17 January 2003
Maori face an increasing risk of being hit by the incurable disease multiple sclerosis to which they were previously "immune", a Wellington epidemiologist warned yesterday.
"People with Maori and Pacific Island ancestry have traditionally been immune to multiple sclerosis, but this apparent immunity appears to be fading," Dr Lou Gallagher said.
The rising incidence of the disease in the Maori population appeared to be linked to mixing of Polynesian genes with those of people with European ancestry, who tended to have relatively high prevalence of the disease,
"We're starting to see some Maori people being diagnosed, which suggests there may be a 'washout effect' for their genetic immunity as their gene pool becomes more and more infused with Caucasian bloodlines," Dr Gallagher said.
She had not yet encountered the disease in people from the Pacific Islands who were living in New Zealand.
Reasons for the variations were not clear, but appeared to be rooted in both genetic heritage, and how far people lived from the equator.
According to the Multiple Sclerosis Society, MS generally becomes more common in a population the further it is from the equator: the prevalence of MS is much higher in the South Island, Scotland and Canada than it is in tropical and sub-tropical areas.
The prevalence in Southland is over twice that in the Waikato.
It is rarely seen in Africans who still live in Africa, or in Asians living in Asia, or some ethnic groups retaining a strong Asian genetic heritage, such as Inuit and American Indians.
However, American Blacks, descended from slaves, tend to develop MS more frequently than Africans, and less frequently than Caucasians.
Studies have suggested that in addition to a genetic susceptibility, there are likely environmental factors, such as the amount of ultra violet radiation a person gets, or some "trigger" such as a common virus.
Women are two or three times more likely to be affected than men, and mothers are far more likely to pass susceptibility genes on to their children than fathers.
The definite cause of MS still remains a mystery, because even when one twin has the disease, a genetically identical sibling still only has a 35 per cent chance of also having it.
"It is a disease with no known cure, and no definitive cause, and we don't even know for certain how many people in New Zealand have it," Dr Gallagher said.
Dr Gallagher, who works at Victoria University's health services research centre, has organised a meeting in Wellington tomorrow of many of the nation's 33 neurologists, other scientists, and representatives of the MS society in a bid to set up a national registry of people with the disease.
There are registries in Denmark and Norway, but New Zealand would be the first Southern Hemisphere country to have a national database.
"A registry with anonymous data would allow scientists to perform detailed investigations of multiple sclerosis risk factors and protective effects," she said.
New Zealand was particularly suited to investigation of the effects of latitude on prevalence, because of its long narrow north-south shape, and to genetic aspects of MS susceptibility.
World experts on research databases, including Professor Christian Confavreux,
from France, and Dr Rex Simmons, from Canberra, will speak at the meeting.
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