Selective population chemotherapy among schoolchildren in Beheira governorate: the UNICEF/Arab Republic of Egypt/WHO Schistosomiasis Control Project.

Selective population chemotherapy using a single dose of praziquantel (40 mg per kg body weight), which was offered to 29,365 schoolchildren in Abu El Matameer and 40,241 in Abo Homos districts, Beheira governorate in the Nile delta, reduced the prevalence of schistosomiasis from 75.4% to 40.9% (reduction of 45.8%) and from 80.5% to 30.8% (reduction of 61.7%), respectively. Of those with only S. mansoni infection, 10.6% before treatment and 1.7% one year later had more than 800 eggs per gram of faeces. The prevalence of S. haematobium in Abu El Matameer was reduced from 35.4% to 7.4% after a single treatment. Infections with both S. mansoni and S. haematobium were reduced by more than 90% after one year. These reductions in prevalence and intensity of schistosomiasis in the face of continuing transmission and water contact augur well for the future role of chemotherapy in control programmes.     

Schistosomiasis in Ethiopia

The literature on schistosomiasis in Ethiopia is reviewed with the objective of bringing together in one paper diverse sources which may not be available to those interested in schistosomiasis. Particular attention is given to the influence of altitude and climate, snail ecology and government economic programs on the distribution of schistosomiasis. Out of 365 communities studied between 1961 and 1986 for Schistosomiasis mansoni, cases were reported from 225 (62%), and in 85 (23%) the prevalence ranged from 10 to 92%. Most transmission sites and S. mansoni infections are in agricultural communities along streams between 1300 and 2000 m altitude infested with Biomphalaria pfeifferi, the major snail intermediate host. S. mansoni transmission above 2200 m and below 800 m is precluded in many parts of Ethiopia by low and high water temperatures, respectively. Schistosomiasis haematobium cases have been reported from 30 of the 54 communities studied, 17 of them with infection rates between 14 and 75%. Endemic S. haematobium appears to be confined in its distribution to lowlands below 800 m altitude. The highly focal distribution of S. haematobium transmission is largely due to the nonsusceptibility of most bulinine snails to the Ethiopian strain of the parasite and low water temperatures in the highlands. Water resources development, resettlement programs, refugee migration and other population movements may result in the spread of endemic S. mansoni. Lack of information on snail host/parasite relationships and the ecology of proven and suspected snail hosts does not permit predictions on the spread of endemic S. haematobium. Past and present schistosomiasis control programs in Ethiopia are reviewed and recommendations made for the national control program.     

Bilharziasis in Swaziland

Although no full-scale survey of the prevalence of bilharziasis in Swaziland has been carried out, examinations of schoolchildren have revealed S. mansoni infection rates of up to 49% in some areas, and S. haematobium infection rates ranging from 3% to 75%. The highest prevalence occurs in areas where there are thickly populated African reserves, or irrigation schemes. The spread of infection is encouraged by the use of rivers, dams and canals for bathing and washing purposes. Preventive measures are recommended, including the provision of more suitable bathing, washing and latrine facilities for the population, the control of waste waters, and the use of molluscicides.     

Changes in human schistosomiasis levels after the construction of two large hydroelectric dams in central C?te d'Ivoire.

The construction of large dams has been shown to increase the prevalence and intensity of human schistosomiasis. However, until now no study had been carried out to assess the impact of such a project in Côte d''Ivoire. For Kossou and Taabo, two large dams which became operational in the 1970s, baseline data are available on schistosomiasis prevalence in the surrounding area before dam construction, so that the changes in schistosomiasis levels can be assessed. We re-evaluated the prevalence of Schistosoma haematobium and S. mansoni in November 1992, by analysing 548 urine and 255 stool samples, respectively, from schoolchildren from five villages around each lake. A marked increase in the overall prevalence of S. haematobium was observed, from 14% to 53% around Lake Kossou and from 0 to 73% around Lake Taabo. Baseline data for S. mansoni are only available for Lake Taabo, where a prevalence of 3% was found in 1979 and where the prevalence in 1992 was still low at 2%. The construction of these two large dams therefore led to little change in S. mansoni prevalence but to a significant increase in that of S. haematobium.     

