What Happens in a Dog's Body with Cyanotoxin?

By Dr. Jennifer Coates, DVM

When it’s hot, very few dogs can resist taking a dip and probably a sip from whatever water is nearby. Usually, that’s not a problem, but if the water is home to large numbers of blue-green algae (also called cyanobacteria), owners should do everything in their power to keep their dogs away.

Here’s why.

Many species of blue-green algae produce toxins that collectively are called cyanotoxins. 

In truth, there are more than 30 species of potentially dangerous blue-green algae that produce several different types of toxin, but for our purposes, we can divide cyanotoxins into two main categories:

1. Neurotoxins—toxins that primarily affect the nervous system
2. Hepatotoxins—toxins that primarily affect the liver

Routes of Exposure

The most serious damage from cyanotoxin occurs when a dog ingests blue-green algae. This typically happens when a dog drinks from a contaminated body of water but can also be associated with swimming when dogs either inadvertently get a mouthful of water or try to lick themselves clean after they get out.

Blue-green algae primarily live in stagnant or slow-moving bodies of fresh water that are warm and carry a large nutrient load (e.g., are polluted with fertilizer, animal waste, etc.). Salt or brackish water cyanotoxin poisonings are possible but occur much less frequently. Most cases occur in the late summer.

When people swim in blue-green algae contaminated water, we can develop skin rashes, eye irritation, ear inflammation, and respiratory problems. Similar symptoms probably occur in dogs as well, but they tend to be overshadowed by the effects of neurotoxins and hepatotoxins.

The Effects of Blue-Green Algae Neurotoxins on Dogs

Blue-green algae neurotoxins take effect very quickly.

They work by overstimulating the nervous system, which then essentially “wears out” over a short period of time if the dose is high enough.

Within minutes of ingestion, a dog develops symptoms like weakness, unsteadiness, muscle cramps, twitching, tremors, salivation, excessive tear production, urination, defecation, and difficulty breathing. Soon thereafter, severely affected animals may exhibit seizures, heart failure, and paralysis. Most die even if they receive prompt and appropriate treatment.

The Effects of Blue-Green Algae Hepatotoxins on Dogs

Blue-green algae hepatotoxins do their damage a little more slowly.

Symptoms can take hours or even a day or two to before they become evident but are all related to the death of liver cells and liver failure. Signs typically include some combination of lethargy, weakness, vomiting, diarrhea, abdominal pain, loss of appetite, pale or yellow skin and mucous membranes, and abnormal bleeding or bruising.

Supportive treatment for liver failure can be successful in milder cases, but most patients still die or are euthanized due to a poor prognosis. There is one report of a severely affected dog recovering after receiving the drug cholestyramine, but the link between treatment with this drug and the dog’s outcome isn’t clear.

Preventing Cyanotoxin Exposure

Since treatment for cyanotoxin exposure is so rarely successful, prevention is absolutely essential.

Blue-green algae blooms tend to look like a thick soup or a layer of paint floating on the surface of the water. Wind may push them into dense mats. Some types are a bright green color while others are more blue, brown, or a mixture of red and green. It is impossible to know whether an algal bloom with this appearance is toxic without laboratory analysis so it’s always best to be on the safe side and keep your dog (and yourself) away from any body of water that is potentially contaminated with cyanotoxin.

Related articles:
Summer Perils: Blue-Green Algae

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