Cyanobacteria (toxic algae) health warning placed on Lake Rotoroa (Hamilton Lake)
Waikato
National Public Health Service (NPHS) has issued a health warning for Lake Rotoroa (Hamilton Lake) due to a significant increase in cyanobacteria. Cyanobacteria is sometimes referred to as toxic algae.
Health warnings remain in place for Lakes Rotokaeo (Forest Lake), Waahi, and Waikare.
Health risks
“Cyanobacteria (toxic algae) can cause a range of symptoms. These may include asthma or hayfever‑type reactions, skin rashes, and stomach upset. It can also cause effects such as tingling around the mouth, headaches, trouble breathing, or changes in vision” says Dr Kate Meerkerk, Medical Officer of Health. These symptoms may appear hours after contact with affected water.
Scums formed during cyanobacteria (toxic algae) blooms often contain very high concentrations of toxins. They may accumulate along shorelines and can look unusual or interesting, which can attract children and animals, especially dogs. Dogs are extremely sensitive to cyanobacteria (toxic algae). Do not allow them to swim in, drink, or eat anything from affected lakes, as it can make them very ill.
What you should do
- Because any activity in or near these lakes may cause illness through skin contact or swallowing the water, people should stay away from the area.
- If you come into contact with the water, shower and change clothes as soon as possible, even if you feel fine.
- If you develop symptoms, seek medical advice or call Healthline on 0800 611 116
- Report any illness to the NPHS Waikato office on 07 838 2569
Where to check water quality
To find out whether a recreational waterway is safe to swim in, visit: