Cyanobacterial Blooms: Information for Veterinarians

Dogs, livestock, and other animals can suffer severe illness or death within minutes to days of swallowing toxins from cyanobacterial blooms. Providing supportive medical care soon after exposure can save an animal’s life.

Cyanobacterial bloom basics

• Cyanobacteria (also called blue-green algae) can grow quickly, or bloom, when water is warm, slow-moving, and full of nutrients.
• Cyanobacterial blooms are most commonly found in fresh water, such as lakes, rivers, and streams.
• These blooms can discolor the water and look like foam, scum, mats, or paint on the surface, but some blooms are hard to see because they grow below the water’s surface.
• Cyanobacterial blooms sometimes produce toxins (cyanotoxins) that can be lethal to animals.

Exposure and health impacts

• Dogs and other animals are often exposed by drinking contaminated water, swallowing water while swimming, or licking cyanobacteria from their fur.
• Dogs and other animals can become seriously ill or die suddenly after exposure. Signs depend on how they were exposed, how long they were exposed, and the types of toxins they were exposed to.
• Monogastric animals appear to be less sensitive than ruminants or birds; however, the dose-response curve is very steep in dogs—up to 90% of a lethal dose may elicit no clinical signs.

Tests and treatments

• There are currently no clinically available tests or designated treatments.
• Medical care is supportive. There are no known antidotes to these toxins.
• Activated charcoal may be useful within the first hour, and atropine has efficacy with saxitoxin exposure.
• There is some evidence that treatment with cholestyramine may be helpful for dogs exposed to microcystins.

Exposure and clinical information

Information about the health effects is derived from reports of animal poisonings and may be species dependent. Find references on the Publications, Data, and Statistics page.