Dog owners have been warned of an invisible toxin after four pets died in the last three days in a popular swimming spot.
The dogs, one of which was just six months old, died within an hour of coming into contact with the water at Lough Melvin in Co Fermanagh in Northern Ireland.
One devastated owner made it to the vet within 15 minutes but the animal still died.
The toxin, which is invisible to the naked eye, is found in fresh water in lakes, loughs, ponds and even rivers and is associated with algae.
It attacks the liver after being ingested through the dogs consuming water or licking their paws after swimming.
Four desperate owners raced to Lakeland Veterinary Services in Co Fermanagh as their pets started suffering seizures moments after getting out of Lough Melvin, BelfastLive reports.
One of the dogs had only been walking in the water, the other three had been swimming.
And one of the dogs, a six-month-old Shi-Tzu pup, fell ill with such severity and at such speed, that there was no time for emergency veterinary intervention and he passed away before he could even reach the vet.
Aoife Ferris, a vet at the practice, treated three of the four dogs who fell ill.
She said the situation was a tragedy for the dogs, deeply distressing for the owners and very difficult to handle as a vet.
And she warned: "Our warning is clear. Do not let your dogs near fresh water and especially stagnant water at the moment. The toxin associated with blue-green algae blue is not visible to humans, it is not detectable by dogs and it can be a killer. In two days we had four dogs die after being in or around the same body of water.
"The owners are all devoted to their pets and the last thing they would do is knowingly put them at risk. But now we have families grieving for four dogs, two puppies and two adult dogs, all of them fit and healthy before their walk.
"The situation is shocking, distressing and completely heartbreaking. But this toxin is so fast acting, so dangerous and it needs to be avoided at all costs. We had four cases in two days and all four dogs died. An absolute tragedy.
"The toxin attacks the liver and once the liver cannot filter toxins the other organs shut down and when that happens there is just no going back.
"We are advising and warning dog owners and dog walkers to stay away from freshwater while this algae is active. No evidence of the algae to the naked eye does not necessarily mean the water is safe. Please do not take the risk. Keep your dog on a lead near water, do not allow them to drink from the freshwater source, do not let them swim in it or even paddle or walk in it.
"Initially when we had the dogs come into us this week, we thought there may be a chance the dogs could have suffered cardiac arrest but that would be very unusual in dogs and then we realised they'd all been near the same fresh water source. We believe they have died as a result of multi-organ failure brought on by exposure to the blue-green algae toxins.
"This algae can appear as sludge that is brown in colour and as foam along the shore, as well as a green film over the water, but as it washes through areas it can be impossible to see.
"As we head into the weekend with warm weather we know people will want to get out and about with their dogs but we are urging caution. Please do not let your pet near any fresh water, especially stagnant water.
"The main treatment for a dog that has ingested these toxins is to induce vomiting but sadly we know it can be too late."
The Northern Ireland Environment Agency said an investigation for evidence of water pollution was carried out after the deaths of two dogs.
They said: "No visual evidence of an algal bloom or any other signs of water pollution were detected. As a precautionary measure samples have been collected for algal analyses."
Vets notified Fermanagh and Omagh District Council of their concerns, and a spokesperson said: "Dog owners should be aware of the dangers posed by poisonous plants and algae growing in the environment, but especially along riverbanks and in wet grassland or edges of lakes."
