Publications
257 results found
Crellen T, Walker M, Cotton JA, et al., 2016, Reduced efficacy of praziquantel against Schistosoma mansoni is associated with multiple-rounds of mass drug administration, Clinical Infectious Diseases, Vol: 63, Pages: 1151-1159, ISSN: 1537-6591
The efficacy of praziquantel against Schistosoma mansoni was significantly lower in Ugandan schools that had received more prior rounds of mass drug administration, as determined by fitting a statistical model to parasite egg counts before and after treatment.
Fleming FM, Matovu F, Hansen KS, et al., 2016, A mixed methods approach to evaluating community drug distributor performance in the control of neglected tropical diseases, Parasites & Vectors, Vol: 9, ISSN: 1756-3305
BACKGROUND: Trusted literate, or semi-literate, community drug distributors (CDDs) are the primary implementers in integrated preventive chemotherapy (IPC) programmes for Neglected Tropical Disease (NTD) control. The CDDs are responsible for safely distributing drugs and for galvanising communities to repeatedly, often over many years, receive annual treatment, create and update treatment registers, monitor for side-effects and compile treatment coverage reports. These individuals are 'volunteers' for the programmes and do not receive remuneration for their annual work commitment. METHODS: A mixed methods approach, which included pictorial diaries to prospectively record CDD use of time, structured interviews and focus group discussions, was used to triangulate data on how 58 CDDs allocated their time towards their routine family activities and to NTD Programme activities in Uganda. The opportunity costs of CDD time were valued, performance assessed by determining the relationship between time and programme coverage, and CDD motivation for participating in the programme was explored. RESULTS: Key findings showed approximately 2.5 working weeks (range 0.6-11.4 working weeks) were spent on NTD Programme activities per year. The amount of time on NTD control activities significantly increased between the one and three deliveries that were required within an IPC campaign. CDD time spent on NTD Programme activities significantly reduced time available for subsistence and income generating engagements. As CDDs took more time to complete NTD Programme activities, their treatment performance, in terms of validated coverage, significantly decreased. Motivation for the programme was reported as low and CDDs felt undervalued. CONCLUSIONS: CDDs contribute a considerable amount of opportunity cost to the overall economic cost of the NTD Programme in Uganda due to the commitment of their time. Nevertheless, programme coverage of at least 75 %, as required by the World Health
Crellen T, Allan F, David S, et al., 2016, Whole genome resequencing of the human parasite Schistosoma mansoni reveals population history and effects of selection., Scientific Reports, Vol: 6, ISSN: 2045-2322
Schistosoma mansoni is a parasitic fluke that infects millions of people in the developing world. This study presents the first application of population genomics to S. mansoni based on high-coverage resequencing data from 10 global isolates and an isolate of the closely-related Schistosoma rodhaini, which infects rodents. Using population genetic tests, we document genes under directional and balancing selection in S. mansoni that may facilitate adaptation to the human host. Coalescence modeling reveals the speciation of S. mansoni and S. rodhaini as 107.5-147.6KYA, a period which overlaps with the earliest archaeological evidence for fishing in Africa. Our results indicate that S. mansoni originated in East Africa and experienced a decline in effective population size 20-90KYA, before dispersing across the continent during the Holocene. In addition, we find strong evidence that S. mansoni migrated to the New World with the 16-19(th) Century Atlantic Slave Trade.
