Dog walkers warned of deadly algae risk during heatwave

Telegraph

19-07-2025

Dog owners have been warned to keep their pets away from lakes and rivers this summer amid a rise in toxic blue-green algal blooms.
Government officials have seen a high number of so-called blue-green algal blooms around the UK this year as a result of the hot and dry weather.
These events occur when thriving colonies of bacteria use the warmth and sunlight to reproduce rapidly. They create a colourful scum on the water, which if ingested can make humans ill and kill animals, with dogs particularly susceptible to the toxins.
Officials and animal welfare experts have urged caution this summer with people encouraged to keep themselves, children and pets away from plagued rivers and lakes.
Algal blooms have become more common since 2015 because of climate change, experts say.
Charlie Matthias, the senior veterinary surgeon at Dogs Trust, told The Telegraph: 'As temperatures continue to soar and water levels drop, there is a potential for an increase in blue-green algae.
'Blue-green algae can make your dog very sick and, in some cases, prove fatal if ingested even in small quantities.
'We're urging all dog owners to avoid letting their dogs swim in or drink from lakes or rivers that look green, scummy, have surface foam or have warning signs nearby.
'Blue-green algae is not always easy to spot, so if in doubt, don't let your dogs swim in or drink from the water.'
Blue-green algal blooms form when nutrient-rich water, often enriched by chemicals from farms and warm weather, cause bacteria called cyanobacteria to grow rapidly.
Still and slow-moving water are prone to these blooms which emerge quickly following prolonged exposure to sunlight and warm temperatures.
They often persist for several months once formed and until colder weather arrives. Authorities are expecting the issue to endure for several months yet.
The UK Centre for Ecology and Hydrology (UKCEH) runs a 'Bloomin' Algae' project where the public send in images of suspected toxic blooms and experts determine if it is.
Data show that half of the about 200 submissions this year are blue-green algal blooms, with a further 34 being 'plausible'.
The blooms have been found across the UK from Norfolk and Essex to Birmingham and the Lake District and submissions show that some dogs have fallen ill for several days after going for a swim.
Confirmed cases were also sent in by people swimming or paddleboarding in affected bodies of water. Once a bloom is confirmed landowners are obliged to put up signs warning the public.
Symptoms of blue-green algae poisoning in dogs can appear within minutes and include vomiting, diarrhoea, drooling, muscle tremors, seizures, breathing difficulties, and collapse.
Dogs should be taken to a vet immediately as there is no antidote and the cognition can be fatal as the toxins attack the liver and neurological system. If caught early enough a vet can flush the toxins out of the system.
Dr Linda May, a freshwater ecologist from the UK Centre for Ecology and Hydrology, said: 'Dogs are particularly at risk, because they are susceptible to the toxins that some algal blooms release into the water.
'Smaller dogs only need to consume a small quantity to be at high risk of death. So please, take your dog to a vet immediately if they seem unwell after being in contaminated water.'
Anna Ewers Clark, a veterinary standards lead at national pet charity Blue Cross, added: 'Although there is no specific antidote, supportive treatment is essential. These toxins are very dangerous and can kill, sadly even with treatment.'
She added: 'This is very concerning. Even small quantities of water or licking contaminated water off the coat can be dangerous.'
An Environment Agency spokesperson said: 'Blue-green algae, a naturally occurring environmental phenomenon, is more likely to appear during warm, settled, dry weather and can pose risks to both animals and humans.
'We urge the public to call our 24/7 incident hotline at 0800 80 70 60 if they suspect a bloom of blue-green algae in any rivers, streams, or lakes so our teams can collect and test samples to ensure warnings are in place.'