Shellfish Warning!

Posted by Waikato District Health Board on 20/12/2012


Paralytic shellfish poisoning (PSP) warnings are in place on both the east and west coasts of the North Island.

Twenty-six people have already been admitted to hospitals in Tauranga and Rotorua so far this month with presumed shellfish poisoning, after eating pipi or tuatua they had gathered around Papamoa. Two ended up in the Intensive-Care Unit.

A separate health warning, also because of the presence of PSP toxin, on the west coast extends from Taranaki to Kaipara Harbour and has been in place for a month.

“I'm a little concerned that the spate of poisonings being reported from the east coast may be overshadowing the presence of an even more extensive area on the west coast where a ban is also in force, also for PSP toxin,” said Waikato Medical Officer of Health Dell Hood.

“Many people will be heading for their holiday homes at places like Marokopa, Kawhia and Raglan and they may not be aware of the seriousness of the risk, or they may think it is an issue only on the east coast. “There is signage on both coastlines but as events show, some people may ignore them,” Dr Hood said.

The toxins get into shellfish from naturally occurring algae growing in the sea water. This is a natural process, but the toxin becomes concentrated in shellfish because they feed by filtering seawater. There are many different poisons produced by these algae which is why the severity of illness varies. PSP is known to be one of the most serious toxins produced by marine algae.

Waikato-based health protection officer David Cumming said weekly monitoring had shown continuing high levels PSP toxin present in shellfish along the west coast.

“The affected area includes the entire coastline from Motunui (Taranaki) north to Maunganui Bluff (just north of Dargaville), including Kawhia, Aotea, Raglan, Manukau and Kaipara harbours.”

The health warning applies to all bi-valve shellfish including mussels, pipi, tuatua, cockles, oysters, scallops as well as kina.

Paua, crayfish and crabs can still be taken but the gut should be removed before cooking.

Eating shellfish affected by the toxin can cause numbness and tingling around the mouth, face or extremities; difficulty swallowing or breathing; dizziness; double vision; weakness, difficulty walking and in severe cases, paralysis and respiratory failure. There can also be vomiting and or diarrhoea. These symptoms usually occur within 12 hours of a person consuming affected shellfish.

Mr Cumming said if anyone became ill after eating shellfish from an area where a public health warning had been issued, they should contact a doctor immediately, advise their local Health Protection Unit and keep any left over shellfish for testing by health authorities.

Monitoring of toxin levels will continue along the coasts over the summer.

Dr Hood was concerned people were ignoring warning signs. “There have been previous warnings about marine biotoxins but if no serious illness was publicly reported, people may have decided warnings are overcautious. However, the severity of illnesses being reported this year is a wake-up call. All shellfish warnings should be taken seriously because the consequences can be very serious, and even fatal on rare occasions.’’

Mr Cumming said commercially grown and harvested shellfish purchased at a supermarket or fish retailer was safe to eat. “There are extensive monitoring programmes in place for commercial shellfish,” he said.