Effect Of Seasonal Rainfall And Other Environmental Changes, On Snail Density And Infection Rates With Schistosoma mansoni Fifteen Years After The Last Snails\' Study In Kigungu, Entebbe, Uganda

Background: The last study on snail population density in relation to rainfall pattern in Kigungu canoe landing and recreational sites on Lake Victoria shore was earlier carried out about fifteen years ago. This study also reviewed the influence of other environmental factors on the snails\' infection rate. Objective: To reassess the density dynamic of Biomphalaria (B) choanomphala and Biomphalaria (B) pfeifferi, which act as the intermediate host for S. mansoni and Bulinus (B) globosus, and Bulinus (B) tropicus, which act as intermediate host for S. haematobium. Design: Retrospective study. Setting: Busy canoe landing sites along Lake Victoria in Kigungu fishing village were selected for the snail sampling. Results: Nine thousand one hundred and ninety four B. choanomphala were collected over the study period. The numbers of B. choanomphala collected in each year was 4742 (51.6%) and 4452 (48.4%) in 2004 and 2005 respectively. Of the 4742 B.Choanomphala collected in 2004, 82 (1.7%) shed human cercariae and 329 (6.7%) shed non-human cercariae. Whereas in 2005, out of 4452 B. choanomphala collected 302 (6.85%) shed non-human cercariae and 82 (1.8%) shed human cercariae. Similarly, 4173 B. pfeifferi were also collected in the same period. Out of which 2224 (53.3%) were collected in 2004 and 1949 (46.7%) in 2005. For B. pfeifferi, 42 (1.9%) out of 2224 snails collected in 2004 shed human cercariae and 246 (11.1%) shed non-human cercariae. While in 2005, 33 out of 1949 snails (1.7%) shed human cercariae and 159 (8.2%) shed non-human cercariae. Other snails of medical importance collected included 292 B. globosus and 3094 B. tropicus. None of the Bulinus spp. collected shed any human cercariae but 37 (2.1%) and 30 (2.3%) B. tropicus shed non-human cercariae in 2004 and 2005 respectively. In 2004 and 2005, the area received, 1729mm and 1959mm of rainfall respectively. The mean rainfall during the year was 144.05 mm and 163.3 mm in 2004 and 2005 respectively. There was a negative correlation between rainfalls and snail density dynamic. Conclusion: We have found in this study that in spite of the bush clearing of the papyrus swamps which originally was the major habitats for B. choanomphala, B. pfeifferi and the Bulinus spp the intermediate host for schistosome at all canoe landing sites at Kigungu, these snails are still present. Moreover, that their population density dynamic and infection rate are inversely proportional to the rainfall pattern. East African Medical Journal Vol. 85 (11) 2008: pp. 556-56

Social network fragmentation and community health

Community health interventions often seek to intentionally destroy paths between individuals to prevent the spread of communicable diseases. Immunizing individuals through direct vaccination or the provision of health education prevents pathogen transmission and the propagation of misinformation concerning medical treatments. Yet, it remains an open question whether network-based strategies should be used in place of conventional field approaches to target individuals for medical treatment in low-income countries. We collected complete friendship and health advice networks in 17 rural villages of Mayuge District, Uganda. Here we show that acquaintance algorithms, i.e. selecting neighbors of randomly selected nodes, were systematically more efficient in fragmenting all networks than targeting well-established community roles, i.e. health workers, village government members, and schoolteachers. Additionally, community roles were not good proxy indicators of physical proximity to other households or connections to many sick people. We also show that acquaintance algorithms were effective in offsetting potential noncompliance with deworming treatments for 16,357 individuals during mass drug administration (MDA). Health advice networks were destroyed more easily than friendship networks. Only an average of 32% of nodes were removed from health advice networks to reduce the percentage of nodes at risk of refusing treatment in MDA to below 25%. Treatment compliance of at least 75% is needed in MDA to control human morbidity attributable to parasitic worms and progress towards elimination. Our findings point toward the potential use of network-based approaches as an alternative to role-based strategies for targeting individuals in rural health interventions.This study was financially supported by the Vice Chancellor’s Fund of the University of Cambridge, the Schistosomiasis Control Initiative, the Wellcome Trust Programme Grant 083931/Z/07/Z, the Netherlands Organization for Scientific Research Grant 452-04-333, and the Isaac Newton Trust and King’s College, Cambridge Fellowships to G.F.C

