Shellfish toxicity: Human health implications of marine algal toxins

Abstract

Five major human toxic syndromes caused by the consumption of shellfish contaminated by algal toxins are presented. The increased risks to humans of shellfish toxicity from the prevalence of harmful algal blooms (HABs) may be a consequence of large-scale ecological changes from anthropogenic activities, especially increased eutrophication, marine transport and aquaculture, and global climate change. Improvements in toxin detection methods and increased toxin surveillance programmes are positive developments in limiting human exposure to shellfish toxins.

Full text

Proof Delivery Form
Epidemiology and Infection
Date of delivery:
Journal and vol/article ref: hyg 1000085
Number of pages (not including this page): 14
This proof is sent to you on behalf of Cambridge University Press. Please print out the file and
check the proofs carefully.
Corrections should be supplied within three days of receipt of the proof.
Only one set of corrections will be accepted.
Corrections must be supplied by email to the Copy Editor, Steve Parr at the
following email address;
sjparr@ntlworld.com
Please note:
You are responsible for correcting your proofs. Errors not found may appear in the published
journal.
The proof is sent to you for correction of typographical errors only. Revision of the substance
of the text is not permitted, unless discussed with the editor of the journal.
Please answer carefully any queries listed overleaf.
A new copy of a figure must be provided if correction of anything other than a typographical
error introduced by the typesetter is required.
If you have problems with the file please contact hygproduction@cambridge.org
Please note that this pdf is for proof checking purposes only. It should not be distributed to third
parties and may not represent the final published version.
Important: you must return any forms included with your proof.
Please do not reply to this email

Author queries:
AQ1: Please confirm there is no conflict of interest.
AQ2: Supply publisher for ref. 7.
AQ3: Supply English version of article title for ref. 10.
AQ4: Supply place of publication for ref. 11.
AQ5: Check names/initials in author group. Supply full name of editor.
AQ6: Check names/initials in author group for ref. 29.
Note to Author : Papers are generally published online within 4 weeks of receipt of the corrected proof.

Offprint order form
PLEASE COMPLETE AND RETURN THIS FORM. WE WILL BE UNABLE TO SEND
OFFPRINTS UNLESS FULL DETAILS HAVE BEEN SUPPLIED.
VAT REG NO. GB 823 8476 09
Epidemiology and Infection (HYG) Volume: no:
Offprints
The corresponding author will receive free electronic access to their article. To purchase offprints please complete this form and send it to the publisher
(address below). Please give the address to which your offprints should be sent. They will be despatched by surface mail within one month of publication. For
an article by more than one author this form is sent to you as the first named. All offprints should be ordered by you in consultation with your co-authors.
Number of offprints purchased:
Email:
Offprints to be sent to (print in BLOCK CAPITALS):
Post/Zip Code:
Telephone: Date (dd/mm/yy): / /
Author(s):
Article Title:
All enquiries about offprints should be addressed to the publisher: Journals Production Department, Cambridge University
Press, The Edinburgh Building,, Shaftesbury Road, Cambridge CB2 8RS, UK.
Charges for offprints (excluding VAT) Please circle the appropriate charge:
Number of copies 25 50 100 150 200 per 50 extra
1-4 pages £68 £109 £174 £239 £309 £68
5-8 pages £109 £163 £239 £321 £399 £109
9-16 pages £120 £181 £285 £381 £494 £120
17-24 pages £131 £201 £331 £451 £599 £131
Each Additional 1-8 pages £20 £31 £50 £70 £104 £20
Methods of payment
If you live in Belgium, France, Germany, Ireland, Italy, Portugal, Spain or Sweden and are not registered for VAT we are required to charge VAT at the rate
applicable in your country of residence. If you live in any other country in the EU and are not registered for VAT you will be charged VAT at the UK rate.
If registered, please quote your VAT number, or the VAT
number of any agency paying on your behalf if it is registered. VAT Number:
Payment must be included with your order, please tick which method you are using:
 Cheques should be made out to Cambridge University Press.
 Payment by someone else. Please enclose the official order when returning this form and ensure that when the order is
sent it mentions the name of the journal and the article title.
 Payment may be made by any credit card bearing the Interbank Symbol.
Card Number:
Expiry Date (mm/yy): / Card Verification Number:
The card verification number is a 3 digit number printed on the back of your Visa or Master card, it appears after and to the right of your card number. For
American Express the verification number is 4 digits, and printed on the front of your card, after and to the right of your card number.
Signature of
card holder:
Amount
(Including VAT
if appropriate): £
Please advise if address registered with card company is different from above

Transfer of copyright
Please read the notes overleaf and then complete, sign, and return this form to Journals Production, Cambridge University
Press, University Printing House, Shaftesbury Road, Cambridge, CB2 8BS, UK as soon as possible.
In consideration of the publication in EPIDEMIOLOGY AND INFECTION
of the contribution entitled: ..................................................................................................................................................
..............................................................................................................................................................................................
by (all authors’ names):........................................................................................................................................................
..............................................................................................................................................................................................
1 To be filled in if copyright belongs to you
Transfer of copyright
I/we hereby assign to Cambridge University Press, full copyright in all formats and media in the said contribution,
including in any supplementary materials that I/we may author in support of the online version.
I/we warrant that I am/we are the sole owner or co-owners of the contribution and have full power to make this agreement,
and that the contribution contains nothing that is in any way an infringement of any existing copyright or licence, or duty
of confidentiality, or duty to respect privacy, or any other right of any person or party whatsoever and contains nothing
libellous or unlawful; and that all statements purporting to be facts are true and that any recipe, formula, instruction or
equivalent published in the Journal will not, if followed accurately, cause any injury or damage to the user.
I/we further warrant that permission has been obtained from the copyright holder for any material not in my/our copyright
including any audio and video material, that the appropriate acknowledgement has been made to the original source, and
that in the case of audio or video material appropriate releases have been obtained from persons whose voices or likenesses
are represented therein. I/we attach copies of all permission and release correspondence.
I/we hereby assert my/our moral rights in accordance with the UK Copyrights Designs and Patents Act (1988).
Signed (tick one)
□ the sole author(s) □one author authorised to execute this transfer on behalf of all the authors of the above article
Name (block letters) ............................................................................................................................................................
Institution/Company............................................................................................................................................................
Signature: ............................................................. Date:.................................................................................................
(Additional authors should provide this information on a separate sheet.)
2 To be filled in if copyright does not belong to you
a Name and address of copyright holder............................................................................................................................
.........................................................................................................................................................................................
.........................................................................................................................................................................................
b The copyright holder hereby grants to Cambridge University Press the non-exclusive right to publish the contribution in
the journal and to deal with requests from third parties in the manner specified in paragraphs 4 and 5 overleaf.
(Signature of copyright holder or authorised agent) ......................................................................................................
3 US Government exemption
I/we certify that the paper above was written in the course of employment by the United States Government so that no
copyright exists.
Signature: ............................................................. Name (Block letters):.......................................................................
4 Requests received by Cambridge University Press for permission to reprint this article (see
para. 4 overleaf) should be sent to
Name and address (block letters) ....................................................................................................................................
.........................................................................................................................................................................................
08.09 1

