Red Tide – Harmful Algal Bloom (HAB)

Red Tide algal blooms are currently at high levels in areas along the Florida coast.  This type of algae poses a great risk to humans and animals in areas where exposures are high.  The red color of the ocean water comes from colonies of algae (Karenia spp., Chatonella spp.) that bloom or grow out of control. These organisms produce toxins called brevetoxins, which is a suite of cyclic polyether compounds.  Brevetoxins bind to voltage-gated sodium channels in nerve cells leading to disruption of normal neurological processes. This can affect the CNS of fish and mammals in the area.

Clinical signs in people and other animals can occur from direct exposure to affected water or ingesting animals that have died from it.  Shellfish can retain the toxin, thus causing neurotoxic shellfish poisoning (NSP) when eaten. Brevetoxins can be release into the air which can pose a respiratory risk to humans and animals close by. Swimming in the water may result in skin and eye irritation.

Of our companion animals, canines are most likely to be at risk from brevetoxins as they are more likely to get into the water and/or scavenge on dead animals. Clinical signs may occur rapidly and can include bradycardia, fluctuating blood pressure, and muscle fasciculations.

Treatment needs to be initiated immediately and some animals may be found dead near a carcass on the beach. Because brevetoxin effects occur quickly, decontamination may be limited. If the patient is asymptomatic and the exposure occurred recently, emesis may be induced if ingested, or bathing with a liquid dish soap in cases of dermal exposure.  If there are significant signs, the patient must first be stabilized then gastric lavage may be performed in cases of ingestion. If there has been dermal exposure, the pet should be bathed well. Staff should take caution to avoid skin and eye contact.

Treatment will include decontamination, when possible, IV fluids, anticonvulsants, and nursing care. Signs are expected to resolve within 6-72 hours.  Owners should be instructed to rinse and bathe pets immediately if dermal exposure occurs and bring their pets to the nearest veterinary facility right away after any exposure to red tide.


Written by:

Heather Handley, DVM