The increased global distribution of paralytic shellfish poisoning is reported in Hallegraeff (1993). Until 1970, PSP-producing dinoflagellates blooms of A. tamarensis and A. catenella were only known from temperate waters of Europe, North America and Japan. By 1990, PSP was well documented from throughout the Southern Hemisphere in South Africa, Australia, India, Thailand, Brunei Darussalam, Sabah (Malaysia), the Philippines and Papua New Guinea. Of course, the increasing interest in the utilization of coastal waters for aquaculture is leading to an increased awareness of toxic algal species, but whether this is the only explanation remains uncertain.
The presence of PSP toxins in the coastal waters of ICES countries in Europe during the years from 1991 to 2000 is illustrated in Figure 2.2.
At the east coast of Jutland, PSP was found in mussels in 1987 and in 1990 (and possibly also in 1988). The causing algae were A. tamarensis and A. ostenfeldii (CRL, 1995). A PSP episode took place in 1996 and a PSP-like episode followed in 1997. However, in the last case, the presence of PSP toxins was not confirmed (EU-NRL, 1998).
Most of the toxic episodes caused by marine biotoxins were related to diarrhoeic phycotoxins; but some minor toxic episodes were related to paralytic phycotoxins. These episodes occurred only at the northern Brittany coast and were always caused by A. minutum. Maximal toxicity in mussels and oysters was 400 ug STX eq/100 g meat. In late 1992, PSP toxins were found in mussels from the Atlantic coast without any occurrence of toxin producing algae in the water (CRL, 1995). At the end of 1998, A. tamarensis was detected at concentrations of up to 350 000 cells/litre and some production areas for clams, oysters and mussels were closed for two months (EU-NRL, 2000). In 2000, two areas in Brittany were closed due to the presence of PSP toxins (EU-NRL, 2001).
Figure 2.2 Occurrence of PSP toxins in coastal waters of European ICES countries from 1991 to 2000
Since the beginning of the twentieth century, no poisonings related to PSP have been reported after the consumption of mussels collected in German waters. Since 1972 (PSP cases in Germany following consumption of contaminated Spanish mussels), mussels are regularly monitored for PSP toxins. Causative organisms like A. tamarensis, A. minutum and A. ostenfeldii occurred but only in limited numbers. In 1987, three cases of PSP occurred in Lower Saxonia which could, again, be attributed to the consumption of canned Spanish mussels (CRL, 1995). Since March 1992, viable cysts of a species very similar or identical to G. catenatum have been found in German coastal waters of the North and Baltic Seas. The toxicity of the strain has not (yet) been reported. In freshwater, PSP producing blue green algae have been isolated. Other species known to produce PSP toxins have not yet been reported in German waters (IOC, 1995).
In Ireland, a PSP event was noted in Cork Harbour in July 1992 and persisted for one week only. The phytoplankton associated with this event was Alexandrium tamarensis (CRL, 1995). Following a bloom of A. tamarensis in Cork Harbour in June 1996 GNTX2 and GNTX3 were identified in wild mussels (Mytilus edulis) and cultivated oysters (Crassostrea gigas). Maximum recorded levels were 360 and 88 µg STX eq/100 g meat in M. edulis and C. gigas, respectively, determined by LC. The levels in M. edulis dropped by natural depuration, to 25 µg/100 g meat (by LC) within 12 days. The levels in C. gigas declined to 3 µg STX eq/100 g meat within 12 days in a depuration unit (Furey et al., 1998). In 1999 cysts of A. tamarensis were detected in surface sediments in Cork Harbour and viable cultures of A. tamarensis have been grown from these cysts (EU-NRL, 2000). During 2002, PSP toxins were detected above the regulatory limit in both mussels and oysters from Cork Harbour for a three-week period in July (EU-NRL, 2002).
Dinoflagellate red tides are a recurring phenomenon in the Adriatic Sea yet despite the presence of potentially toxic species such as Alexandrium spp., no cases of PSP in humans were reported until 1995. Along the northwest Adriatic coast of Italy, A. minutum was found at sampling stations in Emilia Romagna in 1994, 1995 and 1996 from April to July. In May 1994, some mussel samples showed PSP values greater than 80 µg STX eq./100 g meat but no public health problems were reported (Poletti et al., 1998). Some shellfish samples were subsequently also found to be contaminated by PSP along the Emilia Romagna coast as a consequence of the presence of A. minutum in seawater (CRL, 1995). PSP toxins at a level <40 µg STX eq./100 g of meat, associated with the presence of A. minutum, were detected in April and May 2001 in Friuli Venezia Giulia (EU-NRL, 2001). In late May and early June 2002, PSP toxins were detected in Sardinia (Golf of Olbia) due to the presence of A. catenella and A. minutum. In this case, STX levels were higher than 80 µg STX eq/100 g and a maximum of 2510 µg STX eq/100 g was reached (EU-NRL, 2002).
