Animal and human faecal pollution in New Zealand rivers

Sentinel freshwater mussels (Hydridella menziesi) were immersed in rivers a t sites impacted by faecal pollution. The indicator bacterium, Escherichia coil, was recovered from all mussels including those at a forest control si te, but concentrations were highest at sites impacted by either treated sew age 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 coil at trea ted sewage sites; Salmonella typhimurium and C. jejuni at treated meat-proc essing waste water sites; and C. jejuni and Yersinia enterocolitica at site s impacted only by dairy farms. The FRNA bacteriophage concentration was hi gh in mussels impacted by sewage or sheep-processing waste water but was lo w when the input was only from dairy farms. Mussels up to 23 km from a sewa ge discharge contained a high concentration of FRNA suggesting that there c ould be a health risk due to viruses, although the water did not exceed rec ommended guidelines. Pathogens were also sought in untreated waste waters. C. jejuni and C. coil were recovered from both sheep-processing and beef-pr ocessing waste waters and the only sewage isolate identified was confirmed as C. coil. Salmonella spp. were recovered from all waste waters, with S. t yphimurium 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 dis charge. Y. enterocolitica was recovered from most samples of animal waste w ater. It appears that pathogens are introduced into New Zealand rivers by a ll major sources of faecal contamination.