Scientists from the Centre for Environment, Fisheries and Aquaculture Science and the University of Hull in the UK have reported the first ever detection of tetrodotoxins (TTX) in European bivalve shellfish.
The researchers tested 29 live shellfish samples (mainly oysters and mussels) harvested from the South coast of England between February 2013 and October 2014. The samples were analysed for TTX using a sophisticated chromatography and mass spectrometry method. Samples were also tested for the presence of bacterial pathogens.
The results showed that TTX could be detected in 14 of the samples, although levels were low and did not approach concentrations known to be dangerous for humans. This is the first time that TTX have been detected in shellfish from the temperate waters around the English coast. They have previously only been found in bivalves from New Zealand and Japan.
TTX are usually associated with pufferfish found in tropical waters. They can cause a fatal form of poisoning in humans who eat the fish if they are not expertly prepared. Pufferfish, or fugu, is considered a delicacy in Japan. It is thought that the toxin is of bacterial origin and may be produced by marine species such as Vibrio spp. before accumulating in the fish.
This study found that Vibrio spp. were present in 12 of the shellfish samples and also revealed an association between their presence and the occurrence of TTX. The researchers suggest that rising sea temperatures in temperate regions could make the growth of these bacteria more likely in the future, which could in turn increase the risk of TTX poisoning for shellfish consumers.
A report of the findings of this study is published in the journal Eurosurveillance and can be found in full here.