Occurrence of DSP toxins from 1991 to 2000 in coastal waters of European countries that are members of the ICES is illustrated in Figure 3.3.
During 1999, one out of 350 samples gave a positive result for DSP in the mouse bioassay (EU-NRL, 2000). In Antwerp in February 2002, 403 cases of DSP were reported after consumption of blue mussels imported from Denmark. The mouse bioassay for the presence of okadaic acid, dinophysis toxins, yessotoxin, pectenotoxins and azaspiracid showed a positive result. LC-MS techniques confirmed this result. In the mussels, 5.9 µg AZA/kg of meat was found (below regulatory limit), 229 µg free OA/kg of meat and 300 µg OA eq (conjugated OA or diol ester)/kg of meat. In spectrometry, a significant peak corresponding to pectenotoxin-2-seco-acid (PTX2-SA) was observed, but this toxin could not be quantified. The remainder of the imported mussels was withdrawn from sale (De Schrijver et al., 2002).
Toxin analysis (mouse bioassay and LC) of Mytilus galloprovincialis from the Central Adriatic Sea (Kastela Bay) in the summer of 1994 led to identification of OA and DTX1. No health problems due to consumption of intoxicated seafood were registered (Orhanovic et al. 1996). During an intensive bloom in the summer of 1995 M. galloprovincialis were harvested from Kastela Bay. Mouse bioassay displayed a positive result for DSP toxins. LC analysis showed the presence of OA, the absence of DTX1 and DTX2, and suggested the presence of an unknown derivatized compound at high concentration. The origin of the mussel toxicity was traced to D. sacculus. (Marasoviæ et al., 1998).
Figure 3.3 Occurrence of DSP toxins in coastal waters of European ICES countries from 1991 to 2000
In 1990, 170 mg OA/100 g of meat was detected in mussels on the north Danish coasts. Mussels from this area were imported by France, poisoning 415 persons (Van Egmond et al., 1993). Three toxic events took place during 1999. In the first two cases, domestic production areas were closed for some weeks because of the presence of DSP toxins in blue mussels. The third case was due to mussels caught in the North Sea. Two persons from the staff of a production company became ill because they ate the mussels before the mouse bioassay was carried out (EU-NRL, 2000). In 2000, OA was detected below the limit of 160 µg/kg whole mussel in samples from the East Coast of Jutland. This observation took place during a period where the fishery was restricted and/or closed due to high concentrations of the species Dinophysis acuminata (EU-NRL, 2001). During 2001, DSP toxins were registered in commercially fished blue mussels in concentrations exceeding the regulatory limits in three production areas. In 2002, much more DSP toxins were present than normal. Several production areas were closed for several weeks or months. DSP levels above the regulatory limit were detected in the Limfjord, on the east coast of Jutland, the Roskilde Fjord/Isefjorden and in the Wadden Sea, North Sea. In November and December 2002, people in Germany became ill due to the consumption of mussels containing OA from the production area Isefjorden. In Belgium (see above), people also became ill due to the consumption of Danish mussels (EU-NRL, 2002).
In several areas of France (Normandy, Loire-Atlantique, South Brittany, West Brittany, Mediterranean coasts), cases of DSP poisoning of shellfish consumers have been reported from 1978 onwards. In 1984 and 1985, mussels raised in France caused DSP symptoms in 10 000 and 2 000 people respectively (Durborow, 1999). Maximum algal densities are several thousand cells/litre on the Atlantic and Mediterranean coasts, whereas in the eastern part of the English Channel (north of the Seine estuary) densities can reach more than 100 000 cells/litre. The toxin produced is essentially OA (Van Egmond et al., 1993). Dinophysis species have been found in both Mediterranean and Atlantic coasts (EU-NRL, 1998); twenty seven production areas on the Atlantic and two production areas on the Mediterranean coast were closed due to the presence of DSP (EU-NRL, 2000). 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. Positive DSP results were obtained in shellfish from Ireland and Tunisia in 1999 (EU-NRL, 2000). In 2000, several production areas on the Atlantic coast and one area on the Mediterranean coast were closed due to DSP toxins (EU-NRL, 2001). Several DSP toxic episodes were observed in 2002. Along the southern Brittany coast and the coast near the Loire River, DSP toxins were recorded in shellfish very late in autumn 2002 and a few areas remained closed in December. This was the first time that so many DSP events were observed along the French Atlantic coasts (EU-NRL, 2002).
