Pathogen Pathways – Best management practices
2. Introduction
Faecal contamination of freshwaters is widespread in New Zealand (Parliamentary Commissioner for the Environment 2004; McBride et al. 2002) with concentrations of the faecal indicator E. coli often exceeding 1000 per 100 mL and with Campylobacter and other pathogens often present. These findings, coupled with the high incidence of notified campylobacteriosis (Savill et al. 2001) and cryptosporidiosis (Duncanson et al. 2000) compared to other developed countries, has raised concerns over the public health risk from pathogens of faecal origin (including Campylobacter, Cryptosporidium oocysts, Giardia cysts, and Salmonellae) in New Zealand’s fresh waters. Furthermore, concentrations of faecal microbes have restricted the recreational use of freshwaters and shellfish aquaculture in estuaries and, increased water treatment costs. Recent studies have identified a link between cattle productivity and levels of faecal contamination in cattle drinking water, e.g., Willms et al. (2002).
The sources of faecal contamination of freshwaters are often diverse and can include point source discharges of wastewater from sewage treatment and animal processing plants, and contamination by wild and feral animals (Ferguson et al. 2003). However, good evidence has existed for some time to indicate that grazing livestock are a major, diffuse source of faecal contamination to freshwaters (e.g., Wilcock et al. 1999), typically outweighing other sources in catchments that are predominantly used for pastoral farming. As a consequence, the New Zealand Ministry of Agriculture and Forestry (MAF) established (in 2003) the consortium-based Pathogen Transmission Routes Research Program (PTRRP) to quantify the relative significance of key pathogen transmission routes from farm animals to water bodies. In addition, the study has identified and evaluated measures with which to mitigate the faecal contamination of each transmission pathway.
The purpose of this report is to summarise the key pathogen transmission routes and describe each of the best management practices (BMPs) identified, providing a justification for its selection. Primarily, the focus is upon faecal microbes, however, where a particular BMP has been shown to be effective at mitigating other agricultural pollutants particularly sediment and nutrients, brief details are provided. It should be noted that detailed results from experimental studies are not discussed in this report and, instead, appropriate references are provided. Furthermore, the cost-effectiveness of each BMP and any social implications are not evaluated here. This report summarises the main findings of the PTRRP as regards pathways of contamination, and describes BMPs to achieve improved microbial water quality downstream of pastoral agriculture in New Zealand.
Contact for Enquiries
Phil Journeaux
Manager
North Island Regions
Sector Performance Policy
MAF Policy
Private Bag 3123
Hamilton
NEW ZEALAND
Phone: +64 7 957 8313
Fax: +64 7 957 8315
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