PSP-producing algae have, until now, hardly been observed in the Netherlands. Although Alexandrium species were identified in the North Sea in 1989, shellfish containing PSP toxins were not found. In 1990, symptoms of paralysis were reported in some persons after consumption of shellfish from the Wadden Sea but it was subsequently determined that this was not related to PSP (Mons et al., 1998). Scallops with PSP toxins were once reported but this turned out to be a side-catch from the North Sea (CRL, 1995).
PSP contamination events in Norway are among the earliest recorded in Europe. PSP has been detected frequently in many localities and cases of human intoxication have been reported seven times (1901, 1939, 1959, 1979, 1981, 1991 and 1992) with a total of 32 victims including two fatalities (Mons et al., 1998). Results of a surveillance programme in 1994 showed different closures due to PSP. A similar pattern was found the following years (EU-NRL, 1998). In 1999, 11 percent of samples tested were positive for the presence of PSP toxins. Some cases of human illness, associated with mussels imported from Sweden, have been recorded (EU-NRL, 2000).
From 1986 until 1990, there were occurrences of PSP outbreaks along the Portuguese coast north of Roca Cape. In 1991, the problem did not appear. In 1992, it appeared again but occurred also off the south coast of Lisbon and along the Algarve coast in concentrations of 100-500 mg STX eq/100 g of shellfish. In 1993, PSP was found almost all year round, covering the entire coast. Observed concentrations ranged from 113 mg STX eq/100 g of shellfish in December at the Northern coast up to 9145 mg STX eq/100 g at the Lisboan coast in September. In 1994, PSP outbreaks occurred off the south coast of Portugal and off the Algarve coast. The main causative organism was Gymnodinium catenatum. Alexandrium lusitanicum was also found to be responsible for PSP outbreaks at the Obidos Lagoon (IOC, 1995). During the last two weeks of October 1994, nine patients (six women and three men) were reported to suffer from PSP after consumption of molluscs (Mytilus edulis) from the west coast of Portugual (De Carvalho et al., 1998). In 1997, PSP was found in only one species, Tellina crasa (EU-NRL, 1998). G. catenatum at concentrations >3000 cells/litre were observed in the Algarve area and a precautionary closure was put in place (EU-NRL, 2000).
Mussel aquaculture is an important industry in the Galician Rias, located along the northwestern Atlantic coast of Spain. Since 1976, this region has been seriously affected by incidents of PSP. Spanish mussels contaminated with PSP have caused food poisoning in several other European countries as well as Spain. This occurred in 1976 when mussels exported by Spain caused paralytic shellfish poisoning in European countries including Germany, France, Switzerland and Italy. In total, 120 people in Western Europe were affected by PSP following consumption of these Spanish mussels (Mytilus edulis). However, there were no deaths (IPCS, 1984).
Another particularly bad episode occurred in 1993 when the toxic events lasted for an unusually long period. Many people became ill with unusual symptoms. The chemical analysis of the mussel samples taken revealed a complex toxin profile with both DSP and PSP toxins present. The observed PSP toxins were Bl and the decarbamoylated derivatives of STX, GNTX2 and GNTX3. Small amounts of STX and other (unidentified) PSP toxins were also observed. The contamination of the mussels was probably due to the dinoflagellate A. catenatum (Gago-Martinez et al., 1996). Sporadic episodes of PSP lasting two to three weeks occurred in Galicia during 1995 to 1997 (EU-NRL, 1998). In 2000, there were some toxic events related to the presence of PSP toxins that led to the prohibition of harvesting of bivalves in some production areas in Galicia (EU-NRL, 2001).
Routine toxicity testing of bivalve warty Venus (Venus
verrucosa) in January 1989 on the Mediterranean coast of southern Spain
revealed rising levels of PSP toxins, probably related to the presence of high
levels of naked dinoflagellate cells (Gymnodinium catenatum) in seawater
samples. PSP toxins were detected in different mollusc species (Venus
verrucosa, Venerupis rhomboides, Callista chione, Acanthocardia
tuberculatum) from the affected areas in concentrations higher than
80 mg STX eq/100 g meat, which caused the
collection and sale of molluscs to be banned by the regional health authorities.
This incident affected the southern Mediterranean coast of Spain between Malaga
and Algeciras, a span of approximately
150 km, probably reaching the coast of Morocco, which would explain the toxicity found in A. tuberculatum imported from Morocco in February 1989 (Mons et al., 1998).
