Questionnaires for rapid screening of schistosomiasis in sub-Saharan Africa.

Public Health Reviews Questionnaires for rapid screening of schistosomiasis in sub-Saharan Africa Christian Lengeler,1 Ju¨rg Utzinger,2 & Marcel Tanner3 Abstract 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. Keywords Schistosomiasis haematobia/diagnosis; Schistosomiasis mansoni/diagnosis; Risk assessment; Questionnaires; Africa South of the Sahara (source: MeSH, NLM). Mots cle´s Schistosomiase urinaire/diagnostic; Schistosomiase intestinale/diagnostic; Evaluation risque; Questionnaires; Afrique subsaharienne (source: MeSH, INSERM). Palabras clave Esquistosomiasis haematobia/diagno´stico; Esquistosomiasis mansoni/diagno´stico; Medicio´n de riesgo; Cuestio- narios, Africa del Sur del Sahara (fuente: DeCS, BIREME ). Bulletin of the World Health Organization 2002;80:235-242 Voir page 240 le re´sume´ en franc¸ais. En la pa´gina 241 figura un resumen en espan˜ol. Introduction Schistosomiasis is a widespread parasitic disease of the tropics that places an enormous toll on the public health of affected regions. Of the 200million people infected worldwide, 85% of the burden is concentrated in Africa south of the Sahara (1, 2). In most epidemiological settings, the intermediate host snails cannot be controlled by cost-effective interventions, and in the absence of a vaccine, schistosomiasis control largely relies on chemotherapy, with praziquantel as the drug of choice (1). An important feature of the disease is its focal distribution (3). This results in a patchy distribution of risk, and communities across a region or country do not attach the same importance to schistosomiasis. Praziquantel is therefore not required every- where and proper targeting is crucial, given the limited resources and the many other problems facing primary health care systems in sub-Saharan Africa. The first step in targeting health interventions is to map the disease geographically and rank it according to the risk of infection and morbidity. In 1987, the first attempt to systematically map schistosomiasis on a global scale resulted in the Atlas of the global distribution of schistosomiasis (4). A more recent effort using geographical information systems high- lighted the scarcity of data for Africa (5), and underscored the need for a rapid and inexpensive epidemiological assessment tool that can be fully integrated within existing administrative systems. Such a tool, relying on simple school questionnaires, was developed more than a decade ago for Schistosoma haematobium and has since been validated in a variety of ecological, epidemiological, and sociocultural settings across sub-Saharan Africa. More recently, the approach was extended to S. mansoni and its validity assessed in several large-scale studies. 1 Project Leader, Swiss Tropical Institute, Department of Epidemiology and Public Health, PO Box, CH-4002 Basel, Switzerland (email: christian.lengeler@unibas.ch). Correspondence should be addressed to this author. 2 Visiting Research Fellow, Princeton University, Office of Population Research, Princeton, NJ 08544, USA. 3 Professor and Director of the Swiss Tropical Institute, Basel, Switzerland. Ref. No. 01-1496 235Bulletin of the World Health Organization 2002, 80 (3) # World Health Organization 2002 This article is a comprehensive review of the experiences and evidence from sub-Saharan Africa with questionnaires for rapidly screening for schistosomiasis. The questionnaires can be used at both community and individual levels, and this approach allows communities with a high risk of schisto- somiasis to be identified. Resources for controlling the parasite can thus be allocated in a more cost-effective way (6). We also discuss how this tool will contribute to a more sustainable and integrated system of control of schistosomiasis. Questionnaires for diagnosing Schistosoma haematobium infection at a community level The presence of blood in urine (haematuria) has been associated with S. haematobium infection since ancient times, but its use as an indirect indicator for this parasite was first investigated only two decades ago, in a study that simply asked community members living in Ghana and Zambia about their history of haematuria. These studies showed that haematuria was promising as an indirect indicator, but there was considerable variation in its diagnostic performance between the two settings (7). Urinary schistosomiasis as illness was well perceived and correlated with infection in a rural community of the Kilombero District in the United Republic of Tanzania in the mid-1980s (8, 9). As a result, a district-wide study that emphasized rapid and inexpensive community diagnosis was initiated in 1986. The study aimed to identify high-risk communities, rather than infected individuals, because the highest priority for control was to target praziquantel chemotherapy in areas at greatest risk. A simple question- naire that asked respondents whether they had experienced any of eight symptoms and eight diseases common in the area was developed and administered to all primary schools through the existing education system (10). The key features of this questionnaire are described in Box 1 (11, 12). Within six weeks, 75 of 77 schools returned completed question- naires with a total of 6772 children interviewed. A mobile laboratory team then visited 56 schools for parasitological validation. A comparison between the questionnaires and the parasitological data revealed a striking correlation. The percentage of positive answers to the two key questions ‘‘Did you have blood in urine during the last month?’’ and ‘‘Did you suffer from schistosomiasis during the last month?’’ showed significant positive associations with the prevalence of S. haematobium (for both questions: r = 0.90, P < 0.0001). The questionnaire showed a good diagnostic performance, with a moderate positive and a high negative predictive value. It identified most schools where S. haematobium was of high importance and correctly excluded those schools where the parasite was less of a problem (Table 1). The questionnaire approach was also rapid and cost 20-fold less than standard parasitological examinations. In 1988, the questionnaire approach was successfully replicated in the neighbouring district of Kilosa. In this study, biomedical validation of the questionnaires was carried out by teachers whowere trained in reagent-stick testing during a one- day workshop. The questionnaire showed an excellent diagnostic performance with high predictive values (Table 1). The study confirmed that the questionnaire approach was rapid and low-cost (14). Table 1. The performance of questionnaires for screening for Schistosoma haematobium infections at the community level Country (district) Parasite Questionnaire No. of No. of Best question Diagnostic performance Reference prevalence return ratea children children (thresholdb % % interviewed examined as %) Sensitivity Specificity PPVc NPVd Cameroon 63.6 106/113 (94) 8281 6151e Blood in urine (20) 98 35 75 88 13 United Republic of Tanzania (Kilosa) 60.5 164/168 (98) 15 073 5750f Schistosomiasis (35) 90 91 88 93 14 United Republic of Tanzania (Magu) 57.8 134/155 (86) 29 233 3928g Blood in urine (30) 89 80 92 75 15 Malawi 56.6 85/113 (75) 7201 4841e Schistosomiasis (30) 93 46 67 85 13, 16 Zimbabwe 46.1 110/121 (91) 16 063 5647e Schistosomiasis (25) 92 57 71 87 13, 17 Nigeria 43.7 58/60 (97) 3033 2479f Blood in urine (40) 73 96 89 90 18 Zambia 34.8 87/93 (94) 7875 4833e Blood in urine (20) 71 73 52 85 13 Coˆte d’Ivoire 24.6 124/136 (91) 12 479 5959e Blood in urine (33) 87 96 87 96 19 United Republic of Tanzania (Kilombero) 21.4 75/77 (97) 6772 4469g Blood in urine (25) 100 82 31 100 10 Democratic Republic of the Congo 20.2 136/160 (85) 19 362 2495e Blood in urine (15) 86 86 71 94 13, 20 Congo 18.3 58/58 (100) 5590 5842e Blood in urine (7) 93 82 64 97 13 Ethiopia 17.5 28/28 (100) 2918 2602h Pain when urinating (8) 75 58 64 70 13, 21 a Number of questionnaires completed/number of questionnaires returned by schools. Figures in parentheses are percentages. b The threshold is the percentage of ‘‘yes’’ replies to the question that will classify the school as being at high risk, according to the questionnaire. c PPV = positive predictive value. d NPV = negative predictive value. e Reagent-stick testing by teachers; diagnostic performance calculated at a microhaematuria level of 1+ (1+ or above are positives)’’. f Reagent-stick testing by teachers; diagnostic performance calculated at a microhaematuria level of 2+. g Urine filtration by research team. h Reagent-stick testing by research team; diagnostic performance calculated at a microhaematuria level of 1+. 