08.09 2
Notes for contributors
1 The Journal's policy is to acquire copyright in all contributions. There are two reasons for this: (a) ownership of copyright by one central
organisation tends to ensure maximum international protection against unauthorised use; (b) it also ensures that requests by third parties to
reprint or reproduce a contribution, or part of it, are handled efficiently and in accordance with a general policy that is sensitive both to any
relevant changes in international copyright legislation and to the general desirability of encouraging the dissemination of knowledge.
2 Two ‘moral rights’ were conferred on authors by the UK Copyright Act in 1988. In the UK an author’s ‘right of paternity’, the right to be
properly credited whenever the work is published (or performed or broadcast), requires that this right is asserted in writing.
3 Notwithstanding the assignment of copyright in their contribution, all contributors retain the following non-transferable rights:
• The right to post either their own version of their contribution as submitted to the journal (prior to revision arising from peer review and prior
to editorial input by Cambridge University Press) or their own final version of their contribution as accepted for publication (subsequent to
revision arising from peer review but still prior to editorial input by Cambridge University Press) on their personal or departmental web
page, or in the Institutional Repository of the institution in which they worked at the time the paper was first submitted, or (for appropriate
journals) in PubMedCentral or UK PubMedCentral, provided the posting is accompanied by a prominent statement that the paper has been
accepted for publication and will appear in a revised form, subsequent to peer review and/or editorial input by Cambridge University Press, in
Epidemiology and Infection published by Cambridge University Press, together with a copyright notice in the name of the copyright holder
(Cambridge University Press or the sponsoring Society, as appropriate). On publication the full bibliographical details of the paper (volume:
issue number (date), page numbers) must be inserted after the journal title, along with a link to the Cambridge website address for the journal.
Inclusion of this version of the paper in Institutional Repositories outside of the institution in which the contributor worked at the time the
paper was first submitted will be subject to the additional permission of Cambridge University Press (not to be unreasonably withheld).
• The right to post the definitive version of the contribution as published at Cambridge Journals Online (in PDF or HTML form) on their
personal or departmental web page, no sooner than upon its appearance at Cambridge Journals Online, subject to file availability and
provided the posting includes a prominent statement of the full bibliographical details, a copyright notice in the name of the copyright holder
(Cambridge University Press or the sponsoring Society, as appropriate), and a link to the online edition of the journal at Cambridge Journals
Online.
• The right to post the definitive version of the contribution as published at Cambridge Journals Online (in PDF or HTML form) in the
Institutional Repository of the institution in which they worked at the time the paper was first submitted, or (for appropriate journals) in
PubMedCentral or UK PubMedCentral, no sooner than one year after first publication of the paper in the journal, subject to file availability
and provided the posting includes a prominent statement of the full bibliographical details, a copyright notice in the name of the copyright
holder (Cambridge University Press or the sponsoring Society, as appropriate), and a link to the online edition of the journal at Cambridge
Journals Online. Inclusion of this definitive version after one year in Institutional Repositories outside of the institution in which the
contributor worked at the time the paper was first submitted will be subject to the additional permission of Cambridge University Press (not to
be unreasonably withheld).
• The right to post an abstract of the contribution (for appropriate journals) on the Social Science Research Network (SSRN), provided the
abstract is accompanied by a prominent statement that the full contribution appears in Epidemiology and Infection published by Cambridge
University Press, together with full bibliographical details, a copyright notice in the name of the journal’s copyright holder (Cambridge
University Press or the sponsoring Society, as appropriate), and a link to the online edition of the journal at Cambridge Journals Online.
• The right to make hard copies of the contribution or an adapted version for their own purposes, including the right to make multiple copies for
course use by their students, provided no sale is involved.
• The right to reproduce the paper or an adapted version of it in any volume of which they are editor or author. Permission will automatically
be given to the publisher of such a volume, subject to normal acknowledgement.
4 We shall use our best endeavours to ensure that any direct request we receive to reproduce your contribution, or a substantial part of it, in
another publication (which may be an electronic publication) is approved by you before permission is given.
5 Cambridge University Press co-operates in various licensing schemes that allow material to be photocopied within agreed restraints (e.g. the
CCC in the USA and the CLA in the UK). Any proceeds received from such licences, together with any proceeds from sales of subsidiary
rights in the Journal, directly support its continuing publication.
6 It is understood that in some cases copyright will be held by the contributor’s employer. If so, Cambridge University Press requires non-
exclusive permission to deal with requests from third parties, on the understanding that any requests it receives from third parties will be
handled in accordance with paragraphs 4 and 5 above (note that your approval and not that of your employer will be sought for the proposed
use).
7 Permission to include material not in your copyright
If your contribution includes textual or illustrative material not in your copyright and not covered by fair use / fair dealing, permission must be
obtained from the relevant copyright owner (usually the publisher or via the publisher) for the non-exclusive right to reproduce the material
worldwide in all forms and media, including electronic publication. The relevant permission correspondence should be attached to this form.
If you are in doubt about whether or not permission is required, please consult the Permissions Manager, Cambridge University Press, The
Edinburgh Building, Shaftesbury Road, Cambridge CB2 8RU, UK. Fax: +44 (0)1223 315052. Email: lnicol@cambridge.org.
The information provided on this form will be held in perpetuity for record purposes. The name(s) and address(es) of the author(s) of the
contribution may be reproduced in the journal and provided to print and online indexing and abstracting services and bibliographic databases.
Please make a duplicate of this form for your own records

REVIEW ARTICLE
Shellfish toxicity: human health implications
of marine algal toxins
K. J. J A M ES
1
,
2
*, B. CAREY
1
,
2
, J. O’HALLORAN
2
,
3
, F. van P ELT
2
,
4
AND Z. S
ˇKRABA
´KOVA
´
1
,
2
1
PROTEOBIO (Mass Spectrometry Centre), Cork Institute of Technology, Bishopstown, Cork, Ireland
2
Environmental Research Institute, University College Cork, Lee Road, Cork, Ireland
3
Department of Zoology, Ecology and Plant Science, University College Cork, Distillery Fields, North Mall,
Cork, Ireland
4
Department of Pharmacology and Therapeutics,
Cork, Ireland
(Accepted 24 March 2010)
SUMMARY
Five major human toxic syndromes caused by the consumption of shellfish, contaminated by
algal toxins, are presented. The increased risks to humans of shellfish toxicity from the prevalence
of harmful algal blooms (HABs) may be a consequence of large-scale ecological changes from
anthropogenic activities, especially increased eutrophication, marine transport and aquaculture,
and global climate change. Improvements in toxin detection methods and increased toxin
surveillance programmes are positive developments in limiting human exposure to shellfish
toxins.
Key words: Food safety, toxic fish and shellfish poisoning, toxins.
INTRODUCTION
Shellfish are a rich source of protein, essential min-
erals and vitamins A and D and they feed mainly on
marine microalgae. The importance of algae in the
food chain arises from the fact that they are the only
organisms that can readily make long-chain poly-
unsaturated fatty acids (PUFAs) and the potential
beneficial role of shellfish and finfish in the human diet
has been attributed to the presence of oils that are rich
in PUFAs [1]. Bivalve molluscs filter large volumes of
water when grazing on microalgae, and can concen-
trate both bacterial pathogens and phycotoxins [2].
However, a range of human illnesses associated with
shellfish consumption have been identified as being
due to toxins that are produced by marine microalgae.
When algae populations increase rapidly to form
dense concentrations of cells they may form visible
blooms, the so-called ‘ red tides ’ (Fig. 1), but blooms
are not always visible as they may not be coloured and
they can proliferate well below the surface. The term
‘harmful algal blooms ’ (HABs) is preferred and these
events can have negative environmental impacts in-
cluding oxygen depletion of the water column and
damage to the gills of fish. However, toxin-producing
algae can cause mass mortalities of fish, birds and
marine mammals and human illness via consumption
of seafood. It is estimated that only 60–80 species of
about 4000 known phytoplankton are potentially
toxin-producing and capable of producing HABs [3].
Maximum toxin levels permitted in shellfish are con-
trolled by national and international regulations and
new analytical methods have been developed for the
* Author for correspondence : Professor K. J. James,
PROTEOBIO, Cork Institute of Technology, Bishopstown, Cork,
Ireland.
(Email: kevin.james@cit.ie)
Epidemiol. Infect., Page 1 of 14. fCambridge University Press 2010
doi:10.1017/S0950268810000853
Clinical Investigations Building, Cork University Hospital,

determination of toxins in shellfish, especially liquid
chromatography–mass spectrometry (LC–MS). These
methods have recently been reviewed and will not be
discussed in detail [4]. The European Food Standards
Agency has recently published a scientific opinion on
marine biotoxins with proposals to lower some toxin
limits and other measures that will hasten the re-
placement of lethal mouse bioassay (MBA) methods
that have traditionally been used to monitor toxin
levels in shellfish for human consumption [5]. Un-
fortunately, the lack of clinical testing methods
has led to a large underestimation of the incidence
of human poisonings due to algal toxins, especially
since many of the symptoms are similar to viral and
bacterial infections. In addition, only acute intoxi-
cations due to algal toxins are recognized and there
is very little knowledge of the human impacts due
to chronic exposure to these toxins. The high potency
and target specificity that many of these marine toxins
possess has led to their exploitation as research
tools [6].
The main vectors of algal toxins to humans are
filter-feeding bivalve molluscs and herbivorous finfish
that ingest toxic algae (Fig. 2). The bivalve molluscs
that are mainly affected with algal toxins include
mussels, clams, scallops and oysters. Although crus-
taceans can also be contaminated with toxins, the ex-
tent of toxicity is generally low and the incidences of
human intoxications due to crustacean consumption
are rare. Other significant environmental impacts of
HABs include major fish kills and large mortalities
to birds and marine mammals [7, 8]. One of the most
dramatic events involving sea mammals was the ex-
tensive mass mortalities to sea lions in California due
to domoic acid (DA) intoxication where the main
vector was anchovy [9]. Figure 2 summarizes the
interrelationships and potential vectors for toxins
arising from HABs but the toxic impact to humans is
predominantly from shellfish consumption. Bivalve
shellfish graze on algae and concentrate toxins, if
present, very effectively.
Historically, there have been sporadic reports of
shellfish poisoning ; one fatal incident that occurred
in British Columbia in 1793 was reported by Captain
Vancouver and the earliest scientific reference to
shellfish poisoning appeared in 1851 [10]. Prohibitions
regarding the consumption of shellfish are found in
several cultures and, together with religious beliefs,
this has limited the role of shellfish as a potential
food source. Such prohibitions are found in the Old
Testament:
These ye shall eat of all that are in waters : all that have fins
and scales shall ye eat : And whatsoever hath not fins and
scales ye may not eat ; it is unclean unto you. (Deuteronomy
14: 9–10 ; King James Version).
In this review, five major human toxic syndromes
caused mainly by the consumption of bivalve mol-
luscs contaminated by algal toxins are discussed
(Table 1), together with the identification of the in-
creased risks to humans of shellfish toxicity.
SHELLFISH TOXIC SYNDROMES
Paralytic shellfish poisoning (PSP)
Mild symptoms include a tingling sensation or
numbness around the lips which gradually spreads to
the face and neck, accompanied by a prickly sensation
in fingertips and toes. Greater intoxications induce
headache, nausea, vomiting and diarrhoea with in-
creasing muscular paralysis and pronounced respir-
atory difficulty. In the absence of artificial respiration
there is a high risk of death as a consequence of acute
PSP intoxication [7]. The onset of symptoms of PSP
in humans is dose dependent and can occur rapidly
(within 30 min) after the consumption of shellfish.
PSP toxins are collectively called saxitoxins (STXs)
and at least 21 analogues of these cyclic guanidines
are known in shellfish, with saxitoxin (Fig. 3a) being
the most common toxin. STXs exert their effect by a
direct binding on the voltage-dependent sodium
channel that block the flux of sodium ions in and out
COLOUR
Fig. 1. A dramatic algal bloom (red tide) in the South China
Sea. This bloom, Noctiluca scintillans, was non-toxic.
(Reproduced with permission of Springer SBM NL. In :
Okaichi T, Fukuyo Y, eds. Red Tides, Berlin, Heidelberg :
Springer, 2004.)
2 K. J. James and others

