Harmful algal blooms (HABs)

Animal’s history

Several questions should be asked to determine if the animal’s history points to a potential exposure:

• Has your sick animal been in or near a water source?
• Was that water source discolored?
• Did you notice any green mats on the surface?
• Has the water been tested for HABs?
• Is the physical exam consistent with any particular HAB toxin?

Physical exam findings/Clinical signs

The animal’s symptoms may indicate exposure to hepatotoxins, neurotoxins, or dermatoxins. Common clinical signs include:

• Vomiting and diarrhea
• Jaundice
• Seizures with no history of seizure activity
• Ataxia
• Changes in reflexes
• Whole body rash that is acute
• Coughing, dyspnea

Clinical pathologic findings

Abnormal blood work may also substantiate HAB toxin exposure. 

CBC:

• Thrombocytopenia – leading to poor clotting
• HCT – normal to increased at first, then decreased

Clotting times:

• APTT/PTT – clotting times increased

Chemistry:

• May see codocytes and acanthocytes in the red blood cells due to hepatic disease
• Metabolic acidosis
• Elevation in all liver enzymes and total bilirubin
• Potential for hypoglycemia
• Hypocalcemia
• Possible evidence of prerenal azotemia

Confirming HAB exposure

Several laboratories test animal samples for evidence of toxicosis from harmful algal blooms. Samples of vomitus and/or urine can be submitted for testing; follow the recommendations of the laboratory conducting the test. Do not submit vomitus after charcoal has been given. It is important to acquire samples at presentation and not to delay supportive treatment.

Guidelines for vomitus or urine sampling:

• 250 ml
• No preservatives in containers
• Freeze if not sending immediately

It is easier to find laboratories that do water testing. If the owner is able to bring a water sample from the suspected source on the same day the animal was exposed, it can be helpful for diagnosis. Toxins in the water change rapidly, and collecting the water more than 24 hours post-exposure may not give accurate results. Water samples can be frozen and tested for toxins at a later time. Fresh samples are required for identification of the type of bloom.

Water sampling:

• 250 ml
• No preservatives in container
• Send fresh sample to identify bloom

Laboratories that analyze for cyanobacteria and cyanotoxins

Acute treatment at presentation

• Washing of hair/coat/feathers/skin
• Induction of emesis if conscious and not vomiting
• Cholestyramine over activated charcoal if an alert pet has probably ingested microcystin or nodularin
• IV fluids for volume resuscitation and optimization
• IV fluids +/- dextrose
• Antibiotics: Ampicillin, enrofloxacin, metronidazole
• Gastroprotection/antiemetics
• Vitamin K
• Plasma

Long-term treatments

• Antioxidants
• Vitamin E
• Silymarin
• S-adenosyl-L-methionine
• N-acetylcysteine
• Ursodeoxycholic Acid
• Cholestyramine

The best way to avoid exposure to toxic algal blooms is to prevent their overgrowth.

Climate change and anthropogenic changes add to the growth of these blooms. Studies have shown that each bloom has a different reaction to increased water temperature. Some increase in toxicity or the number of toxic subspecies, while other species increase in growth. Climate change also causes changes in the mixing of the water column, which can cause oxygen depletion, resulting in hypoxic events. Hypoxic events lead to beneficial growing conditions for HABs over other microalgae.

High levels of phosphorus and nitrogen in the water also increase the growth of all species of HABs. Increases in these nutrients might result from runoff from fertilizers from agriculture, private housing, or golf courses, or from industrial pollution (including pollutants absorbed from the air).

In addition, migration of organisms through the attachment to large shipping containers in conjunction with water temperature increases have allowed for movement of HABs into new areas.

Preventing algal blooms and exposure to HABs locally

• Prevent runoff of nutrient-rich deposits into the water source.
• Work with state and local health departments. Veterinarians can notify these agencies of suspected HAB toxicosis, and health departments can communicate to veterinarians and animal owners when a HAB is suspected in the area.
• Notify your local government officials about HABs, and talk with them about the impacts to animals and owners, and how HABs can be prevented.
• Plant nitrogen- and phosphorous-metabolizing plants.
• Keep herds away from any water suspected of harmful algal blooms. Block off the leeward side of a water supply to avoid contact with the bacteria.
• Monitor water for toxins regularly and educate clients to look for warnings in local water before allowing their pets to go near the water.

Proper reporting of HABs varies by state and by what the report involves. The U.S. Environmental Protection Agency (EPA) maintains a list of state HABs-monitoring programs and resources. If your state resource page does not have information on reporting animal exposures, check with your state animal health official (state veterinarian) or your state public health veterinarian (for states that have one).