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Table 2 Epidemiological and clinical studies reporting prevalence, intensity of infection and morbidities associated with schistosomiasis in Tanzania

From: Epidemiology and control of human schistosomiasis in Tanzania

Articles Parasites Major findings Geographical area
Jordan, 1961[14] S. haematobium and S. mansoni A total of 203 individuals were examined. Higher incidence of S. haematobium in the age group 6–12 year olds (78%) and 50% in the > 12 years of age. Only 12 individuals had S. mansoni ova in their stool. Usagara, Sukuma-land, north-western Tanzania
Forsyth and Bradley, 1966[113] S. haematobium and S. haematobium A total of 2,338 people (1580 males, 758 females) were studied. Overall prevalence was 42% (42% vs 41% between males and females) and the age group 6–17 years having a prevalence of 69%. The prevalence of S. mansoni was 24% with the majority having light infection and showing a sex difference in prevalence, being common in men (31% versus 15%). Schistosoma mansoni infection was common in individuals living in villages close to the lake and S. haematobium was higher in villages located in the hinterland. Bukumbi chiefdom, north-western Tanzania.
- Prevalence of splenomegaly (Hackett grade 2 or more) was 25% and 8% for individuals identified to have S. mansoni infections.
- Splenomegaly and hepatomegaly was also seen in individuals who had no S. mansoni infections and was presumed to be caused by malaria infection.
Forsyth and MacDonald 1965[112] S. haematobium Three urine samples collected from each of the 517 school children. The overall prevalence of S. haematobium was 45.3% (234/217) and sex difference in prevalence was observed with boys having a prevalence of 51% versus 37% in girls. Infected children were observed to excrete up to more than 4000 eggs/10mls of urine. The prevalence of S. haematobium was observed to vary with villages divided as “good and bad villages”. In terms of pathological lesions, 43.4% had different urological lesions (calcified bladder, deformed ureters, hydronephrosis) from “bad villages” and 17.4% from “good” villages. Unguja (Zanzibar)
McMahon 1967[82] S. mansoni and S. haematobium 640 individuals examined and 200 went through a thorough clinical examination. The prevalence of S. mansoni was 65.2%, 12.2% for S. haematobium and 3.4% had mixed infections (S. mansoni and S. haematobium). On clinical examination, 57% and 19.3% of individuals of different age groups infected with S. mansoni had palpable splenomegaly and hepatomegaly. Similarly, 29.4% and 12.8% of the individuals infected with only S. haematobium had palpable spleens and liver. Other parasitic infections such as malaria contributed to hepatomegaly and splenomegaly. Mwanza and Ukerewe, north-western Tanzania.
Forsyth, 1969[114] S. haematobium A two year longitudinal study which studied 1004 people. Overall prevalence of S. haematobium was 65.1% and the prevalence was higher in the age group between 7 and 17 years (90% - 100%). The prevalence of urological abnormalities (based on urograms results) was 35.4%. Unguja (Zanzibar)
- The infection intensities (number of eggs excreted) were reported to exceed 2000 eggs/10mls of midday urine.
- Haematuria was common in young children and less in older and adult individuals. The urograms of 201 (45.8%) males and 80 (22.5%) were abnormal. The overall prevalence of pathological lesions was 35.4% [calcified bladder 14%, deformed ureters 23.8%, hydronephrosis 15%, non-functioning kidney 4.5% and stones 0.5%]. These pathological lesions were more common in males than in females and were observed to increase with age.
Rugemalila., 1981[18] S. haematobium 900 individuals examined from two communities, prevalences of S. haematobium ranged from 54% to 57% with peaks of 66% - 67% among the 5–9 years olds. Almost 90% of the infected individuals had symptomatic vesical lesions and radiological examination of 100 individuals selected randomly revealed that 28% had bilateral uretero-renal lesions. Mwanza, north-western Tanzania.
Zumstein, 1983[98] S. haematobium 3,478 school children examined for S. haematobium. The overall prevalence of S. haematobium infection among the school children (6–19 years) was 21%. The highest prevalence was observed in both sexes in the age group 15–19 years. Distinct variations in prevalence were found between the individual schools examined, ranging from 5 to 71% and indicating a focal transmission of the disease. The intensity of S. haematobium infection in the individual schools was relatively low, ranging from 5 to 36 eggs/10 ml urine. However, the frequency of microhaematuria among infected subjects was high, reaching 100% from an egg output of 50 eggs/10 ml onwards. Forty-nine water-bodies, most of them man-made-with Bulinus (Ph.) globosus and/or B. (Ph.) nasutus were identified. Ifakara, South-Eastern Tanzania.
