Blue-Green Algae: A Summer Danger on Burlington’s Waterfront

The call comes in on a hot afternoon. A dog splashed through a patch of green, scummy water down by the lake, and now the owner is second-guessing that quick dip.

We hear this every summer. The water looked a little off, the dog was already soaked, and the family just wants to know whether they should be worried.

Here on Brant Street, we’d rather you call us with that question ten minutes too early than an hour too late. This one moves fast.

Blue-green algae are photosynthetic bacteria called cyanobacteria, not true plants, according to Cornell’s Riney Canine Health Center. Some blooms release toxins that injure a dog’s liver or nervous system. Cornell reports the two most serious cyanotoxins are microcystin and anatoxin. There is no antidote, so exposure is a true emergency.

If this is happening right now, call us at (905) 336-4002 or the Pet Poison Helpline at 855-764-7661. Outside our hours, head straight to the nearest emergency hospital. Our after-hours care page has the details. Don’t wait for symptoms to appear before you make the call.

What does blue-green algae look like in water?

According to the Government of Ontario, dense blue-green algal blooms can look like green pea soup or spilled turquoise paint, and may also show up as yellow, purple, red or brown. The province cautions that you cannot tell whether a bloom holds harmful toxins just by looking, so it advises assuming toxins are present.

That last point is the one we repeat most. A bloom that looks harmless can still be dangerous, and a scary-looking mat might be nothing at all.

Some water simply looks dirty or foamy. Cornell’s Riney Canine Health Center advises steering dogs away from any water with visible blooms, scum, foam, or an odour, rather than trying to judge safety by sight.

Because the appearance changes so much, we don’t ask Burlington families to become algae experts. If the water looks off, smells off, or has a film on top, treat it as off and keep your dog out.

How quickly does blue-green algae affect a dog?

It depends on the toxin, and it can be frighteningly fast. The Merck Veterinary Manual reports that anatoxin-a is absorbed so rapidly that clinical signs are almost immediate, and affected dogs can die of respiratory failure within minutes. Merck adds that microcystin can trigger signs within minutes to days of ingestion.

Merck explains that anatoxin-a acts as an agonist at nicotinic receptors, causing continuous stimulation at the neuromuscular junction, a state Merck describes as a depolarizing neuromuscular blockade. In plain terms, the toxin jams the signal between nerve and muscle, and the muscles that control breathing can fail.

Microcystin works on a different timeline and a different organ. Merck reports it causes severe liver damage, and that blood pooling in the injured liver can lead to hemorrhagic shock, meaning dangerous blood loss into the organ itself.

Either way, minutes matter. If your dog was in questionable water and starts drooling, vomiting, staggering, or trembling, that is a reason to call us on your way to the car, not after you’ve watched to see if it passes.

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

Cornell’s Riney Canine Health Center lists the clinical signs of blue-green algae poisoning in dogs as vomiting, diarrhea, drooling, weakness, pale gums, collapse, muscle tremors, muscle rigidity, difficulty breathing, seizures, and sudden death. Signs can involve the stomach and gut, the liver, or the nervous system, depending on which toxin the dog was exposed to.

We want owners watching for two broad patterns. One looks like sudden stomach upset with drooling and weakness. The other looks neurological, with trembling, stiffness, trouble walking, or trouble breathing.

The two main toxins hit different organs, which is why the signs vary so widely. Here is how Cornell and Merck describe them side by side.

No owner should try to sort out which toxin is involved at home. That is our job once your dog is in front of us, and the diagnostics we run help guide care. Your job is to notice something is wrong and call.

Is there an antidote or treatment for blue-green algae poisoning in dogs?

There is no specific antidote for these toxins. The Pet Poison Helpline reports that treatment is intensive, supportive care, and that starting it as early as possible after exposure is critical. Merck adds that although the prognosis is often poor, some dogs have survived with intensive management.

That combination of facts is the whole reason we push so hard on speed.

The Pet Poison Helpline notes that supportive treatment can include oxygen and anti-seizure medication, with aggressive monitoring and supportive care. Merck adds that tremors and seizures may be managed with muscle relaxants, benzodiazepines, and barbiturates as needed.

This is the kind of hands-on, minute-by-minute work that belongs in a hospital setting with critical care support. It is not something to manage at home or wait out overnight.

We say this plainly because families sometimes hope a dog will “sleep it off.” With blue-green algae, that hope can cost you the window when treatment does the most good.

Can a dog survive blue-green algae poisoning?

Some do. Merck reports that although the prognosis is often poor, some dogs have survived with intensive management. The Pet Poison Helpline stresses that because prognosis is very poor once clinical signs appear, immediate veterinary intervention is essential. The dogs with the best odds are the ones seen fastest.

We never promise an outcome, and we won’t here. What we can say is that early action is the single factor most within a family’s control.

Survival is more likely when a dog is brought in before it is critically ill, so the supportive care described by the Pet Poison Helpline and Merck has time to work. So we would rather examine a healthy-looking dog and find nothing than see one arrive already in crisis.

