Toxic algae blamed for death of two dogs

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By Mark Price on Wed, 10 Feb 2010
Your Town: Mosgiel | News: Dunedin | Environment

A toxic algae is being blamed for the death of two dogs in Mosgiel and has prompted warnings to parents and caregivers.

Otago Regional Council director of environmental information and science Dr John Threlfall said last night he was still awaiting the result of tests.

However, it was probable the dogs had swallowed the algae Phormidium while drinking from the low-flowing Silver Stream.

The black, shiny algae gives off a toxin and Dr Threlfall said it could be harmful to humans.

"Caregivers should supervise young children playing close to the Silver Stream to ensure they don't touch or eat any algal material.

"Dog owners should also keep their pets clear of the river."

Otago medical officer of health Dr Derek Bell said the algae could cause allergic reactions including asthma, eye irritations, rashes, blistering around the mouth and nose and gastro intestinal disorders including abdominal pain, cramps and diarrhoea.

He advised anyone affected to seek medical advice.

Dr Threlfall said it was the first time the algae had been noted in the Silver Stream and council staff would be puting up warning signs today and trying to determine the extent of the problem.

The algae was common in many waterways, including the Kakanui and Waianakarua Rivers which frequently had small patches.

"As long as it's not in places where people swim or dogs frequently get walked it's probably there and nobody knows anything about it."

However, the area at Mosgiel where it had been found was popular with dog-walkers and people with children.

mark.price@odt.co.nz

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Another poison that is harmless?

Submitted by caz on Wed, 10/02/2010 - 8:39pm.

These poisons are being laid everywhere in NZ. Did the brains behind our Government officials never think to look up the dangers in laying these poisons so close to our houses? Obviously most of them live in Auckland or Wellington and they will never come in contact with any of these poisons. But we will and so will our children and grand children. I'm just hoping that a vet will tell us the truth once these dogs have been tested.

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Phormidium

Submitted by srusak on Wed, 10/02/2010 - 4:29pm.

Like broadifacoum, the toxin produced by Phormidium is considered lipophilic and not very soluble in water.
Interestingly, Phormidium is a genus of cyanobacteria that is not usually toxic, but it can produce toxins under certain conditions. Thus, the presence of Phormidium does not confirm the presence of the toxin. I would like to know what tests are being done to determine cause of death for the dogs, and who is doing those tests.

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Nasty stuff indeed...

Submitted by srusak on Wed, 10/02/2010 - 3:59pm.

True, I can't imagine anyone would eat 750g of poison pellets, but a dog which has a taste for dead possums could certainly get a lethal dose, as could a human who eats wild pig.

Broadifacoum is indeed lipophilic and its solubility in water is indeed low. As a result, water is an unlikely vector for movement of this poison through the ecosystem. As a result of its lipophilicity, broadifacoum accumulates in the fatty tissue of organisms - not just possums and rats; insects and birds are poisoned too.

Broadifacoum is subject to a process called bioaccumulation. (This bioaccumulation is why you don't see as many Australasian harriers in Silverstream, since the poisoning operations started there.) Because of its persistence, cumulative potential and high toxicities for various wildlife species and humans, it is rightly considered an environmental pollutant.

A poisoned animal will suffer progressively worsening internal bleeding, leading to shock, loss of consciousness, and eventually death. Nasty stuff indeed. Just Google it if you need more information.

Regarding poisoning the water; I think they have that covered with the cyanide baits which are also used in the silverstream area. The cyanide pellets used for possum
control in New Zealand contain 800g/kg (80%) of potassium cyanide, which is soluble in water to the tune of 71.6 g/100 ml at 25 degC. The average lethal dose for an adult human is about 0.3 g. You do the math.

Come on people, this is basic ecology: organisms interact with each other and with their physical and chemical environments. We are not just poisoning the possums and rats; we are poisoning the entire ecosystem.

The information sheet for cyanide baits in NZ can be found at the link below. It says "Never lay poison near a house or in a public place." nasty stuff indeed.

http://www.nzfsa.govt.nz/acvm/publications/notes/cyanide-study-notes.pdf

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Nasty stuff, but...

Submitted by jamesg on Wed, 10/02/2010 - 1:09pm.

The 15mg fatal dose for a human would mean eating 750g of pellets. That's quite a lot.
You also note that broadifacoum is lipophilic, which it is. And like many other lipophilic substances, it doesn't dissolve in water. So how exactly is it polluting the water?

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Cyanide and brodifacoum in Silverstream

Submitted by srusak on Wed, 10/02/2010 - 10:17am.

During a recent hike in the Silver Stream area near Mosgiel I noticed lots of poison bait stations had been set up. I guess the intent of these poison bait stations is to poison animals. It seems probable that the dead dogs mentioned in this article were poisoned by either cyanide or brodifacoum from the poison baits. There are simple tests for this.
It is too bad that Dunedin's natural environments are being poisoned in the name of "pest control." I wish Silver Stream was a safe place for dogs and children to explore and play, but unfortunately the water and soil have been poisoned by "Pestbusters". Brodifacoum is highly lethal to mammals and birds, and extremely lethal to fish. It is a highly cumulative poison, due to its lipophilicity and extremely slow elimination.The estimated average fatal dose for an adult man is about 15 mg.
The Dunedin City Council should check the use of all poisons (cyanide, brodifacoum, 1080, etc.) for pest control purposes on council land. Any objective cost-benefit analysis would show that it is not worth poisoning our land and water to kill a few possums and rats.
This article is about poisoned dogs. The next article could be about poisoned australasian harriers (kahu) in the Silverstream area. I hope we do not need an article about poisoned children before action is taken to stop the use of poison for "pest control" purposes on council land.

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