Sarda et al., 1985[99] S. haematobium 2,500 school children from 12 primary schools. The prevalence in the schools ranged from 5.3 to 55.1%, with an overall prevalence of 19.3%. More males (23.5%) than females (15.0%) were infected, and the highest prevalence was recorded in the 11–16 year old age group. Intensity of infection was higher, ranging from 12 to 96 eggs/10 ml urine in individual schools. 26% of the infected excreted more than 50 eggs/10 ml urine and high rates of haematuria and proteinuria were observed in infected children. Malacological surveys showed two potential vectors, Bulinus globosus and B. nasutus. Dar Es Salaam, Eastern Coast, Tanzania
Kitinya et al., 1986[117] S. haematobium Histopathological examination of 172 cases of urinary bladder cancer, 72% had squamous cell carcinomas and 46% had S. haematobium eggs. Northern Tanzania
Savioli et al., 1990[25].   520 individuals examined for visual haematuria and parasitological examination. Strong variability of day to day of egg excretion within the study participants was observed both in the whole population and the age group 5–19 years. The prevalence of participants excreting one or ≥ 50 eggs/10 ml of urine ranged between 36% - 61%. Gross haematuria had higher specificity (100%) in relation to positive filtration on any day of examination and egg counts of ≥ 50 eggs/10mls of urine. Also a positive reaction of haematuria of any day of examination was associated with the study participants having a high egg count (≥ 50 eggs/10ml urine). Pemba
Savioli et al. 1989[26] S. haematobium 879 individuals examined for S. haematobium and 520 had six days complete urine samples examination. Overall prevalence based on urine filtration technique was 26-34% and in the age group 5–19 years and the highest prevalence of heavy infection was in the age group 10–14 years. The prevalence of haematuria detected by the reagent strips was similar to prevalence of infection as measured by the highest egg counts. Thus, urine reagent strips are useful diagnostic indicators of S. haematobium. Pemba Island
Mgeni et al., 1990[101] S. haematobium 4,113 individuals examined at least once during two years period. First survey, 2,685 individuals examined, 49.3% had S. haematobium infections and 19.3% with heavy infection. The age group 10–14 years had higher prevalence of heavy infection (30.2%). Second survey, 1887 examined, 39.8% had infection and 13.5% with heavy infection. The age group 5–9 years old, 27.2% had heavy infection. Third survey, 2,458 individuals were examined, 34.5% had infection and 10.9% were heavily infected. Fourth survey, 1719 individuals were examined, 23.2% had infection and 7.3% were heavily infected. S. haematobium is highly endemic in the areas and the age group 5–14 years had highest prevalence and heavily infected. Zanzibar
Albonico et al., 1997[107] S. haematobium 3,605 school children examined for S. haematobium and other parasitic infections, 31% of the children had detectable haematuria and about 67% of them had co-infections of S. haematobium and geohelminths. Pemba Islands
Kardorff et al., 1997[83] S. mansoni Parasitological and ultrasonographical examination of 1,659 and 898 individuals for S. mansoni. High prevalence and intensity of infection in all the three villages was observed, with children and adolescents more infected than adults, and males excreting more eggs than females. Overall prevalence of S. mansoni infection was 86.3% and mean egg output was 514 epg (geometrical mean egg output was 161.1 epg). Prevalence of hepatomegaly (detected by ultrasonography) was 35% and 80% had splenomegaly. Organomegaly was strongly associated with heavy epg. For periportal fibrosis, 29.8% had grade I, 5.1% had grade II, 1.1% had grade III and fibrosis was observed to increase with age. Late stage disease with a high degree of periportal fibrosis, shrinking of the right lobe of the liver and features of portal hypertension was seen in 2.1% of the individuals. The overall level of schistosomal morbidity was classified as intermediate. Ukerewe, north-western Tanzania.