of nerve and muscle cells, leading to paralysis [11].
The primary site of action of STXs in humans is the
peripheral nervous system. The lethal dose in humans
is 1–4 mg STX, or equivalent STXs, and since levels
up to 100 mg STX equivalents/g shellfish have been
reported, consumption of only a few contaminated
shellfish have proved fatal in these rare cases.
However, hospitalization of affected individuals is
critical to deal with respiratory paralysis and STXs
clear from the blood within 24 h leaving no organ
damage or long-term effects [12]. Saxitoxin has
reached notoriety by being included, along with ricin,
in the Schedule 1 list of the Chemical Weapons
Convention. Detection and control of PSP toxins in
shellfish is less problematic than the control of lipo-
philic toxins. PSP toxins are efficiently extracted from
shellfish tissues using a strong acid and a MBA has
been validated as an official method by AOAC
International [13].
Dinoflagellates that produce STXs belong to three
genera; Alexandrium,Gymnodinium and Pyrodinium
and HABs involving blooms of these dinoflagellates
occur in both Northern and Southern Hemispheres [8]
(Table 2). It has been estimated that there are 2000
human intoxications per year and PSP outbreaks
are seasonal [14, 15]. Although there is anecdotal
evidence of human intoxications associated with
shellfish for centuries, a PSP outbreak that occurred
in northern California in 1927 led to a major in-
vestigation of this phenomenon. Poisoning of 102
individuals from mussel consumption caused six
deaths [16]. PSP outbreaks have occurred on both the
eastern and western coastlines on North America,
with Alaska being particularly badly affected and
toxic events have been reported for more than 130
years [17, 18]. Large marine mammals have also been
affected by PSP and 14 humpback whales died in Cape
Cod Bay in 1987 from exposure to STXs where
mackerel was suspected to be the main vector [19].
Although STXs are detected in the coastal waters
and shellfish in many European countries, human in-
toxications are rare. In the 1970s, there were several
PSP intoxications involving 80–120 individuals,
caused by mussels produced in Spain, Portugal and
the UK [20–22] but implementation of good regulat-
ory control has effectively eliminated further major
outbreaks. There have been repeated PSP outbreaks
in Chile and Argentina during the past 40 years, with
21 PSP deaths reported in Chile since 1991 [23], and
these investigations included one of the rare identifi-
cations of toxins in the body fluids of victims [24]. In
the Philippines, there have been an estimated 2000
cases of PSP between 1983 and 1998, with 115 deaths
[25]. Blooms of Pyrodinium spp. were the main cause
of these intoxications and these blooms have spread
throughout the tropical Pacific region. Climate
change has been implicated with an apparent corre-
lation between these HABs and the occurrence of El
Nin
˜o Southern Oscillation events [26]. PSP events in
geographically remote locations cause higher death
Human
Toxic phytoplankton & bacteria
Finfish
Marine mammals
Bivalves
Crustaceans
Fig. 2. The toxin cycle: diagram illustrating the interrelationships between harmful algae and shellfish, finfish, birds and
mammals.
Shellfish toxicity 3

rates due to the lack of hospital facilities with respir-
atory support equipment.
Diarrhoetic shellfish poisoning (DSP)
DSP is a gastrointestinal illness and the main symp-
toms are diarrhoea followed by nausea, vomiting and
abdominal cramps. DSP can occur within 30 min to a
few hours after ingestion of contaminated shellfish
and complete recovery occurs within 3 days. Since
clinical tests are rarely used for DSP toxins, this con-
dition is often confused with bacterial enterotoxin
poisoning. DSP is caused by the ingestion of con-
taminated filter-feeding bivalve molluscs, especially
mussels and scallops, where the lipophilic toxins are
accumulated mainly in the digestive glands (hepato-
pancreas) [27].
DSP toxins were originally divided into three
different structural classes : (a) okadaic acid (OA)
(Fig. 3b) and its analogues, dinophysistoxins (DTXs),
(b) pectenotoxins (PTXs) and (c) yessotoxins (YTXs)
[28]. However, YTXs have now been excluded from
the DSP classification because they are not orally
toxic and do not induce diarrhoea [29, 30]. PTXs
Table 1. Confirmed outbreaks of human poisonings due to shellfish toxins
Toxic syndrome Location of outbreak (year) Shellfish species
Number of
poisonings Ref.
PSP USA – California (1927–1936) Mussels >100 (6 deaths) [16]
USA – Alaska (1973–1992) 117 [14]
USA (1998–2002) 43 [123]
Canada (1880–1970) 187 [17]
Spain Mussels 120 [20]
UK (1968) Mussels 78 [22]
Norway (1901–1992) 32 (2 deaths) [124]
Portugal (1994) 9 [21, 23]
Chile (1991–2002) Mussels, oysters 21 deaths [24, 26]
Philippines (1988–1998) 877 (44 deaths) [25]
DSP Japan (1976–1984) Mussels, scallops >1000 [39, 40]
France (1980–1987) Mussels 7600 [41]
Denmark (1990–2002) Mussels 800–900 [43, 47]
Norway (1984–1985) Mussels >400 [125]
Spain (1978–1981) Mussels >5000 [43]
Portugal (2002) Mussels 58 [126]
UK (1997) Mussels 49 [45]
Ireland (1984–1994) Mussels ? [46]
Canada (1990) Clams, mussels 16 [127]
Chile (1970–1991) Mussels, cholgas >100 [128]
Argentina (2000) Mussels 40 [129]
New Zealand 13 [59]
NSP USA – North Carolina (1987) Oysters 48 [60, 130, 131]
USA – Florida (1996–2006) Whelks, clams 23 [56, 61]
New Zealand (1993) Green mussels,
Cockles, oysters
186 [58, 132]
ASP Canada (1987) Mussels 107 (3 deaths) [66, 67]
USA – Washington State (1991) Razor clams 24 [73, 77]
AZP The Netherlands (1995) Mussels 8 [85, 133]
Ireland – Arranmore Island (1997) Mussels 20–24 [86]
Italy (1998) Mussels 10 [89]
France (1998) Mussels 20–30 [89, 94]
UK (2000) Mussels 16 [93]
France (2008) Mussels 200 [134]
PSP, Paralytic shellfish poisoning ; DSP, Diarrhoetic shellfish poisoning ; NSP, Neurotoxic shellfish poisoning; ASP, Amnesic
shellfish poisoning; AZP, Azaspiracid poisoning.
4 K. J. James and others

and YTXs are toxic to mice upon intraperitoneal in-
jection, which is the official, but primitive, DSP test-
ing procedure. However, no case of human poisoning
due to these toxins has been reported. The strange
scenario when using the official MBA is that the least
toxic substances, YTXs, elicit the highest toxic re-
sponse [7]. Not only are these lethal bioassays pro-
hibited in several countries, including Germany, The
Netherlands and Sweden, alternative methods for
toxin determination can only be implemented in the
EU when they have been validated against the MBA
which itself has never been validated [31]. A recent
pronouncement from the European Food Safety
Authority belatedly acknowledged the unacceptable
current regulatory situation and stated :
The mouse bioassay (MBA) is the official reference method
for lipophilic biotoxins. The Panel on Contaminants in the
Food Chain (CONTAM Panel) noted that this bioassay has
shortcomings and is not considered an appropriate tool
for control purposes because of the high variability in re-
sults, the insufficient detection capability and the limited
specificity [5].
The mechanism of action of the OA group toxins is
via inhibition of serine-threonine protein phosphatase
2A (PP2A) [32], which plays important roles in many
regulatory processes in cells. OA probably causes
diarrhoea by stimulating phosphorylation of proteins
that control sodium secretion in intestinal cells [33].
Protein phosphatase assays are very sensitive and can
be readily applied for detecting OA and analogues in
shellfish but LC–MS methods are more widely used
[34, 35]. Although DSP is not fatal, this type of
poisoning deserves attention, because in addition to
the severe acute effects, the chronic effects may be
important as OA and DTX1 have been shown to
be potent tumour promoters [36, 37]. A major risk
factor for colorectal cancer from shellfish consump-
tion has been proposed due to the presence of DSP
toxins [38].
The first confirmed outbreak of DSP occurred
in Japan in the late 1970s with 164 cases of shellfish
poisoning [39]. There were 34 outbreaks of DSP in
Japan between 1976 and 1984, affecting more than
1000 people [40]. DSP outbreaks have involved large
population numbers and have affected the greatest
number of individuals compared to the other shellfish
toxic syndromes (Table 1). In Europe, DSP outbreaks
involving several thousand individuals have been re-
ported since 1978 in France [41, 42], Norway and
Denmark [43], Spain [44, 45] and mussels exported
from Ireland have caused DSP outbreaks throughout
Europe [46]. Despite this DSP monitoring, mussels
from Denmark caused DSP intoxications to more
than 1000 individuals in Belgium [47]. DSP is
now recognized as a worldwide problem and also af-
fects Canada, Chile, Argentina and New Zealand
(Table 1).
DSP toxins are produced by the dinoflagellates,
Dinophysis spp. and Prorocentrum spp. (Table 2) and
their toxin profiles can vary within a single species
NH2COO
H
H
HN
N
NNH
OH
HO
HO
OH
OH
OH
OH
+
NH2
+
NH2
CH3
CH3
CH3
CH3
CH3
CH3
CH3
HOOC
COOH
COOH
N
H
CH2
(a)
(c)
(b)
(d)(e)
O
O
OOO
O
H
O
O
H
O
O
O
O
O
O
O
O
OO
O
OO
O
O
O
O
O
O
H
O
H
H
HHO
H
H
H
H
H
H
H
H
NH
OH
HO
CH2CCH
Fig. 3. Structures of the most abundant toxin responsible for each of the five shellfish toxic syndromes; (a) saxitoxin (PSP),
(b) okadaic acid (DSP), (c) brevetoxin (NSP), (d) domoic acid (ASP), (e) azaspiracid (AZP).
Shellfish toxicity 5