OA was detected in mussels from the Wadden Sea in 1987.
Dinophysis acuminata was found regularly along the coasts of German
Bight. Mussels causing DSP generally came from North and East Frisia between
1986 and 1989. In 1990, more than 1 000 Dinophysis cells/litre (max
25 000 cells/litre) were detected in the areas as mentioned above. The mussel beds were closed and no cases of human DSP poisoning occurred (Van Egmond et al., 1993). In 1998, OA was detected in September (EU-NRL, 1998). During 1999, two samples contained DSP toxins but below the regulatory limit (EU-NRL, 2000). There was one case of DSP intoxication in 2000 involving two elderly women (EU-NRL, 2001). During October 2001, increased cell density of D. acuminata (5.9 x 103 cells per litre) was observed at the East Frisian coast waters. DSP toxins in mussels increased and a ban was placed on mussel harvesting in the contaminated area (Anonymous, 2001b).
A total of 10 positive DSP samples were recorded during 1999. D. acuminata was detected at a concentration of 1 500 cells/litre (EU-NRL, 2000). During April to June 2000, one production area was closed due to the presence of DSP toxins (EU-NRL, 2001).
The first events of DSP poisoning occurred in the 1980s. Mussels showed variable toxicity levels in 1984, and from 1987 to 1991. In 1988, D. acuminata (1500 cells/l) and D. acuta (240 cells/l) were detected on the southwest coast in Roaring Water, Dunmanus, Bantry, Kenmare and Dingle Bays and up to 200 mg OA/100 g and 25 mg DTX1/100 g of mussel meat was found. In Glengariff in 1990, an isomer of OA contributed to the residual toxicity observed in mussels after the total disappearance of OA, while toxicity during the winter was detected for the first time that year (Van Egmond et al., 1993). Both OA and DTX2were present in mussels in a DSP episode in 1991. Examination of similar mussel cultivation locations in 1994 showed that DTX2 was even more predominant (OA levels were less than 0.7 mg/g and max DTX2 levels 6.3 mg/g hepatopancreas) The toxicity in shellfish was seen soon after high cell counts of Dinophysis acuta (Carmody et al., 1996). In addition, a new isomer of DTX2, named DTX2B, was isolated and identified in Irish mussel extracts (James et al., 1997). In shellfish from Irish waters acyl-derivatives of OA and DTX2 were also detected (EU-NRL, 1996). Unexplained human intoxication with DSP symptoms following the consumption of mussels from Killary, Ireland, was resolved by the isolation of a new toxin (C47H71NO12), tentatively named KT3, which represents a new class of polyether shellfish toxin later called azaspiracids (Satake et al., 1997) (see also Chapter 6).
During 1999, five percent of 1 800 samples tested for DSP/AZP were positive in the mouse bioassay (EU-NRL, 2000). In August 2000, 30 areas were closed for the harvesting of bivalve shellfish. People developed symptoms of DSP (Anonymous, 2000a). In 2001, 17 percent of samples were positive in the mouse bioassay compared to 3.4 percent in 2002. During 2002, the highest level of DSP toxins (OA, DTX2) found in oysters was 30 µg/kg. Seven percent of sampled mussels contained OA or DTX2 above the regulatory limit (EU-NRL, 2002).
