Wilderness Medicine
Harmful Algal Blooms
Background
- Definition
- Rapid proliferation/accumulation of toxin-producing cyanobacteria
- Potential to cause illness in humans
- History/Current Information/News
- Brevenal, an investigational cystic fibrosis (CF) disease modifying drug, is being evaluated as a potential brevetoxin antagonist
- Synopsis
- Also known as Red Tide
- Symptoms associated with HAB exposure
- Skin, eye, ear irritation
- Liver damage
- Gastrointestinal, respiratory, and neurologic signs/symptoms
- Supportive management
- Currently no available tests or specific treatments for HAB-associated illnesses
- Management geared towards prevention and community awareness
Pathophysiology
- Mechanism
- Toxic effects/disease from exposure to/swimming in contaminated waters during blooms
- Accumulation of biotoxins produced by cyanobacteria
- Etiology/Risk Factors
- Etiology
- Phytoplankton overgrowth producing toxins
- Cyanobacteria: algal blooms in fresh water and occasionally in marine water
- Dinoflagellates: most common cause of HABs in marine waters
- Diatoms: marine and brackish waters, including estuaries
- Identified toxins
- Saxitoxin
- Cylindrospermopsin
- Anatoxin
- Note
- Snow algae ("watermelon" or "pink" snow) can also cause toxin effects when ingested/exposed
- Human laboratory workers and fishermen with Possible estuary-associated syndrome (PEAS)
- Routes of Exposure
- Inhalation of toxin aerosols
- Ingestion of contaminated shellfish
- Risk Factors
- Corals in fish tanks or sea air
- Warm waters or during warm seasons
- HABs have occurred in every region of the United States
- Usually occur in the summer and early fall
- Increases in nutrient levels (e.g., phosphorus, nitrates)
- Fertilizer run-off (i.e., residences, agricultural lands)
- Sewage discharges
- Run-off from cities and industrial facilities
- Changes in nutrient levels associated with ocean upwelling (i.e., El Niño, El Niña)
- Low water flows (i.e., drought)
- Changes in
- Water temperature (especially increases in temperature)
- Chemical factors (e.g., pH, turbidity)
- Ocean currents
- Local ecology (interactions of organisms)
- Epidemiology
- Incidence/Prevalence
- Warming temperatures in Lake Erie
- Resulted in more extensive blooms of cyanobacteria Microcystis aeruginosa, last into early winter months
- Increasing frequency and in more locations in the US in the past several years
- Mortality/Morbidity
- Mortality
- Human fatalities are rare
- Isolated cases have been reported throughout the world
- Most were due to consumption of contaminated shellfish
- Morbidity
- Vision impairment
- Neurocognitive impairment (e.g., paralysis, amnesia)
- Asthma/COPD exacerbation
- Scarring from rashes
- Death
Diagnostics
- History/Symptoms
- May present soon after exposure
- Fever
- Headache
- Eye irritation
- Sneezing
- Cough
- Nausea
- Neurologic symptoms (e.g., confusion)
- Human laboratory workers and fishermen with PEAS
- Respiratory, eye irritation
- Rashes
- Abdominal cramps
- Vomiting
- Cognition, personality changes
- Most neurocognitive symptoms appear to resolve within several months post-exposure
- Symptoms may vary
- Mild respiratory irritation (due to inhalation of toxin aerosols)
- Severe systemic toxicity (caused by ingestion of toxins)
- Physical Exam/Signs
- Rash
- Vomiting, diarrhea
- Respiratory distress, wheezing
- Paresthesias
- Labs/Tests
- CBC +Diff
- BMP
- Electrolytes
- Urinalysis as needed
- Imaging
- Usually not necessary unless suspect other etiology
- Table 1. Effects by Organism
| Organism |
Water Source |
Color |
Toxin |
Target Tissue |
Effects |
| Alexandrium spp. |
Salt |
Red/Brown |
Saxitoxins |
|
- Paralysis, Death
- Paralytic shellfish poisoning
|
| Karenia brevis |
Salt |
Red |
Brevetoxins |
- Nervous System
- Respiratory System
|
- GI illness, muscle cramps seizures, paralysis
- Respiratory, especially asthmatics
|
| Pseudonitzschia |
Salt |
Red/Brown |
Domoic acid |
Nervous System |
- Amnesiac shellfish poisoning
- Vomiting, diarrhea, confusion, seizures
- Permanent short term memory loss
- Death
|
| Microcystis |
Fresh |
Blue-green |
Microcystin |
Liver |
|
- Microscopy of water source
- Biopsy of skin as needed
- Rule out other dermatological disorders
- Differential Diagnosis
