High risk from toxic algae in Hutt River

Greater Wellington and Regional Public Health are warning that the risk from toxic cyanobacteria in the Hutt River remains high, following the death of a dog in Upper Hutt over the weekend.

A one year old cocker spaniel died shortly after coming into contact with cyanobacteria on the edge of the Hutt River near Heretaunga Park. Dogs are particularly susceptible to cyanobacteria toxins because they like to scavenge at the rivers edge.

Cyanobacteria is identifiable as thick clumps (mats) of algae washed up at the rivers edge, which is brown or black in colour.

River users should avoid contact with mats of algae, taking extra care that children do not touch mats.  These mats may contain toxins which can cause vomiting, diarrhoea and skin irritation in humans.

Symptoms of poisoning in animals exposed to the type of cyanotoxins identified in the Hutt River and Waikanae River during a similar incident in 2005/06 included lethargy, muscle tremors, fast breathing, twitching, paralysis and convulsions. In extreme cases death can occur within 30 minutes of signs first appearing. Pet owners are urged to contact their veterinarian immediately if they are concerned their pet may have been poisoned by the algae.

Latest monitoring by Greater Wellington shows that the amount of cyanobacteria is high in the Hutt River from Birchville downstream.

It’s been three weeks since there has been a decent rainfall event in the area, which combined with warm weather, has resulted in rapid cyanobacteria growth. Algal cover is likely to remain high until there’s another decent rainfall.

Other areas at risk

There is also moderate risk from cyanobacteria mats in the Waikanae and Waipoua rivers.  River users should keep an eye out for cyanobacteria mats in these rivers and avoid contact with them if present.

Further information

Local councils have posted warning signs at key access points along the river.  See www.gw.govt.nz/current-warnings for up to date information.

For general information about toxic algae, including pictures and what to do if you are worried about possible contact see www.gw.govt.nz/toxic-algae.

Practices may also wish to download the Greater Wellington Toxic Algae warning to display.

For more information, please contact:
Medical Officer of Health
Regional Public Health
(04) 570 9002 or (04) 570 9007 (after-hours)
Email: healthprotection [at] huttvalleydhb [dot] org [dot] nz

Summer Greenfield
Senior Environmental Scientist
Environment Monitoring and Investigations
Greater Wellington Regional Council
(04) 830 4069
Email: summer [dot] greenfield [at] gw [dot] govt [dot] nz