Hatz et al., 1998[96] S. haematobium 533 school children examined for urinary tract pathologies. Baseline data collection found urinary tract pathology in 67% of 533 children. Lesions of the bladder were significantly associated with egg positivity and microhematuria. The attributable fraction estimate of major bladder lesions due to S. haematobium was 75%. In a cohort study, 224 infected children were examined by ultrasound and then treated with a standard dose of 40 mg of praziquantel/kg of body weight. They were re-examined at two, four, six, 12, 18, and 24 months after treatment. Before treatment, 76% had pathologic lesions of the urinary tract. The proportion showing lesions decreased sharply during the first months after treatment to 11% at six months. At 24 months, lesions were detected in 57%, and 11% had developed new severe pathology. In 18 cases, pathology was present throughout, and 34 did not show any pathology throughout the study. Ifakara district, southeastern Tanzania
Lwambo et al., 1999[110] S. haematobium, S. mansoni and geohelminths 6,897 school children aged 7–20 years. Parasitological examination of S. haematobium and S. mansoni. Prevalence of S. haematobium was 56.5%, S. mansoni 10.9% (overall schistosomiasis infection was 63.4%) and mixed infection at 4% (S. haematobium and S. mansoni). Schistosoma haematobium infections was observed to increase with age. Magu district, north-western Tanzania.
Ndyomugyenyi and Minjas 2001[97]. S. haematobium 1,200 schoolchildren examined. The overall prevalence, based on microscopic examination of a single urine sample/subject, was 47.6%. Compared with the girls, the boys were more likely to be excreting schistosome eggs (54.6% versus 40.8%; P = 0.004) and they had higher intensities of infection (54 versus 38 eggs/10 ml urine; P = 0.001). The children aged 10–14 years had higher prevalences and intensities of infection than those in the younger or older age-group studied. Dar Es Salaam, East Coast, Tanzania
Stothard et al., 2002[106]. S. haematobium 400 school children from ten different primary schools were examined for S. haematobium; the overall prevalence was 12% with five schools recording no infection. Primary schools on the west of 39o degrees 19'E and north of 6o 10'S harboured nearly all the infections, with highest prevalence (55%) recorded in an area with a high number of B. globosus habitats. The knowledge of schistosomiasis was poor and individuals self-diagnosis was poor (sensitivity, 8.5%). Freshwater-contact patterns of schoolchildren differed significantly between schools and correlated well with prevalence of infections within schools. Unguja (Zanzibar)
Poggensee et al., 2005[109] S. haematobium and S. mansoni 634 school children examined in two villages, prevalence of S. haematobium was 37% and 86.3% respectively. For S. mansoni, prevalence was22.9% and 43.5% among the school children. Six years after the intervention, the prevalence of S. haematobium remained almost constant, at 33.5% and 70% in the two villages. The prevalence of heavy infection (≥ 50 eggs/10ml urine) decreased from 53.8% to 34.4%. Mwanga district, northern Tanzania
Rollinson et al., 2005[108] S. haematobium 305 schoolchildren examined. Prevalence of S. haematobium based on parasitological examination was 53.9%. Negative association between haemoglobin level and S. haematobium infection intensity was observed. An association between reported pain during micturitions and elevated urine-albumin levels was observed. Unguja (Zanzibar)
Ajanga et al. 2006[118]. S. mansoni 972 pregnant women examined. Overall, 63.5% were infected with S. mansoni with prevalence being highest among younger women and decreased with increased age. Overall, 66.4% of the women were anaemic and the increased risk of anaemia was associated with heavy (≥ 400 epg) infection of S. mansoni. Ukerewe, north-western Tanzania
Rudge et al., 2008[59].   150 school children examined for S. haematobium and a questionnaire to assess water contact pattern. Overall prevalence of S. haematobium was 50.6% with more boys frequently and more heavily infected than girls. In addition, the mean exposure scores was significantly higher in boys than girls. Water contact activities and proximity of children’s home to a site harbouring S. haematobium-infected B. globosus were associated with S. haematobium infection. Unguja (Zanzibar)
Malenganisho et al. 2008[119]. S. mansoni Parasitological and ultrasonographic examination of 1,447 individuals from two communities (aged 14–87 years). The prevalence of S. mansoni was 78% and 38%. The geometrical mean egg output was 156 epg and 47 epg for the two communities respectively. The prevalence of periportal fibrosis was 41.5% and 16.7% and was associated with high prevalence and intensity of S. mansoni. Periportal fibrosis, increased segmental branch wall thickness and dilated portal vein diameter were more common in males than females. Ukerewe and Ilemela district, north-western Tanzania.
