Schistosomiasis japonica

Schistosomiasis japonica is a disease caused by the parasitism of Schistosoma japonicum in the portal venous system. Infection occurs through skin contact with contaminated water containing cercariae. The main pathological changes are granulomas in the liver and colon caused by eggs. The acute phase is characterized by fever, hepatomegaly with tenderness, diarrhea or the passage of purulent bloody stools, and a marked increase in blood eosinophils; the chronic phase is mainly characterized by hepatosplenomegaly; the advanced stage is predominantly characterized by periportal fibrosis, progressing to portal hypertension, massive splenomegaly, and ascites. Schistosomiasis japonica is the most serious parasitic disease endangering the health of farmers in China. According to surveys conducted in the early period after the founding of the People's Republic of China, there were approximately 12 million patients nationwide, distributed across 381 counties in 12 provinces, municipalities, and autonomous regions along the Yangtze River basin and to its south. In severely endemic areas, large numbers of people died, fields were left barren, creating a scene of devastation. Since the founding of the People's Republic of China, after decades of large-scale systematic control efforts, great achievements have been made. By the end of 2003, 5 of the 12 endemic provinces, municipalities, and autonomous regions (Shanghai, Zhejiang, Guangdong, Fujian, and Guangxi) had reached the standard for transmission interruption. According to the current administrative divisions, of the 433 counties (cities, districts) that were once endemic for schistosomiasis, 260 have reached the standard for transmission interruption, 63 have reached the standard for transmission control, and 110 counties (cities, districts) have not yet controlled transmission. Areas currently still endemic are mainly distributed in the lake and marsh regions with difficult-to-control water levels in Hubei, Hunan, Jiangxi, Anhui, and Jiangsu, as well as the complex mountainous areas with difficult environments in Sichuan and Yunnan. During flood seasons, small-scale outbreaks of acute schistosomiasis often occur. According to sample survey data published in 1998, there were still approximately 865,084 people infected with Schistosoma japonicum and approximately 100,251 infected cattle in China.