No abstract

This paper summarises findings from the Pathogen Transmission Routes Research Program, describing pathogen pathways from farm animals to water bodies and measures that can reduce or prevent this transfer. Significant faecal contamination arises through the deposition of faeces by grazing animals directly into waterways in New Zealand. Bridging of streams intersected by farm raceways is an appropriate mitigation measure to prevent direct deposition during herd crossings, whilst fencing stream banks will prevent access from pasture into waterways by cattle that are characteristically attracted to water. Riparian buffer strips not only prevent cattle access to waterways, they also entrap microbes from cattle and other animals being washed down-slope towards the stream in surface runoff. Microbial water quality improvements can be realised by fencing stock from ephemeral streams, wetlands, seeps, and riparian paddocks that are prone to saturation. Soil type is a key factor in the transfer of faecal microbes to waterways. The avoidance of, or a reduction in, grazing and irrigation upon poorly drained soils characterised by high bypass flow and/or the generation of surface runoff, are expected to improve microbial water quality. Dairyshed wastewater should be irrigated onto land only when the water storage capacity of the soil will not be exceeded. This "deferred irrigation" can markedly reduce pollutant transfer to waterways, particularly that via subsurface drains and groundwater. Advanced pond systems provide excellent effluent quality and have particular application where soil type and/or climate are unfavourable for irrigation. Research needs are indicated to reduce faecal contamination of waters by livestock.

A series of field experiments assessed the ability of sloping (8°) 5-m-long by 2-m-wide grass buffer strips to trap the faecal microbes Escherichia coli and Campylobacter. The microbes, applied within dairy-farm effluent, were washed into the strips by surface runoff generated at rates of 4-13 litres/min using a water sprinkler system. The effluent and surface and subsurface outflows at the lower end of each plot were sampled for microbial analysis. Flow rate influenced the timing of peak microbial concentration in outflow and the recovery of both microbes. Under high flow, recovery rates varied from 15-100%, and hence entrapment was often minimal. Under the slowest rate of water application, entrapment was much greater (95%), at least over the 40 min of water application. During large runoff events, and where preferential flowpaths A04026; Online publication date

cDairy cows have been identified as common carriers of Campylobacter jejuni, which causes many of the human gastroenteritis cases reported worldwide. To design on-farm management practices that control the human infection sourced from dairy cows, the first step is to acquire an understanding of the excretion patterns of the cow reservoir. We monitored the same 35 cows from two dairy farms for C. jejuni excretion fortnightly for up to 12 months. The objective was to examine the concentration of C. jejuni and assess the genetic relationship of the C. jejuni populations excreted by individual cows. Significant differences (P < 0.01) in C. jejuni fecal concentration were observed among the 35 cows, with median concentrations that varied by up to 3.6 log 10 · g ؊1 feces. A total of 36 different genotypes were identified from the 514 positive samples by using enterobacterial repetitive intergenic consensus (ERIC)-PCR. Although 22 of these genotypes were excreted by more than one cow, the analysis of frequencies and distribution of the genotypes by model-based statistics revealed a high degree of individuality in the C. jejuni population in each cow. The observed variation in the frequency of excretion of a genotype among cows and the analysis by multilocus sequence typing (MLST) of these genotypes suggest that excretion of C. jejuni in high numbers is due to a successful adaptation of a particular genotype to a particular cow's gut environment, but that animal-related factors render some individual cows resistant to colonization by particular genotypes. The reasons for differences in C. jejuni colonization of animals warrant further investigation.

Sentinel freshwater mussels (Hydridella menziesi) were immersed in rivers at sites impacted by faecal pollution. The indicator bacterium, Escherichia coli, was recovered from all mussels including those at a forest control site, but concentrations were highest at sites impacted by either treated sewage or treated meat-processing waste water, or by inputs from dairy farms. The three pathogens sought were recovered from mussels, except those at the forest (control) site: Campylobacter jejuni and Campylobacter coli at treated sewage sites; Salmonella typhimurium and C. jejuni at treated meat-processing waste water sites; and C. jejuni and Yersinia enterocolitica at sites impacted only by dairy farms. The FRNA bacteriophage concentration was high in mussels impacted by sewage or sheep-processing waste water but was low when the input was only from dairy farms. Mussels up to 23 km from a sewage discharge contained a high concentration of FRNA suggesting that there could be a health risk due to viruses, although the water did not exceed recommended guidelines. Pathogens were also sought in untreated waste waters. C. jejuni and C. coli were recovered from both sheep-processing and beef-processing waste waters and the only sewage isolate identified was confirmed as C. coli. Salmonella spp. were recovered from all waste waters, with S. typhimurium phage type 135, isolated from a sample of meat-processing waste water, and from mussels immersed 1 and 5 km down stream of that plant's discharge. Y. enterocolitica was M 980 3 7