On the Northern and Central Adriatic coast, Dinophysis spp. were present from 1989 onwards and DSP cases have been reported. A monitoring programme over the Italian shellfish banks was started in 1989. Species implicated were D. sacculus, D. fortii and Dinophysis spp., with maximum concentrations of 4 000 cells/l (Tubaro et al., 1992). Samples of toxic mussels and of algae of Dinophysis genus, both collected in occasion of algal blooms from the coastal area of Cesenato, have been analysed by ionspray LC-MS (LC-ISP-MS) for DSP toxins. OA was present in all mussel samples and its concentration (0.178-0.286 mg per g of edible tissue) exceeded the regulatory limit (0.16 mg per g of edible tissue). DTX1 was also found in some samples and its concentration (£0.076 mg per g of edible tissue) was lower than the amount which was thought to cause toxic effects in mice (0.13 mg per g of edible tissue). However, this toxin was never detected in toxic phytoplankton. LC-ISP-MS analysis of algal cells has for the first time unambiguously shown that Dinophysis fortii produced or transmitted OA to shellfish (Draisci et al., 1996b). As Dinophysis spp., particularly D. sacculus, are common species along the Italian coast, the presence in 1988 of large summer blooms (40 000 cells/l) in the briny lagoons of northeastern Sicily can be considered as a potential restriction to the expansion of aquaculture in these areas (Van Egmond et al., 1993). Salati and Meloni (1994) mentioned that Dinophysis spp. and Prorocentrum spp. are in fact common in Italian seas and that cases of DSP in Italy occurred in 1989, 1990 and 1991. The presence of PTXs has been recorded in the Adriatic Sea (EU-NRL, 1996). The occurrence of different DSP producing species such as Dinophysis spp., Lingoludinium polyedra and Protoceratum reticulatum in Italian waters was stated. A mixture of OA, low levels of DTX1, YTX and PTX has been found in phytoplankton and shellfish (EU-NRL, 1998).
In the digestive gland of mussels from the Adriatic Sea, besides YTX, 2 new analogues of YTX, homoyessotoxin and 45-hydroxyhomoyessotoxin were identified (Ciminiello et al., 1997). Gonyaulax polyhedra was implicated as responsible for the YTX contamination in these mussels (Tubaro et al., 1998).
During 1999, DSP toxins were detected in 350/900 samples of Mytilus galloprovincialis from the Northern Adriatic. The main problem area was Emilia Romagna. YTX always dominated over OA (EU-NRL, 2000). During 2000, DSP toxins were detected in M. galloprovincialis with 13 percent of the samples giving positive mouse bioassays. In the Emilia Romagna region, closures were enforced from late August through to end December, in the Veneto region closures were enforced from late October through to end December, and in Fruili Venezia Giulia closures were enforced in late December. The closures were mainly due to YTXs. In 2001, DSP toxins were detected in M. galloprovincialis with 18 percent of samples giving positive bioassay results. Closures were enforced in the Emilia Romagna region in January, February and early March, which was a continuation of the 2 000 closures, and also later during the period mid-June to late October. In Veneto, closures were enforced during July while in Friuli Venezia Giulia closures were enforced from January to mid-February and again from start of July to early August (EU-NRL, 2001). During 2002, DSP was detected in the Northern Adriatic Sea (Friuli Venezia Giulia, Veneto and Emilia Romagna coast). Harvesting was forbidden. In July, Pecten maximus samples from Scotland appeared to be positive for DSP (EU-NRL, 2002).
The first reported cases of DSP in the Netherlands were in the
1960s (Fleming, 2003). From 1961, DSP has occurred on the Wadden Sea coasts.
Maximal concentration of D. acuminata was
10 000 cells per litre in 1981 and dropped to only 80 cells/ per litre in 1986 and 1987 but with the same toxic effects. It seems that water temperature and mussel toxicity are strongly correlated. At 10 °C only 30 cells per litre would be required to maintain high mussel toxicity. Maximum level of D. acuminata occurs every year in August and September on the Wadden Sea coasts, with salinities of 30 o/oo and a certain correlation with wind velocity. Densities above 10 000 cells/litre occur only when the wind is equal to or less than two on the Beaufort scale (Van Egmond et al., 1993). In 1998, it was reported that DSP producing species were present in Dutch waters, but no DSP toxins were found in bivalves (EU-NRL, 1998). In the summer of 2001, blooms of D. acuminata occurred in the Dutch Wadden Sea and mussels were contaminated. The blooms were caused by salt stratification and warm weather (Peperzak et al., 2002). A toxic event occurred in Grevelingen in the spring of 2002. Rat bioassay pointed to DSP. In the autumn of 2002, DSP was found in mussels from the Wadden Sea area (OA levels of 160-320 µg/kg by rat assay) (EU-NRL, 2002).
