On October 26, 2011, Texas governmental agencies halted oyster harvesting off the coast of the state. The reason – red tide associated with Karenia brevis algae. Red tide is an interesting phenomena. Basically, an algal bloom tints the ocean waters a reddish or brownish hue. The problem is that these algae can produce toxins which decimate fish and shellfish. Consumers who consume fish or shellfish, including oysters or mussels, tainted by these toxins, can suffer neurotoxic shellfish poisoning. Neurotoxic shellfish poisoning, like many forms of foodborne illness will cause nausea. However, this form of food poisoning can also lead to dizziness and tingling sensations throughout a victim’s body. In rare, more severe cases, a victim may suffer paralysis and difficulty breathing. This can result in a fatality.
There are three different forms of algae associated with red tide in different geographic areas of the world. Alexandrium fundyense is found in northeastern U.S. and Canadian waters. Alexandrium catenella affects pacific waters, while karonia brevis is centered in Gulf of Mexico waters.
The press release issued by the Texas health department is reprinted below.
The Texas Department of State Health Services announced today that oyster harvesting in all Texas coastal waters is closed due to red tide, an algal bloom of Karenia brevis.
Red tide has been detected along the Texas coastline from Brownsville to Galveston. As a result, all Texas coastal waters are closed to the commercial and recreational harvesting of oysters, clams and mussels until further notice. Normally, the public can harvest oysters from Nov. 1 through April 30.
The algae contain a toxin that can accumulate in the tissue of oysters, clams, mussels and whelks and cause neurotoxic shellfish poisoning, or NSP, in humans who consume them. NSP symptoms can include nausea, dizziness, dilated pupils and tingling sensations in the extremities.
DSHS is advising people not to harvest and eat oysters, clams, or mussels from Texas coastal waters. Oysters can be toxic without any indication of red tide such as discolored waters, respiratory irritation or dead fish. People are also advised not to harvest and eat whelks from Texas waters as these species also accumulate toxin from the red tide organism.
The warning does not apply to other types of seafood such as shrimp, finfish, crabs or to commercial seafood products from other states or countries. Oysters in the market place that were harvested before the red tide began or from other states are not affected by this algal bloom.
The red tide toxin also can become aerosolized and cause coughing and irritation of the throat and eyes. People with respiratory conditions such as asthma may experience more pronounced symptoms. Respiratory symptoms usually subside when affected people leave the red tide areas.
Richard J. Arsenault, 2011
