Professor Elliott said the blooms of algae can release toxins and can be identified as a "messy green colour" in the water.Northern Ireland Environment Agency said there was no visual algae bloom in the water (Image: Getty).

Explaining what happened when he took the dogs for a walk on farmland near their rural home in Dunham-on-Trent, Nottinghamshire, Russell, 56, said: ‘There’s a beck and a pond and they were playing happily in and around the water for about an hour.

"There have been blue-green algae blooms in Austin in previous years, but we have not been aware of any effects from neurotoxins," Austin city officials said in a recent statement warning owners not to let their dogs swim in an area lake..

Dogs are typically very ill and need immediate intensive veterinary treatment to survive.The risk to cats is smaller as they are unlikely to swim but may come into contact with the algae on the banks of an affected lake.David Grant MBE was a vet at the RSPCA Harmsworth Hospital for Animals.