D. acuminata is often seen on Norwegian coasts. During a DSP outbreak in the Oslo Fjord in 1979, 1 900 cells/l were counted concomitant with proliferation of Prorocentrum minimum. P. lima blooms also occur sometimes in the Oslo Fjord (Van Egmond et al., 1993). Since 1984, DSP has been detected annually in mussels from the southeast and parts of the western coast of Norway. DSP has not been detected in oysters. Dinophysis spp. are regularly found in rather high numbers for long periods of the year. During 1984/85, widespread intoxications due to DSP occurred (Underdal, 1989).
Three to four hundred cases of DSP were recorded in 1984 in southeast Norway during a contamination period lasting from October 1984 to April 1985 at toxicity levels of approximately 7 mg OA-equivalents/100 g of hepatopancreas and 30 000 cells/litre of D. acuta and D. norvegica. D. acuminata and D. acuta blooms were seen in Skagerrak in 1985 and 1986, and DSP levels in mussels exceeded toxic thresholds in 1989 and 1990. Mussels from Arendal and Sognefjord showed multiple toxin patterns in 1985 and 1986; OA at Arendal and DTX1 and YTX at Sognefjord (Van Egmond et al., 1993). YTXs have also been reported in shellfish from Norway (EU-NRL, 1996). In Sognefjord DTX1 is the major DSP toxin, while OA is the relevant toxin in the rest of the coast (EU-NRL, 1998). Different closures due to DSP occurred in 1994. The same pattern was seen the following years (EU-NRL, 1998).
Mussel samples from four different locations along the Norwegian coast were found to be highly toxic in the mouse bioassay with symptoms indicating the presence of non-diarrhoeic toxins (cramps). Chemical analysis showed that OA and DTX1 were each present at one location but only a minor part of total toxicity could be attributed to these toxins. OA and DTX1 were absent at the two other locations. Incubation of extracts of samples from the four locations with freshly prepared rat hepatocytes indicated the presence of unknown toxin(s). Intraperitoneal and oral administration of purified mussel samples to baby mice showed that oral toxicity was 25 to 50 times lower than i.p. toxicity. The preliminary results indicate a large margin of safety between the amount of mussels consumed by humans and the large amounts of mussel extract needed to yield toxic effects in the intestine and liver in mice after oral exposure (Aune et al., 1998). During 1999, 135/473 samples gave positive results for DSP. On many occasions, YTX was the dominant toxin and in approximately 33 percent of cases, closures of production areas were due to the detection of YTX (EU-NRL, 2000). In 2000, 45 percent of 414 samples gave positive results in the DSP mouse bioassay. In late July, closures of production areas due to DSP toxins occurred in the southern part of Norway and the locations stayed closed until Easter 2001. Until October 2001, 26 percent of 915 samples were positive for DSP in the mouse bioassay (EU-NRL, 2001). Another species that probably caused problems in southern Norway (Lysefjorden) in 2000 and 2001 was Gonyaulax grindleyi. An indicator was the high rate of yessotoxin in cultured mussels. However, until now it cannot be said for sure that it was due to G. grindleyi (Hufnagl, 2001).
DSP toxins have been detected in Portugal since 1987 but no human poisoning has occurred. At levels of 200 cells/litre of D. sacculus and D. acuta shellfish are contaminated after a brief latency period. On the north coast of Portugal, molluscs were contaminated by DSP toxins in 1988. The species involved was D. acuta. In 1988, the occurrence of DSP toxins was also reported after a Prorocentrum lima bloom in the Ria Formosa Lagoon. In 1989, D. acuminata, D. sacculus and D. caudata (around 1 600 cells/litre) caused DSP contamination on the Algarve coast (Van Egmond et al., 1993). OA was the main toxin responsible for DSP cases in Portugal (Gago-Martinez et al., 1993) but DTX2 was also recorded in shellfish and phytoplankton, and acyl derivatives of OA and DTX2 in shellfish (EU-NRL, 1996).