During April and May 1995, the water in the harbour of Palma de Mallorca (Balearic Islands) appeared abnormally reddish brown as a result of the proliferation of the toxic dinoflagellate Alexandrium minutum, reaching concentrations up to 45x106 cells/L. Mouse bioassays in natural populations of bivalve molluscs (Mytilus galloprovincialis, Chamelea gallina and Lithopaga lithopaga) produced positive results with a maximum of 1 170 STX eq/100 g tissue. The red tide recurred in the same area of the harbour in April 1996, although it lasted only ten days, and during three weeks in February 1997 (Forteza et al., 1998).
In October and November 1994, a PSP outbreak was observed on the Atlantic shores of Spain after a bloom of G. catenatum (Tahri Joutei, 1998). During 2002, there were short toxic events related to the presence of PSP toxins in Galicia (northwest Spain) due to the presence of A. minutum and A. catenella. In Andalusia, production areas, especially for Acanthocardia tuberculata and scallops, were closed due to the presence of G. catenatum (EU-NRL, 2002).
Contamination with PSP in mussel farming in Sweden occurs at the end of spring and beginning of summer. PSP toxins have been detected in mollusc meat between 1985 and 1988, with the highest level of toxicity being reached in 1986 and 1987, i.e. 1 000 MU/100g meat. The species involved was A. excavatum (Mons et al., 1998). Samples were sent to Norway when performance of the bioassay was necessary, yielding high levels (approximately 300 µg STX eq/100 g) of PSP toxins in May 1997 (EU-NRL, 1998).
The United Kingdom of Great Britain and Northern Ireland
The first cases of PSP intoxication occurred in 1968 after consumption of local mussels (Mytilus edulis) containing 600-6 000 mg STX eq/kg from the northeastern coast of England; 78 people were admitted to hospital, however there were no deaths (IPCS, 1984). From then on, PSP has been detected very often with levels below 400 MU/100 g shellfish in 1972 and 1973 only. In 1977, toxicity reached 1 792 MU/100 g and from 1978 to 1981 PSP events were annual occurrences on the northeast coast spreading towards Scotland. However, during this entire period, the monitoring network prevented human intoxication. In 1990, the first cases of PSP were recorded along the west coast of Scotland with maximum toxin concentrations in the order of 16480 MU/100 g in mussels and scallops (Mons et al., 1993).
In 2000/2001, low levels of PSP toxins were detected in some areas of England and Wales (EU-NRL, 2001). In Scotland, PSP toxins were detected from 2000 to 2001 in early May in mussels from aquaculture sites along the west coast, and in scallop gonad tissue from scallop fishing grounds in Orkney. Levels in scallop tissue rose to 158 µg STX eq/100 g by mid-May and restrictions on fishing activity were imposed. By the end of May, aquaculture sites in the Shetlands and scallop grounds on the east coast were also affected. Levels in mussels from the Shetlands reached 211 µg STX eq/100 g, in Orkney 2999 µg STX eq/100g, and on the west coast 220 µg STX eq/100 g. Restrictions on harvesting mussels from aquaculture sites were subsequently imposed. By mid-July, toxins were no longer detectable in mussels, although toxins in scallops and in scallop gonad tissue were still detectable in mid-October. In some areas, toxins in scallop tissues remained above 80 µg STX eq/100 g and fishing restrictions continued (EU-NRL, 2001).
In the period from 1 April 2002 to 31 March 2003, shellfish from 76 primary inshore production areas, 36 secondary areas and offshore fishing areas in Scotland were examined. A total of 5 409 mollusc samples were analysed. Out of all these samples, 1 690 were analysed for PSP. Twenty-one samples were positive for PSP (Anonymous, 2003c). In August 2001, the United Kingdom Food Standards Agency announced a ban on scallop fishing in the sea adjacent to Northern Ireland after the detection of PSP toxins in scallops (Anonymous, 2001a).
In Atlantic Moroccan waters, G. catenatum has sometimes appeared in late summer and early autumn. The most important event was the bloom of October to November 1994, associated with a PSP outbreak that was also observed on the Spanish Atlantic shores and Portuguese waters in September and October 1994, respectively (Tahri Joutei, 1998). PSP toxin analysis in bivalve molluscs was carried out from 1994 to 1996. Along the Atlantic coast, PSP levels in Mytilus galloprovincialis in November 1994 showed a maximum of about 6 000 µg STX eq/100 g meat (Taleb et al., 1998).
Along the Mediterranean coast, A. tuberculatum was found to contain high levels of PSP toxins during all years in which there was monitoring (up to approximately 800 µg STX eq/100 g meat). However, other species, i.e. Venus verrucosa, Callista chiona and Donax trunculus, from the same site were only temporarily contaminated, generally from January to March in 1995, and PSP levels never exceeded 250 µg STX eq/100 g meat (Taleb et al., 1998).
In 1969 and 1979, 6 and 17 cases of PSP, respectively, were reported after consumption of local black mussels (Chloromytilus meridionalis) containing up to 84 000 mg STX eq/kg. Two fatalities occurred (IPCS, 1984). Along the South African coast, Gonyaulax catenella is regularly present on the west coast and has caused several human deaths (Collins, 2001).
