Dog owners are being told to keep pets on leads around rivers and ponds over fears the recent hot weather will lead to a spike in the growth of highly toxic blue-green algae.

The British Veterinary Association says walkers should take extra precautions over the coming weeks to prevent their animals coming into contact with the poisonous bacteria that likes to sit on the surface of freshwater.

Blue-green algae, or cyanobacteria, are a group of bacteria which contain dangerous toxins harmful and potentially fatal to pets, livestock and birds if ingested in even the smallest quantities.

The algae often appears as green or greenish-brown coloured scum on the surface of water and dogs are most prone to swallowing it by drinking from an affected lake, river or pond or while licking their fur after going for a swim.

It’s also possible for dogs to swallow it even if they don’t go into the water for a paddle, as the toxic blooms are often blown to the edges of water bodies where animals will stop, prompting the warning from vets to keep pets well away at this time of year.

The British Veterinary Association says in late April a cocker spaniel died of suspected blue-green algae poisoning after a swim in Hampshire while the UK Centre for Ecology and Hydrology's citizen science Bloomin' Algae app, which relies on the public submitting photos and reports of suspected blue-green algae they see when out and about, is also currently tracking a number of locations in the UK, so far none in Kent this year.

Suspected or confirmed cases of sickness caused by blue green algae toxins usually peak across July and August during the height of the summer season, making it crucial that owners now begin keeping their animals away from places where the water may be at risk.

British Veterinary Association President Justine Shotton said while dogs loving nothing more than a paddle to cool off, owners needed to be aware of the dangers.

She added: "The majority of blooms are toxic and it is impossible to tell the difference visually, so it is better to be safe than sorry.

"It is also important to be aware of the symptoms of exposure. These commonly include vomiting, diarrhoea, drooling, disorientation, trouble breathing, seizures, and blood in faeces. They can appear within a few minutes or hours of exposure, depending on the type of toxin ingested, and can cause liver damage and ultimately be rapidly fatal if left untreated.

"There is currently no known antidote for the toxins, so dog owners should seek prompt veterinary treatment to tackle their effects and ensure a good chance of recovery for their pet."

Dog walkers when out and about should remain vigilant and look out for any signs that have been put up warning of sightings of blue green algae while pets must be kept away from any water known to have blue-green algal bloom.

Any pet who has been swimming outside should have its coat washed thoroughly with clean water as soon as possible afterwards and if in doubt as to whether your pet could have ingested toxic algae, seek emergency veterinary treatment straight away.

Dr Linda May, a freshwater ecologist at UKCEH, says her organisation's app is there to provide a service to those enjoying the great outdoors by collating reports from the public who take the trouble to send them in, with the technology also enabling notifications for specific areas.

She explained: "All reports of suspected blue-green algae are rapidly available to view via the Bloomin’ Algae app, so by submitting records, people are providing a useful early warning to pet owners and watersports enthusiasts.

"A photograph must be included with all reports so we can quickly check if the bloom is blue-green algae or something harmless."