Does mass drug administration for the integrated treatment of neglected tropical diseases really work? Assessing evidence for the control of schistosomiasis and soil-transmitted helminths in Uganda

This paper was one of four papers commissioned to review the role of social sciences in NTD control by TDR, the Special Programme for Research and Training on Tropical Diseases, which is executed by WHO and co-sponsored by UNICEF, UNDP, the World Bank and WHO.This article has been made available through the Brunel Open Access Publishing Fund.Background: Less is known about mass drug administration [MDA] for neglected tropical diseases [NTDs] than is suggested by those so vigorously promoting expansion of the approach. This paper fills an important gap: it draws upon local level research to examine the roll out of treatment for two NTDs, schistosomiasis and soil-transmitted helminths, in Uganda. Methods: Ethnographic research was undertaken over a period of four years between 2005-2009 in north-west and south-east Uganda. In addition to participant observation, survey data recording self-reported take-up of drugs for schistosomiasis, soil-transmitted helminths and, where relevant, lymphatic filariasis and onchocerciasis was collected from a random sample of at least 10% of households at study locations. Data recording the take-up of drugs in Ministry of Health registers for NTDs were analysed in the light of these ethnographic and social survey data. Results: The comparative analysis of the take-up of drugs among adults revealed that although most long term residents have been offered treatment at least once since 2004, the actual take up of drugs for schistosomiasis and soil-transmitted helminths varies considerably from one district to another and often also within districts. The specific reasons why MDA succeeds in some locations and falters in others relates to local dynamics. Issues such as population movement across borders, changing food supply, relations between drug distributors and targeted groups, rumours and conspiracy theories about the 'real' purpose of treatment, subjective experiences of side effects from treatment, alternative understandings of affliction, responses to social control measures and historical experiences of public health control measures, can all make a huge difference. The paper highlights the need to adapt MDA to local circumstances. It also points to specific generalisable issues, notably with respect to health education, drug distribution and more effective use of existing public health legislation. Conclusion: While it has been an achievement to have offered free drugs to so many adults, current standard practices of monitoring, evaluation and delivery of MDA for NTDs are inconsistent and inadequate. Efforts to integrate programmes have exacerbated the difficulties. Improved assessment of what is really happening on the ground will be an essential step in achieving long-term overall reduction of the NTD burden for impoverished communities.This article is available through the Brunel Open Access Publishing Fund

Observed Reductions in Schistosoma mansoni Transmission from Large-Scale Administration of Praziquantel in Uganda: A Mathematical Modelling Study

To date schistosomiasis control programmes based on chemotherapy have largely aimed at controlling morbidity in treated individuals rather than at suppressing transmission. In this study, a mathematical modelling approach was used to estimate reductions in the rate of Schistosoma mansoni reinfection following annual mass drug administration (MDA) with praziquantel in Uganda over four years (2003-2006). In doing this we aim to elucidate the benefits of MDA in reducing community transmission.Age-structured models were fitted to a longitudinal cohort followed up across successive rounds of annual treatment for four years (Baseline: 2003, TREATMENT: 2004-2006; n = 1,764). Instead of modelling contamination, infection and immunity processes separately, these functions were combined in order to estimate a composite force of infection (FOI), i.e., the rate of parasite acquisition by hosts.MDA achieved substantial and statistically significant reductions in the FOI following one round of treatment in areas of low baseline infection intensity, and following two rounds in areas with high and medium intensities. In all areas, the FOI remained suppressed following a third round of treatment.This study represents one of the first attempts to monitor reductions in the FOI within a large-scale MDA schistosomiasis morbidity control programme in sub-Saharan Africa. The results indicate that the Schistosomiasis Control Initiative, as a model for other MDA programmes, is likely exerting a significant ancillary impact on reducing transmission within the community, and may provide health benefits to those who do not receive treatment. The results obtained will have implications for evaluating the cost-effectiveness of schistosomiasis control programmes and the design of monitoring and evaluation approaches in general