Macro-epidemiologic aspects of schistosomiasis mansoni: analysis of the impacts of irrigation systems on the spatial profile of the endemic in Bahia,Brazil

Studies in African countries have shown an association between irrigation projects and the spread of schistosomiasis mansoni and haematobium. The aim of this study was to investigate the potential association between irrigation levels and the occurrence and spread of Schistosoma mansoni infection in the State of Bahia. Two forms of irrigation were developed in the State of Bahia: the first is capital-intensive and mechanized, requiring little manual labor. The second is labor-intensive and characterized by limited mechanization. According to the study, the municipalities with the largest irrigated areas are not the ones with the highest S. mansoni infection rates. In most of these counties, irrigation is capital- and technology intensive. According to the findings, unlike Africa, in the State of Bahia irrigation has had little impact on the spatial profile of the schistosomiasis endemic.     

Schistosomiasis control in Saudi Arabia with special reference to the period 1983–1988

Schistosomiasis control operations carried out between 1983 and 1988 are described, together with information of the impact of schistosomiasis. The prevalence of schistosomiasis has declined from 9.5% in 1983 to 1.8% in 1988 (P less than 0.05). Bulinus truncatus, B. beccarii, and B. reticulatus wrighti are the intermediate hosts of S. haematobium in Saudi Arabia and are distributed unevenly in the different regions. Biomphalaria arabica is the intermediate host of S. mansoni and is found wherever the disease is endemic. The influx of expatriate workers from countries where schistosomiasis is endemic, inaccessible water sources, the constant movement of large numbers of bedouins in some regions, and manpower shortages in some regions are considered to be the main obstacles for schistosomiasis control programmes in Saudi Arabia.     

Emergence of Schistosoma mansoni in the Niger River valley, Niger

Urinary and intestinal schistosomiasis are both endemic in Niger with a dominance of Schistosoma haematobium. This study pointed out the appearance of the infection to S. mansoni in the Niger River valley, where it was until then unknown in Niger. In one year the prevalence increased from 5.9 to 19.5%.     

Differences in the rate of hepatosplenomegaly due to Schistosoma mansoni infection between two areas in Machakos District, Kenya.

The relationship between intensity of Schistosoma mansoni infection and the degree of related morbidity was suspected to differ locally within the Machakos district of Kenya. To test this possibility, prevalences of hepatomegaly and splenomegaly among 1483 school children were compared between 2 areas, Kangundo and Kambu, within this district. These areas, which were similar in many geographical and economic respects and populated by the same tribe (Akamba), had comparable levels of S. mansoni infection and no S. haematobium infection. A relationship was observed between the prevalence of hepatomegaly and intensity of S. mansoni infection, which showed no consistent difference between the 2 areas. In contrast, a relationship between the prevalence of splenomegaly and intensity of S. mansoni infection was observed only in the Kambu schools, and not in the Kangundo schools where the overall prevalence of splenomegaly was much lower. It was possible that part of the splenomegaly observed in Kambu was due to malaria. However, the observation that malaria and schistosomiasis in 2 Kambu schools were not positively correlated allowed approximations to be made of the relative contributions of each to the prevalence of splenomegaly. It was concluded that, in a school close to the river that formed the main transmission site of S. mansoni, schistosomiasis-related hepatosplenomegaly was present in at least 17% of children. The reason for the high prevalence in Kambu of hepatosplenic schistosomiasis remains uncertain, but it could include a synergistic interaction of schistosome infection with malaria.     

Irrigation,farming and schistosomiasis: A case study in the Nile delta

Schistosomiasis has long been a serious rural health problem in Egypt. Changing irrigation systems are recognized as affecting the distribution of Schistosoma haematobium and S. Mansoni and its snail vectors. In the Nile delta, although the proportion of full-time farmers is declining, an increasing number of women and men are part-time farmers and may be exposed to schistosomiasis. Epidemiological data from two villages indicate that full-time and part-time farmers, both men and women, have relatively high rates of infection with S. mansoni. Water contact studies identify the exposure patterns associated directly with irrigation, and with washing after farm work and cleaning vegetables in the canals. Farmers are aware of the risk of exposure during farming yet feel that they have no alternative but to come into contact with canal water during irrigation. Data on the distribution of the snail vector, and water quality, show that infection in canals flowing through fields in the study villages is possible. Interventions to protect farmers from schistosomiasis include community supported cleaning of canals, health education targeting farmers and improving treatment strategies. In one study village the modification of the water flow of canals may be feasible. In all settings intersectoral collaboration is essential for effective disease control.     

