The Vet Bristol is urging dog owners to be vigilant about the waterways from which their dogs drink this summer.

Vets at the Hengrove-based clinic warn that still, or slow moving, water may contain contaminants that are harmful, and potentially deadly, to dogs.

The warning follows reports of the tragic deaths of three dogs who became ill after drinking from a lake that was contaminated with blue-green algae. Initial animal symptoms, which include muscle tremors, vomiting, diarrhoea and seizures, can lead to death in as little as 15 minutes.

Other dangers of slow-moving waterways include water tainted with rodent urine, which can cause potentially fatal leptospirosis. Bristol and neighbouring areas including Somerset and South Wales have seen a number of cases of dogs contracting leptospirosis.

Liz Gath, a veterinary surgeon at The Vet Bristol said: “The summer months are now upon us, and so it’s not surprising that dog owners take their pets on long walks in the countryside. It’s one of the joys of dog ownership and dogs, being dogs, love to follow their noses and jump into our waterways for a refreshing drink.

“However, these three deaths have brought to the forefront the fact that people should only really let their pets drink from waterways that are flowing, such as rivers. Still waters can harbour all sorts of contaminants that aren’t visible to the naked eye.”

Liz added: “One of the best things you can do for your pet is to ensure that its vaccinations are up to date, as these can protect them from diseases such as leptospirosis.

“They will not however protect pets from contaminants such as blue-green algae. But as a commonsense safeguard it’s wise not to allow pets to drink from puddles, lakes and other still waters.”