Elimination of schistosomiasis transmission in Zanzibar: baseline findings before the onset of a randomized intervention trial.

BACKGROUND: Gaining and sustaining control of schistosomiasis and, whenever feasible, achieving local elimination are the year 2020 targets set by the World Health Organization. In Zanzibar, various institutions and stakeholders have joined forces to eliminate urogenital schistosomiasis within 5 years. We report baseline findings before the onset of a randomized intervention trial designed to assess the differential impact of community-based praziquantel administration, snail control, and behavior change interventions. METHODOLOGY: In early 2012, a baseline parasitological survey was conducted in ~20,000 people from 90 communities in Unguja and Pemba. Risk factors for schistosomiasis were assessed by administering a questionnaire to adults. In selected communities, local knowledge about schistosomiasis transmission and prevention was determined in focus group discussions and in-depths interviews. Intermediate host snails were collected and examined for shedding of cercariae. PRINCIPAL FINDINGS: The baseline Schistosoma haematobium prevalence in school children and adults was 4.3% (range: 0-19.7%) and 2.7% (range: 0-26.5%) in Unguja, and 8.9% (range: 0-31.8%) and 5.5% (range: 0-23.4%) in Pemba, respectively. Heavy infections were detected in 15.1% and 35.6% of the positive school children in Unguja and Pemba, respectively. Males were at higher risk than females (odds ratio (OR): 1.45; 95% confidence interval (CI): 1.03-2.03). Decreasing adult age (OR: 1.04; CI: 1.02-1.06), being born in Pemba (OR: 1.48; CI: 1.02-2.13) or Tanzania (OR: 2.36; CI: 1.16-4.78), and use of freshwater (OR: 2.15; CI: 1.53-3.03) showed higher odds of infection. Community knowledge about schistosomiasis was low. Only few infected Bulinus snails were found. CONCLUSIONS/SIGNIFICANCE: The relatively low S. haematobium prevalence in Zanzibar is a promising starting point for elimination. However, there is a need to improve community knowledge about disease transmission and prevention. Control measures tailored to the local context, placing particular attention to hot-spot areas, high-risk groups, and individuals, will be necessary if elimination is to be achieved.

The relative contribution of co-infection to focal infection risk in children.

Co-infection is ubiquitous in people in the developing world but little is known regarding the potential for one parasite to act as a risk factor for another. Using generalized linear mixed modelling approaches applied to data from school-aged children from Zanzibar, Tanzania, we determined the strength of association between four focal infections (i.e. Ascaris lumbricoides, Trichuris trichiura, hookworm and self-reported fever, the latter used as a proxy for viral, bacterial or protozoal infections) and the prevalence or intensity of each of the helminth infections. We compared these potential co-infections with additional risk factors, specifically, host sex and age, socioeconomic status and physical environment, and determined what the relative contribution of each risk factor was. We found that the risk of infection with all four focal infections was strongly associated with at least one other infection, and that this was frequently dependent on the intensity of that other infection. In comparison, no other incorporated risk factor was associated with all focal infections. Successful control of infectious diseases requires identification of infection risk factors. This study demonstrates that co-infection is likely to be one of these principal risk factors and should therefore be given greater consideration when designing disease-control strategies. Future work should also incorporate other potential risk factors, including host genetics which were not available in this study and, ideally, assess the risks via experimental manipulation.

DNA barcoding of Schistosoma haematobium on Zanzibar reveals substantial genetic diversity and two major phylogenetic groups.

