Toxic blooms of blue-green algae can be deadly for humans and animals

It’s a warm, still day in the middle of September; a good day to take a walk around the yard. The walk is going well until you notice algae in your bird bath. This type of algae is normally classified as blue-green algae. It can be identified by its blue, bright green, white or brown coloring. Blue-green algae is referred to as cyanobacteria. One of the causes for cyanobacteria is warm water temperatures.

“The key part in algae control is the phosphorus to nitrogen ratio,” said Rebecca North, assistant professor, University of Missouri School of Natural Resources. “Phosphorus can be controlled by eutrophication, but there is no good way to control the nitrogen component. Researchers have an increasing interest in limiting the nitrogen input in lakes to stop the algal blooms, but it’s not effective because cyanobacteria will grab nitrogen from the air.”

Cyanobacteria cannot be detected by sight, but the color provides a clue.  

“A green lake is a good indicator that there may be toxins present, but recent tests have shown that a lake can have cyanobacteria without the harmful cyanotoxins,” North said.

The Missouri Department of Natural Resource can test green lakes as long as they are a part of public land. Another harmful aspect of cyanobacteria is that it is deadly to humans, livestock and dogs if it is ingested.

“Both forms of cyanobacteria affect the central nervous system and causes liver damage,” said Leah Cohn, professor, small animal internal medicine, MU College of Veterinary Medicine. “If your dog has ingested the cyanobacteria, signs will start to develop anywhere from 15 minutes to eight hours after exposure. Signs of exposure include vomiting, diarrhea, weakness, collapse, seizures, muscle fasciculation, ataxia or sudden death.”

The best thing to do if your dog shows these signs is to take it to a local veterinarian in case the signs are from another cause and not cyanobacteria exposure. Cyanobacteria exposure is not zoonotic; it cannot be transmitted from a pet to a person. The algae have to be ingested to cause harm.

Even with winter’s chill, these algae blooms can still occur, according to the Missouri Department of Natural Resources.