56 results found
Meginnis K, Hanley N, Mujumbusi L, et al., 2022, Using choice modelling to identify popular and affordable alternative interventions for schistosomiasis in Uganda, ENVIRONMENT AND DEVELOPMENT ECONOMICS, ISSN: 1355-770X
Trienekens SCM, Faust CL, Besigye F, et al., 2022, Variation in water contact behaviour and risk of Schistosoma mansoni (re)infection among Ugandan school-aged children in an area with persistent high endemicity, PARASITES & VECTORS, Vol: 15, ISSN: 1756-3305
Sun M-T, Gu M-M, Zhang J-Y, et al., 2022, Meta-analysis of variable-temperature PCR technique performance for diagnosising Schistosoma japonicum infections in humans in endemic areas., PLoS Negl Trop Dis, Vol: 16
BACKGROUND: As China is moving onto schistosomiasis elimination/eradication, diagnostic methods with both high sensitivity and specificity for Schistosoma japonicum infections in humans are urgently needed. Microscopic identification of eggs in stool is proven to have poor sensitivity in low endemic regions, and antibody tests are unable to distinguish between current and previous infections. Polymerase chain reaction (PCR) technologies for the detection of parasite DNA have been theoretically assumed to show high diagnostic sensitivity and specificity. However, the reported performance of PCR for detecting S. japonicum infection varied greatly among studies. Therefore, we performed a meta-analysis to evaluate the overall diagnostic performance of variable-temperature PCR technologies, based on stool or blood, for detecting S. japonicum infections in humans from endemic areas. METHODS: We searched literatures in eight electronic databases, published up to 20 January 2021. The heterogeneity and publication bias of included studies were assessed statistically. The risk of bias and applicability of each eligible study were assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 tool (QUADAS-2). The bivariate mixed-effects model was applied to obtain the summary estimates of diagnostic performance. The hierarchical summary receiver operating characteristic (HSROC) curve was applied to visually display the results. Subgroup analyses and multivariate regression were performed to explore the source of heterogeneity. This research was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines and was registered prospectively in PROSPERO (CRD42021233165). RESULTS: A total of 2791 papers were retrieved. After assessing for duplications and eligilibity a total of thirteen publications were retained for inclusion. These included eligible data from 4268 participants across sixteen studies. High heterogeneity exis
Francoeur R, Atuhaire A, Arinaitwe M, et al., 2021, ABO Blood Groups Do Not Predict Schistosoma mansoni Infection Profiles in Highly Endemic Villages of Uganda, MICROORGANISMS, Vol: 9
Arinaitwe M, Adriko M, Kibwika B, et al., 2021, Residence Time, Water Contact, and Age-driven Schistosoma mansoni Infection in Hotspot Communities in Uganda, AMERICAN JOURNAL OF TROPICAL MEDICINE AND HYGIENE, Vol: 105, Pages: 1772-1781, ISSN: 0002-9637
Ayabina DV, Clark J, Bayley H, et al., 2021, Gender-related differences in prevalence, intensity and associated risk factors of Schistosoma infections in Africa: A systematic review and meta-analysis, PLOS NEGLECTED TROPICAL DISEASES, Vol: 15, ISSN: 1935-2735
Ssali A, Pickering L, Nalwadda E, et al., 2021, Schistosomiasis messaging in endemic communities: Lessons and implications for interventions from rural Uganda, a rapid ethnographic assessment study, PLOS NEGLECTED TROPICAL DISEASES, Vol: 15, ISSN: 1935-2735
Clark J, Arinaitwe M, Nankasi A, et al., 2021, Reconciling Egg- and Antigen-Based Estimates of Schistosoma mansoni Clearance and Reinfection: A Modeling Study, CLINICAL INFECTIOUS DISEASES, Vol: 74, Pages: 1557-1563, ISSN: 1058-4838
Berger DJ, Crellen T, Lamberton PHL, et al., 2021, Whole-genome sequencing of Schistosoma mansoni reveals extensive diversity with limited selection despite mass drug administration, NATURE COMMUNICATIONS, Vol: 12, ISSN: 2041-1723
Champion TS, Connelly S, Smith CJ, et al., 2020, Monitoring schistosomiasis and sanitation interventions-The potential of environmental DNA, WILEY INTERDISCIPLINARY REVIEWS-WATER, Vol: 8, ISSN: 2049-1948
Faust CL, Osakunor DNM, Downs JA, et al., 2020, Schistosomiasis Control: Leave No Age Group Behind, TRENDS IN PARASITOLOGY, Vol: 36, Pages: 582-591, ISSN: 1471-4922
