Alarm at E coli found in Canterbury rivers
An antibiotic-resistant E coli strain has been found in three Canterbury rivers, a discovery that could have far-reaching consequences for human health.
Canterbury District Health Board clinical microbiologist Dr Joshua Freeman says news an antibiotic-resistant E coli and other E coli strains are now in the Ashley, Selwyn and Rangitata rivers means it is time for a national survey of just what human health-threatening bacteria are in our livestock.
The Fish and Game NZ finding was the first time Freeman had heard of antibiotic-resistant cTXM genes in E coli in New Zealand rivers, he said.
‘‘We know these can confer resistance to a lot of antibiotics – penicillin products – in hospitals and communities. That takes out a huge range of workhorse antibiotics and leaves us with second-tier antibiotics.’’
The last livestock bacteria survey was about 10 years ago, Freeman said.
‘‘We didn’t find much at the time. This suggests the landscape has changed.’’
The river sampling was undertaken after anglers raised concerns about the risk of infection due to river pollution and the increasing number of dairy cows in Canterbury. Water was collected from the Ashley, Selwyn and Rangitata rivers in May and September and tested at Massey University.
The results showed the rivers contained E coli, antibiotic resistant E coli and a dangerous strain of bacteria called shiga toxinproducing E coli or STEC.
STEC infection can cause severe gastroenteritis, including bloody diarrhoea and kidney failure. The two most common E coli strains found in the testing only come from ruminants, such as cows. Fish and Game said the test results showed the harmful organisms were present at levels that could impact on human health. Otago University, Wellington, department of public health professor Michael Baker said about a quarter of people affected by the shiga-toxin E coli had to be hospitalised. About 10 per cent contracted hemolytic uremic syndrome, a potentially life-threatening condition that could damage the kidneys.
Dairy cattle put 250,000 tonnes of untreated sewage into the environment every day, Baker said.
‘‘That all has to go somewhere. ‘‘We really do have a major health hazard there to manage.
‘‘We have to weigh that Martin Taylor Fish and Game NZ against it being a major industry.
‘‘It’s disappointing now that we have another thing to worry about, rather than enjoying our freshwater rivers and swimming holes. As a New Zealander, I find it really disappointing.’’
Canterbury medical officer of health Dr Alistair Humphrey said the concern was that antibioticresistant cTXM genes could spread from one bacteria to another. ‘‘Then there will be some infections that cannot be treated if the population of bacteria that cause the infection become antibiotic-resistant.
‘‘Our rivers are getting dirtier, even with our farmers being as compliant as they are meant to be. We have got too many cows.’’
ECan chief scientist Dr Tim Davie said the regional council took the presence of E coli in rivers and streams seriously.
‘‘STEC are derived from ruminant mammals, including both sheep and cattle, and can be ingested by humans through contact with animals or swallowing infected water.
‘‘We manage this risk through stock exclusion rules as well as encouraging fences and buffer strips at the edges of rivers and streams to prevent stock excrement entering the water.’’
There was ‘‘urgent need’’ for research into the health risks associated with differing concentrations of STEC and other pathogens in the waterways.
Fish and Game NZ chief executive Martin Taylor said the results were disturbing.
‘‘The results indicate swimming in these rivers could be like playing Russian roulette with the health of you and your family.’’
‘‘Swimming in these rivers could be like playing Russian roulette with the health of you and your family.’’