Risk and Prioritization of Gaps in Knowledge in Managing Pathogens Associated with Intensive Livestock Production

Abstract

From this review it is clear that the relative risk posed by zoonotic pathogens in hog manure to human health in this region is low, provided guidelines in place for manure handling are followed. Nonetheless, education and vigilance are needed to prevent unforeseen occurrences that might affect the risk level. In contrast, there is significant potential risk to health associated with the application of untreated manure to fields cropped for human food production, particularly fields containing horticultural and other crops likely to be consumed without cooking. Since manure used as fertilizer in Manitoba is continuously commingled while stored in EMS (where it is biologically stable at ≤4°C, the possibility for application of manure containing viable pathogens is high. Risk is minimized by early spring application but ≥90 d at 25°C are required (we hypothesize) to ensure absence of pathogens from manure. This is an issue of immediate concern that should be addressed by development of minimum hold periods in EMS and/or treatments of manure to shorten pathogen viability. Temperature and pH are two options to consider, but it must be borne in mind that Campylobacter, Yersinia, and Listeria are all alkali-tolerant pathogens. The potential long term risk is that with continued increases in hog production in Manitoba, pathogens will be recycled with greater frequency and at higher concentrations. Eventually, animal densities will be reached in regions of the province that cannot be safely sustained without transport of manure to outlying districts for land application which will further increase pathogen distribution.