236 Bulletin of the World Health Organization 2002, 80 (3) Public Health Reviews Between 1990 and 1992, a multicountry initiative was carried out to validate the questionnaire approach more extensively. The initiative was supported financially by the United Nations Development Programme/World Bank/ WHO Special Programme for Research and Training in Tropical Diseases (TDR), and it used a standardized questionnaire in areas that were endemic for S. haematobium and that had many different ecological and sociocultural features. The participating countries were Cameroon, Congo, Democratic Republic of the Congo, Ethiopia,Malawi, Zambia, and Zimbabwe (13, 16, 17, 20, 21). More recently, similar questionnaires were validated in Coˆte d’Ivoire (19), Nigeria (18), and in the Magu and Muheza districts of the United Republic of Tanzania (15, 22, 23). In summary, a total of 133 880 children were interviewed in 1282 schools, and 54 996 children were screened using urine filtration and/or reagent-stick testing. In all countries except one, questionnaires proved to be accurate, well accepted, operationally feasible (school return rates: 75–100%), and of low-cost (Table 1). Positive predictive values ranged from 31% to 92% (median: 71%) and negative predictive values from 75% to 100% (median: 89%). The school system proved to be outstanding for this task, despite sociopolitical crises and conflicts in some of the countries. Ethiopia was the only countrywhere the diagnostic performance of the questionnaire was deemed insufficient for large-scale application (although the results for the question ‘‘Did you have pain while urinating?’’ were moderately good). This was explained by the low awareness of schistosomiasis (the study population had recently immigrated from non-endemic highlands) (13, 21). At country level, there was also a strong relationship between the overall prevalence of S. haematobium and the percentage of positive answers to ‘‘Did you have blood in urine?’’ and ‘‘Did you have schistosomiasis?’’. Regression analysis of 12 studies carried out in Africa revealed a highly significant correlation between the overall prevalence of S. haematobium and the prevalence of reported blood in urine (r = 0.90, P < 0.001; Fig. 1a), as well as reported schisto- somiasis (r = 0.88, P < 0.001; Fig. 1b). In most settings, a second questionnaire aimed at teachers was distributed with the questionnaire addressed to children. In the United Republic of Tanzania, a third questionnaire was addressed to community leaders (10). The questionnaires for teachers and community leaders inquired about priorities among health problems, as well as the priority of health among other issues in the community. This simple approach clearly demonstrated the proposed link between schistosomiasis endemicity and its priority for control (13, 24). Interestingly, the threshold at which schistosomiasis became a top health priority (rank: 1–3) was around an infection prevalence of 50%,which is also the high-endemicity threshold suggested by WHO (25). Questionnaires for diagnosing Schistosoma haematobium infection in individuals Recent studies investigated whether the questionnaire approach could be adapted for diagnosing S. haematobium in individuals, to see if chemotherapy could be targeted more selectively. Recent evidence from Egypt, Ghana, Nigeria, and theUnited Republic of Tanzania suggested that reported blood in urine and reported schistosomiasis were also useful indicators for individual infection status (10, 15, 22, 23, 26– 29). Although questionnaires alone missed a significant proportion of infected children, most of those missed had light infections, so this might not be a problem for a morbidity control programme. Two studies carried out in the United Republic of Tanzania observed that girls were more likely to be missed than boys (15, 23). This confirmed previous reports of under- reporting of blood in urine and schistosomiasis by girls at school level from Cameroon, the Democratic Republic of the Congo, andMalawi (13), and from the island of Pemba, United Republic of Tanzania (30). As a result, the sensitivity and specificity of questionnaires may differ by sex (15, 23), just as it may differ by age and overall endemicity. These factors need to be taken into account when planning large-scale screening, and appropriate questionnaire cut-offs should be selected. Finally, it is unclear how the questionnaire approach would work over time. For example, once the children become aware that receiving treatment depends on the answer to a single question, the potential for response bias is obviously high. Schistosoma mansoni illness For intestinal schistosomiasis due to S. mansoni there are no simple, sensitive, and specific signs or symptoms. Several epidemiological and hospital-based studies have been carried 237Bulletin of the World Health Organization 2002, 80 (3) Questionnaires for rapid screening of schistosomiasis out in sub-Saharan Africa to relate clinical symptoms and perceived morbidity indicators to S. mansoni infection. Study participants were usually interviewed with a standardized clinical questionnaire, followed by the examination of one or more stool specimens to assess infection intensity. These