In March 1994 A. tamarensis was present in a bloom and tests revealed that mussels and oysters contained PSP toxins beyond the safe limit of toxicity (Anonymous, 2003a). Pitcher et al. (2001) reported the presence of PSP toxins in cultured abalone Haliotis midae on two West Coast farms in April 1999. Analysis of wild animals from the west coast also revealed the accumulation of PSP toxins in these gastropods. Toxin content (AOAC mouse bioassay) varied from non detectable to 1609 µg STX eq/100 g. The dinoflagellate A. catenella was the probable cause of the abalone toxicity.
More than 700 tonnes of cultured sea bass and sea bream and several species of wild fish were found dead in the lagoons of Burger and Gar el Melh. Mortality was probably caused by PSP toxins producing Alexandrium minutum and A. tamarensis and by a hemolytic substance producing Girodinium aureolum (Rhomdane et al., 1998).
2.7.4 North America
The presence of PSP toxins in coastal waters of ICES countries in North America from 1991 to 2000 is illustrated in Figure 2.3.
PSP has been documented in British Columbia since 1793 when four crewmen with Captain Vancouvers expedition became sick and one died shortly after eating shellfish from the coastal waters of British Columbia. PSP has been documented in the St. Lawrence Estuary (Quebec) and the Bay of Fundy (between New Brunswick and Nova Scotia) since the 1880s (Todd, 1997). In 1978 and 1982, two and five cases of PSP, respectively, were reported after eating local mussels or clams containing 430 000 and 21 000 mg STX eq/kg, respectively. One death occurred (IPCS, 1984). Overall, from 1880 to 1995, 106 PSP incidents involving 538 cases and 32 deaths have been documented. The largest concentration of illnesses occurred between 30 April and 18 August 1974 in the St. Lawrence Estuary demonstrating toxin levels up to 4 900 µg/100 g and involving 43 cases. The butter clam Saxidomus giganteus on the west coast can remain toxic throughout the year (Todd, 1997). In May 1999, two employees of a salmon farm in Herbert Inlet, British Columbia showed symptoms of PSP after eating wild scallops at the farm site (Anonymous, 1999b).
Figure 2.3 Occurrence of PSP toxins in coastal waters of North American ICES countries from 1991 to 2000
The United States of America
In the New England region, the first documented case of PSP was in the far eastern sections of Maine near the Canadian border in 1958. In 1972, a massive visible red tide of A. tamarensis stretched from southern Maine through New Hampshire and into Massachusetts, causing shellfish toxicity in southern areas for the first time. Thirty-three people were affected, however no one died. Low levels of toxicity were occasionally reported in southern Maine, west of Penobscot Bay prior to 1972, but present-day outbreaks in this area are far more numerous and involve much higher levels of toxicity. Virtually every year since the 1972 outbreak in Maine, New Hampshire and Massachusetts have experienced PSP outbreaks, a direct result of Alexandrium cysts being retained in southern waters once introduced there by massive blooms. In 1979, mussel beds were closed in Narragansett Bay, Rhode Island, when PSP was detected but no causative organism was ever identified. In subsequent years, PSP toxicity and A. tamarensis cells and cysts were documented in small embayments in Connecticut and Long Island. Cysts and motile cells of A. tamarensis have also been reported as far as south as New Jersey but no PSP toxicity has ever been detected that far south. Recent history suggests a gradual, southward dispersal of toxic Alexandrium species in the northeast of the United States over the last several decades. This is certainly true with respect to the effects of the 1972 bloom, but some of the spreading can also be attributed to the detection of indigenous, low-toxicity populations in southern waters (Anderson, 1997). In 1980, 51 people were reported to be affected by PSP after consuming local mussels and oysters containing 3 000 to 40 000 mg STX eq/kg, however no one died (IPCS, 1984).
In June 1990, the Massachusetts Department of Public Health was notified that food-borne illnesses had occurred in six fishermen aboard a fishing boat in the Georges Bank area off the Nantucket coast. Onset of illness occurred after the men had eaten cooked blue mussels (Mytilus edulis) harvested in deep water about 115 miles from the island of Nantucket. Subsequently, 244 000 µg STX eq/g were detected in raw mussels and 4 280 µg STX eq/g in cooked mussels (Anonymous, 1991).
Connecticut, Long Island (New York) and New Jersey occasionally experience PSP toxins (or Alexandrium) at low levels but these areas seem to define the southern extreme of this organisms geographic distribution. The offshore waters of Georges Bank experienced a serious PSP outbreak several years ago, leading to the extended closure of the surfclam fisheries and the demise of a fledgling roe-on scallop fishery (Boesch et al., 1997).