[48–50]. In Europe, OA and its isomer, DTX2, are the
predominant DSP toxins and they co-occur in shell-
fish from Ireland [46], Portugal and Spain [51]. DTX1,
the methyl analogue of OA, is the predominant DSP
toxin in Japan [49, 52]. The regulatory level for these
toxins in Europe is currently 0.16 mg/g.
Neurotoxic shellfish poisoning (NSP)
NSP is a illness caused by the consumption of bivalve
molluscs contaminated with neurotoxins that are
produced by the marine dinoflagellate, Karenia brevis
(formerly known as Gymnodinium breve and
Ptychodiscus brevis) [53, 54]. Brevetoxin (Fig. 3 c)
and its analogues can also affect finfish, aquatic
mammals and birds and this topic has been recently
reviewed [55, 56]. The symptoms of NSP include
gastroenteritis and neurological problems [53].
Brevetoxin-producing HABs have caused problems in
the Gulf of Mexico for many decades and have been
responsible for respiratory problems and eye irri-
tation in humans due to exposure to aerosol sprays
along Florida beaches [55]. Brevetoxins have also
been responsible for the deaths of large marine ani-
mals, including manatees and bottlenose dolphins
[57]. In New Zealand, brevetoxins have also caused
problems and new analogues have been identified
[58, 59]. The first confirmed NSP outbreak in New
Zealand occurred in 1993, affected 186 individuals,
and caused both gastrointestinal symptoms and
respiratory problems due to aerosol inhalation
(Table 1) [59].
In humans, the onset of symptoms of NSP occurs
within 0.5–3 h after consumption of shellfish and can
include gastroenteritis, chills, sweats, hypotension,
arrhythmias, numbness, peripheral tingling and, in
severe cases, broncho-constriction, paralysis, seizures
and coma. NSP symptoms can persist for a few days
[53, 60, 61].
In addition to ingestion, the second route of ex-
posure to brevetoxins is by inhalation of sea spray and
this affects individuals who are near to a beach.
K. brevis is a very fragile dinoflagellate and during
rough seas this organism readily ruptures releasing
toxins into the water. This exposure to aerosols
containing brevetoxins can cause irritation of the
eyes and nasal membranes, as well as respiratory
problems [62].
The mode of action of brevetoxins is by receptor
binding to the sodium channels which control the
generation of actin potentials in nerve, muscle and
cardiac tissue, enhancing sodium entry into the cell.
This leads to the incessant activation of the cell which
causes paralysis and fatigue of these excitatory cells
[63]. A recent NSP outbreak in Florida affected 20
individuals, of which seven were hospitalized. Six in-
dividuals complained of uncontrolled muscle con-
tractions and psychotic outbursts [56].
The monitoring of shellfish for NSP has tradition-
ally involved MBAs that involve a non-specific ex-
traction process but this test can be effective for
control in situations where other lipophilic toxins are
not prevalent. The action level is 20 mouse units
(MU) per 100 g shellfish tissue which is equivalent to
Table 2. Seafood toxic syndromes, toxins and the phytoplankton source of toxins
Toxic syndrome Toxins Affected seafood Toxic algae
1. Paralytic shellfish
poisoning (PSP)
Saxitoxin (STX), Neosaxitoxin (NEO),
Gonyautoxin (GTX) and 18 other
analogues
Bivalve shellfish,
Crustraceans
Alexandrium spp. [135],
Gymnodinium spp. [136]
2. Diarrhoetic shellfish
poisoning (DSP)
Okadaic acid (OA), Dinophysistoxins
(DTXs), Pectenotoxins (PTXs)
Bivalve shellfish Dinophysis spp. [49, 137],
Prorocentrum spp.
[138, 139]
3. Neurotoxic shellfish
poisoning (NSP)
Brevetoxins (PbTx) Bivalve shellfish Karenia brevis (formerly
Gymnodinium breve and
Ptychodiscus brevis)
[140, 141]
4. Amnesic shellfish
poisoning (ASP)
Domoic acid (DA) and analogues Bivalve shellfish,
Finfish
Pseudonitzschia spp. [68]
5. Azaspiracid
poisoning (AZP)
Azaspiracids (AZAs) and analogues Bivalve shellfish Protoperidinium crassipes
[105], Azadinium spinosum
[106]
6 K. J. James and others

0.8mg brevetoxin (PbTx-2)/g tissues [56]. There are
a number of sensitive receptor-binding assays that
utilize the specific binding of brevetoxins to sodium
channels [64]. LC–MS is the only method for identi-
fying individual brevetoxins in seafood [55]. Overall,
it can be concluded that NSP is relatively rare [56], it
is not geographically widespread and therefore poses
the least threat to human health of the five toxic syn-
dromes discussed in this review.
Amnesic shellfish poisoning (ASP)
ASP first came to attention in Canada in 1987 when
human fatalities occurred from eating mussels
(Mytilus edulis) cultivated in Prince Edward Island
[65]. In addition to gastrointestinal disturbance, un-
usual neurological symptoms, especially memory im-
pairment, were observed. Of the 107 cases involved in
this ASP event, three individuals died within 18 days
after admission to hospital [66]. The neurological
symptoms included headache, confusion, disorien-
tation, seizures and coma within 48–72 h. However,
the permanent loss of short-term memory in some of
the survivors led this toxic syndrome to be named
ASP. Epidemiological studies revealed age-dependent
responses to ASP. Those aged <40 years were more
likely to suffer gastrointestinal problems whereas in-
dividuals aged >50 years were more likely to suffer
from memory loss [66]. DA was identified as the
causative toxin (Fig. 3 d) [67] and a short time later,
marine diatoms of the Pseudonitzschia spp. were
identified as the source of this toxin [68]. DA was a
previously known marine natural product and was
originally discovered in seaweed in Japan where the
latter was used for its anthelminthic and insecticidal
properties [69]. In addition to mussels, DA can enter
the food chain through vectors such as scallops, razor
clams and crustaceans [70–72]. There was a second
report of human intoxications from consumption of
razor clams, cultivated in Washington State, USA,
but only two individuals experienced slight neuro-
logical problems [73].
Although there are many analytical methods for
the determination of DA in seafood, liquid chro-
matography with ultra-violet detection is used by most
regulatory agencies. The permitted limit of 20 mg DA/
g shellfish tissue has been generally adopted [74]. DA
is a tricarboxylic amino acid and analysis is compli-
cated somewhat by the presence of isomers of DA,
as well as tryptophan, in naturally contaminated
samples [75]. There have been many worldwide
reports of DA contamination of seafood and mor-
talities to marine animals and birds [76]. An event that
generated worldwide publicity was when 70 sea lions
were washed up onto beaches in California. It was
evident that they were suffering from neurological
problems including seizures and 47 animals died. DA
was identified in faecal samples from these animals
and in anchovies collected nearby [9].
In 1991, an outbreak of DA poisoning was reported
in Monterey Bay, California, USA, where pelicans
and cormorants were behaving strangely, e.g. vomit-
ing, exhibiting unusual head movements, scratching,
with many deaths [77]. In this case the vector was the
northern anchovy and it is probable that the making
of the Alfred Hitchcock film The Birds was prompted
by a similar event that happened in the summer of
1961, near Santa Cruz in California. Flocks of shear-
waters began acting erratically, flying into houses and
cars, pecking people, breaking windows and vomit-
ing. These ‘strange ’ events were reported in local
newspapers and these clippings were included with
Alfred Hitchcock’s studio proposal to make the film,
based on Daphne du Maurier’s novella. In subsequent
years, several similar incidents occurred along the
same coastline which have been attributed to DA
produced by blooms of Pseudonitzschia spp. [78].
Soon after the establishment of monitoring
programmes in Europe, DA was found in shellfish
from Galicia, Spain [79], Ireland [80], Portugal [81],
Scotland [82] and France [83]. In Ireland, only the
king scallop (Pecten maximus) exhibited high levels of
toxin. Although a record high level of DA (2820 mg
DA/g) was found in the digestive glands of scallops,
the adductor muscle and gonad contained levels be-
low or just over the regulatory limit of 20 mg DA/g
[71]. It would therefore be a prudent and simple food
safety measure to recommend the non-consumption
of the digestive glands of these shellfish to reduce the
risk of exposure of humans to ASP. DA has also been
found in shellfish from New Zealand, Australia and
Chile, but there have been no major toxic incidents
involving humans. Further information regarding
ASP and DA can be found in a recent review [84].
Azaspiracid shellfish poisoning (AZP)
AZP is the most recently discovered toxic syndrome
from shellfish consumption and several analogues
belonging to this new class of toxins were identified in
contaminated mussels [85–87]. The first confirmed
event was in 1995 in The Netherlands and was caused
Shellfish toxicity 7

