Farmers have been warned to take extra precautions and keep all dogs on leads when walking around freshwater bodies.
The British Veterinary Association (BVA) has said that recent warm weather sparks concerns about an increased risk of toxic blue-green algae growth over the coming months.
The warning follows confirmed algal bloom sightings in freshwater lakes, ponds or rivers in around 50 locations across the UK, including Copeland Reservoir, Conlig Reservoir and Craigavon Balancing Lakes in Northern Ireland.
In late April, a cocker spaniel died of suspected blue-green algae poisoning after a swim in Anton Lakes, Hampshire.
Blue-green algae, or cyanobacteria, are bacteria that can contain dangerous toxins which can be harmful and potentially fatal to pets, livestock and birds if ingested - even in small quantities.
The algae may appear as green or greenish-brown scum on the surface of water.
Dogs can swallow it by drinking water from an affected lake, river or pond or while licking their fur after going for a swim.
It’s possible for dogs to come into contact with the bacteria even if they don’t go into water for a paddle, as toxic blooms are often blown to the edges of water bodies.
BVA president Justine Shotton said:
“Many dogs love nothing more than a paddle in a lake to cool off in this weather, but we’d urge pet owners to keep them on a lead during walks near water bodies confirmed to have algal blooms this summer.
“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.”