Basking in the summer sunshine? Vets have warned owners to beware of a toxic and fatal danger for dogs on walks, especially around freshwater lakes and ponds.

During this time of year, blue-green algae are generally more prevalent due to the warmer water temperatures and increased sunlight, creating ideal conditions for their rapid growth.

Blue-green algae are a type of bacteria that live in fresh, brackish, and salt waters worldwide.

"As we make the most of warmer temperatures and bright, sunny days, many owners will enjoy scenic summer walks with their dog, but bacteria are lurking in lakes and streams that can seriously harm our beloved pets," PDSA Vet Nurse Nina Downing told Country Living.

"Blue-green algae can grow in all aquatic environments, but they're most prevalent in still or stagnant water, like lakes or rivers, during summer. This particular type of bacteria is highly poisonous to animals, and can sadly be fatal, or result in long-term health problems for those that survive."

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Why are dogs more at risk of blue-green algae?

Dogs are at risk as they are more likely to drink or swim from ponds during a walk.

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"If your pet has jumped in and you're worried about the water, don't let them lick at their fur and wash them thoroughly as soon as possible. If you're concerned or if your pet shows any signs of being unwell, contact your vet," says Nina.

Why is blue-green algae so dangerous?

Caroline Reay, Veterinary Standards Lead at national pet charity Blue Cross, adds: "Some species of these bacteria produce poisonous substances which can be irritant or have dangerous toxic effects on the nervous system or liver.

"Even small quantities of water or licking contaminated water off the coat can be dangerous."

How can you spot blue-green algae?

Blue-green algae are easily identifiable as "green or blueish scum" with a light tint of brown.

"It can sometimes clump up, and the blooms can create foam on the shoreline. There's no way of telling if algae is toxic just by looking at it, and some types of blue-green algae are only dangerous at certain times of year, but always be cautious and don't take any risks around it," says Nina.

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How can you protect your dog from blue-green algae?

"Be vigilant when walking your dog near any form of water, and if it looks bright green, avoid at all costs," urges Nina.

"Never let your dog drink from a pond or lake with dead fish or animals in either, the water could be dangerously toxic and make your pet extremely ill, with potentially fatal consequences.

"Your local council will put up signposts in areas regularly affected by blue-green algae, so make sure you scan the surroundings for any indication of danger before letting your dog go for a swim."

What are the symptoms of blue-green algae poisoning in dogs?

The tell-tale signs to look out for include vomiting, twitching, seizures, diarrhoea, increased thirst, drooling, breathing difficulties, or a collapse.

"Symptoms of blue-green algae poisoning can occur very quickly, within 15 minutes to several days after exposure, and even a small amount can be lethal to a dog, so it’s important to act quickly and contact your vet immediately," says Nina.

"If you spot blue-green algae but there are no signposts to warn dog owners, you should report it to the Environment Agency on 0800 80 70 60. They'll test the water and put up signage in the surrounding area to warn owners and help prevent any potential future cases."

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Lisa Joyner
Deputy Daily Editor, Country Living and House Beautiful

 Lisa Joyner is the Deputy Daily Editor at House Beautiful UK and Country Living UK, where she's busy writing about home and interiors, gardening, dog breeds, pets, health and wellbeing, countryside news, small space inspiration, and the hottest properties on the market. Previously, she has written for Conde Nast Traveller, House & Garden and Marie Claire magazine. Lisa studied at University For The Creative Arts, where she completed a BA in Fashion Journalism.