Efficacy and safety of antiparasitic therapy for neurocysticercosis in rural Tanzania: a prospective cohort study.

PURPOSE: Neurocysticercosis is common in regions endemic for Taenia solium. Active-stage neurocysticercosis can be treated with antiparasitic medication, but so far no study on efficacy and safety has been conducted in Africa. METHODS: We conducted a prospective cohort study on treatment of neurocysticercosis in Tanzania between August 2018 and January 2022. Patients were initially treated with albendazole (15 mg/kg/d) for 10 days and followed up for 6 months. Additionally in July 2021, all participants who then still had cysts were offered a combination therapy consisting of albendazole (15 mg/kg/d) and praziquantel (50 mg/kg/d). Antiparasitic treatment was accompanied by corticosteroid medication and anti-seizure medication if the patient had experienced epileptic seizures before treatment. RESULTS: Sixty-three patients were recruited for this study, of whom 17 had a complete follow-up after albendazole monotherapy. These patients had a total of 138 cysts at baseline, of which 58 (42%) had disappeared or calcified by the end of follow-up. The median cyst reduction was 40% (interquartile range 11-63%). Frequency of epileptic seizures reduced considerably (p < 0.001). Three patients had all active cysts resolved or calcified and of the remaining 14, eight received the combination therapy which resolved 63 of 66 cysts (95%). Adverse events were infrequent and mild to moderate during both treatment cycles. CONCLUSION: Cyst resolution was unsatisfactory with albendazole monotherapy but was very high when it was followed by a combination of albendazole and praziquantel.

Schistosoma japonicum in Samar, the Philippines: infection in dogs and rats as a possible risk factor for human infection.

The role that animals play in the transmission of Schistosoma japonicum to humans in the Philippines remains uncertain and prior studies have not included several species, adjustment for misclassification error and clustering, or used a cohort design. A cohort study of 2468 people providing stool samples at 12 months following praziquantel treatment in 50 villages of Western Samar, the Philippines, was conducted. Stool samples from dogs, cats, rats, and water buffaloes were collected at baseline (2003-2004) and follow-up (2005). Latent-class hierarchical Bayesian log-binomial models adjusting for misclassification errors in diagnostic tests were used. The village-level baseline and follow-up prevalences of cat, dog, and rat S. japonicum infection were associated with the 12-month cumulative incidence of human S. japonicum infection, with similar magnitude and precision of effect, but correlation between infection levels made it difficult to divide their respective effects. The cumulative incidence ratios associated with a 1% increase in the prevalence of infection in dogs at baseline and in rats at follow-up were 1·04 [95% Bayesian credible interval (BCI) 1·02-1·07] and 1·02 (95% BCI 1·01-1·04), respectively, when both species were entered in the model. Dogs appear to play a role in human schistosomiasis infection while rats could be used as schistosomiasis sentinels.

Prevalence case-control study of epilepsy in three Burkina Faso villages.

PURPOSE: To estimate the association between the prevalence of epilepsy and potential risk factors in three Burkina Faso villages. METHODS: Three villages were selected based on local reports of high numbers of epilepsy cases and pig-rearing practices. One person aged 7 or older was selected at random from all households of selected concessions for epilepsy screening and blood sampling. Epilepsy was confirmed by a physician using the ILAE definition. The cross-sectional associations between epilepsy and selected factors and seroresponse to the antigens of Taenia solium were estimated using a Bayesian hierarchical logistic regression. Prevalence odds ratios (POR) and their 95% Bayesian Credible Intervals (95% BCI) were estimated. RESULTS: Of 888 individuals interviewed, 39 of 70 screened positive were confirmed to have epilepsy for a lifetime prevalence of 4.5% (95% CI: 3.3; 6.0). The prevalence of epilepsy was associated with a positive reaction to cysticercosis Ag-ELISA serology (POR = 3.1, 95% BCI = 1.0; 8.3), past pork consumption (POR = 9.7, 95% BCI = 2.5; 37.9), and being salaried or a trader compared to a farmer or housewife (POR = 2.9, 95% BCI = 1.2; 6.4). DISCUSSION: Several factors were associated with prevalent epilepsy, with Ag-ELISA suggesting the presence of neurocysticercosis. The association between epilepsy and some occupations may reflect differences in local attitudes toward epilepsy and should be further explored.

Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a 'gold standard'.

The accuracy of the Kato-Katz technique in identifying individuals with soil-transmitted helminth (STH) infections is limited by day-to-day variation in helminth egg excretion, confusion with other parasites and the laboratory technicians' experience. We aimed to estimate the sensitivity and specificity of the Kato-Katz technique to detect infection with Ascaris lumbricoides, hookworm and Trichuris trichiura using a Bayesian approach in the absence of a 'gold standard'. Data were obtained from a longitudinal study conducted between January 2004 and December 2005 in Samar Province, the Philippines. Each participant provided between one and three stool samples over consecutive days. Stool samples were examined using the Kato-Katz technique and reported as positive or negative for STHs. In the presence of measurement error, the true status of each individual is considered as latent data. Using a Bayesian method, we calculated marginal posterior densities of sensitivity and specificity parameters from the product of the likelihood function of observed and latent data. A uniform prior distribution was used (beta distribution: alpha=1, beta=1). A total of 5624 individuals provided at least one stool sample. One, two and three stool samples were provided by 1582, 1893 and 2149 individuals, respectively. All STHs showed variation in test results from day to day. Sensitivity estimates of the Kato-Katz technique for one stool sample were 96.9% (95% Bayesian Credible Interval [BCI]: 96.1%, 97.6%), 65.2% (60.0%, 69.8%) and 91.4% (90.5%, 92.3%), for A. lumbricoides, hookworm and T. trichiura, respectively. Specificity estimates for one stool sample were 96.1% (95.5%, 96.7%), 93.8% (92.4%, 95.4%) and 94.4% (93.2%, 95.5%), for A. lumbricoides, hookworm and T. trichiura, respectively. Our results show that the Kato-Katz technique can perform with reasonable accuracy with one day's stool collection for A. lumbricoides and T. trichiura. Low sensitivity of the Kato-Katz for detection of hookworm infection may be related to rapid degeneration of delicate hookworm eggs with time.

A health-education intervention trial to reduce porcine cysticercosis in Mbulu District, Tanzania.

We conducted a randomised community controlled trial to estimate the effectiveness of health and pig-management education intervention in reducing the incidence rate of porcine cysticercosis caused by Taenia solium in Mbulu District, northern Tanzania, between April 2002 and July 2004. We included a random sample of 827 pig-keeping households from 42 randomly selected villages in our 27-month study. We collected baseline data on the prevalence of porcine cysticercosis based on lingual examination of live pigs, and pig-management and sanitation knowledge and practices based on questionnaire interviews and observations. We allocated 21 of the villages to the health-education intervention, developed with community participation; we used stratified randomisation to balance the village-level baseline prevalence of porcine cysticercosis. From July 2003 to March 2004 following the intervention, we gave each participant household a sentinel piglet to raise (the timing was balanced between the intervention groups). Knowledge about the transmission and prevention of porcine cysticercosis was improved >42% in both groups when measured 10-12 months post-intervention. There was no improvement in observed practices in either group throughout the study period. However, the intervention had a significant reduction in the reported cases of household consumption of infected pork (a reduction by 20%). The intervention was associated with a considerable decrease in the incidence rate of porcine cysticercosis (incidence rate ratio 0.57) as measured by antigen-ELISA in sentinel pigs. Public education could lead to a reduction of the risk of infection in humans.

Prevalence of Schistosoma japonicum infection among animals in fifty villages of Samar province, the Philippines.