If you are ever unsure whether an exposure counts, call us and describe what happened. We would much rather talk it through than have you talk yourself out of a visit.

What should I do if my dog swam in or drank suspect water?

Treat it as an emergency. The Pet Poison Helpline reports that onset can come within minutes to hours and that prognosis is very poor once signs appear, so immediate veterinary care is essential. Call us at (905) 336-4002, or the Pet Poison Helpline at 855-764-7661, and head in right away.

Rinse your dog off with clean water if you can do it quickly and safely, so it can’t keep licking toxins from its coat. Then get moving. Don’t wait for symptoms.

Bring what you know. The location, roughly how much water your dog drank or swam through, and what the water looked like all help us and the Pet Poison Helpline make fast decisions.

If it’s after our regular hours, go straight to the nearest emergency veterinary hospital rather than waiting for us to open. Our after-hours care page lists where to go, and this is exactly the situation it’s meant for.

How do I keep my dog safe on Burlington’s waterfront?

Prevention is straightforward. Cornell’s Riney Canine Health Center advises keeping dogs from drinking, walking, or swimming in water with visible blooms, scum, foam, or an odour. Halton Region monitors its beaches by visual observation during sampling and advises residents not to let pets use the water when blue-green algae is visible.

Around here, that means paying attention at the places dogs love. Along the Lake Ontario nearshore, the warmer, more enclosed water of Burlington Bay, and the ponds and slow creeks across Halton, warm summer water is exactly what cyanobacteria favour.

The Government of Ontario reports that blooms are most common in late summer and early fall, though they can occur in other seasons. Halton Region similarly notes that visible surface blooms tend to form in late summer and early fall as temperatures and nutrient levels rise.

Off-leash and unsupervised dogs are the ones most likely to reach untested water, backwater ponds, or scummy shoreline mats away from the monitored swimming areas. A leash near questionable water is a simple, effective safeguard.

If you spot a suspected bloom, the Government of Ontario asks the public to report it to the Ministry of the Environment, Conservation and Parks Spills Action Centre, available 24 hours a day, 7 days a week at 1-866-MOE-TIPS (1-866-663-8477). You can also check current Halton beach water results before you head out.

Frequently asked questions

Are Burlington beaches safe for dogs to swim in?

It varies by day and location. Halton Region monitors its beaches by visual observation during sampling and posts warnings when conditions are unsafe, advising residents not to let pets use the water when blue-green algae is visible. Check current beach water results before you go, and keep your dog out of any water with visible scum or film.

How do I report a suspected blue-green algae bloom in Ontario?

The Government of Ontario asks the public to report suspected blooms to the Ministry of the Environment, Conservation and Parks Spills Action Centre. It’s open 24 hours a day, 7 days a week at 1-866-MOE-TIPS (1-866-663-8477). Reporting helps the province track blooms and protect other families and pets using the same water.

Can blue-green algae make cats sick too?

Cats can be exposed to the same cyanotoxins, though dogs are far more likely to wade in or drink from open water. A cat that grooms toxins off wet fur could still ingest them. If you think your cat contacted a bloom, treat it as urgently as you would for a dog and call us right away.

Does the water always smell bad when it’s dangerous?

Not reliably. The Government of Ontario cautions that you can’t tell whether a bloom holds harmful toxins just by looking, and advises assuming toxins are present. Cornell also flags odour as one warning sign to avoid, but a lack of smell is not a green light. Judge by scum, film, and colour, not scent alone.

My dog seems fine after swimming. Do I still need to worry?

Keep watching closely. The Merck Veterinary Manual reports that anatoxin signs can be almost immediate, while microcystin signs may take minutes to days to appear. A normal-looking dog right after a swim is not proof it’s safe. If you saw a bloom or scum, call us to talk it through rather than waiting.

This article is educational and isn’t veterinary advice or a substitute for an exam. If you’re worried about your pet right now, call us at (905) 336-4002 or your nearest emergency veterinary hospital.

Blue-green algae is one of those summer risks that’s easy to prevent and hard to reverse, so a quick call is always worth it. If you’ve had a scare at the water or just want your dog looked over, we’re right here on Brant Street.

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Sources

Veterinary and toxicology references

1. Cornell University College of Veterinary Medicine, Riney Canine Health Center. “Blue-Green Algae Poisoning (Cyanobacteria Toxicosis).” https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-topics/blue-green-algae-poisoning-cyanobacteria-toxicosis
2. Merck Veterinary Manual. “Algal Poisoning of Animals.” https://www.merckvetmanual.com/toxicology/algal-poisoning/algal-poisoning-of-animals
3. Pet Poison Helpline. “Blue-Green Algae Poisoning: Tips for Pet Owners on How to Diagnose and Treat.” https://www.petpoisonhelpline.com/pet-safety-tips/blue-green-algae-poisoning-tips-for-pet-owners-on-how-to-diagnose-and-treat/

Government and public health

1. Government of Ontario. “Blue-green algae.” https://www.ontario.ca/page/blue-green-algae
2. Halton Region. “Beach water.” https://www.halton.ca/for-residents/water-and-wastewater-services/recreational-water/beach-water