Lyons et al., 2009[116] S. haematobium 160 from north (highly endemic) and south (low endemic) of the individuals screened for S. haematobium and ultrasonographical examination of urinary tract morbidities. Individuals from endemic areas had higher urinary tract morbidities as compared to individuals from a low endemic area. Having two out of urgency urination, self reporting of previous infections and detection of eggs in urine were good proxy predictors of urinary tract morbidities as detected by ultrasound. Unguja
Sousa-Figueiredo et al., 2009[104] S. haematobium 147 school children and 47 adult men examined for S. haematobium prevalence and urinary tract pathologies. The prevalence of egg-patent urinary schistosomiasis was 36.4% and 46.8% and that of urinary tract pathologies was 39.4% and 64.4% respectively. In school-children, raised urine-albumin concentration (>40 mg/L) was not associated with the prevalence of S. haematobium but was strongly associated with the prevalence of micro-haematuria (76.7, P<0.0001). In adults, elevated urine-albumin excretion was associated with urinary tract pathologies, particularly lesions of the bladder was (OR=8.4, P= 0.013). Albuminuria was a good indicator of detecting lower urinary tract pathologies (bladder wall lesions). Unguja
Stothard et al., 2009[105] S. haematobium 66 children examined for urogenital schistosomiasis and urinary tract pathologies. Prevalence of egg-patent schistosomiasis was 65.2%, while 77.3% had micro-haematuria and 66.1% had at least one ultrasound-identified urinary tract pathology. Unguja
Massa et al., 2009[111]. S. haematobium and S. mansoni 585 children from the community and 555 children from school were examined for S. haematobium, S. mansoni and geohelminths. The prevalence of S. mansoni was 29.4% for children from the community and 26.8% for school children. For S. haematobium was 27.6% and 25.2% respectively. Umba division, Lushoto district, Tanga. Northern Tanzania.
Poggensee et al., 2000[120] S. haematobium 657 women examined for S. haematobium and the prevalence was 36% and median intensity of infection was 2.1eggs/10ml of urine. The proportion of schistosomiasis of the lower urinary tract on gynecological examination among 359 women was 37% and the proportion of their urinary schistosomiasis was 42%. Among the 134 women with Female Genital schistosomiasis, 56% had detectable eggs in urine. Cervical lesion occurred in 75% of the women with female genital schistosomiasis. Mwanga district, Kilimanjaro region, Northern Tanzania.
Downs et al., 2011[121] S. haematobium and S. mansoni 457 women aged 18–50 years were examined for female urogenital schistosomiasis. The prevalence of female genital schistosomiasis was 5% (ranged from 0% - 11%) and female urogenital schistosomiasis was associated with HIV infection and younger age. Overall HIV prevalence was 5.9% but was 17% among women with female urogenital schistosomiasis. A significant geographical clustering of schistosomiasis was observed: northern villages near Lake Victoria had more S. mansoni infections, and southern villages further from the lake had more S. haematobium. Sengerema and Misungwi districts, north-western Tanzania
Scheich et al., 2012[122] S. mansoni 360 schoolchildren (aged 6–17 years) were parasitologically and ultrasonographically examined, 62 % and 57.7% of males and female were infected with S. mansoni respectively. The infection intensity ranged from 1–2,440 epg with 32% having low grade, 53.2% having moderate and 14.8% having heavy infection intensities. On ultrasonographical examination, 90.7% had splenomegaly, 89.3% and 30.9% had right and left lobe hepatomegaly. Only 5.4% of the children had overt signs of portal fibrosis and 28.5% had portal vein dilatation. No association was observed between portal fibrosis and infection intensities. Ukerewe district, north-western Tanzania.
Stothard et al., 2012[66]   238 children from nine primary schools were examined for S. haematobium. The prevalence of micro-haematuria and egg-patent infection was 18.1% and 4.2% respectively. Females had higher prevalence of micro-haematuria compared to males. All egg-patent infections were of light-intensity (<10 eggs/10ml). No clear associations between infection prevalence and local water-contact, by school, were found and all 10 of the egg-positive children had a travel history to the nearby mainland or Zanzibar. Retrospective hospital data revealed a low proportion (< 2%) of egg-patent infections for 20,306 samples tested between the 2000–2005. Malacological survey revealed that four Bulinus species were common in the area (Bulinus nasutus, B. forskalii, B. barthi). No collected snail was observed to shed schistosome cercariae. Mafia district, Coastal region, Tanzania.