A number of water bodies around the country have been closed this summer due to the presence of high levels of blue green algae. Under certain environmental conditions blue-green algae (cyanobacteria) can quickly form extensive blooms which can be blown over the surface and concentrate close to shore making them more accessible to animals. Water bodies are monitored and warning signs posted but these may be missed.

Many blue green algae contain or produce a variety of toxic substances (cyanotoxins) including gastrointestinal irritants, compounds causing dermatological effects, neurotoxins and hepatotoxins. Gastrointestinal effects are often the primary presenting sign after cyanobacteria exposure with salivation, vomiting, haematemesis and abdominal tenderness. Dermatitis can occur but is rare in dogs, possibly because their hair provides some degree of protection from direct skin contact.

Dogs are most commonly exposed to hepatotoxic cyanotoxins and liver enzymes usually increase within 24 hours of exposure. Initial signs of hepatotoxic cyanotoxin ingestion are non-specific with vomiting, diarrhoea, anorexia and lethargy, followed by weakness, pale mucous membranes, evidence of haemorrhage, hypotension or hypovolaemic shock and jaundice. Death can occur within a few hours to a few days after exposure.

With neurotoxic compounds signs can be very rapid in onset (usually within an hour), with death following soon after. Signs include mild salivation, muscle rigidity and tremors, ataxia, paralysis, cyanosis, bradycardia, respiratory distress and convulsions.

Following suspected blue green algae exposure aggressive and rapid treatment is essential with decontamination, liver protectants and supportive care. Survival is rare in animals with significant clinical signs.

Diagnosis is usually based on clinical signs and history of swimming in or drinking from an affected water body. In the UK blue green algae incidents should be reported to the Environment Agency which has a 24-hour Incident Hotline (telephone 0800 80 70 60). If identification is required, then contact the local or government authority for advice. Samples should be refrigerated not frozen.

If you have an annual contract with VPIS you will be able to access an article on blue green algae we published last year in Companion Animal.