Studies on schistosomiasis in the Niger Delta: Schistosoma intercalatum in the urban city of Port Harcourt, Nigeria

Ova of S. intercalatum have been found in the urban city of Port Harcourt in the Niger Delta area of Nigeria, following examination of stool and urine samples from 1,709 persons (5-15 years of age) resident in various parts of the city. The ova occurred only in urine, with prevalence ranging from 1.0% to 9.8% with an overall prevalence of 5.7%. The intensity of the infection was low. Most infected individuals had counts of less than 500 ova in total bladder content. There was no significant difference in either the prevalence or intensity of the infection among the sexes (Male; prevalence 6.1%, intensity 527.3 vs Female; prevalence 5.4%, intensity 500.9). No case of infection with either S. haematobium or S. mansoni was encountered in the study. Malacological surveys in the gutters, creeks, streams and stagnant waterbodies within the city showed the presence of Lymnaea natalensis, Bulinus forskalii, Pila ovata, Melanoides tuberculata, Physa sp., Lanistes ovum and Segmentorbis sp. B. forskalii is indicated as the probable vector of S. intercalatum in the city. The growing problem of urban schistosomiasis in tropical Africa is discussed. Further studies on urban transmission and epidemiology of schistosomiasis in the Niger Delta area of Nigeria is also indicated.     

Cross sectional study of schistosomiasis among military recruits in Alexandria.

A cross-sectional survey for schistosomiasis infection was carried out among 1170 military recruits in Alexandria. Data on prevalence-intensity of infection-subjective symptoms and history of antischistosomal chemotherapy administration were collected from participants. The results confirmed the endemicity of S. mansoni and the low prevalence of S. haematobium infection in Delta region (33.1% and 1.1%) respectively. Previous antischistosomal chemotherapy administration was associated with decreased geometric mean egg count inspite the increase in prevalence. It is recommended that mass chemotherapy with praziquantel of this young active adult group would be of beneficial effect in decreasing schistosomiasis morbidity among an important large section of the community.     

Questionnaires for rapid screening of schistosomiasis in sub-Saharan Africa

New initiatives are aiming to reduce the global burden of schistosomiasis, mainly through the large-scale application of chemotherapy. To target chemotherapy effectively, rapid assessment procedures are needed for identifying high-risk communities that are foci for the disease. In this review, we examine the development and validation of simple school questionnaires for screening communities for Schistosoma haematobium and S. mansoni rapidly and inexpensively. The focus is on sub-Saharan Africa, where 85% of the current schistosomiasis burden is concentrated. For more than a decade, the questionnaire approach has been validated in 10 countries, with 133 880 children interviewed in 1282 schools, and with 54 996 children examined for S. haematobium. The questionnaires were well accepted, highly reliable, and of low cost. The success of the questionnaires is explained by the fact that S. haematobium infections were easily perceived through the presence of blood in urine. Evidence from 48 258 children interviewed in 545 schools indicated that reported blood in stools and bloody diarrhoea are valuable indicators for community diagnosis of S. mansoni. However, the diagnostic performance of the questionnaires for S. mansoni was weaker than for S. haematobium, and although these results are encouraging, the questionnaires need additional validation. Recently, questionnaires were extended from community to individual diagnosis and showed considerable promise. Questionnaires are now available for promptly defining the magnitude of schistosomiasis in a large area, which will allow limited resources for morbidity control to be allocated optimally.     

Sonographic studies of schoolchildren in a village endemic for Schistosoma mansoni

Parasitological, clinical, and sonographic examinations were performed on 309 school children in a village endemic for schistosomiasis mansoni. Data from the 255 denying treatment within the previous 2 years were analysed separately. On a single Kato examination 42% were uninfected; the remainder had light (26%), moderate (21%), or heavy (11%) infections with Schistosoma mansoni. Hepatomegaly (53%) and palpable spleens (35%) were common but clinical and parasitological findings often were unrelated. Abdominal sonography also demonstrated a high frequency of hepatomegaly (82%) and splenomegaly (49%). Sonographically determined liver span and spleen size correlated with the egg count. Sonographic lesions of periportal fibrosis of schistosomiasis mansoni with thickening of portal tracts and portal vein walls were frequently present and more common in infected than in uninfected children, and were correlated with the number of S. mansoni ova in the stool. Ultrasonographically detected periportal fibrosis was a reliable measurement of the prevalence and morbidity of schistosomiasis mansoni in this population, and provided very useful information, even when the parasitological and clinical findings were equivocal.     

