Publications
60 results found
Unwin HJT, Sherrard-Smith E, Churcher TS, et al., 2020, MODELLING THE IMPACT OF PYRETHROID RESISTANCE ON PERSONAL PROTECTION AND THE MASS COMMUNITY EFFECT OF LONG-LASTING INSECTICIDE TREATED NETS, 68th Annual Meeting of the American-Society-for-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 187-187, ISSN: 0002-9637
Murray GPD, Lissenden N, Jones J, et al., 2020, Barrier bednets target malaria vectors and expand the range of usable insecticides, Nature Microbiology, Vol: 5, Pages: 40-47, ISSN: 2058-5276
Transmission of Plasmodium falciparum malaria parasites occurs when nocturnal Anopheles mosquito vectors feed on human blood. In Africa, where malaria burden is highest, bednets treated with pyrethroid insecticide were highly effective in preventing mosquito bites and reducing transmission, and essential to achieving unprecedented reductions in malaria until 2015 (ref. 1). Since then, progress has stalled2, and with insecticidal bednets losing efficacy against pyrethroid-resistant Anopheles vectors3,4, methods that restore performance are urgently needed to eliminate any risk of malaria returning to the levels seen before their widespread use throughout sub-Saharan Africa5. Here, we show that the primary malaria vector Anopheles gambiae is targeted and killed by small insecticidal net barriers positioned above a standard bednet in a spatial region of high mosquito activity but zero contact with sleepers, opening the way for deploying many more insecticides on bednets than is currently possible. Tested against wild pyrethroid-resistant A. gambiae in Burkina Faso, pyrethroid bednets with organophosphate barriers achieved significantly higher killing rates than bednets alone. Treated barriers on untreated bednets were equally effective, without significant loss of personal protection. Mathematical modelling of transmission dynamics predicted reductions in clinical malaria incidence with barrier bednets that matched those of ‘next-generation’ nets recommended by the World Health Organization against resistant vectors. Mathematical models of mosquito–barrier interactions identified alternative barrier designs to increase performance. Barrier bednets that overcome insecticide resistance are feasible using existing insecticides and production technology, and early implementation of affordable vector control tools is a realistic prospect.
Sherrard-Smith E, Skarp JE, Beale AD, et al., 2019, Mosquito feeding behavior and how it influences residual malaria transmission across Africa, Proceedings of the National Academy of Sciences, Vol: 116, Pages: 15086-15095, ISSN: 0027-8424
The antimalarial efficacy of the most important vector control interventions—long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS)—primarily protect against mosquitoes’ biting people when they are in bed and indoors. Mosquito bites taken outside of these times contribute to residual transmission which determines the maximum effectiveness of current malaria prevention. The likelihood mosquitoes feed outside the time of day when LLINs and IRS can protect people is poorly understood, and the proportion of bites received outdoors may be higher after prolonged vector control. A systematic review of mosquito and human behavior is used to quantify and estimate the public health impact of outdoor biting across Africa. On average 79% of bites by the major malaria vectors occur during the time when people are in bed. This estimate is substantially lower than previous predictions, with results suggesting a nearly 10% lower proportion of bites taken at the time when people are beneath LLINs since the year 2000. Across Africa, this higher outdoor transmission is predicted to result in an estimated 10.6 million additional malaria cases annually if universal LLIN and IRS coverage was achieved. Higher outdoor biting diminishes the cases of malaria averted by vector control. This reduction in LLIN effectiveness appears to be exacerbated in areas where mosquito populations are resistant to insecticides used in bed nets, but no association was found between physiological resistance and outdoor biting. Substantial spatial heterogeneity in mosquito biting behavior between communities could contribute to differences in effectiveness of malaria control across Africa.
Green N, Sherrard-Smith E, Tanton C, et al., 2019, Assessing local chlamydia screening performance by combining survey and administrative data to account for differences in local population characteristics, Scientific Reports, Vol: 9, ISSN: 2045-2322
Reducing health inequalities requires improved understanding of the causes of variation. Local-level variation reflects differences in local population characteristics and health system performance. Identifying low- and high-performing localities allows investigation into these differences. We used Multilevel Regression with Post-stratification (MRP) to synthesise data from multiple sources, using chlamydia testing as our example. We used national probability survey data to identify individual-level characteristics associated with chlamydia testing and combined this with local-level census data to calculate expected levels of testing in each local authority (LA) in England, allowing us to identify LAs where observed chlamydia testing rates were lower or higher than expected, given population characteristics. Taking account of multiple covariates, including age, sex, ethnicity, student and cohabiting status, 5.4% and 3.5% of LAs had testing rates higher than expected for 95% and 99% posterior credible intervals, respectively; 60.9% and 50.8% had rates lower than expected. Residual differences between observed and MRP expected values were smallest for LAs with large proportions of non-white ethnic populations. London boroughs that were markedly different from expected MRP values (90% posterior exceedance probability) had actively targeted risk groups. This type of synthesis allows more refined inferences to be made at small-area levels than previously feasible.
