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 p eople in five fishing villages situated on two islands (large, Qingsha n island; small, Niangashan island) in the Dongting Lake region in Hun an Province, the people's Republic of China. The results of this study indicate that the overall prevalence for schistosomiasis on the two i slands 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%). Fisherme n 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 diffe rence (P < 0.01) in the prevalence of schistosomiasis between males an d females. In general, males had a much higher prevalence (22%) than f emales (8.9%). When the study populations were classified as uninfecte d, lightly infected (10-100 epg), moderately infected (101-400 epg), a nd heavily infected (> 401 egg) with S, japonicum, the distribution pa ttern was similar for each of the five villages. The majority (76-88%) of the population remains uninfected. Lightly infected individuals ha d the highest prevalence (7-12%) followed by moderately infected indiv iduals (1-9%). Only a very small percentage of the population was heav ily infected (0-2%). Hepatomegaly along the midsternal line (MSL great er than or equal to 3) was commonly seen in both uninfected (21%) and infected individuals (19-39%). Subjects heavily infected with S, japon icum reported significantly higher (P < 0.05) cases of liver enlargeme nt when compared with those uninfected. The reported cases of abdomina l pain for both uninfected (9%) and infected individuals (4-19%) was r elatively high. Lightly and moderately infected individuals reported s ignificantly (P < 0.05 and P < 0.01, respectively) more episodes of ab dominal gain than those uninfected. The occurrence of diarrhea was low (5%) for uninfected individuals but this clinical feature was signifi cantly (P < 0.01) more prevalent in both the lightly and heavily infec ted categories (8-17%).