If in doubt, keep out, health warnings for Canterbury waterways

With the long weekend almost here, recreational water users are being reminded to avoid contact with some Canterbury and South Canterbury waterways.

Dr Alistair Humphrey, Canterbury Medical Officer of Health, says health warnings remain in place where there’s potentially toxic blue-green algae (cyanobacteria) in a number of areas around the regions.

"Make sure you check the health warnings for toxic algae before going near any waterways this long weekend,” Dr Humphrey says.

"And if in doubt, keep out.” Algal blooms can produce toxins harmful to humans and animals; people should avoid contact with the water where algal blooms are present until further notice. The algae is particularly dangerous for dogs.

"Animals that show signs of illness after coming into contact with toxic algae should be taken to a vet immediately. Symptoms of cyanotoxin poisoning in dogs include panting, lethargy, muscle tremors, twitching and convulsions – which usually occur within 30 minutes of exposure."

Dr Humphrey says people who come into contact with toxic algae can also experience unpleasant symptoms.

"Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms visit your doctor immediately and please let your doctor know if you have had contact with the water,” Dr Humphrey says.

People should never drink water from a waterway where a health warning is in place and they should also avoid eating fish and shellfish taken from areas where warnings are in place.

"Boiling the water does not remove the toxin. If fish are eaten, remove the gut and liver and wash in clean water."

Dr Tim Davie, Environment Canterbury Chief Scientist, says it is not possible to monitor every reach of every stream and river in Canterbury so we concentrate on sites where we know people swim.

"We monitor 52 popular freshwater swimming sites in Canterbury and similar number of beaches; the results are shown on the Environment Canterbury and the Land, Air, Water Aotearoa (LAWA) websites," Dr Davie says.

"If you're re swimming at non-monitored sites, we encourage you to check the stream bottom for what look like black mats. If there are significant black mats and particularly if pieces are breaking off, you should not swim or allow dogs at the site."

 Potentially toxic algae is currently present in the following locations in the region:

• Te Waihora/ Lake Ellesmere
• Te Roto o Wairewa/ Lake Forsyth
• Lake Rotorua (Kaikoura)
• Hurunui River at State Highway 7 (including the swimming hole behind the Balmoral campground) and State Highway 1
• Waikirikiri/Selwyn River at Glentunnel
• Te Nga Wai River at Te Nga Wai Bridge (near Pleasant Point)
• Opihi River at Saleyards Bridge (near Pleasant Point), near State Highway1 and near the Waipopo Huts
• Pareora River near the Pareora Huts
• Hakataramea River near the State Highway Bridge
• Cust Main Drain near Skewbridge Rd.

Visit the Environment Canterbury website for more information on swimming quality in Canterbury.

You can also contact Community and Public Health for more information on health warnings 03 364 1777.

Facts about cyanobacteria:
• The algae occur naturally but can increase rapidly during warmer months.
• If the water is cloudy, discoloured, or has small globules suspended in it, avoid all contact.
• Not all cyanobacteria blooms are visible to the naked eye and toxins can persist after the blooms disappear.
• Cyanobacteria concentrations can change quickly with changing environmental conditions (e.g. wind). Avoid contact with the water if a health warning is in place.