Webster JP, Gower CM, Knowles SC, et al., 2016, One health - an ecological and evolutionary framework for tackling Neglected Zoonotic Diseases., Evolutionary Applications, Vol: 9, Pages: 313-333, ISSN: 1752-4571
Understanding the complex population biology and transmission ecology of multihost parasites has been declared as one of the major challenges of biomedical sciences for the 21st century and the Neglected Zoonotic Diseases (NZDs) are perhaps the most neglected of all the Neglected Tropical Diseases (NTDs). Here we consider how multihost parasite transmission and evolutionary dynamics may affect the success of human and animal disease control programmes, particularly neglected diseases of the developing world. We review the different types of zoonotic interactions that occur, both ecological and evolutionary, their potential relevance for current human control activities, and make suggestions for the development of an empirical evidence base and theoretical framework to better understand and predict the outcome of such interactions. In particular, we consider whether preventive chemotherapy, the current mainstay of NTD control, can be successful without a One Health approach. Transmission within and between animal reservoirs and humans can have important ecological and evolutionary consequences, driving the evolution and establishment of drug resistance, as well as providing selective pressures for spill-over, host switching, hybridizations and introgressions between animal and human parasites. Our aim here is to highlight the importance of both elucidating disease ecology, including identifying key hosts and tailoring control effort accordingly, and understanding parasite evolution, such as precisely how infectious agents may respond and adapt to anthropogenic change. Both elements are essential if we are to alleviate disease risks from NZDs in humans, domestic animals and wildlife.
Petney TN, Sithithaworn P, Andrews RH, et al., 2016, Foodborne trematodes: a diverse and challenging group of neglected parasites, Transactions of the Royal Society of Tropical Medicine and Hygiene, Vol: 110, Pages: 1-3, ISSN: 0035-9203
Easton AV, Oliveira RG, O'Connell EM, et al., 2016, Multi-parallel qPCR provides increased sensitivity and diagnostic breadth for gastrointestinal parasites of humans: field-based inferences on the impact of mass deworming, Parasites & Vectors, Vol: 9, ISSN: 1756-3305
BackgroundAlthough chronic morbidity in humans from soil transmitted helminth (STH) infections can be reduced by anthelmintic treatment, inconsistent diagnostic tools make it difficult to reliably measure the impact of deworming programs and often miss light helminth infections.MethodsCryopreserved stool samples from 796 people (aged 2–81 years) in four villages in Bungoma County, western Kenya, were assessed using multi-parallel qPCR for 8 parasites and compared to point-of-contact assessments of the same stools by the 2-stool 2-slide Kato-Katz (KK) method. All subjects were treated with albendazole and all Ascaris lumbricoides expelled post-treatment were collected. Three months later, samples from 633 of these people were re-assessed by both qPCR and KK, re-treated with albendazole and the expelled worms collected.ResultsBaseline prevalence by qPCR (n = 796) was 17 % for A. lumbricoides, 18 % for Necator americanus, 41 % for Giardia lamblia and 15 % for Entamoeba histolytica. The prevalence was <1 % for Trichuris trichiura, Ancylostoma duodenale, Strongyloides stercoralis and Cryptosporidium parvum. The sensitivity of qPCR was 98 % for A. lumbricoides and N. americanus, whereas KK sensitivity was 70 % and 32 %, respectively. Furthermore, qPCR detected infections with T. trichiura and S. stercoralis that were missed by KK, and infections with G. lamblia and E. histolytica that cannot be detected by KK. Infection intensities measured by qPCR and by KK were correlated for A. lumbricoides (r = 0.83, p < 0.0001) and N. americanus (r = 0.55, p < 0.0001). The number of A. lumbricoides worms expelled was correlated (p < 0.0001) with both the KK (r = 0.63) and qPCR intensity measurements (r = 0.60).ConclusionsKK may be an inadequate tool for stool-based surveillance in areas where hookworm or Strongyloides are common or where intensity of helmi
