Red Tide

Information for Health Care Professionals

Red Tide is sometimes present along the eastern coasts of Maine and New Hampshire .  Certain shellfish can be contaminated and not safe for consumption.  The types of shellfish contaminated vary by area.

Cause:  Bivalve, and some univalve, shellfish eat toxic plankton algae.  The Alexandrium species of dinoflagellate algae contains saxitoxin. 

Mechanism:  Saxitoxin reversibly blocks voltage-gated sodium channels, preventing action potential and resulting in neuromuscular blockade.  Respiratory paralysis may occur in severe cases.

Clinical effects:
Mild:   paresthesias of tongue, lips and throat that may spread to face, neck, arms, fingers, toes, headache, nausea (gastrointestinal effects may not be noted)
Moderate:  weakness of limbs, ataxia, incoherent speech, difficulty breathing, floating sensation and giddiness, dizziness, rash, fever, tachycardia and hypertension, dyspnea
Severe:  choking sensation, severe respiratory difficulty/failure (usually within 12 hours)

Onset: 30 minutes to 10 hours (usually within 2 hours)

Duration:  hours to days (muscle weakness may last weeks)

Treatment:  If patients presents soon after ingestion, consider lavage and activated charcoal; symptomatic/supportive; possibly IV fluids and sodium bicarbonate

Shellfish that may be unsafe:  

• Clams [Soft Shell, Hard Shell (Quahogs), Surf or Hen]
• Mussels
• Oysters (both American and European)
• Quahogs
• Snails
• Whelks

Odor and taste are unaffected.  The toxins are heat stable and water soluble.  Cooking/freezing will not destroy saxitoxin.  Cooking broth may contain toxins. 

Fish that currently appear safe (not all-inclusive):   

• Crab (eat only cleaned and picked muscle tissue, not whole crabs)
• Lobster (avoid tomalley)
• Scallops (as long as only the adductor muscle is eaten – typical)
• Shrimp
• Finfish

Clinical Consultation/Reporting:  Call 1-800-222-1222 for clinical assistance.  Please report cases to the Northern New England Poison Center , which will forward information to the Maine Center for Disease Control or the New Hampshire Department of Health and Human Services.
 
The State of Maine Department of Marine Resources provides information regarding Red Tide Closures at  and through a 24-hour hotline (1-800-232-4733 or 207-633-9571). 

The State of New Hampshire Department of Environmental Services provides information on Red Tide Closures on their Webs ite.

The Maine Center for Disease Control and Prevention provides updated information on Red Tide on their Web site.

The Northern New England Poison Center provides clinical assistance 24 hours daily at 1-800-222-1222, 207-662-4720 for callers outside the States of Maine, New Hampshire or Vermont .