Blue-Green Algae and Dogs: How to Spot It and Stay Safe
In August 2019, a woman in Wilmington, North Carolina, took her three dogs to a pond near a walking trail: two Westies and a doodle who worked as a therapy dog. Within 15 minutes of leaving, one of the Westies was having a seizure. Within hours, all three had died. Her vet said the cause was blue-green algae poisoning (CNN).
Stories like this are still uncommon, and we don’t want to scare anyone away from the water. But many of our clients have never heard of toxic algae, and it’s hard to spot even when you know what to look for. Prevention matters most: there’s no antidote, and signs of illness can start within minutes to hours (CDC).
What blue-green algae is
Blue-green algae, also called cyanobacteria, are tiny organisms that live in water. In the right conditions they multiply quickly into a bloom. Some blooms make toxins that can sicken or kill people and animals. These are called harmful algal blooms, or HABs. You can’t tell by looking whether a bloom is harmful. It takes a lab test (PA DEP).
Where and when it shows up
In Pennsylvania, blooms usually show up in the warmer months, roughly mid-June to early September. They’re most common in calm, slow-moving, warm water with lots of nutrients (PA DEP), like ponds, lakes and slow stretches of creeks. Fertilizer and other runoff help feed them.
Before a hike near water, check the Pennsylvania HABs Dashboard, a map of recent bloom monitoring across the state, and watch for advisory signs at the water. Our guide to dog-friendly hikes near Philadelphia has more on what to bring.
How to spot a bloom
Blooms don’t all look alike. Compare the photo above with the one at the top. Signs to watch for (PA DEP, CDC):
Water that has turned bright green, cloudy or otherwise discolored, evenly or in globs
Water that looks like pea soup
Streaks that look like spilled paint or grass clippings
Scum or mats on the surface or along the shore
Foam on the water
If the water looks or smells bad, keep your dog out (CDC).
Why dogs are at higher risk
Dogs swim in the water, drink it, and lick it off their fur afterward, and they’re smaller than we are (PA DEP). They can also get sick from eating algae or dead fish on the shore (CDC).
Keeping your dog safe
Stay out of suspect water. No swimming, wading or drinking, and keep your dog away from scum along the shore (CDC).
Bring fresh water. Carry water and a bowl, so your dog isn’t tempted to drink from a pond or creek.
Rinse right away. If your dog goes in, wash them off with clean water right away, before they can lick their fur (CDC). Keep the water out of your own eyes and mouth, and wash your hands afterward.
Follow posted warnings. Watch for HAB watch, advisory and warning signs, and follow any closures (PA DEP).
If you think your dog was exposed
Call your vet or an emergency vet right away. Don’t wait for symptoms. Warning signs include (CDC):
Vomiting or diarrhea
Drooling or foaming at the mouth
Loss of energy or appetite
Stumbling
Tremors, seizures or convulsions
Signs can start within minutes to hours, and there’s no antidote, so fast care matters (CDC). Call your vet about any unexplained illness within a day or so after your dog was in the water (CDC).
For poison advice, you can also call the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661. Both charge a fee (CDC).
Reporting a bloom
If you see a suspected bloom in Pennsylvania, report it with the Department of Health’s reporting form, or email the state’s HABs task force at HABS@pa.gov (PA DEP). Since 2016, the CDC has also tracked illnesses in people and animals linked to blooms (CDC). Reports help health officials spot blooms and warn others.
A note on our walks
For more warm-weather risks, see our 13 summer safety tips for dogs. Our walks are one-on-one, for 20, 30 or 60 minutes, and you get photos, notes and the GPS route after every walk.
Every new client starts with a free meet & greet at home. Book a free meet & greet or call (267) 571-9373.