by the consumption of mussels (M. edulis) that were
cultivated in Killary Harbour in the west of Ireland.
At least eight individuals were affected and the
symptoms, nausea, vomiting, diarrhoea and abdomi-
nal cramps were similar to DSP. Azaspiracid (AZA1)
was isolated from these mussels and the structure was
later modified following the total synthesis of AZA1
(Fig. 3e) [88]. Several other AZP outbreaks occurred
in the following years due to the consumption of
mussels cultivated in Ireland (Table 1) [89]. Following
the development of sensitive LC–MS methods for
their determination [90–92], azaspiracids were ident-
ified in five other European countries, including the
UK, Norway [93], France, Spain [94] and Denmark
[47], as well as throughout the western coastline of
Ireland [95]. Azaspiracids have also recently been
found in North Africa [96] and Japan [97]. More than
20 analogues of AZA1 have been identified in shellfish
[86, 87, 98, 99], which complicates the regulatory
control of these toxins as most have not yet been
toxicologically evaluated.
Toxicological studies have indicated that azaspir-
acids can induce widespread organ damage in mice
and that they are probably more dangerous than
previously known classes of shellfish toxins [100, 101].
AZA1 is distinctly different from DSP toxins as its
target organs include liver, spleen, the small intestine
and it has also been shown to be carcinogenic. Using
oral administration to mice, multiple organ damage
was observed ; (a) fatty change and single-cell necrosis
in liver, (b) erosion epithelial cells of small intestinal
villi and (c) lymphocyte necrosis in the thymus and
spleen. In the most severe cases, inflammation and
oedema in the lungs and stomach occurred. The
chronic study showed tumour formation in lungs and
malignant lymphomas. All mice used in these studies
developed interstitial pneumonia and had shortened
small intestinal villi, even at low doses (1 mg/kg)
[100, 101]. Cytotoxicity studies using neuroblastoma
cells showed that AZA1 disrupts cytoskeletal struc-
ture, inducing a time- and dose-dependent decrease in
F-actin pools. A link between F-actin changes and
diarrhoeic activity has been suggested and this may
explain the severe gastrointestinal disturbance in AZP
outbreaks. Azaspiracids were found to induce a sig-
nificant increase in [Ca
2
+
] levels in lymphocytes.
Elevation of [Ca
2
+
] levels can lead to cell death
[102–104].
Azaspiracids have been identified in two dino-
flagellates, Protoperidinium crassipes [105] and a new
species, Azadinium spinosum [106]. AZA2 has also
recently been found in a sponge (Echinoclathria sp.)
in Japan, representing the first report of this class
of toxins in Asia [97]. Although confirmed reports
of AZP have only been associated with mussel
consumption, several other types of bivalve shellfish
species have been found to accumulate these toxins,
including oysters, clams and scallops [95]. The
exclusive reliance on the DSP live animal bioassays,
recommended by the EU, to monitor azaspiracids
contamination of shellfish failed to prevent human
intoxications [89]. This was a consequence of poor
sensitivity of the assay and the incorrect assumption
that azaspiracids were exclusively concentrated in the
shellfish digestive glands that were used for testing
[107]. Most regulatory agencies in Europe now com-
ply with a strict regulatory control of azaspiracids in
shellfish (<0.16 mg/g edible tissues) by frequent test-
ing of shellfish using sensitive LC–MS/MS analytical
methods, as outlined in recent reviews [4, 108].
GLOBAL INCREASE IN HABs
There has been an apparent global increase in the
occurrence of algal toxins in shellfish, with several
new toxin classes identified in recent years. However,
the reasons behind the apparent expansion in HABs
and shellfish toxicity remain unclear with a number of
factors being implicated including, climate change,
anthropogenic activities, changes in shellfish culti-
vation, eutrophication, increased global marine traf-
fic, improved toxin detection and better food control
and toxin monitoring programmes [15, 109–112].
Projected increases in ocean temperatures are pre-
dicted to change global circulation that may lead
to an increase of HABs. Moreover, the increased
concentrations of greenhouse gases are expected
to reduce pH, increase surface-water temperatures
and affect vertical mixing and upwelling [113].
Phytoplankton growth is dependent on the avail-
ability of nitrogen. Atmospheric deposition of nitro-
gen, from agricultural and urban sources, can lead
to increased algal blooms [3, 114]. Most marine HABs
are comprised of dinoflagellates. The mobility
characteristics of dinoflagellates allow them to swim
under stratified layers of the water column to access
nutrients in deeper layers. This may give dino-
flagellates a competitive edge over other phyto-
plankton that cannot swim [113]. The potential
consequences of these changes for HABs have re-
ceived relatively little attention and are not well
understood. Several studies have emphasized the
8 K. J. James and others

relevance of coastal eutrophication to increased
HABs and this is especially relevant to shellfish pro-
duction and intoxication [110]. Increased coastal
aquaculture activities can lead to local nutrient en-
richment and eutrophication which not only increases
the growth of toxic algae but also acts as the main
vector for increased exposure of humans to toxins.
A remarkable example of the positive effects of re-
ducing nutrient loading was in Hong Kong harbour
where the frequency of algal blooms declined after
several years of nutrient reduction [115]. However,
many algal blooms are not due to national anthro-
pogenic activities and toxic algae can be transported
from remote oceanic regions to affect coastal regions
which have normally pristine waters. Thus, in Europe,
the major shellfish toxicity from HABs occurs along
the western Atlantic coastline, affecting Scotland,
Norway, Ireland, France, Spain and Portugal, but the
Mediterranean region which has a high nutrient
loading, has a low incidence of such problems. It is
therefore prudent to caution against a rush to judge-
ment until there has been an extensive database
of algal population flux over an extended period of
years.
The emergence of non-indigenous toxic algal
species in various geographical locations has been
linked to an increase in global marine traffic. In par-
ticular, the release of ballast waters has been shown to
be responsible for invasions of exotic species, includ-
ing algae, bacteria and zooplankton. Algal cysts
in ballast waters have been identified as the cause of
new PSP events in regions of Australia that were
previously unaffected and led to new ballast water
guidelines to limit exposure to exotic species [8, 116].
Recent evidence of an increased global expansion
of HABs includes the first reports of palytoxin and
tedrodotoxin in European waters and the discovery of
azaspiracids in Japan [97]. An outbreak of respiratory
illness in people exposed to marine aerosols occurred
in Genoa, Italy, in 2005 and a palytoxin analogue
was identified as the probable causative agent [117].
Ostreopsis spp. are widely distributed in tropical and
subtropical areas, but recently these dinoflagellates
have also started to appear in the Mediterranean
where they produce palytoxins [118, 119].
Tetrodotoxin is a well known paralytic toxin that
is found in pufferfish and causes fatalities in Japan
almost annually [120]. Once again, a toxin that is
usually found in tropical and sub-tropical waters
appeared in a trumpet shellfish (Charonia sauliae),
harvested from the Atlantic coastline of Portugal. An
individual was hospitalized and suffered general par-
alysis, including the respiratory muscles, a few min-
utes after the consumption of several grams of this
shellfish [121]. The investigation of the extent and
implications of these new toxic problems in Europe is
currently the subject of a collaborative EU project
(ATLANTOX) [122].
CONCLUSIONS
The impact on human health from the consumption
of biotoxins in shellfish has apparently increased in
recent decades. There is evidence, although not con-
clusive, that the increase in HABs is a consequence of
large-scale ecological changes from anthropogenic
activities, especially increased eutrophication, marine
transport and aquaculture. Global climate change has
also been implicated. Recent improvements in toxin
detection methods and increased toxin surveillance
programmes are positive developments in limiting
human exposure to shellfish toxins. However, there is
a requirement for the development of clinical tests to
improve the correct diagnosis of shellfish poisoning in
humans.
ACKNOWLEDGEMENTS
We acknowledge funding from the Higher Education
Authority of Ireland, as part of Ireland’s EU
Structural Funds Programmes (2007–2013) and the
European Regional Development Fund ; Programme
for Research in Third Level Institutions (PRTLI-4),
‘Environment and Climate Change : Impacts and
Responses’.
DECLARATION OF INTEREST
None. AQ1
REFERENCES
1. Martinez R, Dubinsky Z. Useful products from algal
photosynthesis. In: Archer M, ed. Molecular to Global
Photosynthesis, vol. 2. London: Imperial College
Press, 2004, p. 340.
2. Huss HH. Control of indigenous pathogenic bacteria
in seafood. Food Control 1997; 18 : 91–98.
3. Smayda TJ. Harmful algal blooms: their ecophysi-
ology and general relevance to phytoplankton blooms
in the sea. Limnology Oceanography 1997; 42 : 1137–
1153.
4. James KJ, et al. Phycotoxins. In : Pico Y, ed.
Comprehensive Analytical Chemistry Vol. 51, Food
Shellfish toxicity 9