To shed light on the genetic diversity of Schistosoma haematobium on Zanzibar a DNA barcoding study was performed on parasite material isolated from different time-points 4 years apart. Substantive sequence variation was found within the mitochondrial cytochrome oxidase subunit I (cox1) and the NADH-dehydrogenase subunit 1 (nad1) with 27 and 22 unique haplotypes identified respectively and 38 when both gene regions were considered. Upon phylogenetic analysis and comparison with other S. haematobium isolates, haplotypes or barcode types partitioned into two discrete major groups, designated Group 1 and Group 2. Whilst Group 1 isolates were recovered from both Zanzibar and the African mainland, Group 2 isolates were exclusive to Zanzibar. A mixture of Group 1 and 2 parasites were recovered from individual children with no child shedding parasites of a single group haplotype alone. Whilst changes in general levels of genetic diversity between the two parasite isolation time-points were observed, no obvious change in genetic diversity was detected, despite large-scale drug distribution of praziquantel during the intervening period and there was no biased of Group 1 or 2 parasites persisting at the different time-points. To assist in future genetic screening of schistosome larval stages e.g. eggs, miracidia or cercariae, two new DNA-typing assays based on group-specific PCR primers and SNaPshot™ probes have been developed to distinguish Group 1 and 2 haplotypes.

Parasitological and malacological surveys reveal urogenital schistosomiasis on Mafia Island, Tanzania to be an imported infection.

To confirm the local endemicity of Schistosoma haematobium on Mafia Island, Tanzania, conjoint parasitological and malacological surveys were undertaken in July 2006 with parasitological investigations supplemented with case-history questionnaires. A total of 238 children (125 girls and 113 boys, mean age of 13.9 years) across 9 primary schools were examined. The prevalence of micro-haematuria and egg-patent infection was 18.1% (CI95=9.6-33.6) and 4.2% (CI95=1.9-7.6), respectively but a strong female bias was observed for micro-haematuria (5.6F:1M) contrasting with a strong male bias for the presence of eggs (1F:4M). All egg-patent infections were of light-intensity (<10eggs/10ml). No clear associations between infection prevalence and local water-contact, by school, were found and all 10 of the egg-positive children had a travel history to the nearby mainland or Zanzibar. Inspection of community diagnostic registers at Kilindoni Hospital revealed a low proportion (<2%) of egg-patent infection for 20,306 samples tested in the 2000-2005 period. A total of 43 freshwater sites, a third of which were previously sampled in 1999 and 2002, were surveyed and 11 species of freshwater mollusc were found. Four species of Bulinus (B. nasutus, B. forskalii, B. barthi and B. sp.) were encountered across 13 sites with B. nasutus restricted to 3 of these towards the north of the island. No collected snail was observed to shed schistosome cercariae. Further characterisation of B. nasutus and S. haematobium included infection challenge on two occasions, with miracidia obtained from egg-patent children from Mafia and Unguja islands as well as DNA barcoding of snails and schistosomes. B. nasutus was shown refractory to infection. With the substantial travel to and from Mafia, the refractory nature of local snails and evidence from DNA barcoding in schistosomes and snails, we conclude that urogenital schistosomiasis is an imported infection.

From morbidity control to transmission control: time to change tactics against helminths on Unguja Island, Zanzibar.

In Zanzibar, the prevalence and intensity of helminth infections have markedly declined over the past 25 years, which is generally attributed to morbidity control programmes emphasising 'preventive chemotherapy'. Here we provide an update of the current situation of soil-transmitted helminthiasis and urinary schistosomiasis on Unguja Island, and highlight socioeconomic development, improvement in sanitation and health education as additional drivers against helminthiases. Our data were obtained from cross-sectional surveys carried out between 2006 and 2009 with stool and urine samples from 2858 and 879 individuals, respectively, examined for helminth eggs and larvae. Additionally, several hundred people were interviewed on sanitation and hygienic behaviour. Data on Unguja's economic growth and improvements in access to clean water and household latrines in the recent past were derived from the extant literature. Pooled prevalences of Trichuris trichiura, Schistosoma haematobium, Ascaris lumbricoides, hookworm and Strongyloides stercoralis were 35%, 29%, 12%, 10% and 6%, respectively. However, there were considerable differences in prevalences between different age-groups and at village and district level. Moreover, some hotspots for A. lumbricoides, T. trichiura and S. haematobium were identified with prevalences above 60% among school-aged children. Availability of a latrine and washing hands before eating did not significantly lower the risk of helminth infections in our study population. Nevertheless, a considerable increase in access to household latrines (from 49% to 72%) and piped water (from 45% to 71%) between 1991 and 2005 is likely to have contributed to reducing the force of transmission of helminthiases in Zanzibar. The next logical step in Unguja is to change the tactics from morbidity control to interruption of helminth transmission and ultimately local elimination. Hence, 'preventive chemotherapy' needs to be further consolidated, placing particular emphasis on health education and improved access to clean water and sanitation.