Diffusion of treatment in social networks and mass drug administration

Information, behaviours, and technologies spread when people interact. Understanding these interactions is critical for achieving the greatest diffusion of public interventions. Yet, little is known about the performance of starting points (seed nodes) for diffusion. We track routine mass drug administration—the large-scale distribution of deworming drugs—in Uganda. We collect friendship networks, socioeconomic factors, and treatment delivery outcomes for 16,357 individuals in 3,491 households of 17 rural villages. Each village has two community medicine distributors (CMDs), who are the seed nodes and responsible for administering treatments. Here we show that CMDs with tightly-knit (clustered) friendship connections achieve the greatest reach and speed of treatment coverage. Importantly, we demonstrate that clustering predicts diffusion through social networks when spreading relies on contact with seed nodes whilst centrality is unrelated to diffusion. Clustering should be considered when selecting seed nodes for large-scale treatment campaigns.Financially supported by the Vice Chancellor’s Fund of the University of Cambridge, the Schistosomiasis Control Initiative, the Wellcome Trust (Programme grant 083931/Z/07/Z to D.W.D), and the Netherlands Organization for Scientific Research (N.W.O. grant 452-04-333 to E.B.)

One hundred years of neglect in paediatric schistosomiasis.

: Early in the history of schistosomiasis research, children under 5 years of age were known to be infected. Although this problem was recognized over 100 years ago, insufficient action has been taken to address this issue. Under current policy, such infected children only receive their first antiparasitic treatment (praziquantel - PZQ) upon entry into primary school as current mass drug administration programmes typically target school-aged children. For many infected children, they will wait up to 6 years before receiving their first medication and significant schistosomiasis-related morbidity may have already established. This inequity would not be accepted for other diseases. To unveil some of the reasons behind this neglect, it is paramount to understand the intricate historical relationship between schistosomiasis and British Imperial medicine, to underline its lasting influence on today's public health priorities. This review presents a perspective on the historical neglect of paediatric schistosomiasis, focusing on important gaps that persist from the early days after discovery of this parasite. Looking to end this inequity, we address several issues that need to be overcome to move forward towards the lasting success of schistosomiasis control and elimination efforts.<br/

Community-directed mass drug administration is undermined by status seeking in friendship networks and inadequate trust in health advice networks

Over 1.9 billion individuals require preventive chemotherapy through mass drug administration (MDA). Community-directed MDA relies on volunteer community medicine distributors (CMDs) and their achievement of high coverage and compliance. Yet, it is unknown if village social networks influence effective MDA implementation by CMDs. In Mayuge District, Uganda, census-style surveys were conducted for 16,357 individuals from 3,491 households in 17 villages. Praziquantel, albendazole, and ivermectin were administered for one month in community-directed MDA to treat Schistosoma mansoni, hookworm, and lymphatic filariasis. Self-reported treatment outcomes, socioeconomic characteristics, friendship networks, and health advice networks were collected. We investigated systematically missed coverage and noncompliance. Coverage was defined as an eligible person being offered at least one drug by CMDs; compliance included ingesting at least one of the offered drugs. These outcomes were analyzed as a two-stage process using a Heckman selection model. To further assess if MDA through CMDs was working as intended, we examined the probability of accurate drug administration of 1) praziquantel, 2) both albendazole and ivermectin, and 3) all drugs. This analysis was conducted using bivariate Probit regression. Four indicators from each social network were examined: degree, betweenness centrality, closeness centrality, and the presence of a direct connection to CMDs. All models accounted for nested household and village standard errors. CMDs were more likely to offer medicines, and to accurately administer the drugs as trained by the national control programme, to individuals with high friendship degree (many connections) and high friendship closeness centrality (households that were only a short number of steps away from all other households in the network). Though high (88.59%), additional compliance was associated with directly trusting CMDs for health advice. Effective treatment provision requires addressing CMD biases towards influential, well-embedded individuals in friendship networks and utilizing health advice networks to increase village trust in CMDs.The authors acknowledge financial support from the Vice Chancellor’s Fund of the University of Cambridge, the Schistosomiasis Control Initiative, the Wellcome Trust Programme grant 083931/Z/07/Z to David W. Dunne, the Netherlands Organization for Scientific Research grant 452-04- 333 to Erwin Bulte, and the Isaac Newton Trust and King’s College, Cambridge fellowships to Goylette F. Chami

