• Posted August 31, 2025

Toxic Algae in Lakes Can Kill Pets Within Minutes, Expert Warns

As people enjoy the waning days of summer outdoors, a Virginia Tech veterinary expert reminds pet owners about a potentially deadly hazard: Toxic blue-green algae.

“Toxic cyanobacteria, commonly known as blue-green algae, can be fatal to pets within minutes of exposure,” said Dr. Alexandra Reddy, a veterinarian at the Virginia-Maryland College of Veterinary Medicine in Blacksburg, Va.

“It’s a concern for animals because the toxins produced by the bacteria particularly target the liver and nervous system,” she added.

These harmful algal blooms, which thrive in warm, stagnant water, can look harmless. They often appear as spilled paint or scum on the surface of lakes and ponds.

“Ultimately, even just a few mouthfuls of contaminated water can be fatal to your pet,” Reddy warned.

She offered several tips to keep pets safe:

• Know what to look for: Algal blooms may appear blue-green, red or brown, with scum or foam on the surface. "The water may also have an odor of rotting plants," Reddy added.

• When in doubt, stay out: You can’t tell if a bloom is toxic just by looking, so avoid letting pets near any suspicious water.

• Watch for warning signs: Symptoms of exposure can start within minutes and include vomiting, diarrhea, weakness, drooling, seizures, tremors and trouble breathing. In severe cases, sudden death can occur.

• Act fast: If you suspect exposure, bathe your pet immediately with clean water to prevent them from licking toxins off their fur and seek veterinary care right away.

• Check your local advisories: “Before visiting lakes or ponds, check for local warnings." Your state or county health department’s website is a good place to start.

More information

The U.S. Centers for Disease Control and Prevention has more on the effects of algal blooms on your health.

SOURCE: Virginia Tech, news release, Aug. 27, 2025