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

Abstract

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 ID 50 . 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.

A Quantitative Assessment of the Prion Risk Associated with Wastewater from Carcass‐Handling Facilities

“…The form of Equations (4) and (5) indicate that as more wastewater is produced, any infectivity present becomes more diluted. However, that same amount of infectivity is spread on more land, leading to more animals being exposed.…”

“…These regulations aim to address the environmental impact of spreading wastewater but do not specifically consider the animal health impacts. Several previous risk assessments have investigated the risk of BSE associated with abattoir effluents in Europe, (3,4) Japan, (5) and Australia (6) and for renderer and incinerator effluent in the United Kingdom. (7)(8)(9) However, the prevalence of certain TSEs (BSE in cattle and classical scrapie in sheep) has been steadily declining in recent years, and with considerable changes in the structure of SRM-handling industries in GB, a reappraisal of the TSE risk posed by wastewater is required.…”

Health Effects Associated with Wastewater Treatment, Disposal, and Reuse

“…The risk of bovine spongiform encephalopathy (BSE) infection in cattle through land application of slaughterhouse wastewater treatment sludge was assessed qualitatively and quantitatively (Yamamoto et al, 2006).…”

Prions in the environment

“…The risk of BSE from sources including landfills and rendering facilities contaminating drinking water has been evaluated, 6,7 as well as the risks to cattle from land-applied fly ash, slag, slaughterhouse sludge and meat and bone meal contaminated with BSE. [8][9][10] Due to the large dilution factors, the calculated risk of transmission was extremely low in all cases. However, CWD risks have not been quantified, and it is uncertain if adequate information is available to make credible assessments of prion transmission via environmental pathways.…”