Geographical Distribution of Intestinal Schistosomiasis and Soil-Transmitted Helminthiasis and Preventive Chemotherapy Strategies in Sierra Leone

The common intestinal roundworm, whipworm and hookworm (together known as soil-transmitted helminthes - STHs) together with schistosomes or bilharzia are responsible for extensive ill health, reduced life expectancy and death in sub-Saharan Africa. These diseases are transmitted in areas of poor water supply and sanitation. In order to implement an appropriate national control program, knowledge of the prevalence and geographical distribution of these diseases is required. A national survey was performed in Sierra Leone in 2008. Overall prevalence of intestinal schistosomiasis was 18.4% and that of STHs was 39.1%. Intestinal schistosomiasis was mainly prevalent in the northern and eastern regions while STH is widespread in the country. The results justify routine de-worming for pre-school children, school age children, women of childbearing age, and adults at high risk twice a year. The results also justify using anti-schistosomiasis drug (praziquantel) in school age children, all women of childbearing age, and adults at high risk annually or biennially depending upon the prevalence in the areas

A Rationale for Schistosomiasis Control in Elementary Schools of the Rainforest Zone of Pernambuco, Brazil

In 2001, a World Health Assembly resolution urged member states to ensure treatment against schistosomiasis and soil-transmitted helminthiasis in endemic areas with the goal of attaining a minimum target of at least 75% of all school-aged children by 2010. In the highly endemic Rainforest Zone of Pernambuco (ZMP), northeast Brazil, the Schistosomiasis Control Program has registered a cumulative coverage of only 20% of the population at risk, which jeopardizes the accomplishment of the minimum target for that area. Demographic and parasitological data from a representative municipality of the ZMP provide evidence that the current, community-based approach to control can be complemented with school-based actions. In the most troubled municipalities, individual diagnosis and treatment could be focused on school-aged children rather than whole populations without compromising the principles of the primary health care system. Local health and education teams should be encouraged to include school-based interventions to scale up coverage and achieve a rapid impact on infection

Sensitivity and Specificity of Multiple Kato-Katz Thick Smears and a Circulating Cathodic Antigen Test for Schistosoma mansoni Diagnosis Pre- and Post-repeated-Praziquantel Treatment

Two Kato-Katz thick smears (Kato-Katzs) from a single stool are currently recommended for diagnosing Schistosoma mansoni infections to map areas for intervention. This ‘gold standard’ has low sensitivity at low infection intensities. The urine point-of-care circulating cathodic antigen test (POC-CCA) is potentially more sensitive but how accurately they detect S. mansoni after repeated praziquantel treatments, their suitability for measuring drug efficacy and their correlation with egg counts remain to be fully understood. We compared the accuracies of one to six Kato-Katzs and one POC-CCA for the diagnosis of S. mansoni in primary-school children who have received zero to ten praziquantel treatments. We determined the impact each diagnostic approach may have on monitoring and evaluation (M&E) and drug-efficacy findings