Browsing by Author "Slater, H.C."
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Item Author Correction: The temporal dynamics and infectiousness of subpatent Plasmodium falciparum infections in relation to parasite density(Nature communications, 2019-06-11) Koram, K.; Slater, H.C.; Ross, A.; Felger, I.; Hofmann, N.E.; Robinson, L.; Cook, J.; Gonçalves, B.P.; Björkman, A.; Ouedraogo, A.L.; Morris, U.; Msellem, M.; Koepfli, C.; Mueller, I.; Tadesse, F.; Gadisa, E.; Das, S.; Domingo, G.; Kapulu, M.; Midega, J.; Owusu-Agyei, S.; Nabet, C.; Piarroux, R.; Doumbo, O.; Doumbo, S.N.; Koram, K.; Lucchi, N.; Udhayakumar, V.; Mosha, J.; Tiono, A.; Chandramohan, D.; Gosling, R.; Mwingira, F.; Sauerwein, R.; Paul, R.; Riley, E.M.; White, N.J.; Nosten, F.; Imwong, M.; Bousema, T.; Drakeley, C.; Okell, L.C.Item Model-Based Geostatistical Mapping of the Prevalence of Onchocerca volvulus in West Africa(Public Library of Science, 2016) O’Hanlon, S.J.; Slater, H.C.; Cheke, R.A.; Boatin, B.A.; Coffeng, L.E.; Pion, S.D.S.; Boussinesq, M.; Zouré, H.G.M.; Stolk, W.A.; Basáñez, M.G.Background: The initial endemicity (pre-control prevalence) of onchocerciasis has been shown to be an important determinant of the feasibility of elimination by mass ivermectin distribution. We present the first geostatistical map of microfilarial prevalence in the former Onchocerciasis Control Programme in West Africa (OCP) before commencement of antivectorial and antiparasitic interventions. Methods and Findings: Pre-control microfilarial prevalence data from 737 villages across the 11 constituent countries in the OCP epidemiological database were used as ground-truth data. These 737 data points, plus a set of statistically selected environmental covariates, were used in a Bayesian model-based geostatistical (B-MBG) approach to generate a continuous surface (at pixel resolution of 5 km x 5km) of microfilarial prevalence in West Africa prior to the commencement of the OCP. Uncertainty in model predictions was measured using a suite of validation statistics, performed on bootstrap samples of held-out validation data. The mean Pearson’s correlation between observed and estimated prevalence at validation locations was 0.693; the mean prediction error (average difference between observed and estimated values) was 0.77%, and the mean absolute prediction error (average magnitude of difference between observed and estimated values) was 12.2%. Within OCP boundaries, 17.8 million people were deemed to have been at risk, 7.55 million to have been infected, and mean microfilarial prevalence to have been 45% (range: 2–90%) in 1975. Conclusions and Significance: This is the first map of initial onchocerciasis prevalence in West Africa using B-MBG. Important environmental predictors of infection prevalence were identified and used in a model out-performing those without spatial random effects or environmental covariates. Results may be compared with recent epidemiological mapping efforts to find areas of persisting transmission. These methods may be extended to areas where data are sparse, and may be used to help inform the feasibility of elimination with current and novel tools. © 2016 O’Hanlon et al.Item The temporal dynamics and infectiousness of subpatent Plasmodium falciparum infections in relation to parasite density(Nature Communications, 2019) Slater, H.C.; Ross, A.; Felge, I.; Hofmann, N.E.; Robinson, L.; Cook, J.; Gonçalves, B.P.; Björkman, A.; Ouedraogo, A.L.; Morris, U.; Msellem, M.; Koepfli, C.; Mueller, I.; Tadesse, F.; Gadisa, E.; Das, S.; Domingo, G.; Kapulu, M.; Midega, J.; Owusu-Agyei, S.; Nabet, C.; Piarroux, R.; Doumbo, O.; Doumbo, S.N.; Koram, K.; Lucchi, N.; Udhayakumar, V.; Mosha, J.; Tiono, A.; Chandramohan, D.; Gosling, R.; Mwingira, F.; Sauerwein, R.; Riley, E.M.; White, N.J.; Nosten, F.; Imwong, M.; Bousema, T.; Drakeley, C.; Okell, L.C.Malaria infections occurring below the limit of detection of standard diagnostics are common in all endemic settings. However, key questions remain surrounding their contribution to sustaining transmission and whether they need to be detected and targeted to achieve malaria elimination. In this study we analyse a range of malaria datasets to quantify the density, detectability, course of infection and infectiousness of subpatent infections. Asymptomatically infected individuals have lower parasite densities on average in low transmission settings compared to individuals in higher transmission settings. In cohort studies, subpatent infections are found to be predictive of future periods of patent infection and in membrane feeding studies, individuals infected with subpatent asexual parasite densities are found to be approximately a third as infectious to mosquitoes as individuals with patent (asexual parasite) infection. These results indicate that subpatent infections contribute to the infectious reservoir, may be long lasting, and require more sensitive diagnostics to detect them in lower transmission settings. © 2019, The Author(s).Item The temporal dynamics and infectiousness of subpatent Plasmodium falciparum infections in relation to parasite density(Nature Communications, 2019-03) Slater, H.C.; Ross, A.; Felger, I.; Hofmann, N.E.; Robinson, L.; Cook, J.; Koram, K.; Gonçalves, B.P.; Björkman, A.; Ouedraogo, A.L.; Morris, U.et.al.Malaria infections occurring below the limit of detection of standard diagnostics are common in all endemic settings. However, key questions remain surrounding their contribution to sustaining transmission and whether they need to be detected and targeted to achieve malaria elimination. In this study we analyse a range of malaria datasets to quantify the density, detectability, course of infection and infectiousness of subpatent infections. Asymptomatically infected individuals have lower parasite densities on average in low transmission settings compared to individuals in higher transmission settings. In cohort studies, subpatent infections are found to be predictive of future periods of patent infection and in membrane feeding studies, individuals infected with subpatent asexual parasite densities are found to be approximately a third as infectious to mosquitoes as individuals with patent (asexual parasite) infection. These results indicate that subpatent infections contribute to the infectious reservoir, may be long lasting, and require more sensitive diagnostics to detect them in lower transmission settings.