Suh E, Grossman MK, Waite JL, et al., 2019, THERMAL ECOLOGY OF MALARIA TRANSMISSION AND THE POTENTIAL IMPACT OF BEHAVIORAL RESISTANCE, 68th Annual Meeting of the American-Society-for-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 421-421, ISSN: 0002-9637
Sherrard-Smith E, Griffin J, Winskill P, et al., 2018, Systematic review of indoor residual spray efficacy and effectiveness against Plasmodium falciparum in Africa, Nature Communications, Vol: 9, ISSN: 2041-1723
Indoor residual spraying (IRS) is an important part of malaria control. There is a growing list of insecticide classes; pyrethroids remain the principal insecticide used in bednets but recently, novel non-pyrethroid IRS products, with contrasting impacts, have been introduced. There is an urgent need to better assess product efficacy to help decision makers choose effective and relevant tools for mosquito control. Here we use experimental hut trial data to characterise the entomological efficacy of widely-used, novel IRS insecticides. We quantify their impact against pyrethroid-resistant mosquitoes and use a Plasmodium falciparum transmission model to predict the public health impact of different IRS insecticides. We report that long-lasting IRS formulations substantially reduce malaria, though their benefit over cheaper, shorter-lived formulations depends on local factors including bednet use, seasonality, endemicity and pyrethroid resistance status of local mosquito populations. We provide a framework to help decision makers evaluate IRS product effectiveness.
Witmer K, Sherrard-Smith E, Straschil U, et al., 2018, An inexpensive open source 3D printed membrane feeder for human malaria transmission studies, Malaria Journal, Vol: 17, ISSN: 1475-2875
BackgroundThe study of malaria transmission requires the experimental infection of mosquitoes with Plasmodium gametocytes. In the laboratory, this is achieved using artificial membrane feeding apparatus that simulate body temperature and skin of the host, and so permit mosquito feeding on reconstituted gametocyte-containing blood. Membrane feeders either use electric heating elements or complex glass chambers to warm the infected blood; both of which are expensive to purchase and can only be sourced from a handful of specialized companies. Presented and tested here is a membrane feeder that can be inexpensively printed using 3D-printing technology.ResultsUsing the Plasmodium falciparum laboratory strain NF54, three independent standard membrane feeding assays (SMFAs) were performed comparing the 3D-printed feeder against a commercial glass feeder. Exflagellation rates did not differ between the two feeders. Furthermore, no statistically significant difference was found in the oocyst load nor oocyst intensity of Anopheles stephensi mosquitoes (mean oocyst range 1.3–6.2 per mosquito; infection prevalence range 41–79%).ConclusionsOpen source provision of the design files of the 3D-printed feeder will facilitate a wider range of laboratories to perform SMFAs in laboratory and field settings, and enable them to freely customize the design to their own requirements.
Sherrard-Smith E, Sala KA, Betancourt M, et al., 2018, Synergy in anti-malarial pre-erythrocytic and transmission-blocking antibodies is achieved by reducing parasite density, eLife, Vol: 7, ISSN: 2050-084X
Anti-malarial pre-erythrocytic vaccines (PEV) target transmission by inhibiting human infection but are currently partially protective. It has been posited, but never demonstrated, that co-administering transmission-blocking vaccines (TBV) would enhance malaria control. We hypothesized a mechanism that TBV could reduce parasite density in the mosquito salivary glands, thereby enhancing PEV efficacy. This was tested using a multigenerational population assay, passaging Plasmodium berghei to Anopheles stephensi mosquitoes. A combined efficacy of 90.8% (86.7–94.2%) was observed in the PEV +TBV antibody group, higher than the estimated efficacy of 83.3% (95% CrI 79.1–87.0%) if the two antibodies acted independently. Higher PEV efficacy at lower mosquito parasite loads was observed, comprising the first direct evidence that co-administering anti-sporozoite and anti-transmission interventions act synergistically, enhancing PEV efficacy across a range of TBV doses and transmission intensities. Combining partially effective vaccines of differing anti-parasitic classes is a pragmatic, powerful way to accelerate malaria elimination efforts.
O'Brien A, Sherrard-Smith E, Sile B, et al., 2018, Spatial clusters of gonorrhoea in England with particular reference to the outcome of partner notification: 2012 and 2013, PLoS ONE, Vol: 13, ISSN: 1932-6203
Background:This study explored spatial-temporal variation in diagnoses of gonorrhoea to identify and quantify endemic areas and clusters in relation to patient characteristics and outcomes of partner notification (PN) across England, UK.Methods:Endemic areas and clusters were identified using a two-stage analysis with Kulldorff’s scan statistics (SaTScan).ResultsOf 2,571,838 tests, 53,547 diagnoses were gonorrhoea positive (positivity = 2.08%). The proportion of diagnoses in heterosexual males was 1.5 times that in heterosexual females. Among index cases, men who have sex with men (MSM) were 8 times more likely to be diagnosed with gonorrhoea than heterosexual males (p<0.0001). After controlling for age, gender, ethnicity and deprivation rank, 4 endemic areas were identified including 11,047 diagnoses, 86% of which occurred in London. 33 clusters included 17,629 diagnoses (34% of total diagnoses in 2012 and 2013) and spanned 21 locations, some of which were dominated by heterosexually acquired infection, whilst others were MSM focused. Of the 53,547 diagnoses, 14.5% (7,775) were the result of PN. The proportion of patients who attended services as a result of PN varied from 0% to 61% within different age, gender and sexual orientation cohorts. A third of tests resulting from PN were positive for gonorrhoea. 25% of Local Authorities (n = 81, 95% CI: 20.2, 29.5) had a higher than expected proportion for female PN diagnoses as compared to 16% for males (n = 52, 95% CI: 12.0, 19.9).Conclusions:The English gonorrhoea epidemic is characterised by spatial-temporal variation. PN success varied between endemic areas and clusters. Greater emphasis should be placed on the role of PN in the control of gonorrhoea to reduce the risk of onward transmission, re-infection, and complications of infection.
