Algae Blooms Toxicity in Dogs

Algae Blooms Toxicity in Dogs - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Algae Blooms Toxicity?

The wind can cause the floating blooms to move together and form blue-green “mats”, near the shore. The bacteria grow best in nutrient-rich water and are more abundant during summer and early fall months. 

Most algae blooms are not toxic but some species of cyanobacteria produce toxins called cyanotoxins. Harmful algal blooms can appear quickly and may also have a foul odor. Sometimes dead fish may be seen floating in water with a high concentration of the toxic bacteria.  

Pet owners can not differentiate between non-threatening or poisonous bacteria blooms. Therefore, dogs should not be allowed to swim in blue-green water. If you find your dog swimming or wading in blue-green water, it is important to immediately remove him from the water. He should then be hosed off.   Rinsing him off may inhibit further dermatoxin exposure and will also prevent him from licking the toxins off his coat. As a precaution, your dog should be seen by a veterinarian. Some holistic veterinarians recommend giving Arsenicum album 30C or Nux vomica 30C immediately after exposure to the bacteria and then heading to an emergency veterinarian facility. The homeopathic medicine may slow down the effects of the toxins.

If your dog was recently swimming and is experiencing symptoms of toxic algae bloom, he must be seen by a veterinarian as soon as possible. Exposure to toxic algae bloom can be fatal in animals.  There have been no human deaths in the United States caused by cyanotoxins but the exposure to the toxic blooms can also make humans very sick.

Toxic algae blooms can be found in a pond, lake, river or brackish water. Toxic algae blooms are also known as blue-green algae because the blooms give the water source a blue-green appearance. The harmful algal bloom (HAB) may look like algae but they are a type of photosynthetic bacteria called cyanobacteria. Exposure to the harmful algal bloom can be hazardous to animals and people.

Symptoms of Algae Blooms Toxicity in Dogs


Symptoms may take 12 to 24 hours to appear. 

  • Vomiting
  • Diarrhea
  • Dark Urine 
  • Blood in stool or black, tarry stool
  • Elevated liver enzymes
  • Liver Damage


 Symptoms usually occur 30 to 60 minutes after exposure to the blooms.

  • Stumbling
  • Seizures
  • Disorientation
  • Increased heart rate
  • Incoordination
  • Labored breathing
  • Muscle tremors
  • Muscle rigidity
  • Lethargy
  • Paralysis


  • Rashes
  • Hives
  • Blisters
  • Excessive drooling
  • Tearing
  • Seizures


  • Drooling
  • Vomiting
  • Diarrhea
  • Stumbling
  • Pain
  • Dehydration
  • Thirst


Toxins produced by cyanobacteria are:

  •  Microcystin (hepatotoxin) damages the liver
  • Anatoxin (neurotoxin) is destructive to the nervous symptom
  • Lyngbyatoxin (dermatoxin) attacks the skin and the mucous membrane; exposure to dermatoxin can lead to skin necrosis
  • Cylindrospermopsin (nephrotoxin) damages the cells of the kidneys

Causes of Algae Blooms Toxicity in Dogs

Toxic algae blooms are caused by a combination of:

  • Excess nutrients (such as phosphorus, nitrogen) in the water; phosphorus and nitrogen are found in animal and human wastes and in fertilizers 
  • Fertilizer run-off into brooks, streams and creeks, which make its way into river and lakes
  • Low-water
  • Non-flowing fresh water
  • Warmer temperatures
  • Lakes with zebra mussels are more susceptible to toxic blooms

Diagnosis of Algae Blooms Toxicity in Dogs

It is important to let your veterinarian know that your dog was swimming in blue-green water.  If possible take a sample of the water to the veterinarian. A microscopic examination of the water sample can confirm the presence of the toxigenic bacteria.

The veterinarian team will first need to stabilize your dog. The veterinarian may want to run a serum chemistry panel, which can determine organ function. He may check the patient’s reflexes, coordination, heart rate and balance.  To help determine neurological damage the veterinarian may recommend a magnetic resonance imaging test (MRI) or computed tomography (CT scan).  The MRI can produce detail images of the tissues, bones, organs and nerves. The CT scan can provide two-dimensional images of organs, bones and tissues. Your dog will need to be sedated for a CT scan or for an MRI.

Treatment of Algae Blooms Toxicity in Dogs

The toxins attack the body rapidly.  Prompt diagnosis and treatment is essential for the survival of the your companion.  The veterinary team will treat your dog with intravenous fluids, electrolytes and anti-seizure medication. He may also be given activated charcoal. Your dog will need to be hospitalized to provide him with 24/7 intensive care.

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Recovery of Algae Blooms Toxicity in Dogs

The recovery prognosis is very grave. Dogs that do recover may suffer repercussions due to the poisoning incident, such as chronic liver disease, neurological damage or tumors. Follow-up visits will be necessary to monitor his progress.

Algae Blooms Toxicity Questions and Advice from Veterinary Professionals





One Year


4 found this helpful


4 found this helpful

My pet has the following symptoms:
My dog swam in a lake with confirmed blue green algae 4 days ago. We weren’t aware of the issue and didn’t see any along the shore line where he swam. He is not showing any signs Or symptoms that I am aware of. Should I still have him seen?

July 29, 2020

Answered by Dr. Michele K. DVM

4 Recommendations

Thank you for your question. I'm sorry for the other dog passing away. The signs of blue-green algae tend to be quite sudden and abrupt, and I would think four days later that you should be fine. If you do notice any signs of vomiting or diarrhea, or lethargy or sudden collapse, it would be best to have Whiskey seen by a veterinarian immediately, but it seems to me that you would be out of the Danger Zone by now.

July 30, 2020

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