Foci of Schistosomiasis mekongi, Northern Cambodia: II. Distribution of infection and morbidity

tion of the east and west shore of the Mekong for prevalence (P 5 0.3) or intensity (P 5 0.9) of infection. Severe morbidity was very frequent. Hepatomegaly of the left lobe was detected in 48.7% of the population. Splenomegaly was seen in 26.8% of the study participants. Visible diverted circulation was found in 7.2% of the population, and ascites in 0.1%. Significantly more hepatomegaly (P 5 0.001), splenomegaly (P 5 0.001) and patients with diverted circulation (P 5 0.001) were present on the west bank of the Mekong. The age group of 10-14 years was most affected. The prevalence of infection in this group was 71.8% and 71.9% in the population of the West and East of the Mekong, respectively. The intensity of infection was 172.4 and 194.2 epg on the West and the East bank, respectively. In the peak age group hepatomegaly reached a preva- lence of 88.1% on the west and 82.8% on the east bank. In the 20 schools 2391 children aged 6-16 years were examined. The overall prevalence of infection was 40.0%, ranging from 7.7% to 72.9% per school. The over- alls mean intensity of infection was 110.1 epg (range by school: 26.7-187.5 epg). Both prevalence (P 5 0.001) and intensity of infection (P 5 0.001) were significantly higher in schools on the east side of the Mekong. Hepatomegaly (55.2%), splenomegaly (23.6%), diverted circulation (4.1%), ascites (0.5%), reported blood (26.7%) and mucus (24.3%) were very frequent. Hepatomegaly (P 5 0.001), splenomegaly (P 5 0.001), diverted circulation (P 5 0.001) and blood in stool (P 5 0.001) were significantly more frequent in schools of the east side of the Mekong. Boys suffered more frequently from splenomegaly (P 5 0.05), ascites (P 5 0.05) and bloody stools (P 5 0.004) than girls. No difference in sex was found for the prevalence and intensity of infection and prevalence of hepatomegaly. On the school level prevalence and intensity of infection were highly associated (r 5 0.93, P 5 0.0001). The intensity of infection was significantly associated only with the prevalence of hepatomegaly (r 5 0.44, P 5 0.05) and blood in stool (r 5 0.40, P 5 0.02). This comprehensive epidemiological study documents for the first time the public health importance of schistosomiasis mekongi in the Province of Kracheh, Northern Cambodia and points at key epidemiological features of this schisto- some species, in particular the high level of morbidity associated with infection.