In the Philippines, there is a need to understand the contribution of different domestic and wild animals in transmitting Schistosoma japonicum infection to humans better. The current study describes variation in animal S. japonicum prevalence across 50 endemic villages of Samar Province, the Philippines. A total of 50 villages were selected, 25 with predominantly rain-fed farms and 25 with some irrigation system. At least 35 cats, dogs, pigs, and water buffaloes each were randomly selected and 30 rat traps were set in each village. Fecal samples were collected for up to three consecutive days for each species. The Danish Bilharziasis Laboratory method (DBL method) was used to determine S. japonicum infection status. A hierarchical logistic regression model with clustering by village and with adjustment for measurement error of the DBL method was used to estimate the prevalence of infection per village and species. Stool samples were collected from 23.4% (1189), 28.6% (1274), 36.3% (1899), and 49.4% (873) of the censused dogs, cats, pigs, and water buffaloes, respectively, and from 663 rats. The adjusted prevalence of S. japonicum infection varied greatly across villages ranging from 1.6% (95% Bayesian Credible Interval: 0.1%-10.2%) to 86.3% (65.9%-97.8%) for dogs, from 0.1% (0%-2.1%) to 21.7% (4.7%-51.2%) for cats, from 0.01% (0.0%%-1.0%) to 18.4% (7.1%-34.7%) for pigs, from less than 0.1% (0.0%-1.2%) to 72.5% (46.0%-97.4%) for water buffaloes, and from 0.7% (0.0%-9.0%) to 95.4% (77.2%-99.9%) for rats. This is the most comprehensive study of animal S. japonicum infection conducted to date. Our results show that, unlike what has been reported in China, very few water buffaloes were infected whereas rats and dogs show high prevalence proportions of infection. This, combined with significant village-to-village variation in prevalence of S. japonicum infection, suggest possible different transmission dynamics of the infection in the Province of Samar in the Philippines and China.

Concurrent comparison of three water contact measurement tools in four endemic villages of the Philippines. The schistosomiasis transmission ecology in the Philippines project (STEP).

BACKGROUND: Schistosomiasis japonica is a chronic helminthic infection contracted through contact with water infested with Schistosoma japonicum. The infection is associated with severe disease and is an important public health concern in Philippines. OBJECT: To estimate the agreement in the frequency of water contact between bimonthly interviews, self-administered diaries and observations. METHODS: A total of 286 individuals were followed over either a 4 or a 6 months period. Agreement between direct observation and both the bimonthly and diary methods were estimated. RESULTS: The agreement between the observation and the bimonthly interview was 71.8% when days without any water contacts were considered, but decreased to 23.3% when only days with at least some water contact were considered. The agreement between the observation and the diary was 78.7% when days without any water contacts were considered and 40.8% when only days with some water contacts were considered. CONCLUSIONS: Agreement about the degree of water contact is poor between the different measurement tools. This has important implications for future research, since a high degree of measurement error can severely bias any results from studies involving water contact.

Estimation of the cost of Taenia solium cysticercosis in Eastern Cape Province, South Africa.

OBJECTIVES: To provide a comprehensive estimate of the societal costs of Taenia solium cysticercosis for the Eastern Cape Province (ECP), South Africa, as an objective measure of its impact in this endemic area. METHODS: Epidemiological data on the prevalence of epilepsy, proportion of epilepsy cases due to neurocysticercosis (NCC) and consequences of cysticercosis were gathered from published and unpublished sources. Economical data were mostly obtained from governmental sources. Three methods were used for estimating productivity losses. Monte Carlo sampling was used to represent the uncertainty of the estimates with 95% Credible Intervals (95% CI). The estimation is for 1 year using a societal approach. All costs are reported in 2004 US Dollars. RESULTS: Overall, there were an estimated 34 662 (95% CI: 17 167-54 068) NCC-associated cases of epilepsy in ECP in 2004. The overall monetary burden (in million of US Dollars) was estimated to vary from US Dollars 18.6 (95% CI: US Dollars 9.0-32.9) to US Dollars 34.2 (95% CI: US Dollars 12.8-70.0) depending on the method used to estimate productivity losses. The agricultural sector contributed an average of Dollars 5.0 million. The prevalence of epilepsy, proportion of productivity reduction and the proportion of epilepsy cases attributable to NCC had the largest impact on the overall estimates. CONCLUSION: This preliminary estimate suggests that T. solium cysticercosis results in considerable monetary costs to a region that is already economically constrained. Because this infection is preventable, these results could guide stakeholders in deciding where to invest scarce health and agricultural resources in their countries.