DSP episodes in southern Portugal have increased in frequency. D. acuta has been related with the occurrence of DTX2. Preventive closures have been due to DSP (EU-NRL, 1998). In 2000, OA and DTX2 were detected at high concentrations in the Aveiro Lagoon where the green crab, a shellfish predator, also accumulated these toxins. Several people became ill (EU-NRL, 2001). In the summer of 2001, an outbreak of DSP was reported after eating razor clams (Solen marginatus) containing 50 µg OA eq/100 g, harvested at Aveiro lagoon. All shellfish species tested in this region (except oysters) contained levels of OA and its esters above the regulatory limit (57-170 µg/100 g). One patient may have developed DSP after eating a large number of green crabs (Carcinus maenas, a shellfish predator) containing at least 32 µg OA eq/100 g (Vale and De Sampayo, 2002). In 2002, blooming of D. acuminata led to prolonged closures of wild intertidal mussel and bentonic bivalve harvesting areas along the entire northwest coast. Recreational harvest of rock mussels, as well as cockles, caused several events of human poisoning. A maximum level of 1 860 µg total OA/100 g whole flesh was registered in wild mussels in September at Povoa do Varzim, connected to a dozen cases of severe gastroenteritis. Eighteen percent of 738 samples were positive in the mouse bioassay and PTXs were detected for the first time. So far, PTX1 and PTX2 levels have not exceeded 160 µg/kg by LC-MS. Contamination is mostly due to PTX2-SA (EU-NRL, 2002).
D. acuminata has been the main problem in the Spanish Rias, except for some years (1989 and 1990) when D. acuta was the causative species involved in DSP outbreaks. The first confirmed DSP event was in 1978. Gymnodinium catenatum and Dinophysis acuta have sometimes entered the estuaries together and caused mixed PSP/DSP contaminations. In 1981, D. acuminata and D. acuta were associated with DSP events causing 5 000 cases of gastroenteritis throughout Spain. Other cases of DSP contamination were observed from 1982 to 1984. This phenomenon subsequently spread from 1989 to 1990 when D. acuta rather than appearing in September and October, was present from July to December reaching maximums of 7 000 to 22 000 cells/litre. Prorocentrum lima might have been associated with DSP contamination of mussels cultivated on ropes. In addition to OA, this species produced DTX1 and other compounds such as palytoxin (Van Egmond et al., 1993).
In 1993, a particularly bad episode occurred in Galicia, which lasted for an unusually long period. Analyses of Galician mussel samples revealed a very complex toxin profile with both DSP and PSP toxins present. Two DSP toxins, OA and DTX2, were detected. (Gago-Martinez et al., 1996). Intense DSP episodes led to prolonged closures in Galicia from April to December 1995. In 1996, closures took place only in January as a continuation of the 1995 episodes. In 1997, closures due to DSP occurred in spring, summer and/or autumn depending on the locations (EU-NRL, 1998). Fernández et al. (1996) reported, besides OA and DTX2, the occurrence of two polar derivatives of OA and DTXs in Spanish shellfish or phytoplankton: 7-O-acylesters containing a fatty acyl group attached to the 7-OH group and diol esters in which the carboxylic group of the toxins has been esterified. Throughout 1999 and 2000, there were different toxic events related a.o. to the presence of DSP toxins that led to the prohibition of harvesting of bivalves in some production areas (EU-NRL, 2000; EU-NRL, 2001). During 2002, toxic events occurred in Galicia (D. acuminata and D. acuta) and Andalucia (D. acuminata) causing long closure periods, and in Cataluña causing short closure periods (EU-NRL, 2002).
Experimental mussel farming started in Sweden in 1971. During the developmental period from 1971 to 1980, mussels were harvested throughout the year. In 1983, DSP was observed among people consuming mussels. Consequently, a surveillance system to detect DSP toxins in mussels was launched in 1986. DSP toxin found in Swedish mussels is OA produced by Dinophysis spp. DSP toxin concentrations found in mussels from the outer archipelago are higher than in mussels from more sheltered waters. During the winter of 1989 to 1990, the harvest of farmed mussels was stopped for a long period due to high OA concentrations. The appearance of OA in mussels was ascribed to the inflow of water from the open sea containing toxic plankton. Appreciable concentrations of toxic dinoflagellates in offshore waters have been demonstrated in Skagerrak. The few observations of increased OA-concentrations in mussels in the sheltered fjords north of Orust occurred in connection with greater inflows of offshore water (Haamer, 1995). In 1997, OA and DTX2 were found, but isolated to minor cases (EU-NRL, 1998). During 1999, there was a peak in DSP toxicity in June and July. Closures of production areas are common in Sweden during the period September to March (EU-NRL, 2000).
