WATERBORNE DISEASES UNIT
Harmful Algal Bloom Facts for Veterinarians
What are cyanobacteria (bluegreen algae) and cyanotoxins?
Algal blooms, often found in warm,
nutrient-rich water, are sometimes made
up of cyanobacteria, commonly called bluegreen algae. Cyanobacterial blooms are
often described as looking like pea soup or
spilled green paint. Blooms can also
produce an offensive odor when the cells
decompose. Some cyanobacteria can
produce toxins, called cyanotoxins that
affect the liver or nervous system.
Microcystin, a hepatotoxin, is the primary
cyanotoxin identified in Minnesota lakes.
What is a harmful algal bloom
(HAB)?
Harmful algal blooms (HAB) are
cyanobacterial algal blooms containing
toxins, which can pose harmful health risks.
Not all cyanobacterial blooms produce
toxins, but it is impossible to tell if a bloom
is toxic or not just by looking at it;
laboratory tests are required. Since
cyanotoxins can be lethal to animals even in
small amounts, caution should always be
taken when a bloom occurs. Advise your
clients, “When in doubt, stay out.”
Where and when are HABs found?
Cyanobacteria can be found everywhere in
Minnesota, but thrive in warm, shallow,
nutrient-rich lakes commonly found in
central and southern Minnesota. Blooms
usually occur during late summer and early
fall, but can occur in early summer if
conditions are right.
How can an animal be exposed?
Animals can be exposed when they drink
from, swim in, or lick fur or hair containing
toxic water or algae. Animals are more
likely than humans to be exposed because
they do not always naturally avoid entering
and ingesting green, foul-smelling water.
For this reason, animals are commonly used
as sentinels for human illness.
What treatment options are
available?
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. Activated
charcoal slurry may be useful to bind toxins
in the gut and reduce absorption. 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. Milk thistle
(Silybum mariamum) has also been used
intravenously for general liver protection;
this is also experimental.
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Cyanotoxin Exposure and Clinical Information
Toxin
Exposure
Route
Onset to
Symptoms
Neurotoxins
Anatoxin-a
Anatoxin-a(s)
Saxitoxins
Dermatotoxins
Aplysiatoxin
Lyngbyatoxin-a
Hepatotoxins
Cylindrospermopsins
Microcystins
Nodularins
Likely Symptoms
Differential Diagnosis
1 to 2
hours, or
more
Acute depression
Weakness &
incoordination
Loss of appetite
Excessive drooling
Vomiting & diarrhea
Abdominal tenderness
Jaundice
Dark urine
Ingestion
Minutes to
hours
Skin
contact
Minutes to
hours
Excessive drooling
Apprehension &
anxiousness
Vomiting
Muscle twitching
Seizures
Respiratory failure
Rash
Hives
Allergic reaction
Acetaminophen
Nonsteroidal antiinflammatories
Aflatoxin
Mushrooms
Sago/cycad palm
Metals: copper, zinc, iron
Xylitol (dogs only)
Rodenticides
Other hepatotoxins
Organophosphates
Carbamates
Chlorinated hydrocarbon
Bromethalin
Metaldehyde
Mushrooms
Other neurotoxins
Other dermal allergens
Ingestion
Possible Laboratory or Other
Findings
Elevated bile acids & liver enzymes
Hypoglycemia
Proteinuria
Prolonged clotting times
Presence of toxin in biological
specimens (liver, stomach contents,
stool) collected from animals that
became ill
Blue-green staining of fur or hair
Presence of toxin in biological
specimens (stomach contents,
urine, serum) collected from
animals that became ill
Blue-green staining of fur or hair
Blue-green staining of fur or hair
Notes: Information about health effects from exposure to cyanobacteria and toxins is derived from reports of animal poisonings. For more
information see the Merck Veterinary Manual.
To better understand the incidence and geographic distribution
of HAB-related illnesses in Minnesota, we request veterinarians
report suspected cases of HAB-related illness to the MDH
Waterborne Diseases Unit. If you have questions or comments
please contact us at: 651-201-5414 or toll free 1-877-676-5414.
Minnesota Department of Health
Waterborne Diseases Unit
PO Box 64975,
St. Paul, MN 55164
651-201-5414 or 1-877-676-5414
www.health.state.mn.us
To obtain this information in a different format, call: 651-201-5414.
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