- Chemical poisoning/dermatitis
- Shellfish allergy
- Puffer fish neurotoxicity
- Anaphylaxis
- Food poisoning
- Cercarial dermatitis
- Drug reaction
Treatment
- Initial/Prep/Goals
- ABCs, IV access as needed, monitor
- Prep for intubation if respiratory failure
- Anaphylaxis
- Medical/Pharmaceutical
- PEAS
- If visual contrast sensitivity reduction
- Dermatitis, rashes, pruritis
- Mild
- Severe
- If face involvement
- Nausea, vomiting
- Diarrhea, abdominal cramps
- Fluid Hydration
- Loperamide: 4 mg PO plus 2 mg after each loose stool (max dose 16 mg daily)
- Respiratory symptoms
- Antihistamines
- Consider for mild respiratory irritation from inhalational exposure
- Albuterol: 1-2 inhalations q4-6h PRN
- Neurologic symptoms
- Complications
- Cholestyramine
- Edema
- Dizziness, fatigue, headache
- Skin rash, urticaria
- Abdominal pain, constipation, nausea
- Easy bruising, prolonged PTT
- Tinnitus
- Asthma, wheezing
- Triamcinolone and fluocinonide
- Contact dermatitis
- Hypersensitivity
- Prochlorperazine
- Hypotension, peripheral edema, ECG abnormalities
- Tardive dyskinesia, pseudoparkinsonism, NMS
- Lupus-like syndrome, tremor
- Blurry vision
- Asthma
- Ondansetron
- Headache, fatigue
- Constipation
- Hypoxia
- Loperamide
- Constipation, abdominal cramps
- Albuterol
- Tachycardia
- Tremors
- Hyperglycemia
- Prevention
- Avoid contact with water that is discolored or has scum or film floating on the surface
- Recreational, fishing, swimming
- Avoid drinking untreated water from lakes, streams, or rivers
- Persons with chronic respiratory illness (asthma, COPD) should avoid Red Tide areas
- Food safety
- Commercially bought seafood is safe to eat
- Do not eat clams or oysters taken from waters affected by the Red Tide
- Shrimp and crabs are safe to eat
- Recreational fishing
- Finfish caught live can be eaten if filleted first
Disposition
- Admission Criteria
- Severe symptoms require close monitoring
- Breathing difficulty
- Anaphylactic symptoms
- Consult(s)
- Infectious diseases
- Gastroenterology (if needed)
- Dermatology (if needed)
- Neurology (if needed)
- Ophthalmology (if needed)
- Discharge/Follow-up Instructions
- Report to local/regional/state dept of public health in order to be investigated and prevent exposure of population
- Follow-up with PCP
References
- Figgatt M, Hyde J, Dziewulski D, et al. Harmful Algal Bloom - Associated Illnesses in Humans and Dogs Identified Through a Pilot Surveillance System -- New York, 2015. MMWR. Nov 3, 2017;66(43):1182-1184
- Centers for Disease Control and Prevention (CDC). Harmful Algal Bloom (HAB) - Associated Illness. Available at: https://www.cdc.gov/habs/general.html. [Accessed October 2018]
- Poison Control - National Capital Poison Center. Harmful Algal Blooms. Available at: https://www.poison.org/articles/2015-jun/algal-blooms. [Accessed October 2018]
- Hilborn ED, Roberts VA, Backer L, et al. Algal bloom-associated disease outbreaks among users of freshwater lakes--United States, 2009-2010. MMWR. Jan 10, 2014;63(1):11-15
- Shoemaker RC, Hudnell HK. Possible estuary-associated syndrome: symptoms, vision, and treatment. Environ Health Perspect. May 2001;109(5):539-545
- NIH-National Institute of Environmental Health Sciences. Harmful Algal Blooms. Available at: https://www.niehs.nih.gov/health/topics/agents/algal-blooms/index.cfm. [Accessed October 2018]
- Fleming LE, Kirkpatrick B, Backer LC, etc. Review of Florida Red Tide and Human Health Effects. Harmful Algae. Jan 1, 2011;10(2):224-233
- Bourke J, Coulson I, English J, British Association of Dermatologists Therapy Guidelines and Audit Subcommittee. Guidelines for the management of contact dermatitis: an update. Br J Dermatol. May 2009;160(5):946-954
- Fleming LE, Kirkpatrick B, Backer LC, et al. Aerosolized red-tide toxins (brevetoxins) and asthma. Chest. Jan 2007;131(1):187-194
- Bourdelais AJ, Campbell S, Jacocks H, et al. Brevenal Is a Natural Inhibitor of Brevetoxin Action in Sodium Channel Receptor Binding Assays. Cellular and molecular neurobiology. 2004;24(4):553-563.
- MOTE Marine Laboratory & Aquarium. Florida Red Tide FAQs. Available at: https://mote.org [Accessed October 2018]
Contributor(s)
- Ho, Nghia, MD
- Pacheco Caleb S, MD
Updated/Reviewed: October 2018