The United Kingdom of Great Britain and Northern Ireland
The first occurrence of DSP in the United Kingdom was in 1997 when 49 patients presented symptoms 30 minutes after consuming mussels in two London restaurants (Durborow, 1999). In 1999, DSP events seemed to have become more frequent and prolonged (EU-NRL, 2000). At the beginning of 2000, DSP toxins were still detectable in mussels from Cornwall. Later that year, toxins were found in cockles from the southeast of England and from south Wales. Harvesting restrictions were enforced (EU-NRL, 2001). From July 2001 up to August 2002, there was an on-and-off ban on the harvesting of cockles in south Wales because of the presence of DSP toxins (Anonymous, 2002d).
Bans were put on shellfish harvesting in several parts of England in March 2002 (Hatchett, 2002). In September 2002, a ban was put on the harvesting of queen scallops from an area off the West Coast of the Isle of Man because of the presence of DSP toxins (Anonymous, 2002c). In Scotland in 2000 and 2001, DSP toxins were first detected on the west coast and subsequently in mussels from Shetland in late March. The outbreak was short lived. The toxins re-appeared in late May, and were detected in mussels and scallop hepatopancreas in several areas on the west coast. By mid-June, DSP was found in mussels at numerous locations, and was still being found in mid-October. Restrictions on harvesting were enforced at all sites affected (EU-NRL, 2001).
In the period from 1 April 2002 to 31 March 2003, shellfish from 76 primary inshore production areas, and 36 secondary areas and offshore fishing areas in Scotland were examined. A total of 5 409 mollusc samples were analysed, out of which 931 were analysed for DSP. It emerged that 66 samples were positive for DSP (Anonymous, 2003c). In Northern Ireland in 2001, positive DSP results were obtained in 25 oyster samples, 10 mussel samples, 1 cockle sample and 23 scallop samples (EU-NRL, 2001). The United Kingdom Food Standards Agency announced a ban on scallop fishing in the sea adjacent to Northern Ireland following these findings (Anonymous, 2001a).
DSP was identified on the west coast of South Africa during autumn 1991 and on both the west and the south coasts during the autumn of 1992. The causative organism was Dinophysis acuminata (Pitcher et al., 1993).
3.7.3 North America
The presence of DSP toxins in North America during the years from 1991 to 2000 is illustrated in Figure 3.4.
In 1989, DTX1 was isolated from Prince Edward Island mussels at a level of 0.15 µg/100 g digestive gland (Todd, 1997). In August 1990, 13 out of 17 persons in eastern Nova Scotia (Canada) developed gastroenteritis between one and eight hours after consuming boiled or steamed locally cultured mussels. Dinophysis norvegica was found in the digestive gland of some mussel samples and in low numbers in the water column at the harvest site. DTX1 appeared to be the toxin involved (Todd et al., 1993). However, another dinoflagellate, Prorocentrum lima, which was found to be a producer of DSP toxins in unialgal culture, was isolated also from the toxic area (Marr et al., 1992).
Based on the assumption that 100 µg DTX1/100 g of mussel soft tissue were present, the victims ingested between 1.4 and 6.0 µg DTX1/kg bw (Todd, 1997).
In Bonavista Bay, Newfoundland in October 1993, several persons developed diarrhoeic shellfish poisoning following consumption of mussels containing DTX1. Water samples contained Dinophysis norvegica up to 2000 cells/litre. Digestive tissue of the contaminated mussels revealed up to 40 000 cells of D. norvegica per mussel (McKenzie et al., 1994). The mussels contained up to 4 µg DTX1/100 g digestive gland (Todd, 1997).
