Stagnant water can cause seizures in your pet

A deadly poisonous algae has been thriving in the heatwave Photo: Reuters

Water plays an important part in human leisure activities. Swimming, surfing, sailing, and canoeing are popular pastimes, with the urban population descending on lakes, rivers and beaches at weekends. Many dogs also enjoy water, with owners using swimming as a regular form of exercise for their pets. Swimming is a useful form of physical exertion. The muscles work hard, but because of the buoyancy of the body in water, the joints are not stressed by the full weight of the animal. Swimming can be especially beneficial for animals recovering from injuries, or for older animals suffering from arthritis. During hot spells, it can be a way of exercising animals that’s less likely to lead to overheating: every year, dogs collapse during walks on sunny days from hyperthermia; swimming in cold water avoids this risk.

Dog owners are being warned today about a dangerous poison that’s become more common in ponds and lakes across the UK after the recent hot spell: blue-green algae. Dogs are at risk when they drink or swim in water where there’s been an algal bloom, typically seen in stagnant pools of water after warm, calm weather. These blooms are often concentrated on the windward side of ponds, lakes or reservoirs, so it’s well worth checking these areas out for visible signs of green or blue slime or scum before allowing a pet access to the water. If there’s a known problem, local authorities often erect warning signs, but you can’t depend on being warned in this way: a new algal growth can appear in a clean body of water at any time.

There’s a range of different types of algal blooms, each producing a different type of poison. There are three main types of toxins: one causes liver failure, and the other two are neurotoxins. Pets are affected after ingesting the algae, either by drinking affected water, or by grooming themselves after being immersed. Signs of poisoning happen very rapidly, within minutes or hours of exposure, and emergency veterinary treatment is needed.

If the liver toxin has been eaten, a dog becomes dull and weak, often with vomiting and diarrhoea. This is followed by collapse, and then death from massive liver failure. If the ingested algae contain neurotoxins, signs include muscle rigidity, tremors and seizures, followed by paralysis, respiratory paralysis and death.

A diagnosis of algae toxicity is presumed if these signs follow exposure to stagnant water, but it can be difficult to confirm the diagnosis. Attempts can be made to detect either the algae or toxin in stomach contents or in samples of bloom material, but it’s not always easy to do this.

As with most cases of poisoning, there’s no antidote for algal toxins. Treatment is symptomatic and supportive, using drugs and intravenous fluids to keep the dog alive while the poison works its way through the system.

Interestingly, some of toxins from blue-green algae are known to have an anti-viral effect, and work has been done on their use as a potential source of antiviral substances against influenza virus.

There’s no need for dog owners to stop their dogs from swimming completely: the incidence of blue-green algae toxicity is still very low. But it makes sense to be cautious: check out the appearance of that water before allowing your enthusiastic dog to take the plunge.