Will Hehemann | School of Agriculture, Fisheries and Human Science
Stories of pet dogs and livestock being poisoned by exposure to toxic algae in ponds and lakes have recently been making national headlines and circulating on social media, George Selden, University of Arkansas at Pine Bluff (UAPB) Extension aquaculture specialist, said. In several recent cases, fun summer excursions to the lake have turned into nightmares following the death of animals exposed to water containing algae-produced toxins.
“Over the past few weeks people have asked me if they should be worried about their pets, livestock or children being poisoned by toxins released by algae,” he said. “The short answer is ‘possibly.’”
Selden said “algae” is an informal term for a large, diverse group of photosynthetic organisms that are primarily aquatic and can be found in both fresh and salt water. Blue-green algae – or cyanobacteria – are an ancient group of organisms, and there are species within this group that can produce toxins and form harmful algal blooms.
Blue-green algae can form blooms that discolor the water or produce floating mats or scums on the water’s surface that have a paint-like appearance. The bloom might be blue-green, green, yellow, white, brown, purple or red.
It is estimated that 50 of the 1,500 species of cyanobacteria can produce toxins. If the conditions are right for one of the toxin-producing species to become prevalent in a body of water, problems may occur.
Some toxins can cause negative flavors in drinking water or an off-flavor in fish, Selden said. Other toxins can give people skin rashes when they come into contact with water. And some toxins lead to injury and death in animals if ingested in large enough quantities.
What are the effects on animals?
In animals, the symptoms of consuming water containing harmful algae include weakness, staggering, difficulty breathing, convulsions and death, Selden said.
“Poisonings are unpredictable and sporadic,” he said. “It should be noted that reports of animals dying after ingesting water with dense blue-green algae blooms have been recorded since the 1920s but are still relatively rare.”
Dogs can be poisoned by toxic cyanobacteria because of the algae that sticks to their coats. When a dog cleans itself after swimming, it could potentially ingest a lethal dose of toxins in a single exposure.
Livestock are less likely to ingest a lethal dose of toxic water in a single exposure, Dr. David Fernandez, Extension livestock specialist for UAPB, said. However, livestock in the U.S. and around the world have been poisoned or die from acute exposure to the toxins. Little information exists regarding repeated exposure to lower doses.
Dr. Fernandez said producers should watch for signs of intoxication in livestock: loss of appetite, skin problems and reduced milk production (especially noticeable in dairy animals). Abortions may occur. More severe cases include constipation, convulsions, paralysis and death.
What are the effects on people?
People can become ill when they consume water containing harmful algae or inhale toxic water droplets, Selden said. Symptoms, which can include vomiting, diarrhea, rash, eye irritation, cough, sore throat and headache, may appear within two hours of exposure or as late as two days after exposure.
Some species of blue-green algae produce toxins that affect the nervous system (neurotoxins) or the liver (hepatotoxins). Symptoms from neurotoxins can occur within 15-20 minutes and can include tingling in fingers, lip numbness and dizziness.
How to protect children and pets from blue-green algae?
Selden said there are ways to ensure both people and pets don’t fall ill due to blue-green algae.
- When in doubt, stay out. If a body of water seems excessively green or has a floating scum, it should be avoided both in the case of humans and pets. A scum along the shoreline is evidence of a recent bloom. This doesn’t mean that toxins are present, but it is better to be safe.
- If children or other loved ones are showing signs of having been exposed to a toxic blue-green algae bloom, contact a physician. People should bathe after exposure to water potentially containing blue-green algae.
- If a pet is displaying symptoms of exposure to toxins, contact a veterinarian. Pets should be washed after swimming in ponds with obvious blue-green algae blooms.
- Do not let dogs eat sun-dried algal scum around the edges of a pond. Livestock tend not to eat the dried algae, but it is still a good idea to remove it from the edge of the pond before animals have access to it.
- If an alternative source of water is available, livestock should be excluded from a contaminated pond until several days after the bloom ends. This will allow residual toxins time to break down before the animals can be exposed to them again.
- If livestock are not eating their feed or are constipated, prevent them from accessing the contaminated pond and provide clean drinking water.
“Instances of livestock and pets being poisoned by cyanobacteria are infrequent – but they are not something that can be dismissed as unlikely to occur,” Selden said. “Individuals can protect their loved ones and pets by avoiding bodies of water that contain blue-green algae and knowing the symptoms of cyanobacterial poisoning.”
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