Contaminants and Residue Analysis. Amsterdam:
Elsevier, 2008, pp. 429–452.
5. Anon. Scientific Opinion of the Panel on Con-
taminants in the Food Chain on a request from
the European Commission on Marine Biotoxins in
Shellfish – Summary on regulated marine biotoxins.
EFSA Journal 2009; 1306 : 1–23.
6. Fusetani N, Kem W. Marine toxins: an overview In :
Fusetani N, Kem W, eds. Marine Toxins as Research
Tools, vol. 46. Berlin, Heidelberg : Springer, 2009,
pp. 1–44.
7. Aune T. Risk assessment of marine toxins. In: Botana
LM, ed. Seafood and Freshwater Toxins, Pharma-
cology, Physiology and Detection. New York : 2008,
pp. 3–20.
AQ2
8. Hallegraeff GM. A review of harmful algae and their
apparent global increase. Phycologia 1993; 32 : 79–99.
9. Scholin CA, et al. Mortality of sea lions along the
central California coast linked to a toxic diatom
bloom. Nature 2000; 403 : 80–84.
10. Chevallier A. Memoire sur les empoisonnements par
les huitres, les moules, les crabes. Annales d’hygiene
publique et de medecine legale 1851 ; 1.
AQ3
11. Narahashi T. Mechanism of tetrodotoxin and saxitoxin
action. In: Tu AT, ed. Marine Toxins and Venoms,
vol. 3: Marcel Dekker Inc., 1988, pp. 185–210.
AQ4
12. Levin RE. Paralytic shellfish toxins: the origins,
characteristics, and methods of detection : a review.
Journal of Food Biochemistry 1992; 15 : 405–417.
13. Anon. Paralytic shellfish poison. Biological method.
Final action [M]. In : Hellrich K, ed. Official Methods
of Analysis. Arlington, Virginia, USA: Association
of Official Methods of Analytical Chemists, 1990,
pp. 881–882.
14. Gessner BD, Middaugh JP. Paralytic shellfish poison-
ing in Alaska – a 20-year retrospective analysis.
American Journal of Epidemiology 1995; 141 : 766–770.
15. Van Dolah FM. Marine algal toxins : origins, health
effects, and their increased occurrences. Environmental
Health Perspectives 2000; 108 : 133–141.
16. Sommer H, Meyer KF. Paralytic shellfish poisoning.
Archives Pathology 1937; 24 : 560–598.
17. Prakash A, Medcof J, Tennant A. Paralytic shellfish
poisoning in Eastern Canada. Bulletin Fisheries Re-
search Board Canada 1971; 117 : 1–88.
18. Gessner D. Epidemiological impact of toxic episodes :
neurotoxic toxins. In: Botana LM, ed. Seafood and
freshwater toxins, pharmacology, physiology and de-
tection. New York: CRC Press, 2008, pp. 77–103.
19. Anderson DM. Red tides. Scientific American 1994;
August 1994, pp. 52–58.
20. Anderson DM, Sullivan JJ, Reguera B. Paralytic
shellfish poisoning in northwest Spain : the toxicity of
the dinoflagellate Gymnodinium catenatum.Toxicon
1989; 27 : 665–674.
21. de Carvalho M, et al. Paralytic shellfish poisoning:
clinical and electrophysiological observations. Journal
of Neurology 1998; 245 : 551–554.
22. Ingham HR, Mason J, Wood PC. Distribution of toxin
in molluscan shellfish following the occurence of
mussel toxicity in northeast England. Nature 1968;
220: 25–27.
23. Lagos N. Microalgal blooms: a global issue with
negative impact in Chile. Biological Research 1998; 31 :
375–386.
24. Garcı
´aC,et al. Paralytic shellfish poisoning: post-
mortem analysis of tissue and body fluid samples from
human victims in the Patagonia fjords. Toxicon 2004 ;
43: 149–158.
25. Jacinto GA, RV Velasquez IB, Siringan FP. Manila
bay: Environmental challenges and opportunities.
In: EW, ed. AQ5
The Environment in Asia Pacific Har-
bours. Dordrecht, The Netherlands: Springer, 2006,
pp. 309–328.
26. Maclean JL. Indo-Pacific red tides, 1985–1988.
Marine Pollution Bulletin 1989; 20 : 304–310.
27. Murata M, et al. Isolation and structural elucidation
of the causative toxin of the diarrhetic shellfish
Poisoning. Bulletin Japanese Society of Fisheries
Science 1982; 48 : 549–552.
28. Yasumoto T, et al. Diarrhetic shellfish toxins.
Tetrahedron 1985; 41 : 1019–1025.
29. Ogino H, &MK, &TY. Toxicologic evaluation of
yessotoxin. Natural Toxins 1997; 5: 255–259. AQ6
30. Aune T, et al. Comparison of oral and intraperitoneal
toxicity of yessotoxin towards mice. Toxicon 2002 ; 40 :
77–82.
31. EU Commission. Commission decision of 15 March
2002: maximum levels and methods of analysis of
certain marine biotoxins in bivalve molluscs, echino-
derms, tunicates and marine gastropods. Official
Journal of the European Communities, vol. L 75 (2002/
225/EC), 2002, pp. 62–64.
32. Bialojan C, Takai A. Inhibitory effect of a marine-
sponge toxin, okadaic acid, on protein phosphatases.
Specificity and kinetics. Journal of Biochemistry 1988 ;
256: 283–290.
33. Cohen P, Holmes CFB, Tsukitani Y. Okadaic
acid – a new probe for the study of cellular-
regulation. Trends in Biochemical Sciences 1990; 15 :
98–102.
34. Draisci R, et al. Determination of diarrhoetic shellfish
toxins in mussels by microliquid chromatography-
tandem mass spectrometry. Journal of AOAC
International 1998; 81 : 441–447.
35. James KJ, et al. Chapter 11: Detection methods for
okadaic acid & analogues. In: Botana LM, ed.
Seafood and Freshwater Toxins: Pharmacology,
Physiology and Detection. New York: Marcel Dekker,
2000, pp. 217–238.
36. Suganuma M, et al. Okadaic acid : an additional non-
phorbol-12-tetradecanoate- 13-acetate-type tumor
promoter. Proceedings of the National. Academy of
Sciences USA 1988; 85 : 1768–1771.
37. Fujiki H, et al. Significant marine natural products in
cancer research. Gazzetta Chimica Italiana 1993; 123 :
309–316.
38. Manerio E, et al. Shellfish consumption: a major risk
factor for colorectal cancer. Medical Hypotheses 2008 ;
70: 409–412.
10 K. J. James and others