Albonico M, Levecke B, LoVerde PT, et al., 2015, Monitoring the efficacy of drugs for neglected tropical diseases controlled by preventive chemotherapy, JOURNAL OF GLOBAL ANTIMICROBIAL RESISTANCE, Vol: 3, Pages: 229-236, ISSN: 2213-7165
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- Citations: 25
French MD, Churcher TS, Webster JP, et al., 2015, Estimation of changes in the force of infection for intestinal and urogenital schistosomiasis in countries with schistosomiasis control initiative-assisted programmes, PARASITES & VECTORS, Vol: 8, ISSN: 1756-3305
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- Citations: 14
Knowles SCL, Webster BL, Garba A, et al., 2015, Epidemiological interactions between urogenital and intestinal human schistosomiasis in the context of praziquantel treatment across three West African countries, PLOS Neglected Tropical Diseases, Vol: 9, ISSN: 1935-2735
BackgroundIn many parts of sub-Saharan Africa, urogenital and intestinal schistosomiasis co-occur, and mixed species infections containing both Schistosoma haematobium and S. mansoni can be common. During co-infection, interactions between these two species are possible, yet the extent to which such interactions influence disease dynamics or the outcome of control efforts remains poorly understood.Methodology/Principal FindingsHere we analyse epidemiological data from three West African countries co-endemic for urogenital and intestinal schistosomiasis (Senegal, Niger and Mali) to test whether the impact of praziquantel (PZQ) treatment, subsequent levels of re-infection or long-term infection dynamics are altered by co-infection. In all countries, positive associations between the two species prevailed at baseline: infection by one species tended to predict infection intensity for the other, with the strength of association varying across sites. Encouragingly, we found little evidence that co-infection influenced PZQ efficacy: species-specific egg reduction rates (ERR) and cure rates (CR) did not differ significantly with co-infection, and variation in treatment success was largely geographical. In Senegal, despite positive associations at baseline, children with S. mansoni co-infection at the time of treatment were less intensely re-infected by S. haematobium than those with single infections, suggesting competition between the species may occur post-treatment. Furthermore, the proportion of schistosome infections attributable to S. mansoni increased over time in all three countries examined.Conclusions/SignificanceThese findings suggest that while co-infection between urinary and intestinal schistosomes may not directly affect PZQ treatment efficacy, competitive interspecific interactions may influence epidemiological patterns of re-infection post-treatment. While re-infection patterns differed most strongly according to geographic location, interspecific interact
Webster BL, Rabone M, Pennance T, et al., 2015, Development of novel multiplex microsatellite polymerase chain reactions to enable high-throughput population genetic studies of <i>Schistosoma haematobium</i> (vol 8, 432, 2015), PARASITES & VECTORS, Vol: 8, ISSN: 1756-3305
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- Citations: 1
Chevalier FD, LeClec'h W, LoVerde PT, et al., 2015, POPULATION "EXOMICS" OF <i>SCHISTOSOMA MANSONI</i>, Publisher: AMER SOC TROP MED & HYGIENE, Pages: 545-545, ISSN: 0002-9637
Lamberton PH, Mitchell K, Gower CM, et al., 2015, HOTSPOTS OF <i>SCHISTOSOMA MANSONI</i> TRANSMISSION TEN YEARS INTO A MASS DRUG ADMINISTRATION PROGRAM, Publisher: AMER SOC TROP MED & HYGIENE, Pages: 558-558, ISSN: 0002-9637
Fleming FM, Matovu F, Webster JP, et al., 2015, COMMUNITY DRUG DISTRIBUTOR PERFORMANCE IN THE CONTROL OF NEGLECTED TROPICAL DISEASES: ARE WE ASKING TOO MUCH?, Publisher: AMER SOC TROP MED & HYGIENE, Pages: 375-375, ISSN: 0002-9637
Easton AV, Oliveira RG, O'Connell EM, et al., 2015, MULTI-PARALLEL QPCR PROVIDES INCREASED SENSITIVITY AND DIAGNOSTIC BREADTH ALLOWING FOR IMPROVED EVALUATION OF THE IMPACT OF DEWORMING PROGRAMS FOR SOIL-TRANSMITTED HELMINTHS (STH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 18-18, ISSN: 0002-9637
