Harmful Algal Bloom-Related Illness Information for Veterinarians - Minnesota Dept. of Health

Harmful Algal Bloom-Related Illness Information for Veterinarians

On this page:
Disease Reporting
Clinical Features
Laboratory Tests
Fact Sheet for Veterinarians

Disease Reporting

To better understand the incidence and geographic distribution of harmful algal bloom (HAB)-related illnesses in Minnesota, the Minnesota Department of Health (MDH) requests veterinarians report suspected cases of HAB-related illness to the MDH Waterborne Diseases Unit. Illness in animals is often the first sign that a toxic bloom is present in a waterbody due to their smaller size and behavior. Identification and reporting of animal cases can help identify a harmful algal bloom and prevent future animal and human illnesses.

How to report HAB-related illnesses

Clinical Features

Clinical features depend on the type of toxin and route of exposure.

Toxin Exposure Route Onset to Symptoms Likely Symptoms



1 to 2 hours, or more

Acute depression
Weakness & incoordination
Loss of appetite
Excessive drooling
Vomiting & diarrhea
Abdominal tenderness
Dark urine



Minutes to hours

Excessive drooling
Apprehension & anxiousness
Muscle twitching
Respiratory failure


Skin contact

Minutes to hours

Allergic reaction


  • There are no specific antidotes to these toxins.
  • Treatment is symptomatic and supportive.
  • Inducing vomiting within the first 2 hours of ingestion can help minimize absorption of ingested toxins.
  • An activated charcoal slurry may be useful to bind toxins in the gut and reduce absorption. (1)
  • Liver function should be monitored, and animals should be aggressively treated with fluids and corticosteroids to support liver function and prevent shock.
  • Neurologic symptoms may require seizure control and ventilator support.
  • Case reports have suggested that cholestyramine may be effective at treating microcystin poisoning, but this treatment is considered experimental. (2)
  • Milk thistle (Silybum mariamum) has also been used intravenously for general liver protection; this is also experimental. (3)
  1. The Merck Veterinary Manual. “Overview of Algal Poisoning.” Last modified December 2013. Attention: Non-MDH link.
  2. Rankin KA, Alroy KA, Kudela RM, Oates SC, Murray MJ, Miller MA. Treatment of cyanobacterial (microcystin) toxicosis using oral cholestyramine: case report of a dog from Montana. Toxins (Basel). 2013;5(6):1051-1063.
  3. Hackett ES, Twedt DC, Gustafson DL. Milk thistle and its derivative compounds: a review of opportunities for treatment of liver disease. J Vet Intern Med. 2013;27(1):10-16.

Laboratory Tests

If you suspect your client is experiencing a HAB-related illness or died from a HAB-related illness, please contact the Minnesota Department of Health at 651-201-5414 or 877-676-5414 for possible testing options.

Fact Sheet for Veterinarians

Updated Monday, 08-Nov-2021 09:42:58 CST