RED TIDE, SHELLFISH - USA (04): (WASHINGTON) ***********************************************************
A ProMED-mail post
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Date: Tue 25 Sep 2012
From: Andy Reich <Andy_Reich@doh.state.fl.us> [edited]
[Re: ProMED-mail Red tide, shellfish - USA (03): (WA) 20120916.1295932]
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It was rewarding to see an article in ProMED-mail related to health risks from paralytic shellfish poisoning associated with a harmful algal bloom (HAB) in the Pacific Northwest, USA.
The article referred to paralytic shellfish poisoning (PSP) as a "red tide" which is an incorrect description of this toxic event caused by the marine dinoflagellate, _Alexandrium_. Unfortunately, there is persistent confusion about the term "red tide," and we would like to offer some clarification.
"Red tide" has been used as a general term referring to exuberant growth in marine microorganisms, including dinoflagellates and diatoms (sometimes referred to as "micro algae"). The term is used very generally, leading people to misunderstand which organisms are causing a given bloom event and which are relevant associated health risks.
Readers, authors, and reviewers should pay attention to the type of organism and associated toxins when evaluating possible health risks.
Brevetoxins
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In Florida, the organism that causes Florida red tide is the dinoflagellate _Karenia brevis_ (formerly _Gymnodinium breve_). This organism produces brevetoxins, a series of polyether toxins.
Brevetoxins are toxic to all forms of sea life and, when they accumulate in molluscan shellfish, can cause neurotoxic shellfish poisoning (NSP) in people who eat the contaminated seafood. Typically, NSP is a self-limiting disease with gastrointestinal and some neurologic symptoms. In some instances, symptoms are more severe and can lead to hospitalizations. Inhalation of marine aerosols (such as sea spray) containing brevetoxins can cause upper respiratory irritation that may be severe in people with asthma.
Domoic acid
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In the Pacific Northwest, there is a group of different organisms, diatoms, of the genus _Pseudo-nitzschia_, that can produce domoic acid. Domoic acid is another potent neurotoxin that was first associated with human poisoning from eating shellfish harvested from Prince Edward Island in the Canadian Province of the same name. While the number of victims was small, the poisoning has since been identified as amnesic shellfish poisoning (ASP). Perhaps even more importantly, domoic acid poisoning has been responsible for the severe illness and deaths of marine animals including pelicans and sea lions.
[Which has been covered numerous times on ProMED-mail. - Mod.TG]
Saxitoxins
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Finally, in New England, there is another group of dinoflagellates, of the genus _Alexandrium_, that are also known as red tide and a HAB [harmful algal bloom]. These organisms produce saxitoxins, another potent neurotoxin, which can accumulate in shellfish. People who eat these shellfish may get paralytic shellfish poisoning (PSP). If people consume enough saxitoxin they can experience generalized muscle paralysis, including paralysis of the diaphragm and death. There are, however, very few deaths in places with modern medical facilities that can provide the supportive care (including ventilation) for people with this disease. There are a number of marine species that have shown the propensity to accumulate this toxin including clams and puffer fish (only in Florida).
These are only 3 examples of the types of harmful algal blooms that plague the coastal waters of the USA. For more information on other HABs, see the following websites:
<http://www.nwfsc.noaa.gov/hab>
<http://www.whoi.edu/redtide/>
--
Andrew Reich
Aquatic Toxins Program Coordinator
Public Health Toxicology Section
Florida Department of Health
4052 Bald Cypress Way, Bin A08
Tallahassee, Florida 32399-1712
USA
<Andy_Reich@doh.state.fl.us>
Dr Vera Trainer
Research Oceanographer
Marine Biotoxins Program
NOAA Northwest Fisheries Science Center
2725 Montlake Blvd. E.
Seattle, WA 98112
USA
[We appreciate the efforts of Mr Reich and Dr Trainer in helping us keep the various harmful algae blooms and their toxins separate. I am sure this will help our readers and our moderators.
Many of the points Mr Reich and his colleague Dr Trainer make are true. Many of these points are covered in the moderator comments at the bottom of the post and have been addressed in other posts regarding the individual harmful algal blooms.
While Mr Reich and Dr Trainer mention several algal bloom types and their respective toxins, please remember that ProMED-mail divides them for the ease of locating reports and to hopefully avoid confusion. For example, domoic acid is usually a separate post, with a heading of domoic acid, not harmful algae bloom. - Mod.TG]
[see also:
Red tide, shellfish, - USA (03) (WA) 20120916.1295932] .................................................tg/mj/jw/ll
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