Trienekens SCM, Faust CL, Meginnis K, et al., 2020, Impacts of host gender on Schistosoma mansoni risk in rural Uganda-A mixed-methods approach, PLOS NEGLECTED TROPICAL DISEASES, Vol: 14, ISSN: 1935-2735
Meginnis K, Hanley N, Mujumbusi L, et al., 2020, Non-monetary numeraires: Varying the payment vehicle in a choice experiment for health interventions in Uganda, ECOLOGICAL ECONOMICS, Vol: 170, ISSN: 0921-8009
Krauth SJ, Balen J, Gobert GN, et al., 2019, A call for systems epidemiology to tackle the complexity of Schistosomiasis, its control, and its elimination, Tropical Medicine and Infectious Disease, Vol: 4, ISSN: 2414-6366
Ever since the first known written report of schistosomiasis in the mid-19th century, researchers have aimed to increase knowledge of the parasites, their hosts, and the mechanisms contributing to infection and disease. This knowledge generation has been paramount for the development of improved intervention strategies. Yet, despite a broad knowledge base of direct risk factors for schistosomiasis, there remains a paucity of information related to more complex, interconnected, and often hidden drivers of transmission that hamper intervention successes and sustainability. Such complex, multidirectional, non-linear, and synergistic interdependencies are best understood by looking at the integrated system as a whole. A research approach able to address this complexity and find previously neglected causal mechanisms for transmission, which include a wide variety of influencing factors, is needed. Systems epidemiology, as a holistic research approach, can integrate knowledge from classical epidemiology, with that of biology, ecology, social sciences, and other disciplines, and link this with informal, tacit knowledge from experts and affected populations. It can help to uncover wider-reaching but difficult-to-identify processes that directly or indirectly influence exposure, infection, transmission, and disease development, as well as how these interrelate and impact one another. Drawing on systems epidemiology to address persisting disease hotspots, failed intervention programmes, and systematically neglected population groups in mass drug administration programmes and research studies, can help overcome barriers in the progress towards schistosomiasis elimination. Generating a comprehensive view of the schistosomiasis system as a whole should thus be a priority research agenda towards the strategic goal of morbidity control and transmission elimination.
Adriko M, Faust CL, Carruthers LV, et al., 2018, Low praziquantel treatment coverage for schistosoma mansoni in Mayuge District, Uganda, due to the absence of treatment opportunities, rather than systematic non-compliance, Tropical Medicine and Infectious Disease, Vol: 3, ISSN: 2414-6366
The World Health Organization (WHO) recommends praziquantel mass drug administration (MDA) to control schistosomiasis in endemic regions. We aimed to quantify recent and lifetime praziquantel coverage, and reasons for non-treatment, at an individual level to guide policy recommendations to help Uganda reach WHO goals. Cross-sectional household surveys (n = 681) encompassing 3208 individuals (adults and children) were conducted in 2017 in Bugoto A and B, Mayuge District, Uganda. Participants were asked if they had received praziquantel during the recent MDA (October 2016) and whether they had ever received praziquantel in their lifetime. A multivariate logistic regression analysis with socio-economic and individual characteristics as covariates was used to determine factors associated with praziquantel uptake. In the MDA eligible population (≥5 years of age), the most recent MDA coverage was 48.8%. Across individuals' lifetimes, 31.8% of eligible and 49.5% of the entire population reported having never taken praziquantel. Factors that improved individuals' odds of taking praziquantel included school enrolment, residence in Bugoto B and increasing years of village-residency. Not being offered (49.2%) and being away during treatment (21.4%) were the most frequent reasons for not taking the 2016 praziquantel MDA. Contrary to expectations, chronically-untreated individuals were rarely systematic non-compliers, but more commonly not offered treatment.