Lawrence et al. (1998) studied microalgal populations at a mussel farm near Indian Point, Nova Scotia to establish the local source of DSP toxins accumulated in shellfish. In Dinophysis-rich samples, no DSP toxins were found by LC-MS nor by DSP-toxin antibody probing. However, cells of toxin producing Prorocentrum lima were found as epiphytes upon Pilayella littoralis, a macroalga which commonly fouls aquaculture lines in the region.
Figure 3.4 Occurrence of DSP toxins in coastal waters of North American ICES countries from 1991 to 2000
The United States of America
In the New York and New Jersey region, only sporadic cases of DSP were reported prior to 1980. The incidence increased to 31 cases during 1980, 210 cases in 1981, 1 332 cases during 1982 and 1 951 cases in 1983 (Stamman et al., 1987). Four episodes of DSP-like illnesses occurred between 1983 and 1985 in Philadelphia and Long Island, New York after consumption of clams and mussels. Dinophysis spp. or Prorocentrum spp. were involved although no chemical analysis was performed (Todd et al., 1993).
In 1989, high numbers of D. acuta were observed in discoloured water at Long Island. Analysis for OA revealed that mussels from two stations contained over 0.5 MU per 100 g. No cases of human intoxication were reported (Aune and Yndestad, 1993).
Two species of Dinophysis present in Maine coastal waters, D. acuminata and D. norvegica, are frequently found in high numbers from June to September. Prorocentrum lima was found only in the Frenchman Bay-Eastern Bay region. OA-like activity found in mussels was not at levels that present a human health issue (Van Dolah et al., undated). In 1998, the presence of P. lima along the coasts of Maine was reported (Stancioff, 2000).
Analyses of extracts from shellfish and phytoplankton from the Gulf of Mexico demonstrated the presence of OA (0.162 µg/g shellfish) and domoic acid (2.1 pg/cell phytoplankton). Domoic acid is the causative agent of amnesic shellfish poisoning (ASP). No cases of human poisoning have been reported from this area (Dickey et al., 1992a).
3.7.4 Central and South America
D. acuminata and D. fortii were present but no toxicity was detected until 1999 when 40 persons were intoxicated in Patagonia. P. lima was confirmed in the plankton and DSP toxins in mussels (Ferrari, 2001).
In 1990, several persons showed gastrointestinal distress and diarrhoea after eating mussels in Florianapolis. Plankton analysis and mouse bioassay supported the evidence of DSP and D. acuminata. (Ferrari, 2001).
Cases of gastrointestinal disorders were observed in Chile in 1970 and 1971, apparently associated with blooms of Dinophysis spp. (IPCS, 1984). A substantial DSP intoxication was reported in January 1991. Approximately 120 people became ill after ingestion of fresh mussels. D. acuminata was identified in the contents of fresh bivalves and in canned mussels. Toxic samples contained both OA and DTX1 (Aune and Yndestad, 1993). Zhao et al. (1993) detected DTX1 as the major toxin and OA as the minor toxin in mussels from Chile. Recently the presence of YTXs and related compounds in shellfish and phytoplankton in Chile was reported (Quilliam, 1998a).
Lagos (1998) also reported that DSP is present in Chile and well documented. Until 2001, PSP and DSP toxins have had severe public health and economic impacts in Chile. As a consequence, all natural fish beds from 44 °SL southwards were closed and nationwide monitoring programmes were maintained (Suárez-Isla, 2001). Uribe et al. (2001) reported the presence of DSP toxins in the Magellanic fjords (53°19S, 72°30W) in southern Chile in March 1998. DTX1 was found in Mytilus chilensis at a level of 6.5-58 µg/100 g of digestive gland. No OA was detected. D. acuminata was shown to be the causative algal species.
Mouse bioassays with shellfish extracts were shown to be positive for DSP toxins in samples from Bahía Conceptión in the Gulf of California during the spring of 1992, 1993 and 1994. Samples from April 1994 showed the presence (by LC) of OA as well as DTX1. No human intoxications were reported. Dinoflagellate species known as DSP producers are often found in water samples from this area (Sierra-Beltrán et al., 1998).
