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Harmful Algal Blooms

  • Harmful Algal Blooms Home
  • Fact Sheet
  • Causes and Symptoms
  • Prevention
  • Illness in Animals
  • Statistics
  • For Local Government Agencies
  • For Veterinarians

Related Topics

  • Waterborne Illness
  • Recreational Water Illness
  • Infectious Diseases A-Z
  • Reportable Infectious Diseases

Harmful Algal Blooms

  • Harmful Algal Blooms Home
  • Fact Sheet
  • Causes and Symptoms
  • Prevention
  • Illness in Animals
  • Statistics
  • For Local Government Agencies
  • For Veterinarians

Related Topics

  • Waterborne Illness
  • Recreational Water Illness
  • Infectious Diseases A-Z
  • Reportable Infectious Diseases
Contact Info
Infectious Disease Epidemiology, Prevention and Control Division
651-201-5414
IDEPC Comment Form

Contact Info

Infectious Disease Epidemiology, Prevention and Control Division
651-201-5414
IDEPC Comment Form

Harmful Algal Bloom-Related Illness Information for Veterinarians

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

  • Veterinary Harmful Algal Bloom (HAB) Case Report Form (PDF)
    For all animal cases, please fill out this form. Fax completed form to 1-800-233-1817.
  • Phone
    Illnesses may be reported by phone to 651-201-5414 or 877-676-5414.

Clinical Features

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

ToxinExposure RouteOnset to SymptomsLikely Symptoms
Hepatotoxins 
Cylindrospermopsins
Microcystins
Nodularins
Ingestion1 to 2 hours, or moreAcute depression 
Weakness & incoordination 
Loss of appetite
Excessive drooling
Vomiting & diarrhea 
Abdominal tenderness
Jaundice
Dark urine
Neurotoxins 
Anatoxin-a
Anatoxin-a(s)
Saxitoxins
IngestionMinutes to hoursExcessive drooling
Apprehension & anxiousness
Vomiting
Muscle twitching
Seizures
Respiratory failure
Dermatotoxins 
Lyngbyatoxin-a
Aplysiatoxin
Skin contactMinutes to hoursRash
Hives
Allergic reaction

Treatment

  • 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.
     
  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

  • Harmful Algal Bloom Facts for Veterinarians (PDF)
    Information provided includes general HAB facts, symptoms, differential diagnoses, possible laboratory findings, and treatment options.

Resources for Veterinarians

Suspect Illness is Due to Harmful Algae? Harmful Algal Bloom Magnet for VeterinariansSuspect Illness is Due to Harmful Algae? Harmful Algal Bloom Magnet (PDF)
Printable template for magnet or card

  • CDC Animal Safety Fact Sheet (PDF)
    • CDC Animal Safety Fact Sheet, Spanish (PDF)
  • CDC Animal Safety Poster (PDF)
    • CDC Animal Safety Poster, Spanish (PDF)
Tags
  • harmful algal blooms (HABs)
Last Updated: 04/25/2025

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