Screening of Tanzanian women of childbearing age for urinary schistosomiasis: validity of urine reagent strip readings and self-reported symptoms

The screening of women of childbearing age for haematuria, leukocyturia and proteinuria to detect urinary schistosomiasis can be confounded by several factors such as menstruation, pregnancy and genitourinary infections. We therefore undertook a study in an area endemic for Schistosoma haematobium in the United Republic of Tanzania to carry out the following: assess the sensitivity, specificity and predictive values--in women of childbearing age--of indirect indicators of urinary schistosomiasis, as measured by urine reagent strip readings; assess the predictive values of self-reported symptoms; and finally to estimate the morbidity attributable to S. haematobium. A total of 303 women (128 and 175, respectively, living in high- and low-risk sites) participated in the study. Haematuria was more frequent among women excreting S. haematobium eggs than among those who did not (65% versus 32%). The predictive potential of all indirect disease markers was poor in the highly endemic site, while in the sites with low endemicity the negative predictive values were high. Among infected women, 54% of haematuria could be attributed to S. haematobium, but for patients with more than 10 eggs/10 ml the attributable fraction rose to 70%. Symptoms of "bloody urine" and "pain while urinating" were recalled significantly more often by women living in the highly endemic site. On a population level, one-third of the self-reported cases with bloody urine could be attributed to urinary schistosomiasis. Screening of women of childbearing age for urinary schistosomiasis using urine reagent strips can be biased in two directions. The prevalence of S. haematobium will be overestimated if other causes of haematuria, such as reproductive tract infections, are highly endemic. On the other hand, women with light or very light infections will be missed and will not be treated. This is of concern because genital schistosomiasis, a possible risk factor for the transmission of HIV, occurs among women even with light infections.     

Patterns of concurrent hookworm infection and schistosomiasis in schoolchildren in Tanzania

A cross-sectional study of 6897 schoolchildren in 59 out of the 155 primary schools in Magu District on the shores of Lake Victoria, Tanzania, was undertaken in 1997 to determine the prevalence of single- and multiple-species helminth infection. Schistosoma haematobium, hookworm (primarily Necator americanus) and S. mansoni were the most common helminth species infecting schoolchildren in the district. The prevalences of Ascaris lumbricoides and Trichuris trichiura were negligible (< 1%). Anaemia and stunting were highly prevalent and widespread. Hookworm and S. mansoni occurred more frequently in multiple infections with other helminths than as single-species infections, but triple-species infection was rare. Analysis of the frequency distribution of infection amongst schools showed that prevalences of S. haematobium and hookworm tended to be normally distributed, with medians 75% and 45%, respectively, while the distribution of S. mansoni was markedly skewed such that only 17% schools had a prevalence greater than 20%. An inverse association between S. mansoni and S. haematobium was observed. Geographical information system (GIS) analysis indicated that S. mansoni infection was highly prevalent only along the shore of Lake Victoria, whilst S. haematobium was homogeneously prevalent everywhere except the lakeshore. This pattern appears to reflect the distribution of schistosome species-specific snail intermediate hosts. The results imply that joint treatment for hookworm infection and schistosomiasis would be beneficial throughout the district.     

Water resources development and schistosomiasis ecology in the Awash Valley, Ethiopia

This paper examines the impact of water resources development, particularly river regulation and irrigated agriculture, on the occurrence of schistosomiasis and its intermediate host snails in the Awash Valley. An ecologic-geographic approach based on: a combination of comparative schistosomiasis prevalence and human ecological studies of indigenous seminomadic pastoralists and migrant laborers from the Ethiopian highlands; analysis of snail intermediate host ecology-geography; and longitudinal studies of water resources development, is used to evaluate the endemicity status and changing spatial distribution of schistosomiasis mansoni and schistosomiasis haematobium. This study confirms the suitability of epidemiologic-ecologic methods for analyzing relationships between causal processes and the spatiality of schistosomiasis. In this context local schistosomiasis control programs are reviewed and recommendations made for their improvements.     