[Measles, pertussis, rubella and mumps completeness of reporting. Literature review of estimates for industrialized countries]. / Proportion des déclarations de cas de rougeole, de coqueluche, de rubéole et d'oreillons aux systèmes de surveillance. Evaluation des études pour les pays industrialisés.

BACKGROUND: Surveillance data for infectious diseases in industrialized countries have been providing useful epidemiological information for several years. However, surveillance is complex and notifications underestimate the true disease incidence. The goal of this paper is to determine the completeness of reporting of measles, pertussis, rubella and mumps through notification in industrialized countries. METHODS: A thorough literature review of papers published (in French or English) on surveillance data of measles, pertussis, rubella and mumps was undertaken with PUBMED. The review was limited to studies conducted in industrialized countries that quantitatively assessed the completeness of the reporting of these diseases. RESULTS: Fourteen studies published from the 1920s met the inclusion criteria. For measles, the studies suggest that 64-85% of symptomatic patients sought medical care, 13-57% of those were diagnosed with measles and 22-81% of the diagnosed cases were reported for a completeness of reporting ranging from 7% to 63% between 1920 and 1980 and 3% to 41% in recent years. For pertussis, it was estimated that 49-59% of symptomatic patients sought medical care, 12% of those were diagnosed and 19-47% of the diagnosed cases were reported for a completeness of reporting ranging from 5% to 25% between 1920 and 1980 and from 3% to 12% in recent years. Very few studies on rubella and mumps were found and none allowed the determination of the global completeness of reporting. CONCLUSION: Reporting has been found to be considerably incomplete. Continued efforts to improve the recognition and reporting of these diseases are needed.

Estimating sensitivity and specificity of a faecal examination method for Schistosoma japonicum infection in cats, dogs, water buffaloes, pigs, and rats in Western Samar and Sorsogon Provinces, The Philippines.

Schistosoma japonicum causes a chronic parasitic disease, which persists as a major public health concern in The Philippines, the People's Republic of China and Indonesia. This infection is unique among helminthic zoonoses because it can infect humans and more than 40 other mammals. The objective of this study was to estimate the sensitivity and specificity of the Danish Bilharziasis Laboratory technique in cats, dogs, pigs, water buffaloes and rats in the Philippines. Faecal samples from each animal were collected on up to five occasions on five consecutive days in four villages of Sorsogon and Western Samar Provinces between January and July 2003. The faecal samples were analysed with the filtration and sedimentation Danish Bilharziasis Laboratory technique. Sensitivity and specificity of one, two, three, four, and five faecal samples were estimated using a Bayesian latent class approach. A total of 59, 43, 74, and 80% of the censored cats, dogs, pigs, and water buffaloes in the four villages were sampled, respectively. For all species, the sensitivity estimates when using the results of only 1 day of sampling were less than 80%. However, the sensitivity improved to at least 96% in all species when three or more faecal samples were collected on three separate days. The specificity was estimated to be above 92% across all species, even if just a single sample is used. The prevalences and 95% credible intervals of S. japonicum, adjusted for imperfect sensitivity and specificity, in cats, dogs, pigs, rats, and water buffaloes were 11.9% (6.8-18.3%), 19.9% (15.1-25.2%), 2.9% (1.1-5.2%), 31.3% (18.3-45.6%) and 6.3% (2.1-12.6%), respectively. Our results suggest that the Danish Bilharziasis Laboratory technique is valid for the detection of infection with S. japonicum in animals, and that sensitivity estimates are excellent when faecal samples are collected on at least three different days. Monitoring S. japonicum infection in animal reservoirs with a valid test could contribute to more effective public health control programmes.