studies found that S. mansoni infections (especially those which were moderate and heavy) were frequently associated with abdominal pain, blood in stool, (bloody) diarrhoea, colicky cramps, hepatomegaly, and splenomegaly (31, 32). The most consistent finding was the association between a recent history of blood in stools and an S. mansoni infection, especially in individuals with more than 100 eggs/g stool (33–44). We reanalysed the data of these previous studies and found the diagnostic performance of reported and/or observed blood in stool had a low-to-moderate sensitivity (7–66%, median: 16%) and usually a high specificity (54– 96%, median: 94%). These factors resulted in a moderate-to- high positive predictive value for blood in stool (20–88%, median: 64%) and in general a moderate negative predictive value (32–95%, median: 59%) (Table 2). There was considerable variation in the results, which may have stemmed from factors such as the overall prevalence and intensity of infection, individual disease perception and the reference diagnostic techniques used for validation. In two studies, a significant association was also found between reported bloody diarrhoea and S. mansoni (45, 46). For practical applications, the low sensitivity of this approach is a concern, although it remains to be seen what percentage of heavy infections can be detected. Questionnaires for diagnosing Schistosoma mansoni in a community Given the findings on S. mansoni above, and in view of the wide distribution and public health significance of S. mansoni, it was essential to develop and validate questionnaires for rapidly screening for this species. In the first study, in an area of the Democratic Republic of the Congo with mixed S. haematobium and S. mansoni infections, the correlation between the prevalence of reported blood in stools and S. mansoni was moderate, with an adjusted correlation coefficient of 0.33 (P<0.02) (13, 20). Interestingly, the adjusted correlation coefficient was much better for reported schistosomiasis (r = 0.61, P<0.001). Consequently, reported schistosomiasis gave a better diagnostic performance at community level than reported blood in stools (Table 3). Following a promising pilot study carried out in 10 schools in Ethiopia (49), a large-scale study was initiated in the Gondar region, which found an excellent diagnostic performance for both reported blood in stools and schisto- somiasis (44) (Table 3). Another study was carried out in 30 schools of theMorogoro rural district of theUnited Republic of Tanzania (26), but since only two schools had an S. mansoni prevalence above 10%, the results are not reported here. A series of studies were carried out in western Coˆte d’Ivoire, in an area known to be endemic for S. mansoni. A pilot study in three villages investigated common signs and symptoms by conducting focus group discussions with the most heavily infected children. Blood in stool and bloody Table 2. Diagnostic performance of reported and/or observed blood in stool and reported and/or observed bloody diarrhoea for identifying S. mansoni infection Reported and/or observed S. mansoni No. of Diagnostic performance % Reference symptom and country prevalence % subjects (district) Sensitivity Specificity PPVa NPVb Blood in stool Coˆte d’Ivoirec 92.3 209 47 76 66 60 38 Ugandad 89.4 173 66 54 79 38 33 Ethiopiae 88.2 272 13 93 80 32 36 Kenyaf 82.5 416 19 93 76 49 34 Zambiag 63.2 703 17 95 88 33 37 Ethiopiag 43.3 197 15 96 78 55 35 Egypt (Ismailia)h 42.9 6864 15 93 62 59 43 Egypt (Kafr el-Sheikh)h 39.3 1109 24 87 55 63 40 Egypt (Gharbia)h 37.7 1884 9 95 57 57 41 Egypt (Menofia)h 28.5 1477 18 94 55 73 39 Ethiopiah 20.9 8006 52 90 58 88 44 Egypt (Qalyubia)h 17.5 1059 7 96 27 81 42 United Republic of Tanzaniag 5.8 4130 15 96 20 95 26 Bloody diarrhoea Sudani 48.2 1748 39 83 68 59 45 Burundih 32.8 6203 13 95 56 69 46 a See footnote c, Table 1. b See footnote d, Table 1. c Kato–Katz thick smears (4 stool specimens, 1 slide each); threshold for calculating diagnostic performance = 100 eggs/g stool. d Concentration/filtration method (1 stool specimen, 2 slides); threshold for calculating diagnostic performance = 100 eggs/g stool. e Kato–Katz thick smears (1 stool specimen, 1 slide); threshold for calculating diagnostic performance = 100 eggs/g stool. f Kato–Katz thick smears (1 stool specimen, 2 slides ); threshold for calculating diagnostic performance = 100 eggs/g stool. g Kato–Katz thick smears (1 stool specimen, 1 slide); threshold for calculating diagnostic performance = 1 egg/g stool. h Kato–Katz thick smears (1 stool specimen, 2 slides ); threshold for calculating diagnostic performance = 1 egg/g stool. i Concentration/filtration method (1 stool specimen, 1 slide); threshold for calculating diagnostic performance = 1 egg/g stool. 