A local delicacy in north-east Thailand, made from raw fish, has been found to be behind a high incidence of liver cancer in the area, and doctors are trying to educate people about the risk.
The Isaan plateau of north-eastern Thailand is poor, dry, and far from the sea. Home to around one third of the country's population, most of them ethnic Lao in origin, it is renowned for its spicy and inventive cuisine, using whatever ingredients are available.
Where there are rivers or lakes, they use the smaller fish they catch in a pungent dish called koi plaa. The fish are chopped up finely, and mixed by hand with local herbs, lime juice and live red ants, and served up raw.
It is very popular, but also dangerous.
For decades, certain populations in the north-east have been known to have abnormally high levels of liver cancer.
In men it comprises more than half of all cancer cases, compared to an average of less than 10% worldwide.
The high prevalence has long been linked to infection by liver flukes, a kind of parasite, found in raw fish.
But it is only in the last decade that a serious effort has been made to get people to change their eating habits, by cooking koi plaa to kill the flukes before they eat it.