Risk factors for the prevalence of porcine cysticercosis in Mbulu District, Tanzania.

To estimate prevalence of and risk factors for the prevalence of porcine cysticercosis in Mbulu District, Tanzania, 770 live pigs were examined by lingual examination in 21 villages. Structured observations and questionnaire interviews were used to assess pig rearing practices and household use of latrines. Associations between factors were analyzed using a Bayesian hierarchical model to obtain prevalence odds ratio (OR) and 95% Bayesian Credible Intervals (95% BCI). Prevalence was 17.4% (village-specific range 3.2-46.7%). Prevalence of porcine cysticercosis was considerably higher in pigs reared in households lacking latrines than in those reared in households that were using latrines (OR = 2.04; 95% BCI = 1.25, 3.45). About 96% of the pigs were kept under free-range conditions. This study suggests the need for further studies in order to design and implement effective prevention and control measures for porcine cysticercosis in Mbulu District, Tanzania.

Assessing the burden of Taenia solium cysticercosis and echinococcosis.

This collection of articles provides an account of the papers delivered at the 19th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP)(held in New Orleans, LA, USA, from 10 to 14 August 2003) in a symposium session on assessing the burden of Taenia solium cysticercosis and echinococcosis organised and chaired by A. Lee Willingham III from the WHO/FAO Collaborating Center for Research and Training on Emerging and other Parasitic Zoonoses in Denmark and Peter M. Schantz from the Parasitic Diseases Division of the US Centers for Disease Control and Prevention, USA. The focus was on the persistence of the zoonotic parasitic diseases cysticercosis, caused by the pork tapeworm T. solium, and echinococcosis,caused by species of the tapeworm Echinococcus, and why these diseases are given very little attention on the national and international agendas in spite of the availability of tools to detect, treat,control and prevent them when it is quite clear in most instances that they are clearly associated with and help perpetuate poverty. A major reason for this is that in many endemic areas the presence and impact of these diseases are not known due to the lack of investigation and information thus policymakers are not aware of their burden and benefits of their control. Documentation is also needed to help increase awareness of the international community and hopefully result in financial and technical support being made available. Thus, burden assessments of cysticercosis and echinococcosis provide an essential evidence base for securing political will and financial and technical support as well as providing a basis for cost-benefit analysis of prevention and control efforts. In order to make an appropriate and full burden assessment one must consider the health, agricultural, social and other impacts of these parasitic zoonoses comprehensively. During the symposium presentations were given concerning current ongoing initiatives to assess the burden of cysticercosis and echinococcosis and examples of the impact of these diseases in both developing and developed countries were provided. In addition, cost factors related to vaccines for these cestode diseases were discussed and the possibilities for technical and financial support from multilateral agencies for assessments and interventions presented.

The cost of measles in industrialised countries.

The aim of this study is to estimate the costs of measles and measles control in 11 industrialised countries with varying levels of measles vaccine coverage. Country-specific annual incidence of measles, measles immunization policy, coverage and costs data were collected. The average societal costs of measles cases and immunisation programme per capita were calculated. These 11 countries spend together over US$ 151 million every year to treat and control measles. Per capita costs of measles control tend to be higher in countries with poorer measles control programmes (for instance, Italy has the highest incidence and highest overall costs), though many other factors, such as the number of antigens given per clinic visit and the local price of MMR also affect the efficiency of the programme. The costs estimates presented here can be used to estimate potential savings that might accrue from changes to measles control programmes.

The potential role of suppressive therapy for sex partners in the prevention of neonatal herpes: a health economic analysis.

