Possibility of Toxin Profiles
From Paralytic Shellfish
Poisoning as Geographical
Markers in Algae Populations
Jenny McCartney
Paralytic Shellfish Poisoning
Definition
– Paralytic shellfish poisoning (PSP) is a nervous
system disease caused by eating cooked or
raw shellfish that contain environmental
toxins.
– The toxins are not destroyed by cooking,
freezing or pickling.
– It persists due to the life cycle of algae, they
form dormant cysts that sink into the
sediment when conditions are unfavorable and
then bloom when the conditions become
favorable again.
Paralytic Shellfish Poisoning
There are about 1600 cases of PSP reported
per year with about 300 resulting in death
(~19% mortality).
PSP occurs primarily in temperate seas but it
is quickly spreading and outbreaks have been
reported in tropical to boreal waters.
PSP affects more coastline than any other
harmful algae bloom problem.
Map of PSP events 1988-1998
Symptoms of PSP
Neurological symptoms dominate because the
algae produce neurotoxins that block sodium
conductance in nerve and muscle tissue.
Symptoms include tingling or burning
sensations of lips, face and extremities that
may progress to numbness and
lightheadedness, a floating sensation,
weakness, incoherence, thirst, headache,
temporary blindness, respiratory failure due
to paralysis and death.
Cause of PSP
Dinoflagellates in the genera:
– Alexandrium
– Gymnodinium
– Pyrodinium
– Gonyaulax
Primary toxins they produce:
– Saxitoxin
– Brevetoxin
– Ciguatoxin
Alexandrium
Alexandrium cysts Alexandrium catenella Alexandrium tamarense
Gymnodinium
Gymnodinium spp. Gymnodinium catenatum
How does PSP affect you?
Shellfish Industry
– Our rate of consumption of mollusks is
increasing and probably will continue to
increase due to the rapidly increasing
population and the growing demand for
protein food resources.
Closure of fisheries and beaches
– Costs money, not only to be closed but to
fix the problem, not to mention it ruins
these leisurely activities.
Shellfish Warning Sign
How does it affect you?, cont.
Public Health
– People get sick (the maximum safe level is 80
µg toxin/100 g fish = 0.8 ppm).
– PSP bioaccumulates in the food chain (not only
has it been documented in filter feeding bivalves
but also in crabs, gastropods, mackerel and
planktivorous fish).
Costs
– Shellfish and algae monitoring programs, health
care costs, money lost due to fisheries and
beaches being closed, and losses to the shellfish
industry.
Paralytic Shellfish Poisoning
The geographic distribution of PSP is
increasing.
Suspected reasons for this are:
– Long term climatic variability that affects
the temperature, upwelling and currents
that allow cysts to survive in areas where
they did not before.
– Coastal currents carrying them to new
places.
– Traveling in ship ballast water.
Paralytic Shellfish Poisoning
Due to all of the ways this problem affects
people it is becoming increasingly essential
for us to determine how to trace global
dispersal’s of these different populations of
dinoflagellates causing PSP.
Why?
-To find a solution.
Papers Studied to Provide Evidence
for the Possibility of Toxin Profiles as
Geographical Markers in Algae
Populations
“Geographic Differences in Paralytic Shellfish Poisoning Toxin
Profiles Among Japanese Populations of Alexandrium tamarense
and A. catenella (Dinophyceae)” by Yoshido, Sako and Uchida
published in the journal Phycological Research in 2001.
“Singapore Isolates of the Dinoflagellate Gymnodinium
catenatum (Dinophyceae) Produce A Unique Profile of Paralytic
Shellfish Poisoning Toxins” by Holmes, Bolch, Green, Cembella
and Teo published in the Journal of Phycology in 2002.
“Paralytic Shellfish Poisoning In Northwest Spain: The Toxicity
Of The Dinoflagellate Gymnodinium catenatum” by Anderson,
Sullivan and Reguera published in the journal Toxicon in 1989.
Summary of Findings of Support
From All Three Studies
A. tamarense and A. catenella toxin profiles were rather
constant within a geographical area and divergent among
different geographical areas.
Only a few groups of isolates with different toxin profiles
were observed in a geographical area (suggesting that
several representative isolates express the genotype in a
given region).
Toxin composition has been found to have a genetic basis.
Diversity of toxin profile related to regional populations
has been reported in isolates from Japan, North America,
the northeastern Pacific, eastern Canada, Portugal, UK
and New Zealand.
Summary of Findings of Support
From All Three Studies, cont.
Toxin profile was conserved within a region, and major
toxin components of isolates within a region were almost
identical (although their ratios varied).
Comparison of planktonic isolates from Australia, China,
Japan, the Philippines, Portugal, Spain and Uruguay
indicate minor but geographically consistent differences in
the toxin profiles.
Genetic and morphological analysis of laboratory cultures
of G. catenatum in the Singapore isolate illustrated that it
exhibited a unique toxin profile that is distinguishable from
those of other known global populations of this species.
The mixture of saxitoxin and its derivatives in a
dinoflagellate strain does not vary significantly with
growth stage or nutrient status.
Summary of Observations
Illustrating Toxicity Is Not A
Foolproof Marker For Specific
Geographic Populations
Differences in cellular toxicity of populations among
neighboring geographical regions were rather small.
Toxin contents, which are positively correlated to cellular
toxicity, have been reported to vary dependent on growth
phase or environmental factors.
Relatively few investigations of diversity within a
geographical region in the same year or among different
years have been conducted.
Conclusions
Since PSP outbreaks are a major problem and are only
increasing in both incidence and geographical spread, a
solution is becoming imminently necessary.
Improved surveillance on specific dinoflagellate
populations to better understand how and where they are
spreading will more effectively and quickly lead us to
strategies for the prevention and control of PSP.
This is why there has been a fairly new focus on
examining whether toxin profiles can be used as markers
to track populations from specific geographical areas.
From these papers the use of toxin profiles as geographic
markers looks promising, although not foolproof, and in
the absence of an appropriate molecular technique it has
proven to be the finest biochemical marker to discriminate
between populations from different geographical areas so
far.
Literature Cited
Anderson, Donald M., John J. Sullivan and Beatriz Reguera. “Paralytic Shellfish
Poisoning In Northwest Spain: The Toxicity of the Dinoflagellate
Gymnodinium catenatum.” Toxicon 27 No. 6 (1989): 665-674.
Falconer, Ian R, ed. Algal Toxins in Seafood and Drinking Water. London:
Academic Press, 1993.
Halstead, Bruce W and E. J. Schantz. Paralytic Shellfish Poisoning. Geneva: World
Health Organization, 1984.
Holmes, Michael J., Christopher J. S. Bolch, David H. Green, Allan D. Cembella and
Serena Lay Ming Teo. “Singapore Isolates of the Dinoflagellate Gymnodinium
catenatum (Dinophyceae) Produce A Unique Profile of Paralytic Shellfish
Poisoning Toxins.” Journal of Phycology 38 No. 1 (2002): 96-106.
Sze, Philip. A Biology of the Algae. Boston: WCB/McGraw-Hill, 1998.
Yoshido, Takashi, Yoshihiko Sako and Aritsune Uchida. “Geographic differences in
paralytic Shellfish poisoning toxin profiles among Japanese populations of
Alexandrium tamarense and A. catenella (Dinophyceae).” Phycological
Research 49 No. 1 (2001): 13-21.