Since 1 January 2002, 10 cases of PSP were reported after eating pufferfish caught in waters near Titusville, Florida (Anonymous, 2002a).
In Alaska, episodes of PSP have occurred for centuries - the first cases were reported in 1799. Between 1973 and 1994, 66 outbreaks of PSP occurred in Alaska and caused illnesses among 143 people. Eight persons had paralysis of a limb, eight required mechanical ventilation and two died. Most outbreaks occurred during late spring and summer (May to June), on Kodiak Island (the southern edge of the eastern half of the Aleutian Islands) and in southeastern Alaska (Gessner, 1996). During May and June 1994, five outbreaks of PSP involving 12 persons occurred, four who of whom required mechanical ventilation. One patient died. Most people had eaten mussels (Mytilus edulis or Mytilus californianus) (Gessner and Schloss, 1996; Gessner et al., 1997). In April 1995, August 1997 and December 1997, outbreaks of PSP were reported involving three, five and three patients respectively (Anonymous, 1995; 1997a; 1997b).
PSP has a long history in northwestern waters. Several PSP deaths occurred in 1942, which prompted the annual closure of the Strait of Juan de Fuca and the coast. By the 1970s, closures were occurring in the San Juans and Bellingham. In September 1978, heavy rains followed by warm Indian Summer weather produced a number of PSP illnesses from Sarragoto Passage to as far south as Vashon Island. Recurring outbreaks of Alexandrium occurred in the Puget Sound region of Washington in the late 1970s. In 1988, excessive PSP levels were detected in shellfish from Carr and Case Inlets in Puget Sound. (Boesch et al., 1997 in Determan, 1998). In Puget Sound basin the moonsnails (Polinices lewissi), a predatory gastropod, collected from Agate Passage, contained an average of 145 µg STX eq/100 g viscera in September 1994. In October 1994, blue mussels (M. edulis) from Mystery Bay contained 652 µg STX eq/100 g whole body (Wekell et al., 1996). PSP is also a recurrent annual problem along the coast of Northern California and Oregon (Boesch et al., 1997).
2.7.5 Central and South America
In the southern part of Argentina, PSP had been associated with blooms of A. catenella in the Argentine sector of the Beagle Channel and with blooms of A. tamarensis in the southern Atlantic coast to Uruguyan shores (Compagnon et al., 1998). The first recorded toxic bloom of A. tamarensis was at the Valdés Peninsula in 1980. Thereafter, a dramatic episode occurred in which two members of the crew of a ship died after eating contaminated mussels (Ferrari, 2001). Since that time the phenomenon has occurred periodically in the spring and summer seasons.
During an A. tamarensis bloom in 1993, only anchovy (Engraulis anchoita) obtained near Mar del Plata showed toxicity although the A. tamarensis was distributed over a broad area. PSP toxin levels in anchovy were 101 µg STX eq/100 g wet weight of viscera (by mouse bioassay), but the toxins did not accumulate to detectable levels in muscle tissue (Montoya et al., 1998).
During a bloom of A. catenella in the northeastern shore of Beagle Channel in the summer of 1991/1992, mussels (Mitylus chilensis) collected on 20 January 1993 contained 127 200 mg STX eq/100 g (Compagnon et al., 1998). In spring 1993, massive mortality of the mackerel Scomber japonicus in a restricted area of the Buenos Aires shelf known as Rincón, appeared to be caused by the incorporation of PSP toxins (Montoya et al., 1998). During November 1995 to May 1996, A. tamarensis cells and mussels (Aulacomya ater) obtained from eight sampling stations along the Valdés Peninsula contained up to a maximum of 490 fmol PSP toxins/cell and 631 mg STX eq/100 g respectively (Andrinolo et al., 1999b).
Several outbreaks of A. tamarensis have been recorded in Brazilian waters. In addition, other PSP toxin producers were identified namely A. catenella and G. catenatum. Every year A. catenella blooms in the Tierra del Fuego fjords and shellfish toxicity has been registered since 1992. In 1998 G. catenatum, was observed along the coast of Santa Catarina State (Ferrari, 2001).
Reports of PSP due to mussel consumption in native people in the proximity of Ushuaia date from as early as 1886. A. catenella is mainly found in the three most southern regions of Chile. In two of these regions, 329 cases of PSP were reported from October 1972 through January 1997. Twenty six people died from PSP during these years. The bivalve species involved were Aulacomya ater and Mytilus chilensis. PSP toxin content varied from 1 555 to 96 000 MU/100 g (Lagos, 1998). Compagnon et al. (1998) reported a bloom of A. catenella in the early autumn of 1996 in the southern part of Chile resulting in PSP levels up to 113 259 mg STX eq/100 g of whole shellfish in the bivalve A. ater 25 days after the peak of the bloom (3.1 x 104 cells/L). High but diminishing levels persisted for six months after the peak of the bloom. High levels of PSP toxins were also detected in two carnivorous gastropod species Concholepas concholepas (9 164 and 737 mg STX eq/100 g in the digestive gland and foot muscle respectively) and Argobuccinum ranelliformes (14 057 and 31 mg STX eq/100 g in digestive gland and foot muscle respectively). The highest levels in carnivorous gastropods were reached five months after the bloom.