238 Bulletin of the World Health Organization 2002, 80 (3) Public Health Reviews diarrhoea were perceived as common symptoms, with three specific terms for these two symptoms known in the vernacular language. Comparisons between children’s re- sponses and their S. mansoni infection levels revealed that reported blood in stools showed the best diagnostic performance, especially for those children with more than 100 eggs/g stool (38). These findings were subsequently integrated into a large-scale screening. The percentage of positive answers to ‘‘Did you have blood in stool during the last month?’’ and ‘‘Did you have bloody diarrhoea during the last month?’’ were significantly associated with the prevalence of S. mansoni infection, but the diagnostic performance of these symptoms was only moderate (47). Finally, a recent study in Kenya collected pairwise questionnaire and parasitological data from 46 schools. The results confirmed that reported blood in stools was significantly correlated with the prevalence of S. mansoni infection (48), but the diagnostic performance was only moderate (Table 3), in accordance with previous findings from Coˆte d’Ivoire (47). In summary, 48 258 children were interviewed for the presence of S. mansoni in 545 schools, using simple questionnaires. The diagnostic performance of the question- naires was weaker for S. mansoni than for S. haematobium, and although the results are encouraging, additional validation is needed before this approach can be used in a given setting. Extensions of the questionnaire approach The results described inspired more work in sub-Saharan Africa, South America, and Asia that focused on detecting high-risk individuals. It was suggested that questionnaires for S. mansoni screening might be improved by adding a wider range of risk factors for infection, such as migratory status, frequency and nature of water-contact patterns, and history of previous schistosomiasis treatment. This approach was under- taken in Brazil (50–53) and has recently been extended to Egypt (29), Coˆte d’Ivoire (54), and Kenya (48). The studies showed that the questionnaire approach had good potential for identifying infected individuals, but the questions were often very specific for a particular setting and their generalization remains questionable. Potentially useful, however, are recent findings from Kenya that schools located less than 5 km from the shore of Lake Victoria were at high risk for S. mansoni infection (prevalence >50%), whereas schools further away normally had lower infection prevalences (48). In China, a similar approach to screening for S. japonicum in schoolchildren showed a high sensitivity (86%) and specificity (98%), and the high-risk schoolchildren were identified by only three simple yes/no questions (concerning frequent water contact, frequent weakness, and frequent diarrhoea). If successfully validated in other endemic areas, this approach might be more widely applied in Chinese schisto- somiasis control programmes (55). Implications for schistosomiasis control Questionnaires to screen for communities at highest risk of S. haematobium and/or S. mansoni infection in sub-Saharan Africa are well accepted and operationally feasible, and are faster and less expensive than standard parasitological diagnoses. They build directly on a community’s perception of disease, involve the active participation of teachers and schoolchildren, and represent a first step towards involving the community in control activities. A ranked list of schools allows the schistosomiasis risk to be mapped and communities prioritized for control activities. From there, one approach is to decide on the number of schools or communities that will benefit from treatment, taking into account overall available resources. Another possibility is to define an intervention threshold, such as the prevalence of reported blood in urine of >30% (which Table 3. Diagnostic performance of selected signs and symptoms for the diagnosis of S. mansoni infection at the community level Country S. mansoni Questionnaire No. of No. of Threshold Questions Diagnostic performance Reference prevalence return children children or high- (thresholdc % % ratea interviewed examined risk as %) schoolsb Sensitivity Specificity PPVd NPVe Coˆte d’Ivoire 54.4 121/134 (90) 12 227 5047f 50 Blood in stool (22) 88 58 73 79 47 Bloody diarrhoea (14) 88 58 73 79 47 Schistosomiasis (4) 71 58 73 79 47 Democratic Republic of the Congo 31.2 136/160 (85) 19 362 5806g 50 Blood in stool (19) 62 77 44 87 20 Schistosomiasis (34) 62 89 62 87 20 Kenya 29.4 NAh 2913 2913i 50 Blood in stool (25) 60 78 43 88 48 Ethiopia 20.9 142/161 (88) 13 756 8006g 20 Blood in stool (15) 84 80 74 88 44 Schistosomiasis (15) 77 98 96 87 44 Bloody diarrhoea (25) 71 85 76 81 44 a See footnote a, Table 1. b The threshold for high-risk schools is the prevalence level at which a school is said to be at high risk. These are the schools that the questionnaire aims to identify. c See footnote b, Table 1. d See footnote c, Table 1. e See footnote d, Table 1. f Kato–Katz thick smears (2 stool specimens; 1 slide each). g Kato–Katz thick smears (1 stool specimen; 1 slide). h NA = not applicable. Questionnaires were not distributed; the work was done by the research team in 46 schools. i Kato–Katz thick smears (1 stool specimen; 2 slides). 239Bulletin of the World Health Organization 2002, 80 (3) Questionnaires for rapid screening of schistosomiasis often corresponds to an S. haematobium infection prevalence of >50%). When prevalence exceeds 50%, all schools or communities would benefit from specific control measures, for example, universal treatment with praziquantel (25). The evidence for using questionnaires to screen for S. haematobium is now compelling and guidelines have been developed for district health managers (12). Despite the extensive validation, it is still recommended that the diagnostic performance of questionnaires be assessed on a limited scale, either when the questionnaire has been significantly altered or when health authorities need to be convinced about the usefulness of this method (12). The use of large-scale screening with questionnaires to diagnose S. mansoni infections in a community could now be considered, but should always be undertaken after a validation step in the selected setting. Blood in stools, bloody diarrhoea, and suffering from schistosomiasis are valuable markers and can be recommended for screening. Other questions that are relevant to the setting, such as the distance from the lakeshore in the Kenyan study (48), should always be considered. A largely unexplored issue is the performance of the questionnaires in areas with mixed S. haematobium/S. mansoni infections since the answers to the question ‘‘Did you have schistosomiasis during the last month?’’ will be influenced by both infections. These areas represent a significant part of the African continent (4). This issue should always be explored first using available information, either from previous studies or from available health statistics. A simple way to investigate for mixed infections with questionnaires is to plot the answers to ‘‘Did you have schistosomiasis during the last month?’’ against those for ‘‘Did you have blood in urine during the last month?’’. In the presence of S. mansoni infections, the usual tight linear relationship will be altered by schools with a much higher percentage of reported ‘‘schistosomiasis’’ thanwould be expected, as has been demonstrated in the Democratic Republic of the Congo (20). Using questionnaires for programme monitoring is another application that has yet to be explored. It is difficult to predict how well questionnaires can work for this purpose, since effective control through chemotherapy will affect the prevalence and morbidity patterns. On Pemba Island, for example, repeated treatment substantially reduced the level of measured and perceived haematuria over two years, and this followed a similar decline in infection rates (56). Conclusions We have presented the successful development of a rapid assessment procedure that has public health significance. It is important to highlight the long time required for thorough validation. Development and validation of questionnaires has taught us much about how schistosomiasis is perceived by affected individuals and communities, and confirmed that the priority given to the disease is highly dependent on endemicity and morbidity. Questionnaires are now readily available for rapidly screening for schistosomiasis. We believe that novel large-scale control initiatives will find this tool useful as a first step towards defining the distribution and magnitude of the problem, and improving the implementa- tion of control measures by an evidence-based process of resource optimization. n Acknowledgements Most studies reviewed here received financial support from the United Nations Development Fund/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR). CL acknowledges support by the Swiss National Science Foundation (PROSPER grant 32-41632.94). JU is grateful to the SwissNational Science Foundation and the Centre for Health and Wellbeing