Study and implementation of urogenital schistosomiasis elimination in Zanzibar (Unguja and Pemba islands) using an integrated multidisciplinary approach.

BACKGROUND: Schistosomiasis is a parasitic infection that continues to be a major public health problem in many developing countries being responsible for an estimated burden of at least 1.4 million disability-adjusted life years (DALYs) in Africa alone. Importantly, morbidity due to schistosomiasis has been greatly reduced in some parts of the world, including Zanzibar. The Zanzibar government is now committed to eliminate urogenital schistosomiasis. Over the next 3-5 years, the whole at-risk population will be administered praziquantel (40 mg/kg) biannually. Additionally, snail control and behaviour change interventions will be implemented in selected communities and the outcomes and impact measured in a randomized intervention trial. METHODS/DESIGN: In this 5-year research study, on both Unguja and Pemba islands, urogenital schistosomiasis will be assessed in 45 communities with urine filtration and reagent strips in 4,500 schoolchildren aged 9-12 years annually, and in 4,500 first-year schoolchildren and 2,250 adults in years 1 and 5. Additionally, from first-year schoolchildren, a finger-prick blood sample will be collected and examined for Schistosoma haematobium infection biomarkers. Changes in prevalence and infection intensity will be assessed annually. Among the 45 communities, 15 were randomized for biannual snail control with niclosamide, in concordance with preventive chemotherapy campaigns. The reduction of Bulinus globosus snail populations and S. haematobium-infected snails will be investigated. In 15 other communities, interventions triggering behaviour change have been designed and will be implemented in collaboration with the community. A change in knowledge, attitudes and practices will be assessed annually through focus group discussions and in-depth interviews with schoolchildren, teachers, parents and community leaders. In all 45 communities, changes in the health system, water and sanitation infrastructure will be annually tracked by standardized questionnaire-interviews with community leaders. Additional issues potentially impacting on study outcomes and all incurring costs will be recordedand monitored longitudinally. DISCUSSION: Elimination of schistosomiasis has become a priority on the agenda of the Zanzibar government and the international community. Our study will contribute to identifying what, in addition to preventive chemotherapy, needs to be done to prevent, control, and ultimately eliminate schistosomiasis, and to draw lessons for current and future schistosomiasis elimination programmes in Africa and elsewhere. TRIAL REGISTRATION: ISRCTN48837681.

A molecular epidemiological investigation of Ascaris on Unguja, Zanzibar using isoenyzme analysis, DNA barcoding and microsatellite DNA profiling.

Ascariasis is of public health importance on the islands of Zanzibar (Unguja and Pemba). To shed light on the molecular epidemiology of this parasite, 68 Ascaris worms, obtained from 14 individuals in four Ungujan villages, were examined by isoenzyme analysis (ISA), DNA barcoding and microsatellite DNA profiling. ISA revealed genetic variation, which was confirmed by DNA barcoding. Nineteen worms recovered from individuals in Uganda were included for comparison. Sixteen unique DNA barcodes were identified, 15 on Unguja and three in Uganda with two shared between. These two barcodes were found in all four Ungujan villages. Worms from Tumbatu-Jongowe, an isolated village on an islet off Unguja, seemed particularly diverse. Within our barcodes, three exact matches were found with Chinese Ascaris retrieved from pigs, which is perhaps surprising given the present rarity of these animals on Unguja. Microsatellite profiling and population genetic analysis revealed further genetic diversity within our samples although population sub-structuring within Unguja was minor in comparison to that between Unguja and Uganda. As African Ascaris has not been subjected to detailed molecular scrutiny, this new diversity represents an important piece in its evolutionary jigsaw and such population markers are informative in monitoring worm dynamics during ongoing control.

Diagnostic accuracy of Kato-Katz and FLOTAC for assessing anthelmintic drug efficacy.

