Toxic algae in Hutt River deadly to dogs, harmful to humans

The dark "shadow" is the toxic algae mats on the river bed.

Greater Wellington Regional Council is warning swimmers to stay out of the Hutt River from Kaitoke Regional Park to where the river meets Wellington Harbour. This is due to the risk of swallowing pieces of toxic algae. Toxic algae is naturally occurring, but poses a significant risk to human and animal health if ingested.

Because of the warm, dry weather the toxic algae bloom in the Hutt River has increased significantly, and pieces are detaching from the riverbed which poses a risk to swimmers. Even small pieces of toxic algae can be fatal to people and dogs if swallowed. Young children are particularly at risk due to their size.

We advise against swimming anywhere along the Hutt River until further notice.

The algae forms leathery looking mats on rocks in the riverbed, ranging from blackish/brown to dark green in colour. These mats can come loose and wash up on the edge of the rivers, or floating in shallow water. As they dry out they turn light brown or white and produce a strong musty smell.

Deadly for dogs

Dogs love the musty smell and may try to eat the mats if they get the chance. The algae produces a powerful neurotoxin, and in extreme cases, dogs can die within 30 minutes after the first signs of poisoning.

The best thing you can do to keep you and your dog safe is:

-To know what toxic algae looks like and avoid it

-Check our monitoring information for a heads up where algae may be at dangerous levels – if in doubt keep your dog on a lead.

Henley Lake in Masterton often has high levels of toxic algae – we recommend you don’t let your dog swim in or drink from this lake.

If you think your dog may have eaten algae, take it to a vet immediately. Even a 50 cent size piece of algae can be deadly to a dog.

If you have been swimming in a river or lake and you feel unwell and have any of the following symptoms including nausea, vomiting, numbness, tingling, muscle twitches, shaking, weakness, breathing difficulties and potentially convulsions and loss of consciousness see your doctor.

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