Public health warning lifted for Lake Wainamu

Last Updated : 20 Oct 2023

October 20 UPDATE: Latest tests return negative for Leptospira

Following a positive result for Leptospira bacteria in Lake Wainamu last month, the council's Research and Evaluation Unit (RIMU) conducted follow-up sampling (taken on October 10 and 11) at Lake Wainamu, Waitī stream and Bethells lagoon.

The results became available today, and all samples have tested negative for Leptospira.

Public health warnings at the lake and on Safeswim will now be removed, however we ask the public to use caution as they would with any freshwater body after heavy rainfall events which can cause contaminated run-off from farmland.

We would like to remind the public that Lake Wainamu remains closed to the public following storm events earlier this year, as well as Lake Wainamu carpark and Lake Wainamu and Te Henga walkways.

October 6

Recent water testing by Auckland Council’s Research and Evaluation (RIMU) returned positive for leptospira (the bacteria that causes leptospirosis) at Lake Wainamu and we’re asking the public to avoid direct contact with the lake and the stream while further testing is carried out.

Our teams are working closely with Auckland Regional Public Health Service to monitor the contamination and determine the level of risk.

If you have been in or near the lake or the stream, that flows from the lake to Te Henga / Bethells Beach, and become unwell, we advise you to immediately see your GP and mention the possibility of leptospirosis.

As soon as the Safeswim team was made aware of the leptospira reading, ‘high-risk’ flags were issued for water quality concerns (swimming not advised) and safety warning (toxic bacteria leptospira) alerts against Lake Wainamu. 

We have also installed physical signs at the head of the public access track in the car park. The lake has been closed to the public since the storm events of early 2023 (and remains closed). Additionally, as part of the Waitākere Ranges Regional Park, dogs are not permitted in or near Lake Wainamu.

Additional testing is being considered for the lake, and particularly the stream which flows through the Te Henga / Bethells Beach settlement.

What is Leptospirosis?

Leptospirosis is an acute illness caused by infection with Leptospira bacteria. Symptoms can include fever, chills, headache, muscle aches, nausea, diarrhoea, abdominal pain, cough and red eye, and people affected often need hospital treatment.

It is not uncommon to see leptospira in rural waterways where feral animals are present and it can persist for a long time in freshwater bodies such as lakes and streams. (Source and for more: Auckland Regional Public Health Service website)

Where is Lake Wainamu?

Lake Wainamu is approximately two kilometres inland from Te Henga / Bethells Beach. The lake is within Lake Wainamu Scenic Reserve and administered by Auckland Council as part of the Waitākere Ranges Regional Park. A small portion of the lake edge and buffering vegetation is on private property.

How did Auckland Council become aware of this?

Auckland Council was recently contacted by a member of the local community and alerted to a case of leptospirosis. Subsequent testing of the water in the lake (conducted by Massey University) came back positive for leptospira.

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