Center working on CWD composting study

Sybille Wildlife Research Center working on CWD composting study

AUGUST 8, 2024

LARAMIE REGION NEWS

If you have driven Highway 34 through Sybille Canyon recently, your attention may have been grabbed by what have been described by many as “giant coffins” outside of the Game and Fish Wildlife Research Center at Sybille. Rather than coffins, these are actually compost bins, designed to conduct research to evaluate the ability of the composting process to break down the prions that cause Chronic Wasting Disease (CWD). 

CWD is a chronic, fatal disease of the central nervous system that affects deer, elk, and moose. It is caused by abnormally folded proteins called prions. Early in the disease, animals may show no clinical signs of being sick, however as the disease progresses, animals lose weight, become lethargic, and eventually die. A major challenge associated with the spread of CWD is the ability for prions to persist in the environment. This can lead to contamination of habitats for years, facilitating the spread of the disease to new individuals through ingestion of contaminated forage.

Previous research has demonstrated that CWD-infected carcasses that break down naturally in the environment contribute to habitat contamination. This led researchers at Sybille to wonder if a more robust decomposition process, through composting, could reduce the amount of CWD prions left behind when an infected animal carcass breaks down.

“Composting creates a highly alkaline environment (high pH) that can lead to intense microbial activity and high temperatures,” explains Brie Hashem, Game and Fish research biologist at the Sybille Wildlife Research Center. “Those conditions promote protein breakdown, so we think CWD prions could be degraded or eliminated through that process. We have also added certain materials into the bins that we expect to enhance the composting process. Altogether, we are hoping these bins will produce the optimal conditions for the degradation of prions from infected elk carcasses.”

Construction of the bins was completed in late May, and the composting process began in June. Some bins contain whole elk carcasses and others contain butchered waste of elk to determine whether the composting process affects those two forms differently. All bins are outfitted with temperature and moisture sensors that allow researchers to monitor composting conditions for the duration of the experiment. Hashem anticipates that the project will continue through September, when she will test the compost, soil, and any liquids produced for presence of CWD prions. 

If the composting process is successful at reducing or eliminating CWD prions, it may provide another mechanism for disposal of CWD infected carcasses collected from the landscape or harvested by hunters. Current means to dispose of infected animal carcasses include incineration or landfills. If composting proves successful, additional studies could investigate the feasibility of using composting facilities as an added method to address carcass disposal. 

With hunting seasons fast approaching, hunters are encouraged to educate themselves about CWD. Game and Fish will be continuing its CWD surveillance testing program to track prevalence of the disease in deer and elk herds around the state. Any hunter may submit a sample for CWD testing, and certain hunt areas are designated for enhanced monitoring or mandatory sampling this year.

Bins have open tops to allow rainfall in. Additional moisture is also expected to enhance the composting process. The black wires seen in the bottom left corner connect to temperature and moisture sensors spread throughout the bins to monitor composting conditions.

Laramie Regional Office 307-745-4046

https://wgfd.wyo.gov/news-events/sybille-wildlife-research-center-working-cwd-composting-study

Published: 23 December 2022

Biodegradation of bovine spongiform encephalopathy prions in compost

Shanwei Xu, Sujeema Abeysekara, Sandor Dudas, Stefanie Czub, Antanas Staskevicius, Gordon Mitchell, Kingsley K. Amoako & Tim A. McAllister

Abstract To reduce the transmission risk of bovine spongiform encephalopathy prions (PrPBSE), specified risk materials (SRM) that can harbour PrPBSE are prevented from entering the feed and food chains. As composting is one approach to disposing of SRM, we investigated the inactivation of PrPBSE in lab-scale composters over 28 days and in bin composters over 106–120 days. Lab-scale composting was conducted using 45 kg of feedlot manure with and without chicken feathers. Based on protein misfolding cyclic amplification (PMCA), after 28 days of composting, PrPBSE seeding activity was reduced by 3–4 log10 with feathers and 3 log10 without. Bin composters were constructed using ~ 2200 kg feedlot manure and repeated in 2017 and 2018. PMCA results showed that seeding activity of PrPBSE was reduced by 1–2 log10 in the centre, but only by 1 log10 in the bottom of bin composters. Subsequent assessment by transgenic (Tgbov XV) mouse bioassay confirmed a similar reduction in PrPBSE infectivity. Enrichment for proteolytic microorganisms through the addition of feathers to compost could enhance PrPBSE degradation. In addition to temperature, other factors including varying concentrations of PrPBSE and the nature of proteolytic microbial populations may be responsible for differential degradation of PrPBSE during composting.

Snip…

Previously, our research group used protein misfolding cyclic amplification (PMCA) to confirm a reduction of PrPTSE seeding activity with 2 log10 in hamster 263K prions (PrP263K) and 3 log10 in CWD prions (PrPCWD) after 28 days in lab-scale composters18. In this same study, we also measured a 4.8 log10 reduction in PrP263K infectivity based on hamster bioassays after 230 days of field-scale composting. In this study, we (1) assessed the biodegradation of PrPBSE in lab-scale composters using PMCA and (2) in large bin composters in containment to estimate the degradation of PrPBSE using PMCA and an infectivity bioassay. The compost bin model was subjected to multiple heating cycles to generate a thermophilic composting period that was similar to our previous field-scale studies18 which resulted in a 4.8 log10 reduction in PrP263K infectivity.

Snip…

In general, thermophilic composting (i.e., temperature ≥55°C) has a hierarchy of essential factors that facilitate the biodegradation of waste materials and inactivation of pathogens. In this study, we successfully stimulated thermophilic temperature profiles that were similar to that observed during field-scale composting18. However, our composting model in biocontainment did not fully represent the field scale composting systems that could be used for the disposal of SRM or cattle carcasses. In containment, ~2 tonnes of feedlot manure were used over 120 days of composting, resulting in a ~1 to 2 log10 PrPBSE infectivity reduction. In contrast, in our field scale model18, ~100 tonnes of feedlot manure with 16 cattle carcasses were composted over 230 days resulting in a 4.8 log10 reduction in PrP263K infectivity. As a logical extrapolation, a longer composting duration and greater volume of biomass in the field-scale composters would likely enhance PrPBSE degradation. As a 4.8 log10 reduction of PrP263K infectivity was observed in the field-scale composters18, it would be surprising if inactivation of PrPBSE was not further enhanced in field-scale composting. In addition, Belondrade et al.65,66 demonstrated that commercial chemicals fully efficient on sterilization of PrP263K were inefficient for the inactivation of variant PrPCJD, suggesting PrP263K might not be a suitable model to validate the prion resistance to inactivation. Consequently, further investigation of PrPBSE degradation in field-scale composting is needed.

Previous studies documented the more recalcitrant nature of PrPBSE than other TSE agents. After exposure to acidic SDS, PrPBSE was 10 and 10 million fold more resistant to inactivation than PrPCJD and hamster PrPSc, respectively, as assessed by infectivity titration in transgenic mice64. Langeveld et al.67 also reported PrPBSE to be more resistant to wet heat conditions at 115°C than PrP263K and PrPCWD as measured by transgenic mouse bioassay. Our PMCA results suggested that 28 days of lab-scale composting resulted in a reduction of PrPTSE seeding capacity with ~ 2 log10 in PrP263K and ~ 3 log10 in PrPCWD in a previous study18 and ~ 3 log10 in PrPBSE in the current study. Different from chemical treatment of prion inactivation, compost is an exceedingly complex biological system, owning to changing temperatures and pH, and dynamic changes in microbial communities and the enzymes they produce during composting. Once PrPTSE enter the compost environment, a wide variety of physicochemical and microbiological processes can impact PrPTSE infectivity and seeding capacity. These uncontrolled factors might help to account for the variable inactivation observed in our PrPTSE composting studies. While this variability calls into question the utility of our composters for complete PrPTSE inactivation, it is encouraging that when our compost conditions were optimal, 28 days of composting effectively destructed PrPBSE replication capacity in vitro by 3 log10 (i.e., at least 99.9%). Currently, the Canadian government68 enacted a regulation on the limited use of composting for disposal of SRM under a temporary permit. It also requires a 5-year respite from cattle access to pasture or grazing land amended with SRM compost and from direct human consumption of annual crops produced from SRM compost amended field69. A recent study from UK7 reported that the same amount of PrPBSE infectivity remained in both clay and sandy soil over a 5-year period. Our studies suggests that the maximum PrPBSE degradation (up to 3–4 log10) can achieve in the lab-scale composters with the addition of feathers. Therefore, composting of BSE infected-SRM prior to subsequent land application could be an effective approach to reduce the risk of high titer PrPBSE persisting in the environment.

Conclusions

In this study, we successfully quantified PrPBSE degradation using PMCA and bioassay in two-scale composting systems. After 28 days, ~ 3 log10 reduction of PrPBSE seeding activity was observed in lab-scale composters. Addition of chicken feathers to the compost enhanced PrPBSE degradation, likely as a result of enrichment for keratinolytic bacteria. After 106–120 days, both BSE associated seeding activity and infectivity were reduced by 1–2 log10 in the centre, but only by 1 log10 at the bottom of bin composters. This suggests that placement of SRM in the centre of compost piles would be more amendable for the biodegradation of PrPBSE. Current CFIA policy on SRM destruction methods require at least 5 log10 reduction of PrPBSE to approve composting for disposal of BSE positive SRM. Our field-scale composting study18 demonstrated that 230 days of composting resulted in a 4.8 log10 inactivation in hamster PrP263K infectivity. However, PrP263K might be not a suitable surrogate model to validate the PrPBSE resistance in compost. The outcomes generated from this study did not meet this criteria, but do lay the foundational work needed to further optimize the degradation of PrPBSE in compost. Spatial variability in microbial activity within static compost piles makes it unlikely that the procedure will ever achieve the 5 log10 reduction in PrPBSE required for full regulatory approval as a disposal method of SRM.

https://www.nature.com/articles/s41598-022-26201-2

The abandoned UK factory left to rot after disease-ravaged cows were destroyed there

By ZAK GARNER-PURKIS, Investigations Editor

04:00, Sun, Jun 2, 2024

https://www.express.co.uk/news/uk/1905418/abandoned-meat-plant-role-scandal

SUNDAY, MARCH 19, 2023

Abandoned factory ‘undoubtedly’ contains dormant Mad Cow Disease that could threaten humans, Thruxted Mill, Queniborough CJD

https://bseinquiry.blogspot.com/2023/03/abandoned-factory-undoubtedly-contains.html