39. Yasumoto T, Oshima Y, Yamaguchi M. Occurrence of
a new type of toxic shellfish poisoning in the Tohoku
district. Bulletin of the Japanese Society of Fisheries
Science 1978; 44 : 1249–1255.
40. Kawabata T. Regulatory aspects of marine biotoxins
in Japan. In: Natori S, Hashimoto K, Ueno Y, eds.
Mycotoxins and Phycotoxins. Amsterdam: Elsevier,
1989, pp. 469–476.
41. van Egmond HP, et al. Paralytic and diarrhoeic shell-
fish poisons: occurrence in Europe, toxicity, analysis
and regulation. Journal of Natural Toxins 1993; 2:
41–83.
42. Belin C. Distribution of Dinophysis spp. and
Alexandrium minutum along French coast since
1984 and their DSP and PSP toxicity levels. In:
Smayda TJ, Shimizu Y, eds. Toxic Phytoplankton
Blooms in the Sea. New York: Elsevier, 1991, pp. 469–
474.
43. Gestal-Otero JJ. Non neurotoxic toxins. In: Botana
LM, ed. Seafood and Freshwater Toxins, Pharma-
cology, Physiology and Detection. New York: Marcel
Dekker, 2000, pp. 45–64.
44. Gestal-Otero JJ. Epidemiological impact of diarrheic
toxins. In: Botana LM, ed. Seafood and Freshwater
Toxins: Pharmacology, Physiology and Detection.
Boca Raton: CRC Press Taylor & Francis Group,
2008, pp. 53–76.
45. Durborow R. Health and safety concerns in fisheries
and aquaculture. Occupational Medicine : State of the
Art Reviews 1999; 14 : 373–406.
46. Carmody EP, James KJ, Kelly SS. Dinophysistoxin-2:
The predominant diarrhetic shellfish toxin in Ireland.
Toxicon 1996; 34 : 351–359.
47. De Schrijver K, et al. An outbreak of diarrhoeic
poisoning in Antwerp, Belgium. Eurosurveillance
Monthly 2002; 7: 138–141.
48. Murakami Y, Oshima Y, Yasumoto T. Identification
of okadaic acid as a toxic component of a marine
dinoflagellate, Prorocentrum lima.Bulletin of the
Japanese Society of Fisheries Science 1982; 48 :
69–72.
49. Yasumoto T, et al. Identification of Dinophysis fortii
as the causative organism of diarrhetic shellfish
poisoning. Bulletin of the Japanese Society of Fisheries
Science 1980; 46 : 1405–1411.
50. Ferna
´ndez Puente P, et al. Studies of polyether toxins
in the marine phytoplankton, Dinophysis acuta,in
Ireland using multiple tandem mass spectrometry.
Toxicon 2004; 44 : 919–926.
51. Blanco J, et al. A preliminary model of toxin ac-
cumulation in mussels. In: Lassus P et al., ed. Harmful
Marine Algal Blooms Paris: Lavoisier Science Pub-
lishers, 1995, pp. 777–782.
52. Suzuki T, et al. Quantification of lipophilic toxins as-
sociated with diarrhetic shellfish poisoning in Japanese
bivalves by liquid chromatography-mass spectrometry
and comparison with mouse bioassay. Fisheries
Science 2005; 71 : 1370–1378.
53. Baden DG. Marine food-borne dinoflagellate toxins.
International Review of Cytology 1983; 82 : 99–150.
54. Steidinger KA, Baden DG. Toxic marine dino-
flagellates. In: Spector DL, ed. Dinoflagellates. New
York: Academic Press, 1984, pp. 201–299.
55. Furey A, et al. Brevetoxins: Structure, Toxicology and
Origin. In: Botana L, Hui YH, eds. Phycotoxins :
Chemistry and Biochemistry. Ames: Blackwell Pub-
lishing, 2007, pp. 19–46.
56. Watkins SM, et al. Neurotoxic shellfish poisoning.
Marine Drugs 2008; 6: 431–455.
57. Flewelling LJ, et al. Red tides and marine mammal
mortalities: unexpected brevetoxin vectors may ac-
count for deaths long after or remote from an algal
bloom. Nature 2005; 435 : 755–756.
58. Morohashi A, et al. Brevetoxin B3, a new brevetoxin
analog isolated from the greenshell mussel Perna
canaliculus involved in neurotoxic shellfish poisoning
in New Zealand. Tetrahedron Letters 1995; 36 : 8995–
8998.
59. Sim J, Wilson N. Surveillance of marine biotoxins,
1993–1996. New Zealand Public Health Report 1997;
4: 9–16.
60. Morris PD, et al. Clinical and epidemiological features
of neurotoxic shellfish poisoning in North Carolina.
American Journal of Public Health 1991; 81 : 471–471.
61. Poli MA, et al. Neurotoxic shellfish poisoning and
brevetoxin metabolites: a case study from Florida.
Toxicon 2000; 38 : 981–993.
62. Fleming LE, Backer LC, Baden DG. Overview of
aerosolized Florida red tide toxins: Exposure and ef-
fects. Environmental Health Perspectives 2005; 113 :
618–620.
63. Dechraoui MY, et al. Ciguatoxins and brevetoxins,
neurotoxic polyether compounds active on sodium
channels. Toxicon 1999; 37 : 125–143.
64. Poli MA, Rein KS, Baden DG. Radioimmunoassay for
PbTx-2-Type brevetoxins: Epitope specificity of two
anti-PbTx sera. Journal of AOAC International 1995;
78: 538–542.
65. Perl TM, et al. An outbreak of toxic encephalopathy
caused by eating mussels contaminated with domoic
acid. New England Journal of Medicine 1990; 322 :
1775–1780.
66. Todd ECD. Domoic acid and amnesic shellfish
poisoning – a review. Journal of Food Protection 1993 ;
56: 69–83.
67. Wright JLC, et al. Identification of domoic acid, a
neuroexcitory amino acid, in toxic mussels from east-
ern PEI, Canada. Canadian Journal of Chemistry
1989; 67 : 481–490.
68. Bates SS, et al. Pennate diatom Nitzschia pungens as
the primary source of domoic acid, a toxin in shellfish
from Prince Edward Island, Canada. Canadian
Journal of Aquatic Science 1989; 46 : 1203–1215.
69. Daigo K. Studies on the constituents of Chondria
armata, II. Isolation of an anthelmentical constituent.
Journal of the Japanese Pharmaceutical Association
1959; 79 : 353–356.
70. Wekell JC, et al. Occurrence of domoic acid in
Washington state razor clams (Siliqua patula) during
1991–1993. Natural Toxins 1994; 2: 197–205.
Shellfish toxicity 11

71. James KJ, et al. Amnesic shellfish poisoning toxins in
bivalve molluscs in Ireland. Toxicon 2005; 46 :
852–858.
72. Powell CL, et al. Development of a protocol for de-
termination of domoic acid in the sand crab (Emerita
analoga): a possible new indicator species. Toxicon
2002; 40 : 485–492.
73. Wright JLC. Dealing with seafood toxins : present
approaches and future options. Food Research
International 1995; 28 : 347–358.
74. Lawrence JF, Charbonneau CF, Menard C. Liquid
chromatographic determination of domoic acid in
mussels, using AOAC paralytic shellfish poison ex-
traction procedure: collaborative study. Journal of the
Association of Official Analytical Chemists 1991; 74 :
68–72.
75. Lo
´pez-Rivera A, et al. Improved high-performance
liquid chromatographic method for the deter-
mination of domoic acid and analogues in shellfish.
Analytical Bioanalytical Chemistry 2005; 381 : 1541–
1545.
76. Beltran AS, et al. Sea bird mortality at Cabo San lucas,
Mexico: evidence that toxic diatom blooms are
spreading. Toxicon 1997; 35 : 447–453.
77. Work TM, et al. Epidemiology of domoic acid
poisoning in brown pelicans (Pelecanus-Occidentalis)
and Brandt cormorants (Phalacrocorax-Penicillatus)
in California. Journal of Zoological Wildlife Medicine
1993; 24 : 54–62.
78. Trainer VL, Hickey BM, Bates SS. Toxic Diatoms. In :
Walsh PJ et al., eds. Oceans and Human Health : Risks
and Remedies from the Seas. Amsterdam: Elsevier,
2008, pp. 219–237.
79. Miguez A, Luisa Fernandez M, Fraga S. First detection
of domoic acid in Galicia (NW Spain). In : Yasumoto
T, Oshima Y, Fukuro Y, eds. Harmful and Toxic Algal
Blooms. Paris: Intergovernmental Oceanographic
Commission of UNESCO, 1998, pp. 143–145.
80. James KJ, et al. New fluorimetric method of liquid
chromatography for the determination of the neuro-
toxin domoic acid in seafood and marine phyto-
plankton. Journal of Chromatography A 2000; 871 :
1–6.
81. Vale P, Sampayo MA. Domoic acid in Portuguese
shellfish and fish. Toxicon 2001; 39 : 893–904.
82. Hess P, et al. Determination and confirmation of the
amnesic shellfish poisoning toxin, domoic acid in
shellfish from Scotland by liquid chromatography and
mass spectrometry. Journal of AOAC International
2001; 84 : 1657–1667.
83. Amzil Z, et al. Domoic acid accumulation in French
shellfish in relation to toxic species of Pseudo-nitzschia
multiseries and P. pseudodelicatissima.Toxicon 2001;
39: 1245–1251.
84. Pulido OM. Domoic acid toxicologic pathology: a re-
view. Marine Drugs 2008; 6: 180–219.
85. Satake M, et al. Azaspiracid, a new marine toxin
having unique spiro ring assemblies, isolated from
Irish mussels, Mytilus edulis.Journal of American
Chemical Society 1998; 120 : 9967–9968.
86. Ofuji K, et al. Two analogs of azaspiracid isolated
from mussels, Mytilus edulis, involved in human
intoxications in Ireland. Natural Toxins 1999; 7:
99–102.
87. Ofuji K, et al. Structures of azaspiracid analogs, azas-
piracid-4 and azaspiracid-5, causative toxins of azas-
piracid poisoning in Europe. Bioscience Biotechnology
Biochemistry 2001; 65 : 740–742.
88. Nicolaou KC, et al. Total synthesis of the proposed
azaspiracid-1 structure, part 2: Coupling of the
C1-C20, C21-C27, and C28-C40 fragments and
completion of the synthesis. Angewandte Chemie –
International Edition 2003; 42 : 3649–3653.
89. James KJ, et al. Azaspiracid Poisoning, The food-
borne illness associated with shellfish consumption.
Food Additives and Contaminants 2004 ; 21 : 879–892.
90. Draisci R, et al. Development of a method for the
identification of azaspiracid in shellfish by liquid
chromatography-tandem mass spectrometry. Journal
of Chromatography A 2000; 871 : 13–21.
91. Furey A, et al. Determination of azaspiracids in shell-
fish using liquid chromatography-tandem electrospray
mass spectrometry. Rapid Communications in Mass
Spectrometry 2002; 16 : 238–242.
92. Lehane M, et al. Liquid chromatography – multiple
tandem mass spectrometry method for the determi-
nation of ten azaspiracids, including hydroxyl ana-
logues, in shellfish. Journal of Chromatography A
2004; 1024 : 63–70.
93. James KJ, et al. First evidence of an extensive
Northern European distribution of Azaspiracid
Poisoning (AZP) toxins in shellfish. Toxicon 2002; 40 :
909–915.
94. Bran
˜a Magdalena A, et al. The first identification of
azaspiracids in shellfish from France and Spain.
Toxicon 2003; 42 : 105–108.
95. Furey A, et al. Geographical, temporal and species
variation of the polyether toxins, azaspiracids.
Enviromental Science and Technolology 2003; 37 :
3078–3084.
96. Taleb H, et al. First detection of azaspiracids in
mussels in North West Africa. Journal of Shellfisheries
Research 2006; 25 : 1067–1070.
97. Ueoka R, et al. Isolation of azaspiracid-2 from a
marine sponge Echinoclathria sp. as a potent cyto-
toxin. Toxicon 2009; 53 : 680–684.
98. James KJ, et al. Detection of five new hydroxyl ana-
logues of azaspiracids in shellfish using multiple tan-
dem mass spectrometry. Toxicon 2003; 41 : 277–283.
99. Rehmann N, Hess P, Quilliam MA. Discovery of new
analogs of the marine biotoxin azaspiracid in blue
mussels (Mytilus edulis) by ultra-performance liquid
chromatography/tandem mass spectrometry. Rapid
Communications in Mass Spectrometry 2008; 22 :
549–558.
100. Ito, E, et al. Multiple organ damage caused by a new
toxin azaspiracid, isolated from mussels produced in
Ireland. Toxicon 2000; 38 : 917–930.
101. Ito, et al. Chronic effects in mice caused by the oral
administration of sublethal doses of azaspiracid, a new
12 K. J. James and others