Up until 2001, PSP and DSP toxins have had a most severe public health and economic impact on Chile. As a consequence, all natural fish beds from 44 °SL southwards were closed and nationwide monitoring programmes were maintained (Suárez-Isla, 2001). In March 2002, one death and at least eight poisoning cases were reported after consumption of shellfish from the southern region of Chiloé. Catching and trading of shellfish around the whole island of Chiloé was prohibited and the prohibition included also the Ancud community, 100 km further north on Chloé (Carvajal, 2002).
In 1987, an outbreak of PSP involving 187 cases and 26 deaths was reported after consumption of clam soup. The fatalities were the highest among young children (50 percent) compared with seven percent in adults (Rodrigue et al., 1990).
In 1979, 20 cases of PSP were reported linked to consumption of local mussels and three people died (IPCS, 1984). A two-year study of the Tamiahua Lagoon from 1984 to 1986 revealed permanent blooms of Pyrodinium bahamense in estuaries, in areas with banks of Crassostrea virginica. These blooms were displaced hydrodynamically during the windy season from November to March. High densities of P. bahamense were then seen in mangrove areas with slow water currents. This phenomenon also occurred in other coastal lagoons from the Gulf of Mexico and the coastal lagoons of the Sian Kaan Biosphere Reserve in the Mexican Sea (Gómez-Aguirre and Licea, 1998).
In November 1989, a coastal toxic event (from Chiapas to Oaxaca) was caused by P. bahamanse and contaminated oysters and mussels, which were implicated in 99 poisonings and three human deaths by ingestion (Orellana-Cepeda et al., 1998). During May 1992, an extremely high PSP toxicity value of 23 000 MU/100 g was recorded in a single fanshell (Pinna rugosa) at Bahía Concepción (Peninsula of Baja California). No cases of human poisoning have been reported (Ochoa et al., 1997).
During March 1993 and April 1994, densities of the
dinoflagellate A. catenella reached
14 000 cells/litre in Bahía Concepción (Gulf of California). Following this, high PSP levels (up to
2 400 MU/100 g) were found in whole shellfish, mainly Argopecten circularis. The area was closed for shellfish harvesting. No human intoxications were reported (Lechuga-Devéze and Morquecho-Escamilla, 1998).
From 1995 to 1996, an outbreak of P. bahamense off Michoacán and Guerrero caused the death of six people and many illnesses. In the winter of 1995, high levels of PSP toxins were detected by mouse bioassay in oysters (Ostrea iridiscens 608-6 337 µg STX eq/100 g meat) and clams (Donax sp. 520 µg STX eq/100 g meat) in southwest Mexico. In November 1996, an exceptional bloom of P. bahamense occurred on a small area of the Pacific Coast of Mexico (Orellana-Cepeda et al., 1998).
PSP caused 72 percent of the toxic events which occurred during the last decade of the twentieth century. Three of these PSP events represented 87 percent of the poisoning cases (460 individuals poisoned with 32 deaths, including the 1987 Guatemala incident). During the PSP events in Mexico, large numbers of marine animals such as fish and turtles were killed. At first, only STX produced by G. catenatum was reported as the responsible toxin. Since the 1987 event on the Guatemalan coast, G. bahamense dominated the toxic red tides on the Southeast Pacific coasts with dcSTX and STX as the principal components and low amounts of GNTXs. A different toxin profile was seen in Baja California Peninsula suggesting that A. catenella is the responsible species or the recently observed A. tamiyavanichi (Sierra-Beltrán et al., 1998).
PSP was recorded for the first time in waters of Trinidad in 1994. Both the mouse bioassay and the receptor binding assay demonstrated the presence of PSP toxins in a meat extract of the mussel Perna viridis. The quantity of STX equivalents was 28 mg/100 g of meat, which is considerably lower than the 80 mg/100 g of meat considered to be unfit for human consumption. No human intoxications were reported (Ammons et al., 2001)
Coinciding with PSP incidents in Brazil in 1980, 60 persons were affected with neurotoxic symptoms in Uruguay. Although PSP toxins reached high levels, the algal species was never identified. During the summer of 1991, PSP outbreaks were associated with G. catenatum. In coastal sediments high densities of this latter algal species were reported (Ferrari, 2001).
