This issue of Water Resources Update focuses on microbial pathogens. We highlight some surprising research findings and ongoing efforts to reduce faecal contamination of our waterways. – Jim Cooke, Centre Leader.
Why children shouldn't play in duck ponds
It may still surprise some people to learn that water is typically most contaminated in catchments with large numbers of birds, rather than farmed animals.
That’s one finding of a ‘Pathogen Occurrence and Human Health Risk Assessment Analysis’ published by the health and environment ministries. The analysis was produced by a team of experts led by NIWA scientist Graham McBride.
The study covered 10 indicators and pathogens which either point to or pose some degree of human health risk. Every fortnight for about 15 months, participating regional councils sampled water from 25 sites chosen to represent five catchment types: birds, dairy farming, municipal, forestry/undeveloped, sheep/pastoral. Samples were analysed in four national laboratories. Additional information included weather and other water quality data and catchment surveys.
Bird catchments were the most contaminated for almost all microorganisms sampled. Dairy catchments were sometimes the second most contaminated, but were slightly less contaminated with Campylobacter than the sheep/pastoral catchments. Sheep catchments also recorded the greatest numbers of Salmonella. Municipal and forestry/undeveloped catchments were generally the least contaminated.
‘Given recent advances in strain genotyping, I’d like to see more detailed studies of the source and pathogenicity of the microorganisms we found to help better quantify the risks,’ says Mr McBride. ‘For example, the strains of Campylobacter carried by birds may be less hazardous than those carried by ruminants.’
Full report: www.mfe.govt.nz/publications/water/freshwater-microbiology-nov02/