Pathogen Pathways – Contamination of water bodies via artificial drainage
Individual objective summaries
This report covers research outputs for Objectives 3, 6 and 9 of the multifaceted research programme "Pathogen Transmission Routes: Farm Animals to Water Bodies".
Objective 3: Pathogen contamination of artificial drains
(Climate delayed, completed September 2003)
The experimental work was delayed until September 2003 because of insufficient rainfall in spring 2002.
Experimental summary and results
The experimental work was carried out at the research site at No. 4 Dairy Farm, Massey University, during late September/early October 2003. Drainage from plots receiving both natural and simulated rainfall was sampled to compare the effects of either: a recent grazing by dairy cows or a 19-day spell from grazing. Thermophilic Campylobacter, E. Coli, Cryptosporidium oocysts and Giardia cysts counts were determined in the drainage water samples.
Enumeration of thermotolerant Campylobacter by the most probable number (MPN) technique identified that Campylobacter was present in all drainage water samples. Populations ranged widely with the highest populations typically occurring immediately after grazing events. Cryptosporidium oocysts were only confirmed in one drainage water sample, which was not from one of the recently grazed plots. The presence of Giardia cysts was confirmed in samples from three of the four drainage plots. However, numbers and occurrence was higher for the plots that had had a 19-day spell from grazing, compared to the recently grazed plots. This indicates that fresh dung was not a source of Giardia cysts but cysts were able to survive in soil environment since the previous grazing.
Objective 6: Timing of rainfall post grazing and artificial drain contamination
(Completion date June 2004)
Simulated rainfall (October 2003) events were used to test the hypothesis that the prevalence of thermophilic Campylobacter, E. Coli, Cryptosporidium oocysts and Giardia cysts in drainage water would decrease over time with each subsequent post-grazing rainfall event.
Experimental summary and results
Two plots received a single simulated rainfall irrigation following a 12-day spell from grazing, which generated drainage and surface runoff. Two other similar plots received three separate simulated rainfall irrigation events; the first was immediately after grazing (Day 1), again 2 days after (Day 3) and finally 8 days after grazing (Day 9). After overnight grazing, fresh dung samples were sampled for enumeration of thermophilic Campylobacter and E. Coli, as well as screening and enumerating Cryptosporidium oocysts and Giardia cysts. The fresh dung spots were enriched with a cultured Campylobacter spike. Drainage and surface runoff water samples were collected and the prevalence of culturable Campylobacter and E. Coli (Days 1 & 9 only) and numbers of Cryptosporidium oocysts and Giardia cysts were determined.
Campylobacter was present in all fresh dung spots sampled, but concentrations were highly variable confirming earlier observations that individual cow shedding of Campylobacter is highly individualistic. Resampling of dung spots 2 and 8 days after showed that Campylobacter continued to survive in the dung spots for at least 9 days, with no clear trend of populations decreasing with time. Fresh dung did not contain Cryptosporidium oocysts or Giardia cysts.
The prevalence of thermotolerant Campylobacter in drainage water was high immediately after grazing and tended to decrease over time with each subsequent simulated rainfall event. However, Campylobacter was still present in drainage samples collected up to 19 days after grazing. Indicating survival of Campylobacter in the soil environment or another source such as fresh bird faeces. Cryptosporidium oocysts were almost absent in drainage water, with only one sample containing oocysts. Giardia cysts were present in many of the samples coming from both the recently grazed plots and plots having up to a 19 day spell from grazing. The cyst source was not fresh dung but could be cysts surviving in the soil, or old dung spots, from a previous grazing, or from recently deposited bird faeces. Numbers of Giardia cysts were highly variable between plots and with time. The grazing on 25 September 2003 had no clear effect on elevating Giardia cysts numbers, however, at the grazing on 7 October 2003 the highest levels recorded typically came from drainage water generated immediately after grazing.
Objective 9: Contamination of surface runoff under dairying
(Early opportunistic experiment, completion June 2005)
Experiments that were used to complete research Objectives 3 and 6 also generated surface runoff. The opportunity was taken to quantify the volume of surface runoff and collect extra samples to quantify the movement of Campylobacter, E. Coli, Giardia cysts and Cryptosporidium oocysts in runoff.
Experimental summary and results
The experimental summary for this objective is the same as for Objective 6. The prevalence of thermotolerant Campylobacter in surface runoff water showed a similar trend to drainage water. Prevalence was high immediately after grazing and decreased over time with each subsequent simulated rainfall event. Again, Cryptosporidium oocysts were not present in any of the surface runoff water samples, but Giardia cysts were present in some of the samples coming from both the recently grazed plots and plots having up to a 19 day spell from grazing. Like with drainage water, numbers of Giardia cysts in runoff water were highly variable between plots and with time. Again, the grazing on 25 September 2003 had no clear effect at elevating Giardia cysts numbers, however, at the grazing on 7 October 2003 highest levels recorded typically came from surface runoff water generated immediately after grazing.
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