Epidemiologic features of Schistosoma japonicum among fishermen and other occupational groups in the Dongting Lake region (Hunan Province) of China

In this study we examined 1,909 individuals (53% males and 47% females! to determine the current status of Schistosoma japonicum among the people in five fishing villages situated on two islands (large, Qingshan island; small, Niangashan island) in the Dongting Lake region in Hunan Province, the people's Republic of China. The results of this study indicate that the overall prevalence for schistosomiasis on the two islands is 16%. Two distinct peaks in prevalence (29%) were observed at 25-35 years of age and again at 45-55 years of age for both the large and small islands. On the small island the overall prevalence (22.4%) varied significantly (P < 0,01) from the large island (15%). Fishermen had the highest prevalence (22.4%) among all the occupational groups examined but students produced the highest worm intensity (geometric mean = 69 eggs per gram [epg] of feces). There was a significant difference (P < 0.01) in the prevalence of schistosomiasis between males and females. In general, males had a much higher prevalence (22%) than females (8.9%). When the study populations were classified as uninfected, lightly infected (10-100 epg), moderately infected (101-400 epg), and heavily infected (> 401 egg) with S, japonicum, the distribution pattern was similar for each of the five villages. The majority (76-88%) of the population remains uninfected. Lightly infected individuals had the highest prevalence (7-12%) followed by moderately infected individuals (1-9%). Only a very small percentage of the population was heavily infected (0-2%). Hepatomegaly along the midsternal line (MSL greater than or equal to 3) was commonly seen in both uninfected (21%) and infected individuals (19-39%). Subjects heavily infected with S, japonicum reported significantly higher (P < 0.05) cases of liver enlargement when compared with those uninfected. The reported cases of abdominal pain for both uninfected (9%) and infected individuals (4-19%) was relatively high. Lightly and moderately infected individuals reported significantly (P < 0.05 and P < 0.01, respectively) more episodes of abdominal gain than those uninfected. The occurrence of diarrhea was low (5%) for uninfected individuals but this clinical feature was significantly (P < 0.01) more prevalent in both the lightly and heavily infected categories (8-17%).