Blue-Green Algae and Other Water Toxins & Treatments

Pet exposures to blue-green algae (cyanobacteria) increase as summer heats up, so here's information from the ASPCA Animal Poison Control Center to help you with diagnosis and treatment if you encounter it in your practice.

What It Is, How It Forms

Cyanobacteria is a group of organisms known to cause poisoning in dogs, cats, livestock, wildlife, birds and fish. There have also been a few documented toxicities seen in humans. The problem is most likely to occur in bodies of fresh water when the weather has been warm (over 75 degrees F) and sunny.

The overgrowth is stimulated by the presence of high levels of nitrogen, which often occurs following flooding or runoff from heavy rains or snows in fields and pastures where there is manure from livestock or wildlife, heavy fertilizer use or after grass or forest fires. 

There are more than 30 species of cyanobacteria associated with toxic water blooms. Some will produce neurotoxic alkaloids called anatoxins while others produce hepatotoxins called microcystins – and some genera produce both. When both types of toxins are present, neurologic signs will appear within minutes; hepatotoxins will take one or more hours after exposure to cause signs.

Water containing toxic algal blooms will often have the appearance of a pea-green paint or slime on the surface. If certain wind conditions are present the film will often concentrate along the shoreline in areas where animals may drink or swim. With very severe blooms, there may be a die-off of fish or waterfowl in the area.

Treatment Plans

• If possible, tell the owner to wash the pet off in fresh water immediately so the pet doesn’t lick bacteria from the coat.
• Emesis should be induced as early as possible as long as the pet is not at risk for aspiration due to the onset of CNS signs.
• Activated charcoal should be given if there is not a risk of aspiration.
• If readily available, cholestyramine resin may be more effective than charcoal and may be dosed at 0.3-1 g/kg TID X 4 days.
• Liver values should be monitored at baseline, 24 hours and 48 hours. Elevation of bile acids is one of the earliest signs due to the cessation of bile flow from the liver; elevations in ALKP, GGT, and AST are often seen as well. In recumbent animals there may be increases in CK and LDH. Blood glucose should also be monitored as hypoglycemia is a risk, and  5% dextrose can be added to the fluids to help maintain blood glucose. Electrolytes should be monitored and corrected as needed with fluid therapy.
• Pets should be placed on IV fluids and seizures controlled with anticonvulsants. Many animals may develop vomiting and hemorrhagic diarrhea; cerenia should be administered to control vomiting and antibiotics should be considered to prevent secondary infections if signs are severe.
• Intrahepatic hemorrhage may lead to hypovolemic shock; whole-blood transfusions should be considered to help treat these issues. 

Other Freshwater & Saltwater Dangers

Saltwater: Many dogs just love playing in the waves, and when they do they can drink a lot of saltwater in a short time. Because of the salinity, hypernatremia can occur. Clinical signs may include vomiting, polydipsia, ataxia, depression, tremors, and seizures.

Ocean creatures: Starfish, jellyfish, sea urchins, squid – there are a lot of creatures in the water that can cause harm. Fortunately, most of them live far enough out in the water that most pets won’t come in contact with them. Pets often find sea creatures dead on the shore when they are likely to pose less of a problem.

Red tide: This is a common name for an algal bloom caused by certain species of dinoflagellates; they are recognizable by their red-brown color. Not all red tides produce toxins, however when they do regional differences are noted.

Brevetoxins are primarily isolated from blooms in the Gulf of Mexico and the Gulf of California. Concerns may include ocular and respiratory irritation, gastroenteritis, disorientation, ataxia, and possible seizures. Pets can become ill from drinking the water, eating dead fish (mainly bivalves), or inhalation.

On the northern Atlantic and Pacific coasts, paralytic shellfish poisoning may occur and is often noted by ataxia, restlessness, paralysis, tachycardia, and potentially respiratory distress. Pets generally become ill by eating contaminated shellfish, particularly bivalve shellfish.