In 1979 and 1981, 171 and 9 people respectively were reported to be affected by PSP after consuming local mussels (Perma perma) containing 790 to 33 000 mg STX eq/kg. In total, 11 people died (IPCS, 1984).
The first published cases of PSP in China were in Zhejiang Province where 40 separate episodes resulted in 23 fatalities and 423 nonfatal intoxications between 1967 and 1979. The vector was the marine snail Nassarius succinstus (Zhou et al., 1999). In November 1986, PSP was reported in Dongshan (in the south of Fujian Province) with one fatality and 136 hospitalizations. The vector was the clam Ruditapes phillipenensis (Zhou et al., 1999). In February 1989, five persons showed PSP symptoms after eating the clam Pinna pectinata. In November 1989, four fishermen developed PSP symptoms after eating the snail N. succinstus (collected from Fuding in the north of Fujian Province) and one person died. The illnesses occurred in Huizhou but the shellfish probably originated from Daya Bay. In March 1991, there were two human fatalities and four cases of illness after eating the mussel Perna viridis collected from Daya Bay (Zhou et al., 1999).
A survey of the Guandong Province from 1990 to 1992 found PSP toxins in 33 edible marine organisms at levels up to 1 000 mg STX eq/100 g meat. In June 1994, five illnesses and one death were reported in Zhejiang Province following consumption of the snail N. succinstus.
Since shellfish monitoring is minimal along the Chinese coast, it seems likely that the above episodes underestimate the true extent of the PSP problem. From a few isolated algal bloom reports in the early 1970s, the problem has progressed to the stage where 40 to 50 red tides are now reported every year. Only a few are toxic but the trend is ominous and seems to be linked to increases in pollution in Chinas coastal waters during the same interval. The rapid expansion in shellfish aquaculture and the documented presence of PSP-causing algae in Chinese coastal waters suggest that shellfish toxicity will continue to be a major problem for many years (Anderson et al., 1996).
Sediment samples collected from 49 stations at 14 locations along the coasts of the South and East China Seas were checked for living dinoflagellate resting cysts. Cysts from G. catenatum were found in Dapeng Bay only but cysts from A. tamarensis were found in eight relatively contiguous locations from the mouth of the Pearl River through Guangdong and Fujian Provinces to Taizhou Bay in Zhejiang Province. The distribution is generally consistent with the region in which PSP events have been recorded (Qi et al., 1996). During 1996 and 1997, only four samples from three sampling sites, out of a total of 91 samples, contained PSP toxins. The highest level was 79 µg STX eq/100 g which was below the regulatory level of 80 µg/100 g (Zhou al., 1999).
One man died within several hours after ingestion of a
specimen of the crab Zosimus aeneus in Timor-Leste. The total toxin
concentration of the uneaten part of the crab was
163 µg STX eq/100 g tissue (GNTX2, GNTX3 and STX). The dose consumed by the victim was calculated to be between 1 and 2 µg STX eq/kg bw. The victims meal did not consist solely of the toxic crab and the possibility of other food items acting in a synergistic manner with the consumed PSP toxins cannot be ruled out (Llewellyn et al., 2002).
China, Hong Kong Special Administrative Region
There were three outbreaks of PSP in Hong Kong Special Administrative Region in 1992 but details on the number of patients affected and the clinical presentation are not available. It is likely that most outbreaks are not reported (Chan, 1995). In September 1996, a sample of Chlamys nobilis contained 320 mg STX eq/100 g soft tissue. Within 40 days after red tide events in March to April 1998, levels of PSP toxins up to 79 mg STX eq/100 g were found in Perna viridis, however, no cases of human poisoning were reported (Zhou et al., 1999).
In 1981, 98 cases of PSP were reported after consumption of local mussels. One fatality occurred (IPCS, 1984).
The first infestation of shellfish with PSP in Hiroshima Bay was reported in 1992 (Hamasaki et al., 1998). Industrially important bivalves such as scallop and oysters are frequently contaminated with PSP due to toxic dinoflagellates mainly such as A. catenella, A. tamarense and G. catenatum (Noguchi, 2003).
From July 1995 through October 1996, 6 out of 30 species of shellfish collected at Fukue Island, Nagasaki Prefecture were found to contain PSP toxins: Pecten albicans (scallop), Chlamys farreri (scallop), Septifer virgatus (mussel), Pinna bicolor, Arca boucardi and Pseudochama retrove. The two species of scallops (P. albicans and C. farreri) contained amounts above the regulatory limit of 400 MU/100 g. Only the digestive gland was toxic. The highest amount (13 380 MU/g) was found in P. albicans. In addition, P. bicolor contained an amount above the regulatory limit, namely 490 MU/100 g. The lowest values (below the regulatory limit) were found in P. retrove (320 MU/100 g), A. boucardi (230 MU/100 g) and S. virgatus (200 MU/100 g). Toxin profile in P. albicans featured the dominant presence of GNTXs in 1995. In 1996, however, low-toxicity components such as the C group were major, as was the case in the profile of C. farreri. The mossworm contained a low level of PSP toxins whose major components were dcGNTX2 and GNTX2, along with dcGNTX3 and GNTX3, differing clearly from the profile of its host of C. farreri (Takatani et al., 1997).