at Princeton University. Conflicts of interest: none declared. Re´sume´ Questionnaires pour le de´pistage rapide de la schistosomiase en Afrique subsaharienne De nouvelles initiatives visent a` re´duire la charge mondiale de la schistosomiase, essentiellement par l’application de la chimio- the´rapie a` grande e´chelle. En vue d’un ciblage efficace de la chimiothe´rapie, il est ne´cessaire de disposer d’une me´thode d’e´valuation rapide pour identifier les communaute´s a` haut risque qui constituent des foyers de la maladie. Dans le pre´sent article, nous examinons l’e´tablissement et la validation de questionnaires scolaires simples destine´s a` de´pister de fac¸on rapide et peu couˆteuse les infections a` Schistosoma haematobium et a` S. mansoni dans la communaute´. Ces questionnaires s’adressent surtout a` l’Afrique subsaharienne, qui regroupe actuellement 85 % de l’ensemble des cas de schistosomiase. Depuis plus de dix ans, l’approche par questionnaire a e´te´ valide´e dans dix pays, avec 133 880 enfants interroge´s dans 1282 e´coles et 54 996 examine´s a` la recherche de S. haemato- bium. Les questionnaires e´taient bien accepte´s, fiables et de faible couˆt. Le succe`s de l’utilisation des questionnaires s’explique par le fait que les infections a` S. haematobium sont facilement perc¸ues par la pre´sence de sang dans les urines. D’apre`s les donne´es recueillies aupre`s de 48 258 enfants interroge´s dans 545 e´coles, la mention de la pre´sence de sang dans les selles et celle de diarrhe´es sanglantes sont des indicateurs valables en ce qui concerne le diagnostic des infections a` S. mansoni dans la communaute´. En revanche, la valeur diagnostique des questionnaires e´tait moins bonne pour S. mansoni que pour S. haematobium, et malgre´ des re´sultats encourageants, les questionnaires auraient besoin d’un comple´- ment de validation. Re´cemment, des questionnaires ont e´te´ e´tendus au diagnostic individuel et semblent tre`s prometteurs a` cet e´gard. Il existe maintenant des questionnaires pour de´terminer rapidement l’importance de la schistosomiase dans une re´gion de grande e´tendue, ce qui permettra de re´partir de fac¸on optimale les resources limite´es attribue´es a` la lutte contre la morbidite´. 240 Bulletin of the World Health Organization 2002, 80 (3) Public Health Reviews Resumen Cuestionarios para el cribado ra´pido de la esquistosomiasis en el A´frica subsahariana Una serie de nuevas iniciativas tienen por objeto reducir la carga mundial de esquistosomiasis, principalmente mediante la aplica- cio´n de antibioticoterapia en gran escala. A fin de enderezar con precisio´n los esfuerzos de tratamiento antibio´tico, se necesitan procedimientos de evaluacio´n ra´pida para identificar las comuni- dades de alto riesgo que actu´en como focos de la enfermedad. En el presente ana´lisis examinamos el desarrollo y validacio´n de cuestionarios escolares sencillos concebidos para el cribado ra´pido y econo´mico de las comunidades en lo que respecta a la presencia de Schistosoma haematobium y S. mansoni. El centro de intere´s es el A´frica subsahariana, donde se concentra el 85% de la actual carga de esquistosomiasis. Durante ma´s de una de´cada, el me´todo de los cuestionarios se ha validado en 10 paı´ses, habie´ndose alcanzado la cifra de 133 880 nin˜os entrevistados en 1282 escuelas, y de 54 996 nin˜os examinados para detectar S. haematobium. Los cuestionarios tuvieron buena aceptacio´n y fueron una herramienta altamente fiable y de bajo costo. Su e´xito se explica por el hecho de que las infecciones por S. haematobium se detectaban fa´cilmente mediante la presencia de sangre en la orina. Los datos aportados por 48 258 nin˜os entrevistados en 545 escuelas muestran que las referencias a la presencia de sangre en las heces y de diarrea sanguinolenta son indicadores valiosos para el diagno´stico comunitario de S. mansoni. Sin embargo, la eficacia diagno´stica de los cuestionarios para S. mansoni fue menor que para S. haematobium. Aunque estos resultados son alentadores, es necesario validar mejor los cuestionarios. Recientemente se ha ampliado el uso diagno´stico de los cuestionarios del nivel comunitario al nivel individual, con resultados bastante prometedores. Disponemos ahora de cuestio- narios que nos permiten determinar ra´pidamente la magnitud del problema de la esquistosomiasis en un a´rea extensa, lo que permitira´ asignar de forma o´ptima los limitados recursos disponibles para combatir la morbilidad. References 1. Report of the WHO Informal Consultation on Schistosomiasis Control. Geneva: World Health Organization; 1999. 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