Waitangi Marae involved in national shellfish study
Northland shellfish beds are being sampled for stomach-bug causing 'noroviruses' in a bid to develop faster ways of
assessing when shellfish are unsafe to eat.
Iwi from Waitangi Marae are working with ESR collecting pipis from two local historically important shellfish beds as
part of the two-year nationwide project into shellfish safety. Sampling started this week.
Oysters, mussels, cockles and pipis will be collected from 14 commercial and non-commercial shellfish harvesting sites
in Northland, Hawke's Bay and Otago. Other New Zealand sites may be included as the study progresses.
ESR's Gail Greening who is leading the study said that scientists worldwide were grappling with the problem of norovirus
detection in shellfish. Developing a fast reliable test for New Zealand will benefit customary and recreational
shellfish gatherers and the shellfish industry which relies on a clean safe reputation for seafood sales and exports.
"While monitoring programmes are in place to detect bacterial contamination they can't easily detect the "norovirus'
that can concentrate in shellfish in contaminated water, Dr Greening said.
"Until recently it was almost impossible to find these viruses in shellfish. While we have now managed to develop
detection tests they are expensive and difficult to do. The aim of this research is to find faster, more sensitive and
cheaper tests that are easily available for people when they want to check for possible pollution in shellfish beds", Dr
Noroviruses are the most common cause of food-transmitted disease in the world. They are very infectious and cause the
classic tummy-bug symptoms of cramps, vomiting and diarrhoea 10-50 hours after contact.
"Once the virus has passed from person to person it can be difficult to tell if it originally came from someone eating
contaminated shellfish or from some other source", Dr Greening said.
Norovirus initially come from human faeces or sewerage but can be quickly spread by direct contact, eating contaminated
food or through the virus surviving in the environment.
Bivalve shellfish such as oysters, mussels, pipis and cockles pose a particular risk because they are filter feeders. If
the water they grow in becomes contaminated with human sewerage then the shellfish concentrate the virus in their gut.
While bacteria are expelled quickly viruses may persist for long periods, even weeks.
"ESR will sample shellfish from the 14 sites for two years to see what viruses they contain and compare this information
with the levels of E coli which is the normal microbial indicator used for monitoring shellfish. This will let us
compare the presence of different viruses over the seasons, during changes in climate and water temperature and to see
if at certain times of the year there is more risk from faecal contamination".
Overseas it has been found that water temperature can influence how quickly the virus is expelled. Colder temperatures
make shellfish more sluggish and viruses may stay longer but in warm waters they may be lost faster. Another component
of this New Zealand research is comparing how quickly shellfish get rid of norovirus in summer and in winter
Nga Puhi environmental spokesperson Emma Gibbs said the project blended environmental values with tikanga Maori in
research that would provide health benefits nationwide.
"We were keen on being involved in scientific research that will help us protect our kaimoana and our tamariki.
"Kaimoana shellfish is the essence of Maori hospitality which is an integral part of our custom and tikanga.
Historically Waitangi pipi beds played a major role by feeding the people present at the Treaty of Waitangi enabling us
all to be one people" she said. The Foundation of Science, Research and Technology is providing funding for the study. A
range of organisations including the New Zealand Oyster Industry Association, New Zealand Food Safety Authority, MAF,
Northland Regional Council, Northland Health, Health Waikato, Dunedin City Council, Public Health South and the Waitangi
Maori Marae Committee are assisting including collecting the samples and other data.
* Noroviruses are the most common cause worldwide of gastro-enteritis in hospitals, schools, rest-homes
and cruise ships.
* Noroviruses infect the human gut and are spread through contaminated food or water or from faeces or
vomit. Up to 80 percent of people exposed to the virus during an outbreak may become ill.
* There were 38 norovirus outbreaks in rest homes and hospitals in NZ in 2002. Studies indicate
New Zealand has the same incidence of norovirus (from all sources) as the UK where only one in every 1500 cases is
* The virus is very resistant and will persist in the environment for weeks including in carpets, floors
doorhandles etc. Studies from the UK found carpet layers becoming ill two weeks after an outbreak in a rest home and of
people in a restaurant being infected when a guest vomited.
* A norovirus outbreak can also have a major effect on New Zealand's seafood industry. Oyster beds in
Northland were closed for several months in 2001 following norovirus contamination.
* The most likely source of the virus in shellfish is from untreated sewerage outfalls, boats discharging
untreated waste, from leaking septic tanks or through direct contamination from people. .