Evaluation of national surveillance for echinococcosis in Japan, 1999 to 2002

National echinococcosis surveillance has been performed since April 1999 when it was stipulated as a Category IV Disease under the Infectious Diseases Prevention Law. During the last 4 years of surveillance, 7 cases of unilocular hydatid disease (age range 27-81 years; median age 56 years) and 43 cases of alveolar hydatid disease (age range 24-83 years; median age 64 years) have been reported. There was an increase in the number of reported cases of alveolar hydatid with age, and the greatest number of reported cases occurred in the age group > or = 70 years. Thirty-three of the reported echinococcosis cases had clinical symptoms. The greatest number of echinococcosis was reported from health centers in Hokkaido; 94% of all reported cases (47/50) were from this island. After classifying Hokkaido into six regional districts and analyzing cases by district, we found the greatest number of reported cases to be from the Nemuro-Abashiri-Kushiro region (16 cases) and the Ishikari-Shiribeshi-Iburi region (15 cases). However, the greatest number of reported cases per 100,000 residents was found to be from the Souya-Rumoi region (2.05/100,000) and the Nemuro-Abashiri-Kushiro region (2.00/100,000). As the incubation period of echinococcosis is thought to be several years or more, the current data shows the infection rate from several years ago. In order to better understand the current infection rate of echinococcosis, we recommended implementing a seroepidemiological surveillance in addition to the present surveillance.