marine toxin isolated from mussels. Toxicon 2002; 40 :
193–203.
102. Roma
´nY,et al. Azaspiracid-1, a potent, nonapoptotic
new phycotoxin with several cell targets. Cellular
Signalling 2002; 14 : 703–716.
103. Roman Y, et al. Effects of azaspiracids 2 and 3
on Intracellular cAMP, Ca
2
+
, and pH. Chemical
Research in Toxicology 2004; 17 : 1338–1349.
104. Vilarin
˜oN.Marine toxins and the cytoskeleton: azas-
piracids. FEBS Journal 2008; 275 : 6075–6081.
105. James KJ, et al. Ubiquitous ‘benign ’ alga emerges as
the cause of shellfish contamination responsible for
the human toxic syndrome, azaspiracid poisoning.
Toxicon 2003; 41 : 145–151.
106. Tillmann U, et al. Azadinium spinosum gen. et sp. nov.
(Dinophyceae) identified as a primary producer of
azaspiracid toxins. European Journal of Phycology
2009; 44 : 63–79.
107. James KJ, et al. Azaspiracid shellfish poisoning : un-
usual toxin dynamics in shellfish and the increased risk
of acute human intoxications. Food Additives and
Contaminants 2002; 19 : 555–561.
108. James KJ, et al. Azaspiracids: chemistry, bioconver-
sion and determination. In: Botana LM, Hui YH, eds.
Phycotoxins: Detection and Analysis. Boca Raton :
CRC Press, 2008, pp. 763–784.
109. Hallegeaeff GM. Harmful algae blooms: a global
overview. In: Hallegraeff GM, Anderson DM,
Cembella AD, eds. Manual on Harmful Marine
Microalgae. Paris: Intergovernmental Oceanographic
Commission (UNESCO), 1995, pp. 25–49.
110. Maso M, Garces E. Harmful microalgae blooms
(HAB); problematic and conditions that induce them.
Marine Pollution Bulletin 2006; 53 : 620–630.
111. Peperzak L. Future increase in harmful algal blooms
in the North Sea due to climate change. Water Science
& Technology 2005; 51 : 31–36.
112. Kelly V. The Role of eutrophication in the global
proliferation of harmful algal blooms. Oceanography
2005; 18 : 198–209.
113. Moore SK, et al. Impacts of climate variability
and future climate change on harmful algal blooms
and human health. (Centers for Oceans and Human
Health Investigators Meeting). Environmental Health
7. Woods Hole, MA, USA. 24–27 April 2007, BioMed
Central Ltd, 2008; S4.
114. Pearl HW, Whitall DR. Anthropogenically-driven at-
mospheric nitrogen deposition, marine eutrophication
and harmful algal bloom expansion: is there a link ?
Ambio 1999; 28 : 307–311.
115. Hodgkiss IJ, Ho KC. Are changes in N : P ratios in
coastal waters the key to increased red tide blooms ?
Hydrobiologia 1999; 352 : 141–147.
116. Hallegraeff GM, et al. Microalgal spores in ship’s
ballast water: a danger to aquaculture. In : Graneli E
et al., eds. Toxic Marine Phytoplankton. Amsterdam:
Elsevier, 1990, pp. 475–480.
117. Ciminiello P, et al. The Genoa 2005 outbreak.
Determination of putative palytoxin in Mediterranean
Ostreopsis ovata by a new liquid chromatography
tandem mass spectrometry method. Analytical Chem-
istry 2006; 78 : 6153–6159.
118. Louzao MC, Ares IR, Cagide E. Marine toxins and the
cytoskeleton: a new view of palytoxin toxicity. FEBS
Journal 2008; 275 : 6067–6074.
119. Cagide E, et al. Production of functionally active
palytoxin-like compounds by Mediterranean Ostreop-
sis cf. siamensis.Cell Physiolology and Biochemistry
2009; 23 : 431–440.
120. Noguchi T, Arakawa O. Tetrodotoxin – distribution
and accumulation in aquatic organisms, and cases of
human intoxication. Marine Drugs 2008; 6: 220–242.
121. Ferna
´ndez-Ortega JF, et al. Seafood intoxication by
tetrodotoxin: first case in Europe. Journal of Emerg-
ency Medicine 2009 (in press).
122. Anon. EU project. ATLANTOX: advanced tests
about new toxins appeared in the Atlantic, 2009
(http://www.atlantox.com/).
123. Sobel J, Painter J. Illnesses caused by marine toxins.
Clinical Infections Diseases 2005; 41 : 1290–1296.
124. Mons MN, van Egmond HP, Speijers GJA. Paralytic
shellfish poisoning, a review. Report : National
Institute of Public Health and the Environment
(RIVM), The Netherlands, 1998, pp. 1–47.
125. Dahl E, Yndestad M. Diarrhetic shellfish poisoning
(DSP) in Norway in the autumn 1984 related to the
occurrence of Dinophysis spp. In: Anderson DM,
White DW, Baden DG, eds. Toxic Dinoflagellates.
New York: Elsevier, 1985, pp. 495–500.
126. Correia AM, Goncalves G, Saraiva M. Foodborne
outbreaks in northern Portugal, 2002. Eurosuveillance
2004; 9: 18–20.
127. Quilliam MA, et al. Confirmation of an incident of
diarrhetic shellfish poisoning. In: Smayda TJ, Shimizu
Y, eds. Toxic Phytoplankton Blooms in the Sea, 1993,
pp. 547–552.
128. Lembeye G, Yasumoto T, Zhao J, Fernandez R. DSP
outbreak in Chilean fiords. In: Smayda TJ, Shimizu Y,
eds. Toxic Phytoplankton Blooms in the Sea : Elsevier,
1993, pp. 525–529.
129. Gayoso AM, et al. Diarrhetic shellfish poisoning as-
sociated with Prorocentrum lima (Dinophyceae) in
Patagonian Gulfs (Argentina). Journal of Shellfish
Research 2002; 21 : 461–463.
130. Sakamoto Y, Lockey RF, Krzanowski JJ. Shellfish and
fish poisoning related to the toxic dinoflagellates.
Southern Medical Journal 1987; 80 : 866–872.
131. Ahmed FE. Naturally occurring seafood toxins.
Journal of Toxicology and Toxin Reviews 1991; 10 :
263–287.
132. Morohashi A, et al. Brevetoxin B4 isolated from
greenshell mussels Perna canaliculus, the major toxin
involved in neurotoxic shellfish poisoning in New
Zealand. Natural Toxins 1999; 7: 45–48.
133. Satake M, et al. New toxic event caused by Irish
mussels. In: Reguera B, Blanco J, Fernandez ML,
Wyatt T, eds. Harmful Algae. Santiago de
Compostela: Xunta de Galicia and Intergovernmental
Oceanographic Commission of UNESCO, 1998,
pp. 468–469.
Shellfish toxicity 13

134. Anon. Illness due to AZP. Food Safety Authority of
Ireland; 2008 (Newsletter May/June) (www.fsai.ie/
news_centre/newsletters.html).
135. Oshima Y, et al. Dinoflagellate Gymnodinium catena-
tum as the source of paralytic shellfish toxins in
Tasmanian shellfish. Toxicon 1987; 25 : 1105–1111
136. Oshima Y, Blackburn SI, Hallegraeff GM. Com-
parative study on paralytic shellfish toxin profiles of
the dinoflagellate Gymnodinium catnatum from three
different countries. Marine Biology 1993; 116 : 471–
476.
137. James KJ, et al. High-performance liquid chromato-
graphy with fluorimetric, mass spectrometric and
tandem mass spectrometric detection to investigate the
seafood toxin producing phytoplankton, Dinophysis
acuta.Journal of Chromatography 1997 ; 777 : 213–221.
138. Lee JS, et al. Determination of diarrhetic shellfish
toxins in various dinoflagellate species. Journal of
Applied Phycology 1989; 1: 147–152.
139. Dickey RW, et al. Identification of okadaic acid from
a Caribbean dinoflagellate, Prorocentrum concavum.
Toxicon 1990; 28 : 371–377.
140. Lin YY, et al. Isolation and structure of brevetoxin B
from the ‘red tide ’ dinoflagellate Ptychodiscus brevis
(Gymnodinium breve). Journal of the American
Chemical Society 1981; 103 : 6773–6775.
141. Baden DG, Mende TJ, Roszell LE. Detoxification
mechanisms of Florida’s red tide dinoflagellate
Ptychodiscus brevis. In: Okaichi T, Anderson DM,
Nemoto T, eds. Red Tides: Biology, Environmental
Science, and Toxicology. New York : Elsevier, 1989,
pp. 391–394.
14 K. J. James and others