Deol AK, Webster JP, Harrison W, et al., 2015, Development of a Markov transition probability model to predict changes in schistosomiasis infection following treatment, TROPICAL MEDICINE & INTERNATIONAL HEALTH, Vol: 20, Pages: 237-237, ISSN: 1360-2276
King KC, Stelkens RB, Webster JP, et al., 2015, Hybridization in Parasites: Consequences for Adaptive Evolution, Pathogenesis, and Public Health in a Changing World, PLOS PATHOGENS, Vol: 11, ISSN: 1553-7366
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- Citations: 92
Webster BL, Rabone M, Pennance T, et al., 2015, Development of novel multiplex microsatellite polymerase chain reactions to enable high-throughput population genetic studies of <i>Schistosoma haematobium</i>, PARASITES & VECTORS, Vol: 8, ISSN: 1756-3305
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- Citations: 26
Webster JP, Lamberton PHL, McConkey GA, 2015, The Toxoplasma gondii model of schizophrenia., Handbook of Behavioral Neuroscience Series. Modeling the psychopathological dimensions of schizophrenia and related psychoses: from molecules to behavior., Editors: Pletnikov, Waddington, Publisher: Elsevier, Pages: 225-241
Lamberton PHL, Crellen T, Cotton JA, et al., 2015, Modelling the Effects of Mass Drug Administration on the Molecular Epidemiology of Schistosomes, Advances in Parasitology, Vol: 87, Pages: 293-327, ISSN: 0065-308X
As national governments scale up mass drug administration (MDA) programs aimed to combat neglected tropical diseases (NTDs), novel selection pressures on these parasites increase. To understand how parasite populations are affected by MDA and how to maximize the success of control programmes, it is imperative for epidemiological, molecular and mathematical modelling approaches to be combined. Modelling of parasite population genetic and genomic structure, particularly of the NTDs, has been limited through the availability of only a few molecular markers to date. The landscape of infectious disease research is being dramatically reshaped by next-generation sequencing technologies and our understanding of how repeated selective pressures are shaping parasite populations is radically altering. Genomics can provide high-resolution data on parasite population structure, and identify how loci may contribute to key phenotypes such as virulence and/or drug resistance. We discuss the incorporation of genetic and genomic data, focussing on the recently sequenced Schistosoma spp., into novel mathematical transmission models to inform our understanding of the impact of MDA and other control methods. We summarize what is known to date, the models that exist and how population genetics has given us an understanding of the effects of MDA on the parasites. We consider how genetic and genomic data have the potential to shape future research, highlighting key areas where data are lacking, and how future molecular epidemiology knowledge can aid understanding of transmission dynamics and the effects of MDA, ultimately informing public health policy makers of the best interventions for NTDs.
Macdonald DW, Berdoy M, Webster JP, 2015, Brown rats on farmland: ecological citizens or subsidized carpet-baggers?, WILDLIFE CONSERVATION ON FARMLAND, VOL 2: CONFLICT IN THE COUNTRYSIDE, Editors: Macdonald, Feber, Publisher: OXFORD UNIV PRESS, Pages: 222-244
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- Citations: 2
Lamberton PHL, Kabatereine NB, Oguttu DW, et al., 2014, Sensitivity and Specificity of Multiple Kato-Katz Thick Smears and a Circulating Cathodic Antigen Test for <i>Schistosoma mansoni</i> Diagnosis Pre- and Post-repeated-Praziquantel Treatment, PLOS NEGLECTED TROPICAL DISEASES, Vol: 8, ISSN: 1935-2735
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- Citations: 108
Kaushik M, Knowles SCL, Webster JP, 2014, What Makes a Feline Fatal in <i>Toxoplasma gondii</i>'s Fatal Feline Attraction? Infected Rats Choose Wild Cats, INTEGRATIVE AND COMPARATIVE BIOLOGY, Vol: 54, Pages: 118-128, ISSN: 1540-7063
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- Citations: 21
Webster JP, Molyneux DH, Hotez PJ, et al., 2014, The contribution of mass drug administration to global health: past, present and future, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 369, ISSN: 0962-8436
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- Citations: 122