BACKGROUND: The development of suppressive therapy and type specific tests for herpes infections allow for screening to reduce the risk of neonatal herpes. OBJECTIVES: To assess the potential effectiveness, cost effectiveness, and benefit of suppressive therapy among herpes simplex virus serodiscordant sex partners during pregnancy. METHODS: Decision and economic analyses are used to compare the incidence and costs of neonatal herpes in California (2000) for three interventions: (1) no management; (2) current guidelines (caesarean delivery for women with lesions); (3) screening for women at risk and use of suppressive treatment in sex partners. RESULTS: Screening and suppressive therapy are the most effective interventions, while current guidelines have limited effectiveness, but the latter provide the most cost effective results. CONCLUSIONS: While current guidelines are cost saving, they forgo a potential 82% decrease in neonatal herpes incidence that would be possible with screening and suppressive therapy if society were willing to pay the necessary US$363 000 per case prevented. To evaluate HSV screening and drug therapy completely, clinical trials and an economic assessment of infant mortality "value" to society are required.

Assessment of the factors associated with flavivirus seroprevalence in a population in Southern Vietnam.

Dengue and Japanese encephalitis flaviviruses cause severe disease and are hyperendemic in southern Vietnam. This study assesses associations between sociodemographic factors and flavivirus seroprevalence in this region. Sera were collected from 308 community and hospital-based subjects between April 1996 and August 1997 and tested with an indirect ELISA. The factors associated with seroprevalence were assessed using multivariate logistic regression. In this first report of adjusted prevalence odds ratios (POR) for flavivirus infection in Vietnam, seropositivity was associated with increasing age in children (multiple regression coefficients for a child compared to an adult = -4.975 and for age in children = 0.354) and residence in the city compared to surrounding rural districts. The association with age indicates that subjects were most likely to have acquired infection in early childhood. This is key to the design of Vietnamese health education and immunization programmes.

A review of emergency foot-and-mouth disease (FMD) vaccines.

The primary objectives of this paper are to describe emergency foot-and-mouth disease (FMD) vaccines and review literature on emergency vaccine efficacy to protect animals against (1) clinical signs and (2) infection (local virus replication). The reviewed experiments suggest that in cattle, sheep and pigs, the vaccine could be effective in preventing disease within 4-5 days post-vaccination. These studies also suggest that the risk of spreading infection decreases as the interval between vaccine and challenge increases and that vaccination could reduce the amount of virus excreted compared to non-vaccinated animals. We suggest areas of future research to improve our knowledge of emergency vaccines.

Comparison of methods to analyse imprecise faecal coliform count data from environmental samples.

Imprecise values arise when bacterial colonies are too numerous to be counted or when no colonies grow at a specific dilution. Our objective was to show the usefulness of multiple imputation in analysing data containing imprecise values. We also indicate that interval censored regression, which is faster computationally in situations where it applies, can be used, providing similar estimates to imputation. We used bacteriological data from a large epidemiological study in daycare centres to illustrate this method and compared it to a standard method which uses single exact values for the imprecise data. The data consisted of numbers of FC on children's and educators' hands, from sandboxes and from playareas. In general, we found that multiple imputation and interval censored regression provided more conservative intervals than the standard method. The discrepancy in the results highlights both the importance of using a method that best captures the uncertainty in the data and how different conclusions might be drawn. This can be crucial for both researchers and those who are involved in formulating and regulating standards for bacteriological contamination.

A population dynamic approach to evaluating the impact of school attendance on the unit cost and effectiveness of school-based schistosomiasis chemotherapy programmes.

