Dermatitis caused by molluscs

Of the five classes belonging to this phylum, three are particularly toxic: Lamellibranchs, that have a bivalve shell (mussels, clams, oysters, scallops), Gasteropods (nude or covered by a shell) and Cephalopods (octopus, squid, cuttlefish). The bivalves do not produce toxins but because they are filtrating animals they can ingest microrganisms that produce biotoxins, and so become poisonous. Among the Gasteropods, some species of the Conidae family (with conical shells) have a well-developed venom apparatus and can kill a man. A cone shell sting immediately elicits intense burning sensations, torpor and tingling, which rapidly spread from the affected area to the whole body. There may also be disorders of speech and vision (double images, blurred vision). These symptoms are followed by ischemia and cyanosis in the affected area and, in severe cases, by muscular paralysis and coma. The bites of Cephalopods can induce both local and systemic reactions. For instance, the bite of a small venomous octopus (“blue-ringed octopus”) that populates the coasts of Australia may be fatal to man. It is found in tidal rock pools and is very attractive, particularly to children and tourists. Its tetrodotoxin causes the blockade of neuronal sodium channels, leading to weakness, numbness or paraesthesia, breathing difficulties and respiratory paralysis. The onset of the symptoms occurs 5-10 min after the bite. At the site of the wound there is typically prolonged copious bleeding, and an associated urticarial eruption is possible. There is no effective antidote; the treatment is symptomatic and must be administered in a hospital setting.