BACKGROUND: Sensitive diagnostic tools are required for an accurate assessment of prevalence and intensity of helminth infections in areas undergoing regular deworming, and for monitoring anthelmintic drug efficacy. We compared the diagnostic accuracy of the Kato-Katz and FLOTAC techniques in the frame of a drug efficacy trial. METHODOLOGY/PRINCIPAL FINDINGS: Stool samples from 343 Zanzibari children were subjected to duplicate Kato-Katz thick smears and the FLOTAC basic technique in a baseline screening in early 2009. The FLOTAC showed a higher sensitivity than the Kato-Katz method for the diagnosis of Trichuris trichiura (95% vs. 88%, p = 0.012) and Ascaris lumbricoides (88% vs. 68%, p = 0.098), but a lower sensitivity for hookworm diagnosis (54% vs. 81%, p = 0.006). Considering the combined results from both methods as 'gold' standard, the prevalences of T. trichiura, hookworm and A. lumbricoides were 71% (95% confidence interval (CI): 66-75%), 22% (95% CI: 17-26%) and 12% (95% CI: 8-15%), respectively. At follow-up, 3-5 weeks after 174 among the 269 re-examined children were administered anthelmintic drugs, we observed cure rates (CRs) against A. lumbricoides, hookworm and T. trichiura of 91% (95% CI: 80-100%), 61% (95% CI: 48-75%) and 41% (95% CI: 34-49%), respectively, when using the Kato-Katz method. FLOTAC revealed lower CRs against A. lumbricoides (83%, 95% CI: 67-98%) and T. trichiura (36%, 95% CI: 29-43%), but a higher CR against hookworm (69%, 95% CI: 57-82%). These differences, however, lacked statistical significance. Considerable differences were observed in the geometric mean fecal egg counts between the two methods with lower egg reduction rates (ERRs) determined by FLOTAC. CONCLUSION/SIGNIFICANCE: Our results suggest that the FLOTAC technique, following further optimization, might become a viable alternative to the Kato-Katz method for anthelmintic drug efficacy studies and for monitoring and evaluation of deworming programs. The lower CRs and ERRs determined by FLOTAC warrant consideration and could strategically impact future helminth control programs.

Albendazole and mebendazole administered alone or in combination with ivermectin against Trichuris trichiura: a randomized controlled trial.

BACKGROUND: Single-dose albendazole and mebendazole show limited efficacy in the treatment of trichuriasis. The combination of albendazole with ivermectin improves efficacy, but a mebendazole-ivermectin combination has not been previously investigated. METHODS: We performed a randomized controlled trial in 2 schools in Zanzibar, Tanzania, to assess the efficacy and safety of albendazole (400 mg) plus placebo, albendazole plus ivermectin (200 µg/kg), mebendazole (500 mg) plus placebo, and mebendazole plus ivermectin in children with a parasitologically confirmed Trichuris trichiura infection. Cure rate (CR) and egg reduction rate were assessed by intent-to-treat analysis. Adverse events were monitored within 48 h after treatment. RESULTS: Complete data records were available for 548 children. The highest CR against T. trichiura was achieved with a mebendazole-ivermectin combination (55%). Low CRs were observed with albendazole-ivermectin (38%), mebendazole (19%), and albendazole (10%). Compared with placebo, the use of ivermectin statistically significantly increased the CRs from 14% to 47% (odds ratio, 0.19; 95% confidence interval [CI], 0.12-0.28). The highest egg reduction rate (97%; 95% CI, 95%-98%) was observed using the mebendazole-ivermectin combination, followed by albendazole-ivermectin (91%; 95% CI, 87%-94%), mebendazole (67%; 95% CI, 52%-77%), and albendazole (40%; 95% CI, 22%-56%). The adverse events, reported by 136 children, were generally mild, with no significant difference between the treatment arms. CONCLUSIONS: Addition of ivermectin improves the therapeutic outcomes of both albendazole and mebendazole against T. trichiura and may be considered for use in soil-transmitted helminth control programs and individual patient management. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN08336605.