Preliminary evaluation of morbidity due to S. haematobium and S. mansoni in the area of the future Adjarala Dam in Benin

The aim of this study was to provide a preliminary assessment of morbidity due to schistosomiasis in the area of the future Adjarala Dam in Benin. We included 412 schoolchildren from five villages in the study. The mean age of the children was 9.4 +/- 2.3 years and the sex ratio (F/M) was 0.94. These children underwent parasitological examination. The children provided urine samples, which were examined by eye, filtered and tested for blood and protein. Stool samples were examined using Kato's technique and an ultrasound scan of the urinary tract was performed. We carried out a survey of snails at the possible transmission sites of all the villages, with a view to identifying the intermediate hosts. We detected S. mansoni and S. haematobium in the area. Urinary schistosomiasis was mesoendemic (prevalence of 19.7%) whereas schistosomiasis due to S. mansoni was hypoendemic (prevalence of 3. 9%). Ultrasound scans showed that 28% of the children had bladder lesions and that 2.5% were carriers of hydronephrosis. We compared the diagnostic performances of the various indirect indicators of morbidity. We found that a history of hematuria was the most sensitive indicator (88%) but that the sensitivity of this indicator differed significantly according to the sex of the child. Hematuria >= 1+ was the most effective indicator. Snail surveys showed that Biomphalaria pfeifferi and Bulinus globosus were present in the area.     

The epidemiology of schistosomiasis in the later stages of a control programme based on chemotherapy: the Basrah study. 1. Descriptive epidemiology and parasitological results

The association between infection with Schistosoma haematobium and various factors including water contact pattern, past history of haematuria and treatment for schistosomiasis and cercarial dermatitis was investigated in Southern Iraq. The study covered mainly primary schoolchildren in different areas of Basrah and in Al-maadan locality where the majority of households with infected schoolchildren occurred. Urine examination was by the sedimentation and Nuclepore filtration methods. S. haematobium infection was very focal in distribution. There was evidence of local transmission in the Al-maadan locality, while in Abu-al-Jawzi schistosomiasis might have been acquired from endemic areas outside Basrah governorate. Swimming, history of haematuria, and history of treatment of schistosomiasis were significantly associated with the level of infection determined by egg count. Cercarial dermatitis, and bathing, washing clothes and fetching water were not significantly associated. The prevalence of infection among male members of households of infected children was significantly higher than that among male members of the remaining households in Al-maadan. There was no evidence of clustering of cases at household level. The implications of these findings for control and for future research on schistosomiasis in Basrah are discussed.     

Water demand and schistosomiasis among the Gumau people of Bauchi State, Nigeria

A helminthological study of stool and urine samples from 1037 people from 4 rural communities in Gumau District of Bauchi State, Nigeria, was carried out using formol-ether concentration and direct centrifugation methods respectively. 39.0% of persons examined were infected. Ova of Ascaris lumbricoides, Schistosoma haematobium and S. mansoni were the most common. Trichuris trichiura, hookworm, tapeworm and Strongyloides stercoralis were also encountered. 17.9% and 10.8% of examined persons had S. haematobium and S. mansoni infections respectively. A significant relationship was found between water demand index (number of persons per well) and infection with S. haematobium (r = 0.95) and S. mansoni (r = 0.88) (P less than 0.01). Such a relationship was not found with other helminth infections. A significant association was also found between distance from a river and prevalence of S. haematobium (r = 0.94) and S. mansoni (r = 0.95) (P less than 0.01), but not with the other helminth infections. These findings suggest that the water demand index may be an important factor in the epidemiology of schistosome infections in rural communities.     

Schistosomiasis control in Ghana: case management and means for diagnosis and treatment within the health system

An essential component of integrated schistosomiasis control as promoted by WHO is adequate clinical care for patients presenting at health care facilities. We evaluated the functioning of the Ghanaian health system for diagnosis and treatment of schistosomiasis by interviewing health workers from 70 health care facilities in 4 geographical areas in April and May 2000. Results from presentation of 4 hypothetical cases and a subsequent interview demonstrated that patients presenting with symptoms related to schistosomiasis have a small chance of receiving adequate treatment: often health workers do not recognize the symptoms, especially those of Schistosoma mansoni; patients are frequently referred for a diagnostic test or treatment with a large risk of non-compliance; and praziquantel was not available in 78% of the health care facilities with reported schistosomiasis in their coverage area. The overall cost of treatment is considerable: [symbol: see text] 2.13 for S. haematobium and [symbol: see text] 1.81 for S. mansoni patients, with drug costs contributing approximately 40% of the total cost. To better meet WHO recommendations for passive case detection as part of integrated schistosomiasis control, the Ghanaian health system needs to emphasize training of health workers in schistosomiasis case recognition and case management and increase the availability of praziquantel. Experience from other West African countries indicate that this is feasible.