Paralytic shellfish poisoning due to ingestion of contaminated mussels: A 2018 case report in Caparica (Portugal)

Abstract

In Portugal, the potent paralytic shellfish toxins (PSTs) have appeared irregularly since the onset of a national monitoring program for marine biotoxins in 1986. In years where high contamination levels were attained in bivalves, sporadic cases of human poisonings have been recorded, as in 1994 and 2007. The reappearance of high contamination levels led to the appearance of new cases during the autumn of 2018. This study details toxin ingestion, symptomatology and toxin elimination and metabolization in the fluids of two patients, who ingested mussels from the Portuguese southwest coast and required hospitalization due to the severity of symptoms. Toxin elimination was confirmed by ELISA in plasma and urine samples. In mussel samples, the toxin profile obtained by HPLC-FLD displayed a wide diversity of toxins, typical of Gymnodinum catenatum ingestion. However, in the urine samples, the toxin profile was reduced to B1 and dcSTX. Abundant compounds in mussels having an O-sulphate at C11, such as C1+2 and dcGTX2+3, were absent in urine. In plasma, PSTs were not detected by HPLC-FLD. Calculated toxin ingestion, resulting from consumption of an estimated 200-g portion, was in the range of 104-120 μg STX eq./kg b. w.

Keywords: ELISA; HPLC; Human samples; Paralytic shellfish poisoning; Portugal; Saxitoxin; Seafood poisoning.

Graphical abstract

Fig. 1

Location of main Portuguese production areas affected by PSP contamination during October–November 2018. Red areas were more severely affected than yellow areas (geographical details available in http://www.ipma.pt/pt/bivalves/index.jsp). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

PSP levels increased sharply over a short two-week period in Caparica's mussels. The poisoning outbreak coincided with extremely low-tide levels: 0.6 m or below after sun rise, lasting from 8 until 11 October.

Fig. 3

Data of the urine samples collected from the two positive patients during seven days and data of plasma samples collected on the first day of hospitalization by a competitive enzyme immunoassay for quantitative analysis of saxitoxin (ELISA). a) Patient A and b) Patient B.

Fig. 4

HPLC-FLD chromatograms of PSP toxins using pre-column peroxide oxidation from: a) aqueous SPE fraction of blue mussel from Caparica on 2018-10-10; b) urine sample from patient A on 2018-10-11; c) methanolic SPE fraction of same blue mussel with modified gradient separation; d) methanolic fraction after hot alkaline hydrolysis. X denotes interfering compounds; arrows denote compounds altered biologically (b) or chemically (d).

Fig. 5

HPLC-FLD chromatograms after periodate oxidation from: a) overlaid toxins standards of dcNEO (0.37 μM) and dcSTX (0.70 μM), both producing two oxidation products coded ‘1’ and ‘2’; b) urine sample from patient A on 2018-10-11 after C18 cleanup dominated by dcSTX oxidation products.

Fig. 6

Molar profiles of PSP toxins in a) blue mussel on 10-October; b) patient A urine on 11-October. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)