Risk management for disease exposure - Morris Report (M8)

The disease risk assessment was prepared by Professor Roger Morris CNZM, a Registered Veterinary Specialist in Epidemiology. It provides a comprehensive evaluation of pathogen hazards associated with land application of digestate biofertiliser to pasture and feed crops in the New Zealand context, drawing on a meta-analysis of 121 qualifying studies on pathogen reduction in AD systems. Morris reviewed all World Organisation for Animal Health (WOAH) listed animal diseases and major zoonoses (161 diseases in total) against the biofertiliser exposure pathway. The vast majority are not relevant because their transmission route (insect vector, respiratory, etc.) makes it unrealistic for them to be infectious in biofertiliser.

Biofertiliser Disease Risk ExposureThe Morris study concludes that microbiological risks (other than spore-forming Gram-positive organisms) associated with the use of biofertiliser can be eliminated provided that pasteurisation at 70°C for 60 minutes is undertaken, preferably after digestion of Digestate Guidelines DBPAS05 Group A feedstock (e.g. food waste).  Regarding spore-forming Gram-positive organisms, the risk cannot be eliminated but it can be adequately managed by utilising current on-farm animal health vaccinations, observing a 21 day withholding period, adjusting the pathogen monitoring testing, and reporting requirements of the Digestate Guidelines.

These conclusions apply to only for the application on pasture and feed crops; the direct application to human food crops eaten raw or undercooked requires a separate, more comprehensive risk analysis.

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