Hepatosplenic morbidity due to Schistosoma mansoni in schoolchildren on Ukerewe Island, Tanzania
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The study was conducted to assess infection intensity and morbidity due to Schistosoma mansoni in schoolchildren on Ukerewe Island in Lake Victoria, Tanzania, East Africa. Three hundred and sixty pupils who have never been treated previously were enrolled (180 males/180 females, age 6–17 years [median 10 years]) in three different schools of the island. Double stool samples were collected from each pupil and egg excretion was classified according to WHO recommendations. Ultrasound investigations were performed in accordance with the WHO Niamey-Belo-Horizonte protocol. Male (112/180, 62.2%) and female (104/180; 57.7%) pupils were infected (difference, not significant [n.s.]). In the positive 216 cases, egg excretion varied from 1 to 2,440 eggs per gramme stool (epg) [median 165 epg]. There were 69/216 (31.9%) who had a low grade, 105/216 (53.2%) had a moderate and 42/216 (14.8%) had a heavy infection. There was no significant difference between male and female sex nor with regard to age groups. There were 354/360 children who underwent sonography: 321 (90.7%) had splenomegaly, 316 (89.3%) showed a left lobe and 109 (30.9%) had a right lobe hepatomegaly. Overt signs of portal fibrosis (PF) were present in 19 children (5.4%) out of whom 11 presented with echogenic thickening of peripheral portal and 8 with thickening of central portal branches. Non-specific portal wall changes were seen in 6 children (1.7%). Association of PF to quantitative egg excretion was not seen (median in PF, 172 epg vs. median in non PF, 168 epg; difference, n.s.). Portal vein dilatation was seen in 101/354 (28.5%) cases. In Ukerewe, the prevalence of S. mansoni infection and infection intensity in children is high, yet overt hepatic morbidity is low as compared to other endemic foci. Non-specific ultrasonographic abnormalities including hepatosplenomegaly and portal vein dilatation were seen frequently but the fraction attributable to schistosomiasis is difficult to assess.
KeywordsSchistosomiasis Esophageal Varix Gallbladder Wall Infection Intensity Schistosoma Mansoni
First and foremost, we thank the children for their kindness and cooperation, as well as for their curiosity which made this trip more than a study. Furthermore, we thank all members of the NIMR field team and the local representatives for their invaluable help. We were overwhelmed by the hospitality and cooperation of the three participating schools in Gallu, Mahande and Hamkoko. The study was funded by the Section of Tropical Medicine of Heinrich Heine University Düsseldorf, Germany and Friedrich-Ebert-Stiftung, Bonn and Berlin, Germany. Special thanks to Mr. Laban Aggrey founder and director of the Non-Governmental Organization for “Development of Free Education Services Centers for Orphans” (DEFESCO) in Mwanza, Tanzania, for his critical review of the manuscript
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