In March 1997, 20 people were poisoned after eating oysters collected at Fukue Island (Takatani et al., 1997). A bloom of A. tamiyavanichii occurred in Seto Inland Sea in 1999 and 2001 and attacked several oyster farms. On 28 November 2001, PSP toxins in cultured and wild oysters were 17.0 and 3.3 MU/g edible parts respectively (Nishio, 2003).
In 1977, 201 cases of PSP were recorded after eating local clams. Four fatalities occurred (IPCS, 1984). Until 1990, problems related to PSP were relatively simple being confined to the west coast of Sabah in Borneo. The toxin producer was the dinoflagellate P. bahamense. In early 1991, PSP occurred for the first time in Peninsula Malaysia when three people became ill after eating farmed mussels from Sebatu in the Straits of Malacca. A. tamiyanavichi was eventually confirmed as the toxin producer. In early 2000, PSP toxins and shellfish toxicity were reported for the first time from the east coast of Sabah, however the toxin producer has yet to be identified. In September 2001, six people became ill after eating clams harvested from a coastal lagoon on Kelatan on the east coast of peninsular Malaysia. One of the victims eventually died. High levels of PSP toxins were detected in the clams by means of the mouse bioassay and receptor binding assay. A high density of A. tropicale and an unidentified Alexandrium species were found (Usup and Ahmad, 2001).
Marine puffers (Arothron mappa, A. manillensis, A. nigropunctatus, A. hispidus, A. stellatus, A. reticularis) collected in 1992 in the Philippine waters contained considerable amounts of PSP toxins (major component STX) besides TTX (Sato et al., 2000). In 1992, cultured mussels in the Philippines caused PSP in many people (Durborow, 1999). Between 1983 and 1998, 2 000 cases of PSP occurred with a mortality rate of 5.8 percent (Van Dolah et al., 2001).
Taiwan Province of China
In January 1986, two persons died and 30 showed signs of illness after consuming Soletellina diphos. In February 1991, eight cases of illness were registered after eating Soletellina diphos (Zhou et al., 1999). A survey of paralytic toxins in shellfish in the southern part of the island between August 1995 and March 1997 revealed both PSP and TTX in three types of shellfish namely Niotha clathrata, Natica lineata and Natica vitellus (Liao and Hwang, 2000). In Taiwan Province of China, PSP is distributed in purple clam, xanthid crabs and gastropods, and the toxic alga A. minutum appears from December to March (Hwang, 2003).
In 1983, 62 cases of PSP were reported in Thailand after consumption of local mussels (Mytilus spp.) and one fatality occurred (IPCS, 1984). A freshwater puffer (Tetraodon fangi) poisoning case was reported in 1990. The puffer species appeared to contain STX. Tetrodotoxin was not detected (Sato et al., 1997).
Monitoring from 1987 to 1997 in Port Philip Bay and Western Port Bay in Victoria occasionally resulted in very high levels of PSP toxins (maximum level 10 000 µg STX eq/100 g edible shellfish) (ANZFA, 2001).
An outbreak of shellfish poisoning occurred in New Zealand during January 1993. More than 180 cases were registered along with numerous instances of respiratory irritation from air-borne toxin in sea spray. Initially, the toxicity was characterized as NSP because PSP toxins were not very high in the most commercial shellfish. Subsequently, PSP toxins produced by A minutum were found to be responsible for at least part of the toxicity measured in shellfish (pipi, scallop, mussel and tuatua) (MacKenzie et al., 1996; Chang et al., 1997a).
Over the period January 1993 to July 1996, 0.5 percent of samples of shellfish taken around the coastline of New Zealand on a weekly basis exhibited PSP toxin levels above the regulatory limit during a total of 11 PSP events (maximum level 920 µg STX eq/100 g mussel). During the sampling period, there were no cases of human PSP poisoning (Sim and Wilson, 1997). G. catenatum caused extensive closures of North Island and South Island west coast shellfish areas in the summer of 2000 and 2001. The highest PSP level recorded in New Zealand has been 1 007 µg/100 g associated with A. catenella in the eastern Bay of Plenty in 1997 (Anonymous, 2003b).
Testing for PSP in mussels, oysters and scallops during September 1994 and July 1996 revealed maximum levels of 18 429, 699 and 83 µg STX eq/100 g edible shellfish, respectively, and average levels of 636, 123 and 60 µg STX eq/100 g edible shellfish, respectively (ANZFA, 2001).