As summer winds down, many pet owners are eager to enjoy extra time outdoors with their animals. But Dr. Alexandra Reddy, a veterinarian at the Virginia-Maryland College of Veterinary Medicine at Virginia Tech, cautions against letting pets swim or play in lakes and ponds that may contain blue-green algae.
While most algae blooms that appear in warm weather are harmless, those caused by cyanobacteria can pose serious dangers to both pets and people. Dogs exposed to contaminated water may suffer in two ways: toxins that damage the liver can trigger vomiting and diarrhea, while those affecting the nervous system can lead to seizures and even paralysis.
“It’s simply not worth the risk,” Reddy said, advising owners to keep dogs on leash near water showing signs of an algal bloom. If a pet becomes sick after contact, she urges immediate veterinary care, since there is no antidote for these toxins. Treatment is limited to supportive measures such as oxygen therapy, fluids for dehydration, and medication to control seizures.
Even sticks along the shoreline can carry toxic residue. “One small piece is enough to cause harm,” Reddy warned.
Local health departments monitor public waterways for algal blooms and post advisories when hazards are detected. In Virginia, the Department of Health maintains an online dashboard with updated maps of affected areas. Recently, officials in Fairfax County cautioned visitors about algal mats at Lake Accotink, noting that while blooms are common in summer, precautions should always be taken.
However, Reddy stressed that testing does not cover ponds on private property, so owners must remain alert. Public health agencies continue to emphasize the simple rule of thumb: “When in doubt, stay out.”
