The infection rate of the most common food-borne parasitic disease on the mainland has increased by 75 per cent since 1990, according to a nationwide survey. The provinces with the biggest increases in clonorchiasis were Guangdong and Guangxi , where the infection rate more than doubled, and Jilin , where it increased by more than 600 per cent. But experts also warned Hong Kong, which was not included in the survey, about potential problems because of its fish and meat imports from Guangdong and Guangxi. Clonorchiasis, or liver fluke disease, can lead to obstruction of the body's biliary tree and cause liver damage and stunt children's development if untreated. It is commonly caused by eating undercooked, salted, pickled or smoked freshwater fish. The nationwide survey on parasitic diseases released by the Ministry of Health yesterday was conducted between 2001 and last year in all the 31 administrative regions on the mainland. It found the infection rate of all food-borne parasite diseases increased sharply in some provinces. The estimated population of those with liver fluke disease nationwide had increased by 75 per cent since 1990 to 12.94 million. The survey co-ordinator, Xu Longqi of the National Institute of Parasite Diseases, said the problem was most severe in Guangdong, where there were an estimated 5 million sufferers. 'People like to eat uncooked fish or crab. This has led to the increase in the clonorchiasis infection rate,' he said. He said even though the survey did not cover Hong Kong and Macau, the fact that Guangdong and Guangxi exported freshwater fish to Hong Kong, where diners had similar eating habits, represented a threat to the city's health. The infection rate of tapeworm disease also increased, the survey found, but roundworm infection dropped by nearly two-thirds.