An Upper Hutt woman is warning dog owners to be cautious around the Manawatu River after her dog died mysteriously during an outing this week.
Sarah McTaggart took her 4-year-old dog Mack swimming in the river on Tuesday, just up from the boat ramp on Matakarapa Rd, Foxton.
Mack, a border collie cross, was an avid swimmer.
"He just loved the water so he was in there for an hour and a half, or two hours."
He played and chased sticks happily while he was in the water, but almost as soon as he got out, Ms McTaggart realised something was wrong.
"Pretty much as soon as he got in the car, his eyes were dilated, and he was not looking good. His body went really limp and there was no muscle control."
Ms McTaggart believes Mack was also having seizures.
"When we got to Levin we rang the emergency vet, and they tried everything, but they didn't know what was going on."
Mack died soon after the vets arrived - he had been completely healthy before the swim, Ms McTaggart said.
A spokeswoman for Levin and Horowhenua Veterinary Centre, which treated Mack, said the vets had considered the possibility of an algal bloom in the river, which can be fatal for dogs.
The vet centre had immediately notified Horizons regional council, which sent inspectors to check the length of the river.
"They spent hours, lifting boulders and checking the river from where they were right up to Palmerston North. They found no trace of algal bloom, but they are continuing to monitor it just in case. They take this sort of thing very seriously."
Ms McTaggart said she planned to have Mack cremated, and she and her husband would have a small memorial for him at his favourite swimming spot on the Hutt River.
Algal blooms vary in toxicity and are caused by nitrogen getting into waterways from farming.
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