Toxic Algae

Laurie Anne Walden, DVM

Algal blooms on Binder Lake, Iowa. Photo by Dr Jennifer L. Graham, US Geological Survey (public domain).

Toxins from algae in a pond killed 3 dogs in Wilmington earlier this month. The same type of algae has been found in a public park pond in Charlotte. The only way to know if algae is harmful is by testing the water in a laboratory, so for safety, keep your dog away from all scummy or discolored water.
 
Harmful Algal Blooms
Algae are tiny plantlike organisms that live in water. Some algae produce toxins that cause serious illness. Under certain conditions, algae grow quickly into collections called algal blooms. Algal blooms are most likely to form in warm water that is high in nutrients like nitrogen. Hot weather and stagnant water increase the chance of algal growth.
 
Algal blooms can form in either fresh or salt water. The most common type of harmful algae in fresh water is cyanobacteria, or blue-green algae. Another type of algae causes red tide in salt water.
 
Avoid water with signs of potentially harmful algal blooms:

• Green, blue-green, or red-brown water
• Discoloration that looks like a paint spill on the surface of the water
• Scum, foam, or mats floating on the water
• Unpleasant odor (although dogs might not mind the smell)
• Dead fish

 
Symptoms of Exposure
People and animals can be exposed to algal toxins through skin contact with contaminated water, by drinking contaminated water or eating contaminated food (like fish), or by inhaling water droplets in windblown spray. Dogs are typically exposed when they play or wade at the edges of bodies of water with algal blooms.
 
Not all algal blooms are toxic. But with some types of algae, exposure to only a small amount of toxin can be fatal within hours or days. Algal toxins can damage the liver, nervous system, kidneys, and digestive tract. Symptoms depend on the type of toxin and the amount of exposure and include the following:

• Irritation of the skin, eyes, nose, or throat
• Vomiting or diarrhea
• Weakness
• Difficulty breathing
• Stumbling or staggering
• Tremors
• Paralysis
• Seizures
• Coma

 
What to Do if Your Pet Is Exposed
If your dog comes in contact with questionable fresh or salt water, bathe or at least rinse him off with clean (tap) water right away, before he licks his fur. Take precautions to avoid exposure to yourself; wear gloves or wash your hands after rinsing your dog.
 
Take your dog to a veterinary clinic if she has swallowed water containing algae or has licked her fur after wading in water with an algal bloom. Symptoms of toxin exposure constitute a medical emergency, so seek veterinary care immediately if your dog is vomiting or stumbling after water contact.
 
Prevention
The Centers for Disease Control and Prevention (CDC) and the NC Department of Health and Human Services (DHHS) recommend these precautions:

• Keep pets away from water that is scummy/discolored or contains dead fish.
• Rinse off pets that have had contact with potentially contaminated water.
• Do not use questionable water for irrigation or cleaning.
• Do not disrupt algal blooms with jet skis or water skiing.

 
More Information
Cyanobacteria: Protecting Children & Dogs (NCDHHS): https://epi.dph.ncdhhs.gov/oee/algae/protect.html
Harmful Algal Bloom (HAB)-Associated Illness (CDC): https://www.cdc.gov/habs/index.html

Photo source: https://www.usgs.gov/media/images/harmful-algal-blooms-6

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