Comparative cost assessment of the Kato-Katz and FLOTAC techniques for soil-transmitted helminth diagnosis in epidemiological surveys.

BACKGROUND: The Kato-Katz technique is widely used for the diagnosis of soil-transmitted helminthiasis in epidemiological surveys and is believed to be an inexpensive method. The FLOTAC technique shows a higher sensitivity for the diagnosis of light-intensity soil-transmitted helminth infections but is reported to be more complex and expensive. We assessed the costs related to the collection, processing and microscopic examination of stool samples using the Kato-Katz and FLOTAC techniques in an epidemiological survey carried out in Zanzibar, Tanzania. METHODS: We measured the time for the collection of a single stool specimen in the field, transfer to a laboratory, preparation and microscopic examination using standard protocols for the Kato-Katz and FLOTAC techniques. Salaries of health workers, life expectancy and asset costs of materials, and infrastructure costs were determined. The average cost for a single or duplicate Kato-Katz thick smears and the FLOTAC dual or double technique were calculated. RESULTS: The average time needed to collect a stool specimen and perform a single or duplicate Kato-Katz thick smears or the FLOTAC dual or double technique was 20 min and 34 sec (20:34 min), 27:21 min, 28:14 min and 36:44 min, respectively. The total costs for a single and duplicate Kato-Katz thick smears were US$ 1.73 and US$ 2.06, respectively, and for the FLOTAC double and dual technique US$ 2.35 and US$ 2.83, respectively. Salaries impacted most on the total costs of either method. CONCLUSIONS: The time and cost for soil-transmitted helminth diagnosis using either the Kato-Katz or FLOTAC method in epidemiological surveys are considerable. Our results can help to guide healthcare decision makers and scientists in budget planning and funding for epidemiological surveys, anthelminthic drug efficacy trials and monitoring of control interventions.

Patterns and risk factors of helminthiasis and anemia in a rural and a peri-urban community in Zanzibar, in the context of helminth control programs.

BACKGROUND: The control of helminth infections and prevention of anemia in developing countries are of considerable public health importance. The purpose of this study was to determine patterns and risk factors of helminth infections and anemia in a rural and a peri-urban community of Zanzibar, Tanzania, in the context of national helminth control programs. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a community-based cross-sectional study in 454 individuals by examining at least two stool samples with different methods for soil-transmitted helminths (Ascaris lumbricoides, hookworm, Strongyloides stercoralis, and Trichuris trichiura) and one urine sample for Schistosoma haematobium. Finger-prick blood was taken to estimate anemia levels and to detect antibody reactions against ascariasis, strongyloidiasis and schistosomiasis, using an enzyme-linked immunosorbent assay (ELISA) approach. Parasitological methods determined a helminth prevalence of 73.7% in the rural, and 48.9% in the peri-urban setting. Most helminth infections were of light intensity with school-aged children showing the highest intensities. Multiple helminth species infections were pervasive in rural dwellers regardless of age. More than half of the participants were anemic, with a particularly high prevalence in the peri-urban setting (64.7%). Risk factors for helminth infections were age, sex, consumption of raw vegetables or salad, recent travel history, and socio-economic status. CONCLUSION/SIGNIFICANCE: After several years of chemotherapy-based morbidity control efforts in Zanzibar, helminth prevalences are still high and anemia is common, but helminth infection intensities are low. Hence, chemotherapy should be continued, and complemented with improved access to clean water, adequate sanitation, and health education, along with poverty alleviation measures for a more enduring impact.

Changing patterns of soil-transmitted helminthiases in Zanzibar in the context of national helminth control programs.

Helminth control programs have been implemented in Zanzibar for over a decade. In June/July 2007, approximately 6 months after the last school-based anthelmintic treatment, a cross-sectional survey was carried out in two schools, and results were compared with data obtained in the same schools in 1994. Multiple stool samples collected from 368 school children were subjected to the Kato-Katz, Koga agar plate, and Baermann methods. The prevalence of Trichuris trichiura, hookworm, Ascaris lumbricoides, and Strongyloides stercoralis was 46.6%, 21.6%, 16.9%, and 10.2%, respectively. Infection intensities were generally low. Compared with 1994, the prevalence of S. stercoralis, hookworm, A. lumbricoides, and T. trichiura decreased by 81.0%, 80.5%, 70.6%, and 48.6%, respectively. Infection intensities decreased by > 95% for all helminth species studied. Our study confirms that preventive chemotherapy successfully reduces the level and intensity of helminth infections. To consolidate achievements made, additional control measures such as health education and environmental sanitation are needed.