This paper presents a first attempt at modelling the possible cost and effectiveness of reaching non-enrolled children through school-based programmes using empirical data from Egypt. A sex/school-attendance/age-structured population dynamic model was used to predict trends in infection and early disease. Four treatment delivery strategies were compared: school-based (coverage of 85 %) and school-aged targeted (coverage of 25, 50 and 85 %). The school-aged targeted strategies also included the school-based programme. For each alternative strategy, the maximum unit cost was calculated to obtain a cost-effectiveness ratio equal or smaller to the one obtained with the school-based programme (unit cost of US$ 0.60). The analysis showed that, for S. mansoni in Lower Egypt, a programme where only 85% of children attending school were treated would still prevent 77 % of the early disease cases prevented with a programme where 85 % of all school-age children were treated. However, using the school-aged targeted strategy, from US $ 0.06 to US $ 1.03 extra unit costs could be spent to reach non-enrolled children and still be more cost-effective. Treating non-enrolled children is an important consideration in maximizing the effectiveness of treatment programmes while maintaining a cost-effectiveness comparable to school-based delivery.

Comparison between two common methods for reporting cold and diarrhoea symptoms of children in daycare centre research.

BACKGROUND: The increasing number of children attending day care centres (DCCs) in industrialized countries has refocused attention on the occurrence of infections and infectious diseases in these settings. OBJECTIVE: To evaluate the agreement between two methods (parent method vs. educator method) for reporting the occurrence of respiratory and diarrhoeal infections. METHODS: Fifty-two DCCs in Quebec, Canada, participated. Both educators and parents were invited to fill in calendars on which they would indicate the occurrence of colds and diarrhoea. For the parents' method, parents were telephoned biweekly to record their calendar information. For the educators' method, educators returned their calendar pages monthly (following prompting by phone, when necessary). RESULTS: Three hundred and thirty-three parents of toddlers participated in the 15-month reporting period between September 1996 and November 1997. The average agreement between the two methods was low (13.5% for colds and 9.8% for diarrhoea). Overall estimates of the incidence rates of respiratory and diarrhoeal infections based on parents' method were higher than those based on educators' method. CONCLUSIONS: Parents' data lead to larger estimations of incidence rates and are probably more valid than educators' data.

A comparative analysis of the cost-effectiveness of treatment based on parasitological and symptomatic screening for Schistosoma mansoni in Burundi.

OBJECTIVES: To assess the cost-effectiveness of three alternative screening strategies in delivering treatment to patients presenting with symptoms suggestive of S. mansoni, using data collected from 17 PHCCs in the Rusizi Plain, Burundi. The three strategies were: (1) screening all symptomatic patients using a Kato-Katz smear and treating only the ones found positive; (2) treating all symptomatic patients or (3) treating only those presenting with symptoms of severe diarrhoea (blood in stool). METHODS: The database consisted of 41 051 visits of symptomatic patients to the 17 PHCCs during 1990. Effectiveness was measured as the number of infected patients treated (gold standard: 25-mg Kato-Katz smear). Cost-effectiveness ratios (CERs) (cost in US$ per infected patient treated) were used to compare the control strategies. Sensitivity analysis was performed to assess the effect of drug price and prevalence of infection on the CERs. RESULTS: The overall prevalence of S. mansoni infection was 9.5% (95% CI = 9.1%, 9.9%). Treating only those with severe symptoms of infection would have left 92% of infected patients untreated. Performing a Kato-Katz smear to confirm the diagnosis was more cost-effective than treating all symptomatic patients on a presumptive basis, with CERs of 4.2 US$ and 12.43 US$ per infected person treated, respectively. Sensitivity analysis showed that, for a cost of 0.99 US$ per dose of praziquantel, the Kato-Katz option remained the most cost-effective approach for prevalences under 76%. For a drug price of 0.21 US$ per dose, both strategies would have become equivalent. The latter value varied extensively per PHCC (range 0.17 US$ to 0.51 US$), due to the different prevalences of infection (range 0.5% to 34.3%). CONCLUSION: We found that using severe diarrhoea as an indicator for infection was not appropriate, and that screening symptomatic patients with the Kato-Katz method remained the most cost-effective approach in the given setting. The CER of treating all symptomatic patients on a presumptive basis depended very much on the drug price and the endemic level.