MAP Technical Reports Series No. 106 UNEP

7.3.2.3 Methods of analysis for ASP
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The biotoxicological method of analysis on mice for ASP is the same as that used for
PSP. Mice injected intraperitoneally with a dilute hydrochloric acid extract of mussel tissue
containing domoic acid showed that the relative potency of domoic acid is lower than that of PSP
(Subba Rao et al., 1988). The observation time was extended to 24 hr. Within 3 hr it is possible
a simultaneous testing for PSP and domoic acid. Chemical methods have also been defined for
the demonstration and quantification of domoic acid in molluscs (Lawrence et al., 1989). In order
that both domoic acid toxicity and PSP may be identified in shellfish in Atlantic Canada, one half
of the dilute hydrochloric acid extract, from shellfish being tested, is used for mouse bioassay
and the other half for HPLC tests (Lawrence et al., 1989).
7.3.2.4 ASP occurrence in the world
Only in Canada, now. Concentrations of the N. pungens in Cardigan Bay were 10
million cells per litre in 1987. Some suggest that the proper mix of nutrients, sunlight and
stratification due to fresh-water runoff contributed to the diatom blooms (Waldichuk, 1989).
7.3.2.5 Nitzschia spp. and mucilaginous aggregates in Adriatic sea
With regard to health, particular attention must today be paid to the diatoms, in the high
and middle Adriatic sea, in relation above all to the appearance in August 1988, in July 1989 and
in July and August 1991 of the "mucilaginous aggregates", which seems to originate from the
diatoms among which there is a species of Nitzschia. This phenomenon has in fact created
considerable ecological problems and has given rise to worries over health in Italy and former
Yugoslavia. The monitoring of biotoxins ASP, PSP, NSP, DSP in "mucilaginous aggregates" and
in mussels in a coastal area of the Northern Adriatic sea facing Emilia-Romagna in the summer
months (in particular June, July and August) of 1988, 1989 and 1991 has been reported (Viviani
et al., 1995). Using the PSP method which, according to current Canadian legislation is valid for
ASP monitoring, the presence of domoic acid has been excluded. Also PSP, NSP and DSP are
absent from "mucilaginous aggregates" (Viviani et al., 1995).
7.3.2.6 Human intoxication: clinical toxicology
Domoic acid is a mild neurological poison compared to PSP. When mussels
contaminated by domoic acid were eaten in eastern Canada they produced 153 cases of
gastrointestinal distress with nausea, vomiting and diarrhoea within 24 hr; but added to that
disorder, they also caused neurological illness within 48 hr in older victims (ca. over 60 years
old). Three elderly patients died. In the most severely affected cases neurological symptoms still
persisted (Wright et al., 1989; Waldichuk, 1989).
7.3.2.7 Toxicology
The mechanism of action of domoic acid is actually known on excitatory amino acid
receptors and synaptic transmission. Excitatory amino acids, most notably L-glutamate and Laspartate,
have long been considered to be the most likely neurotransmitters (Collingridge et al.,
1987) (Fig. 23). These amino acids are known to act on several receptor types, the best
characterized of which are named after the selective exogenous excitants N-methyl-D-aspartate
(NMDA), kainate and quisqualate (Fig. 24). Glutamate and also NMDA subclass