Measuring morbidity associated with urinary schistosomiasis: assessing levels of excreted urine albumin and urinary tract pathologies.

BACKGROUND: Urinary schistosomiasis is responsible for a variety of debilitating conditions; foremost perhaps are urinary tract pathologies (UTPs). Although portable ultrasonography can be used to detect UTPs visually, there is still a need for rapid morbidity assessment (henceforth referred to as RaMA) tools that can be deployed in the field during implementation, monitoring and evaluation of control programmes. We therefore aimed to determine associations between excreted urine-albumin, as measured using a HemoCue photometer, and UTPs, as detected by ultrasonography, in children and adults from an urinary schistosomiasis endemic area in Zanzibar. METHODOLOGY/PRINCIPAL FINDINGS: In a survey of 140 school-children of both sexes (aged 9 to 15 yr) and 47 adult males (> or =16 yr) on the island of Unguja, the prevalence of egg-patent urinary schistosomiasis was 36.4% (CI(95) 28.5-45.0%) and 46.8% (CI(95) 32.1-61.9%) (P = 0.14), and that of UTPs was 39.4% (CI(95) 31.0-48.3%) and 64.4% (CI(95) 48.8-78.1%) (P = 0.006), respectively. In school-children, raised urine-albumin concentrations (>40 mg/L) were associated, albeit non-significantly, with prevalence of infection (OR = 3.1, P = 0.070), but more specifically and significantly with the prevalence of micro-haematuria (OR = 76.7, P<0.0001). In adults, elevated urine-albumin excretion was associated with UTPs, particularly lesions of the bladder wall (OR = 8.4, P = 0.013). Albuminuria showed promising diagnostic performance, especially in school-aged children with sensitivity of 63.3% and specificity of 83.1% at detecting lower UTPs, i.e. bladder-wall lesions (ultrasonography as 'gold standard'). CONCLUSION/SIGNIFICANCE: This study indicates that albuminuria assays could be used as a RaMA tool for monitoring UTP prevalence during control programmes, as well as a tool for selecting those with more chronic bladder-wall lesions without resorting to ultrasonography.

An evaluation of urine-CCA strip test and fingerprick blood SEA-ELISA for detection of urinary schistosomiasis in schoolchildren in Zanzibar.

To develop better monitoring protocols for detection of urinary schistosomiasis during ongoing control interventions, two commercially available diagnostic tests - the urine-circulating cathodic antigen (CCA) strip and the soluble egg antigen enzyme-linked immunosorbent assay (SEA-ELISA) - were evaluated for detection of Schistosoma haematobium infections in 150 schoolchildren from Zanzibar. The children originated from five primary schools representative of different levels of disease endemicity across the island; using standard urine filtration assessment with microscopy, mean prevalence of S. haematobium was 30.7% (95% confidence interval (CI)=23.4-38.7%) and a total of 35.3% (95% CI=27.7-43.5%) and 8.0% (95% CI=4.2-13.6%) children presented with micro- and macro-haematuria, respectively. Diagnostic scores of the urine-CCA strip were not satisfactory, a very poor sensitivity of 9% (95% CI=2-21%) was observed, precluding any further consideration. By contrast, the performance of the SEA-ELISA using sera from fingerprick blood was good; a sensitivity of 89% (95% CI=76-96%), a specificity of 70% (95% CI=60-79%), a positive predictive value of 57% (95% CI=45-69%) and a negative predictive value of 90% (95% CI=86-98%) were found. At the unit of the school, a positive linear association between prevalence inferred from parasitological examination and SEA-ELISA methods was found. The SEA-ELISA holds promise as a complementary field-based method for monitoring infection dynamics in schoolchildren over and above standard parasitological methods.