Pitaksakulrat O, Webster BL, Webster JP, et al., 2018, Phylogenetic relationships within the Opisthorchis viverrini species complex with specific analysis of O-viverrini sensu lato from Sakon Nakhon, Thailand by mitochondrial and nuclear DNA sequencing, INFECTION GENETICS AND EVOLUTION, Vol: 62, Pages: 86-94, ISSN: 1567-1348
Jourdan PM, Lamberton PHL, Fenwick A, et al., 2018, Strongyloides stercoralis: the need for accurate information reply, LANCET, Vol: 391, Pages: 2323-2323, ISSN: 0140-6736
Prada JM, Touloupou P, Adriko M, et al., 2018, Understanding the relationship between egg- and antigen-based diagnostics of Schistosoma mansoni infection pre- and post-treatment in Uganda., Parasites & Vectors, Vol: 11, ISSN: 1756-3305
BACKGROUND: Schistosomiasis is a major socio-economic and public health problem in many sub-Saharan African countries. After large mass drug administration (MDA) campaigns, prevalence of infection rapidly returns to pre-treatment levels. The traditional egg-based diagnostic for schistosome infections, Kato-Katz, is being substituted in many settings by circulating antigen recognition-based diagnostics, usually the point-of-care circulating cathodic antigen test (CCA). The relationship between these diagnostics is poorly understood, particularly after treatment in both drug-efficacy studies and routine monitoring. RESULTS: We created a model of schistosome infections to better understand and quantify the relationship between these two egg- and adult worm antigen-based diagnostics. We focused particularly on the interpretation of "trace" results after CCA testing. Our analyses suggest that CCA is generally a better predictor of prevalence, particularly after treatment, and that trace CCA results are typically associated with truly infected individuals. CONCLUSIONS: Even though prevalence rises to pre-treatment levels only six months after MDAs, our model suggests that the average intensity of infection is much lower, and is probably in part due to a small burden of surviving juveniles from when the treatment occurred. This work helps to better understand CCA diagnostics and the interpretation of post-treatment prevalence estimations.
Gower CM, Gehre F, Marques SR, et al., 2017, Phenotypic and genotypic monitoring of Schistosoma mansoni in Tanzanian schoolchildren five years into a preventative chemotherapy national control programme., Parasites & Vectors, Vol: 10, ISSN: 1756-3305
BACKGROUND: Schistosoma mansoni is a parasite of profound medical importance. Current control focusses on mass praziquantel (PZQ) treatment of populations in endemic areas, termed Preventative Chemotherapy (PC). Large-scale PC programmes exert prolonged selection pressures on parasites with the potential for, direct and/or indirect, emergence of drug resistance. Molecular methods can help monitor genetic changes of schistosome populations over time and in response to drug treatment, as well as estimate adult worm burdens through parentage analysis. Furthermore, methods such as in vitro drug sensitivity assays help phenotype in vivo parasite genotypic drug efficacy. METHODS: We conducted combined in vitro PZQ efficacy testing with population genetic analyses of S. mansoni collected from children from two schools in 2010, five years after the introduction of a National Control Programme. Children at one school had received four annual PZQ treatments and the other school had received two mass treatments in total. We compared genetic differentiation, indices of genetic diversity, and estimated adult worm burden from parasites collected in 2010 with samples collected in 2005 (before the control programme began) and in 2006 (six months after the first PZQ treatment). Using 2010 larval samples, we also compared the genetic similarity of those with high and low in vitro sensitivity to PZQ. RESULTS: We demonstrated that there were individual parasites with reduced PZQ susceptibility in the 2010 collections, as evidenced by our in vitro larval behavioural phenotypic assay. There was no evidence, however, that miracidia showing phenotypically reduced susceptibility clustered together genetically. Molecular analysis also demonstrated a significant reduction of adult worm load over time, despite little evidence of reduction in parasite infection intensity, as measured by egg output. Genetic diversity of infections did not reduce over time, despite changes in the genetic composit
Viana M, Faust CL, Haydon DT, et al., 2017, The effects of subcurative praziquantel treatment on life-history traits and trade-offs in drug-resistant Schistosoma mansoni, Evolutionary Applications, Vol: 11, Pages: 488-500, ISSN: 1752-4571
