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Toxic Blue-Green Algae Is Serious Health Risk for Humans and Dogs

Blooms Of Dangerous Blu-Green Algae Containing Cyanobacteria Found in Harvard & Hollis Waterways
• What to do if you think your dog has been exposed to deadly cyanobacteria
by Angela Nelson
When we see green, scummy water, we know better than to drink it or even swim in it. But the same is not true for many dogs, and that green scum could be a toxic blue-green algae bloom containing cyanobacteria, which can be fatal to animals and humans.
     Several dogs died last summer after swimming in water contaminated by blue- green algae. Most of the deaths were in southern U.S. states such as North Carolina, Texas, Tennessee, and Georgia. However, dog deaths in Minnesota and Colorado also are suspected to be the result of toxic blue-green algae.
     But blue-green algae containing cyanobacteria are natural components of water bodies worldwide, with blooms and surface scums forming when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored within the cells and released upon cell death. Toxins can cause acute and chronic health effects that range in severity, including death.
     Acute health effects include irritation of skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects may include liver and central nervous system damage. Be cautious of lake water that has a surface scum, changes colors, or appears to have green streaks or blue- green flecks aggregating along the shore.
     Now there is a major bloom of blue-green algae at the town of Harvard’s Bare Hill Pond, one of the Commonwealth’s Great Ponds, a site for boating, swimming and all forms of aquatic recreation. As the climate warms, blooms of toxic blue-green algae have been moving father north and with greater frequency. There was also a bloom of the toxic algae at Silver Lake in nearby Hollis, N.H. in June and July.
     Residents of the town of Harvard have been advised to have no contact with the water in Bare Hill Pond because the algal bloom there may be producing harmful toxins. The advisory was issued Aug. 28 by the Harvard Board of Health and Nashoba Associated Boards of Health. The boards advised keeping pets out of the water. A no-swimming order, issued Aug. 24 remains in effect.
     Harvard authorities are testing to determine if the blue-green algae, called cyanobacteria, is producing toxins that can make people and pets sick. Not all cyanobacteria are harmful, but the boards issued the no-contact order as a cautionary measure. In the meantime, the town has advised the public to refrain from kayaking, paddle boarding, waterskiing, or tubing.
     “Cyanobacteria generally blooms in warm, still waters. That’s why we see surges in the summer,” said Tara Hammond, a Tufts critical care veterinarian at Tufts VETS in Walpole, where she oversees the emergency room and the intensive care unit. But toxic algae blooms can occur at any time of year under the right conditions. Blue-green algae prefers water with high amounts of certain nutrients, such as nitrogen and phosphorus.
     Cyanobacteria often appear green with a blue shimmer, and usually has a foul smell—think rotting plants. The algae may appear thick and scummy, or it may look like spilled paint on the surface of the water. Sometimes toxic algae blooms are small and may not be easily seen, which can make it more difficult for dog owners trying to keep their pets safe.
     “Generally, if there’s green slime in the water, it’s pretty suspicious, and you don’t want your dogs to go in,” Hammond said. Not all algae blooms are harmful, though. They can become dangerous when they produce toxins in high concentrations.
     Animals are exposed to the toxins if they swallow the water—either by drinking it, licking it off their fur, or eating contaminated seafood—swim and come in contact with it on their skin and eyes, or breathe in the toxins, if the toxins have become airborne.
     How can you tell if your dog has been exposed? Hammond said symptoms will be seen within a few minutes of exposure.
     “Sometimes there are minor signs, such as skin or eye irritation. But it can quickly progress to very major signs, including vomiting, diarrhea, lethargy, and potentially liver failure,” she said. “It can cause some neurological signs, like ataxia or seizures, where the dog may go into shock and die.”
     Because the onset of symptoms can be so fast, Hammond said, getting your dog emergency care immediately is vital. “Tomorrow might be too late,” she said.
     “If you suspect your dog has been exposed, rinse them off and seek vet attention right away. There’s no antidote or reversal agent,” said Hammond. “If they received a toxic enough dose, some dogs will die no matter
what we do, which is really scary.”
     Hammond said it’s difficult to tell if a dog has been exposed to blue-green algae because there’s no rapid diagnostic test. Veterinarians can test for liver function, or, if a dog has respiratory symptoms, may use a chest X-ray or ultrasound.
     If there’s a silver lining in all this, it’s that blue-green algae exposure is not common. A 2013 study found 368 documented cases of dogs who died from toxic blue-green algae between the 1920s and 2012, but the increasing incidence of the blue-green algae in local ponds suggests greater vigilance is called for.
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