The epidemiology and control of urinary schistosomiasis and soil-transmitted helminthiasis in schoolchildren on Unguja Island, Zanzibar.

As part of a 4-year control programme beginning in 2003 and entitled Piga Vita Kichocho, around 140,000 school-aged children on Unguja Island, Zanzibar were treated annually with a combination of praziquantel and albendazole. To provide information on the impact of this intervention, a subset of children, originating from 24 sentinel schools, were monitored in 2004, 2005 and 2006 using both parasitological and behavioural questionnaire methods. Overall, prevalence of urinary schistosomiasis fell by 52%, intensity by 55% and gross haematuria by 82%. There was a positive and statistically significant correlation between areas of elevated disease prevalence and areas of predicted high transmission based upon local occurrence of the permissive intermediate snail host. In areas of low transmission, urinary schistosomiasis was greatly reduced, but, by contrast, other intervention strategies are needed to complement and synergise with chemotherapy in high transmission areas. Whereas significant reductions were documented in the prevalence of both Trichuris trichiura and hookworm, prevalence of Ascaris lumbricoides significantly increased over the monitoring period. Through a detailed analysis of named child records, evidence of predisposition to helminth (re)infection and individual bias towards polyparasitism was detected, highlighting the often overlapping distribution of these parasites within the school-aged child.

A single FLOTAC is more sensitive than triplicate Kato-Katz for the diagnosis of low-intensity soil-transmitted helminth infections.

Accurate diagnostic tools are pivotal for patient management and surveillance of helminth control programmes, particularly in the current era of preventive chemotherapy. Three consecutive stool samples were obtained from 279 schoolchildren from Zanzibar, an island where anthelminthic drugs have been administered on a large scale for more than a decade. All stool samples were examined with the Kato-Katz method. Additionally, one sample per child was preserved in sodium acetate-acetic acid-formalin solution, and examined with the FLOTAC technique. Considering the pooled results of both methods as diagnostic 'gold' standard, the observed prevalences of Trichuris trichiura, hookworm and Ascaris lumbricoides were 63.4, 35.8 and 22.9%, respectively. The sensitivity of examining a single stool sample by FLOTAC for diagnosing T. trichiura, hookworm and A. lumbricoides was 88.7, 83.0 and 82.8%, respectively. Lower sensitivities were observed for Kato-Katz even after examining three stool samples: 71.8, 46.0 and 70.3%, respectively. Kato-Katz revealed considerably higher infection intensities than FLOTAC. The kappa agreement between a single FLOTAC and triplicate Kato-Katz was 0.63 for diagnosing A. lumbricoides and 0.50 for T. trichiura, but only 0.30 for hookworm. The high sensitivity of FLOTAC holds promise for patient management, monitoring soil-transmitted helminth transmission and endpoint(s) of control at the population level.

Diagnosis of soil-transmitted helminths in the era of preventive chemotherapy: effect of multiple stool sampling and use of different diagnostic techniques.

BACKGROUND: Soil-transmitted helminth infections are common throughout the tropics and subtropics and they disproportionately affect the poorest of the poor. In view of a growing global commitment to control soil-transmitted helminthiasis, there is a need to elucidate the effect of repeated stool sampling and the use of different diagnostic methods in areas targeted for preventive chemotherapy that are characterized by low-infection intensities. In this study, we focused on schoolchildren on Unguja Island, Zanzibar, an area where anthelminthic drugs have been repeatedly administered over the past decade. METHODOLOGY/PRINCIPAL FINDINGS: Three serial stool samples from each of 342 schoolchildren were examined using the Kato-Katz (K-K), Koga agar plate (KAP), and Baermann (BM) techniques. These methods were used individually or in combination for the diagnosis of Ascaris lumbricoides (K-K), Trichuris trichiura (K-K), hookworm (K-K and KAP), and Strongyloides stercoralis (KAP and BM). The examination of multiple stool samples instead of a single one resulted in an increase of the observed prevalence; e.g., an increase of 161% for hookworm using the K-K method. The diagnostic sensitivity of single stool sampling ranged between 20.7% for BM to detect S. stercoralis and 84.2% for K-K to diagnose A. lumbricoides. Highest sensitivities were observed when different diagnostic approaches were combined. The observed prevalences for T. trichiura, hookworm, A. lumbricoides, and S. stercoralis were 47.9%, 22.5%, 16.5%, and 10.8% after examining 3 stool samples. These values are close to the 'true' prevalences predicted by a mathematical model. CONCLUSION/SIGNIFICANCE: Rigorous epidemiologic surveillance of soil-transmitted helminthiasis in the era of preventive chemotherapy is facilitated by multiple stool sampling bolstered by different diagnostic techniques.