Natural selection acts on all organisms, including parasites, to maximize reproductive fitness. Drug resistance traits are often associated with life-history costs in the absence of treatment. Schistosomiasis control programmes rely on mass drug administration to reduce human morbidity and mortality. Although hotspots of reduced drug efficacy have been reported, resistance is not widespread. Using Bayesian state-space models (SSMs) fitted to data from an in vivo laboratory system, we tested the hypothesis that the spread of resistant Schistosoma mansoni may be limited by life-history costs not present in susceptible counterparts. S. mansoni parasites from a praziquantel-susceptible (S), a praziquantel-resistant (R) or a mixed line of originally resistant and susceptible parasites (RS) were exposed to a range of praziquantel doses. Parasite numbers at each life stage were quantified in their molluscan intermediate and murine definitive hosts across four generations, and SSMs were used to estimate key life-history parameters for each experimental group over time. Model outputs illustrated that parasite adult survival and fecundity in the murine host decreased across all lines, including R, with increasing drug pressure. Trade-offs between adult survival and fecundity were observed in all untreated lines, and these remained strong in S with praziquantel pressure. In contrast, trade-offs between adult survival and fecundity were lost under praziquantel pressure in R. As expected, parasite life-history traits within the molluscan host were complex, but trade-offs were demonstrated between parasite establishment and cercarial output. The observed trade-offs between generations within hosts, which were modified by praziquantel treatment in the R line, could limit the spread of R parasites under praziquantel pressure. Whilst such complex life-history costs may be difficult to detect using standard empirical methods, we demonstrate that SSMs provide robust estimates of life-
Harrington D, Lamberton PHL, McGregor A, 2017, Human liver flukes, LANCET GASTROENTEROLOGY & HEPATOLOGY, Vol: 2, Pages: 680-689, ISSN: 2468-1253
Lamberton PHL, Faust CL, Webster JP, 2017, Praziquantel decreases fecundity in Schistosoma mansoni adult worms that survive treatment: evidence from a laboratory life-history trade-offs selection study, Infectious Diseases of Poverty, Vol: 6, ISSN: 2049-9957
BackgroundMass drug administration of praziquantel is the World Health Organization’s endorsed control strategy for schistosomiasis. A decade of annual treatments across sub-Saharan Africa has resulted in significant reductions of infection prevalence and intensity levels, although ‘hotspots’ remain. Repeated drug treatments place strong selective pressures on parasites, which may affect life-history traits that impact transmission dynamics. Understanding drug treatment responses and the evolution of such traits can help inform on how to minimise the risk of drug resistance developing, maximise sustainable control programme success, and improve diagnostic protocols.MethodsWe performed a four-generation Schistosoma mansoni praziquantel selection experiment in mice and snails. We used three S. mansoni lines: a praziquantel-resistant isolate (R), a praziquantel-susceptible isolate (S), and a co-infected line (RS), under three treatment regimens: untreated, 25 mg/kg praziquantel, or 50 mg/kg praziquantel. Life-history traits, including parasite adult-worm establishment, survival, reproduction (fecundity), and associated morbidity, were recorded in mice across all four generations. Predictor variables were tested in a series of generalized linear mixed effects models to determine which factors had a significant influence on parasite life-history traits in definitive hosts under different selection regimes.ResultsPraziquantel pressure significantly reduced adult-worm burdens across all generations and isolates, including within R-lines. However, previous drug treatment resulted in an increase in adult-worm establishment with increasing generation from P1 to F3. The highest worm numbers were in the co-infected RS line. Praziquantel treatment decreased adult-worm burden, but had a larger negative impact on the mean daily number of miracidia, a proxy for fecundity, across all three parasite isolates.ConclusionsOur predicted cost of resistance was not suppor
Crainey JL, Hurst J, Lamberton PHL, et al., 2017, The genomic architecture of novel simulium damnosum Wolbachia prophage sequence elements and implications for onchocerciasis epidemiology, Frontiers in Microbiology, Vol: 8, ISSN: 1664-302X
Research interest in Wolbachia is growing as new discoveries and technical advancements reveal the public health importance of both naturally occurring and artificial infections. Improved understanding of the Wolbachia bacteriophages (WOs) WOcauB2 and WOcauB3 (belonging to a sub-group of four WOs encoding serine recombinases group 1 (sr1WOs)), has enhanced the prospect of novel tools for the genetic manipulation of Wolbachia. The basic biology of sr1WOs, including host range and mode of genomic integration is, however, still poorly understood. Very few sr1WOs have been described, with two such elements putatively resulting from integrations at the same Wolbachia genome loci, about 2 kb downstream from the FtsZ cell-division gene. Here we characterise the DNA sequence flanking the FtsZ gene of wDam, a genetically distinct line of Wolbachia isolated from the West African onchocerciasis vector Simulium squamosum E. Using Roche 454 shot-gun and Sanger sequencing, we have resolved >32 kb of WO prophage sequence into 3 contigs representing three distinct prophage elements. Spanning ≥ 36 distinct WO open reading frame gene sequences, these prophage elements correspond roughly to three different WO modules: a serine recombinase and replication module (sr1RRM), a head and base-plate module and a tail module. The sr1RRM module contains replication genes and a Holliday junction recombinase and is unique to the sr1 group WOs. In the extreme terminal of the tail module there is an SpvB protein homologue—believed to have insecticidal properties and proposed to have a role in how Wolbachia parasitize their insect hosts. We propose that these wDam prophage modules all derive from a single WO genome, which we have named here sr1WOdamA1. The best-match database sequence for all of our sr1WOdamA1-predicted gene sequences was annotated as of Wolbachia or Wolbachia phage sourced from an arthropod. Clear evidence of exchange between sr1WOdamA1 and other Wolbachia WO phage seq
Pitaksakulrat O, Kiatsopit N, Laoprom N, et al., 2017, Preliminary genetic evidence of two different populations of Opisthorchis viverrini in Lao PDR, PARASITOLOGY RESEARCH, Vol: 116, Pages: 1247-1256, ISSN: 0932-0113
Ding H, Gao Y-M, Deng Y, et al., 2017, A systematic review and meta-analysis of the seroprevalence of Toxoplasma gondii in cats in mainland China, PARASITES & VECTORS, Vol: 10, ISSN: 1756-3305
Gao Y-M, Ding H, Lamberton PHL, et al., 2016, Prevalence of Toxoplasma gondii in pet dogs in mainland China: A meta-analysis, VETERINARY PARASITOLOGY, Vol: 229, Pages: 126-130, ISSN: 0304-4017
Basanez M, Lamberton PHL, Cheke RA, et al., 2016, Onchocerciasis transmission in Ghana: the human blood index of sibling species of the Simulium damnosum complex, Parasites & Vectors, Vol: 9, ISSN: 1756-3305
BackgroundVector-biting behaviour is important for vector-borne disease (VBD) epidemiology. The proportion of blood meals taken on humans (the human blood index, HBI), is a component of the biting rate per vector on humans in VBD transmission models. Humans are the definitive host of Onchocerca volvulus, but the simuliid vectors feed on a range of animals and HBI is a key indicator of the potential for human onchocerciasis transmission. Ghana has a diversity of Simulium damnosum complex members, which are likely to vary in their HBIs, an important consideration for parameterization of onchocerciasis control and elimination models.MethodsHost-seeking and ovipositing S. damnosum (sensu lato) (s.l.) were collected from seven villages in four Ghanaian regions. Taxa were morphologically and molecularly identified. Blood meals from individually stored blackfly abdomens were used for DNA profiling, to identify previous host choice. Household, domestic animal, wild mammal and bird surveys were performed to estimate the density and diversity of potential blood hosts of blackflies.ResultsA total of 11,107 abdomens of simuliid females (which would have obtained blood meal(s) previously) were tested, with blood meals successfully amplified in 3,772 (34 %). A single-host species was identified in 2,857 (75.7 %) of the blood meals, of which 2,162 (75.7 %) were human. Simulium soubrense Beffa form, S. squamosum C and S. sanctipauli Pra form were the most anthropophagic (HBI = 0.92, 0.86 and 0.70, respectively); S. squamosum E, S. yahense and S. damnosum (sensu stricto) (s.s.)/S. sirbanum were the most zoophagic (HBI = 0.44, 0.53 and 0.63, respectively). The degree of anthropophagy decreased (but not statistically significantly) with increasing ratio of non-human/human blood hosts. Vector to human ratios ranged from 139 to 1,198 blackflies/person.ConclusionsDNA profiling can successfully identify blood meals from host-seeking and ovipositing blackflies.
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.
Lamberton PHL, Jourdan PM, 2015, Human Ascariasis: Diagnostics Update, Current Tropical Medicine Reports, Vol: 2, Pages: 189-200, ISSN: 2196-3045
Soil-transmitted helminths (STHs) infect over one billion people worldwide. Ascariasis may mimic a number of conditions, and individual clinical diagnosis often requires a thorough work-up. Kato-Katz thick smears are the standard detection method for Ascaris and, despite low sensitivity, are often used for mapping and monitoring and evaluation of national control programmes. Although increased sampling (number of stools) and diagnostic (number of examinations per stool) efforts can improve sensitivity, Kato-Katz is less sensitive than other microscopy methods such as FLOTAC®. Antibody-based diagnostics may be a sensitive diagnostic tool; however, their usefulness is limited to assessing transmission in areas aiming for elimination. Molecular diagnostics are highly sensitive and specific, but high costs limit their use to individual diagnosis, drug - efficacy studies and identification of Ascaris suum. Increased investments in research on Ascaris and other STHs are urgently required for the development of diagnostic assays to support efforts to reduce human suffering caused by these infections.
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