During March 1993 and April 1994, densities of the dinoflagellate D. caudata reached a maximum of 74 to 90.103 cells/L in the Gulf of California (Punta Arena, Playa Escondia, Amolares and San Ignacio). However, no contamination of shellfish or human intoxications was reported (Lechuga-Devéze and Morquecho-Escamilla, 1998).
In 1990, several persons showed gastrointestinal distress and diarrhoea after eating mussels. Plankton analysis and mouse bioassay supported the evidence of DSP and Dinophysis acuminata (Ferrari, 2001). In January 1992, DSP was detected in shellfish harvested along the coast of Uruguay. At the same time, D. acuminata at concentrations up to 6 000 cells per litre occurred at La Paloma leading to a partial ban on shellfish harvesting (Aune and Yndestad, 1993).
DSP is widely distributed in different shellfish species along the Chinese coast. In 1996 and 1997, 26 out of 89 samples contained DTX1 or OA, but only six samples contained levels above the regulatory limit for human consumption (20 mg/100 g soft tissue). The highest level of 84 mg/100 g was found in Perna viridis from Shenzhen. No DSP poisoning of humans was reported in Shenzhen at that time (Zhou et al., 1999).
DSP was first documented in Japan in late June 1976 and 1977. A total of 164 persons were documented to have suffered severe vomiting and diarrhoea. Epidemiological data indicated that as little as 12 mouse units (MU) was sufficient to induce a mild form of poisoning in humans (Yasumoto et al., 1978). MU was defined as the amount of toxin (later defined as DTX1) killing a mouse by i.p. injection within 24 hours (EU/SANCO, 2001). The first dinoflagellate to be implicated was D. fortii. Between 1976 and 1982, some 1 300 DSP cases were reported in Japan (Hallegraeff, 1993).
A two year study (1984-1986) in India showed that diarrhoeic shellfish toxins were present in several shellfish examined. The levels ranged from 0.37 to 1.5 MU/g hepatopancreas. However, no reports of DSP episodes in the general population are known (Aune and Yndestad, 1993).
Five species of Dinophysis have been recently detected in the Philippines but no cases of human poisoning have been reported (Corrales and Maclean, 1995).
The Russian Federation
D. acuminata, D. acuta, D. fortii and D. norvegica have been identified in the far-eastern coastal waters of the Russian Federation. However, no cases of human poisoning have been reported (Aune and Yndestad, 1993).
Australia and New Zealand
The dinoflagellate P. lima producing OA and methyl-OA was isolated at three locations on Heron Island, Australia. Cases of DSP were not reported (Morton and Tindall, 1995). In New Zealand waters (Northland and Marlborough Sounds), P. lima was also observed and appeared to produce OA (Rhodes and Syhre, 1995). The presence of YTXs and related compounds in shellfish and phytoplankton in New Zealand was reported recently (Quilliam, 1998a).
A pipi (Donax delatoides) shellfish poisoning event (56 cases of hospitalization) in New South Wales, Australia occurred in December 1997 (ANZFA, 2001). According to Quilliam et al. (2000), PTX-2 seco acids may have contributed to the gastrointestinal symptoms, vomiting or diarrhoea in humans (Aune, 2001). Burgess and Shaw (2001) reported that the patients consumed approximately 500 g of pipis containing 300 µg PTX-2SA/kg (~150 µg PTX-2SA/person~2.5 µg/kg bw for a person weighing 60 kg).
Another poisoning incident with pipis occurred on North Stradbroke Island (Queensland) in March 2000 where an elderly woman became seriously ill after eating pipis from one of the local beaches. High levels of PTX-2SA were found in the pipis (Burgess and Shaw, 2001).
DSP toxins from the dinoflagellates Dinophysis fortii and D. acuminata have been detected in wild Tasmanian mussels (both OA and DTX1). However commercial Tasmanian shellfish have thus far proved negative for DSP toxins and no incidents of human poisoning are known (Hallegraeff, 1992).
During the period from September 1994 to July 1996, 0.7 percent of samples of shellfish collected around the coastline of New Zealand on a weekly basis, showed a DSP toxin level above the regulatory limit during a total of nine DSP events (maximum level 96 µg/100 g mussels). During the sampling period, there were three outbreaks of human DSP poisoning involving 13 cases (Sim and Wilson, 1997).