Micro-epidemiology of urinary schistosomiasis in Zanzibar: Local risk factors associated with distribution of infections among schoolchildren and relevance for control.

Although it is well recognised that both behavioural and environmental factors play a role in determining small-scale heterogeneities in schistosomiasis transmission, empirical evidence of their relative importance is often limited. A study was conducted around Chaani, a village in northern Unguja (Zanzibar) where urinary schistosomiasis is endemic, in order to shed light upon the micro-epidemiology of Schistosoma haematobium and patterns of infection within schoolchildren and the intermediate host snail Bulinus globosus, that may help in adjusting recently implemented control programmes. Malacological surveys were conducted to identify transmission foci and questionnaires were devised to assess recalled water-contact patterns of 150 schoolchildren who had been screened for S. haematobium infection, finding an overall prevalence of 50.6%. Boys were more frequently and more heavily infected than girls and, accordingly, mean exposure scores were significantly higher for boys than girls. Univariate statistics revealed significant associations between infection and specific water-contact activities, including washing/bathing (odds ratio [OR]=3.01, 95% confidence interval [CI]=1.36-6.67) and playing (OR=4.03, 95% CI=1.51-10.70) in streams/ponds. In multivariate analysis, however, the strongest predictor of infection was proximity of the child's home to a site harbouring S. haematobium-infected B. globosus (P<0.001), suggesting that geography may be a better proxy for exposure than self-reported water contact. Surveillance programmes may therefore wish to prioritise evaluation of environmental risk to pinpoint transmission at the micro-geographical level, although water-contact questionnaires are also recommended as a complementary tool to rapidly identify the behaviour patterns of children at most risk of infection in the rural communities of Zanzibar. Such knowledge is a prerequisite for focusing and improving schistosomiasis control at the local level.

School-based control of urinary schistosomiasis on Zanzibar, Tanzania: monitoring micro-haematuria with reagent strips as a rapid urological assessment.

OBJECTIVE: To evaluate micro-haematuria, detected by Haemastix reagent strips, for diagnosis of urinary schistosomiasis during a 3-year period of school-based control on Zanzibar. PATIENTS AND METHODS: A sub-set of school children, from a total of 135,000 who were receiving treatment for urinary schistosomiasis and soil-transmitted helminthiasis, were monitored by parasitological and questionnaire methods for Schistosoma haematobium infections: at treatment baseline in 2004 (n=2002), follow up with re-treatment in 2005 (n=3278) and further follow up with re-treatment in 2006 (n=3993). Standard diagnostic scores for micro-haematuria were calculated against parasitological assessment. RESULTS: Diagnostic scores of Haemastix remained strong throughout the 3-year period. In 2006, scores were: sensitivity (SS)=0.86 (95% CI: 0.86-0.88), specificity (SP)=0.99 (0.98-1.00), positive predictive value (PPV)=0.90 (0.88-0.91), negative predictive value (NPV)=0.98 (0.98-0.99) in boys; and SS=0.84 (0.82-0.86), SP=0.98 (0.98-0.99), PPV=0.77 (0.75-0.79) and NPV=0.99 (0.99-1.00) in girls. By comparison, reported blood in urine and pain upon urination were much lower and not as informative. CONCLUSION: At a cost of approximately pound sterling 0.20/test, further use of reagent strips for monitoring of urinary schistosomiasis during ongoing control programmes should be advocated as a rapid, cost-effective and informative disease surveillance tool.