A potentially lethal bacteria infects Horowhenua swim spots, prompting warnings to steer clear.

Cyanobacteria warnings have been issued at many of Horowhenua's major swimming spots.

The warnings were issued by MidCentral District Health Board on December 20 and still haven't been lifted. Horizons Regional Council's swim spot testing show Cyanobacteria present in the Ohau River at Gladstone, Kimberly Reserve or SH1, Wairarawa Stream at Waitarere Beach and Waikawa Estuary at Footbridge Rd.

Warnings to steer clear from swimming at these spots include not allowing your dog to swim there as Cyanobacteria are toxic but can even be deadly if it's ingested.


Environment Canterbury Regional Council state on its website that Cyanobacteria occurs naturally all year round, but are more common during the warmer months.

It says the formation of mats or blooms of cyanobacteria is linked with changes in environmental conditions.

These include a combination of warm temperatures, sunlight, low or stable river flows and nutrients.

It warns that not all cyanobacterial blooms are visible, and toxins can remain after visible blooms disappear.

Symptoms of the poisoning in dogs include panting, lethargy, muscle tremors, twitching and convulsions.

These symptoms usually occur within 30 minutes, and can be fatal.

The website says toxic algae mats produce a nasty neurotoxin that effects the nervous system, as little as one table spoon if ingested can kill a small child or dog.

¦ To check the health of your swim spot you can visit www.horizons.govt.nz and search their safe swim spots map.