Webster JP, Kaushik M, 2014, The impact of Toxoplasma gondii on host behaviour: can this parasite play a role in some cases of human schizophrenia?, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology, Publisher: OXFORD UNIV PRESS INC, Pages: E221-E221, ISSN: 1540-7063
Koukounari A, Donnelly CA, Moustaki I, et al., 2013, A Latent Markov Modelling Approach to the Evaluation of Circulating Cathodic Antigen Strips for Schistosomiasis Diagnosis Pre- and Post-Praziquantel Treatment in Uganda, PLOS Computational Biology, Vol: 9, ISSN: 1553-734X
Regular treatment with praziquantel (PZQ) is the strategy for human schistosomiasis control aiming to prevent morbidity in later life. With the recent resolution on schistosomiasis elimination by the 65th World Health Assembly, appropriate diagnostic tools to inform interventions are keys to their success. We present a discrete Markov chains modelling framework that deals with the longitudinal study design and the measurement error in the diagnostic methods under study. A longitudinal detailed dataset from Uganda, in which one or two doses of PZQ treatment were provided, was analyzed through Latent Markov Models (LMMs). The aim was to evaluate the diagnostic accuracy of Circulating Cathodic Antigen (CCA) and of double Kato-Katz (KK) faecal slides over three consecutive days for Schistosoma mansoni infection simultaneously by age group at baseline and at two follow-up times post treatment. Diagnostic test sensitivities and specificities and the true underlying infection prevalence over time as well as the probabilities of transitions between infected and uninfected states are provided. The estimated transition probability matrices provide parsimonious yet important insights into the re-infection and cure rates in the two age groups. We show that the CCA diagnostic performance remained constant after PZQ treatment and that this test was overall more sensitive but less specific than single-day double KK for the diagnosis of S. mansoni infection. The probability of clearing infection from baseline to 9 weeks was higher among those who received two PZQ doses compared to one PZQ dose for both age groups, with much higher re-infection rates among children compared to adolescents and adults. We recommend LMMs as a useful methodology for monitoring and evaluation and treatment decision research as well as CCA for mapping surveys of S. mansoni infection, although additional diagnostic tools should be incorporated in schistosomiasis elimination programs.
French MD, Churcher TS, Basanez M-G, et al., 2013, Reductions in genetic diversity of <i>Schistosoma mansoni</i> populations under chemotherapeutic pressure: the effect of sampling approach and parasite population definition, ACTA TROPICA, Vol: 128, Pages: 196-205, ISSN: 0001-706X
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- Citations: 15
Webster BL, Webster JP, Gouvras AN, et al., 2013, DNA 'barcoding' of <i>Schistosoma mansoni</i> across sub-Saharan Africa supports substantial within locality diversity and geographical separation of genotypes, ACTA TROPICA, Vol: 128, Pages: 250-260, ISSN: 0001-706X
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- Citations: 21
Gower CM, Gouvras AN, Lamberton PHL, et al., 2013, Population genetic structure of <i>Schistosoma mansoni</i> and <i>Schistosoma haematobium</i> from across six sub-Saharan African countries: Implications for epidemiology, evolution and control, ACTA TROPICA, Vol: 128, Pages: 261-274, ISSN: 0001-706X
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- Citations: 56
Gouvras AN, Kariuki C, Koukounari A, et al., 2013, The impact of single versus mixed <i>Schistosoma haematobium</i> and <i>S</i>. <i>mansoni</i> infections on morbidity profiles amongst school-children in Taveta, Kenya, ACTA TROPICA, Vol: 128, Pages: 309-317, ISSN: 0001-706X
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- Citations: 24
Garba A, Lamine MS, Barkire N, et al., 2013, Efficacy and safety of two closely spaced doses of praziquantel against <i>Schistosoma haematobium</i> and <i>S</i>. <i>mansoni</i> and re-infection patterns in school-aged children in Niger, ACTA TROPICA, Vol: 128, Pages: 334-344, ISSN: 0001-706X
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- Citations: 48
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