Sherrard-Smith E, Skarp J, Beale A, et al., 2018, THE BEHAVIORAL AND PHYSIOLOGICAL ADAPTATIONS OF MALARIAL MOSQUITOES SINCE 2000 AND CONSEQUENCES FOR PUBLIC HEALTH IMPACT IN AFRICA, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 452-452, ISSN: 0002-9637
Sherrard-Smith E, Churcher TS, Upton LM, et al., 2017, THE COMBINED IMPACT OF TRANSMISSION-BLOCKING INTERVENTIONS AND PRE-ERYTHROCYTIC VACCINES FOR MALARIA ELIMINATION, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 90-91, ISSN: 0002-9637
Smallbone WA, Chadwick EA, Francis J, et al., 2017, East-West Divide: temperature and land cover drive spatial variation of <i>Toxoplasma gondii</i> infection in Eurasian otters (<i>Lutra lutra</i>) from England and Wales, PARASITOLOGY, Vol: 144, Pages: 1433-1440, ISSN: 0031-1820
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- Citations: 8
Sherrard-Smith E, Churcher TS, Upton LM, et al., 2017, A novel model itted to multiple life stages of malaria for assessing eicacy of transmission-blocking interventions, Malaria Journal, Vol: 16, ISSN: 1475-2875
BackgroundTransmission-blocking interventions (TBIs) aim to eliminate malaria by reducing transmission of the parasite between the host and the invertebrate vector. TBIs include transmission-blocking drugs and vaccines that, when given to humans, are taken up by mosquitoes and inhibit parasitic development within the vector. Accurate methodologies are key to assess TBI efficacy to ensure that only the most potent candidates progress to expensive and time-consuming clinical trials. Measuring intervention efficacy can be problematic because there is substantial variation in the number of parasites in both the host and vector populations, which can impact transmission even in laboratory settings.MethodsA statistically robust empirical method is introduced for estimating intervention efficacy from standardised population assay experiments. This method will be more reliable than simple summary statistics as it captures changes in parasite density in different life-stages. It also allows efficacy estimates at a finer resolution than previous methods enabling the impact of the intervention over successive generations to be tracked. A major advantage of the new methodology is that it makes no assumptions on the population dynamics of infection. This enables both host-to-vector and vector-to-host transmission to be density-dependent (or other) processes and generates easy-to-understand estimates of intervention efficacy.ResultsThis method increases the precision of intervention efficacy estimates and demonstrates that relying on changes in infection prevalence (the proportion of infected hosts) alone may be insufficient to capture the impact of TBIs, which also suppress parasite density in secondarily infected hosts.ConclusionsThe method indicates that potentially useful, partially effective TBIs may require multiple infection cycles before substantial reductions in prevalence are observed, despite more rapidly suppressing parasite density. Accurate models to quantify effica
Sherrard-Smith E, Sala KA, Betancourt M, et al., 2017, USING ANTIBODIES TO SIMULATE THE CO-ADMINISTRATION OF TRANSMISSION-BLOCKING AND PRE-ERYTHROCYTIC VACCINES ACCELERATES MALARIA ELIMINATION IN MICE, 66th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 532-532, ISSN: 0002-9637
Sherrard-Smith E, Winskill P, Griffin JT, et al., 2017, A SYSTEMATIC REVIEW OF INDOOR RESIDUAL SPRAYING TO INVESTIGATE THE IMPACT OF PYRETHROID RESISTANCE ON MALARIA TRANSMISSION, 66th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 137-137, ISSN: 0002-9637
Sitko J, Bizos J, Sherrard-Smith E, et al., 2016, Integrative taxonomy of European parasitic flatworms of the genus Metorchis Looss, 1899 (Trematoda: Opisthorchiidae), Parasitology International, Vol: 65, Pages: 258-267, ISSN: 1873-0329
Finnie TJR, South A, Bento A, et al., 2015, EpiJSON: A unified data-format for epidemiology, Epidemics, Vol: 15, Pages: 20-26, ISSN: 1878-0067
Sherrard-Smith E, Stanton DWG, Cable J, et al., 2015, Distribution and molecular phylogeny of biliary trematodes (Opisthorchiidae) infecting native Lutra lutra and alien Neovison vison across Europe, Parasitology International, Vol: 65, Pages: 163-170, ISSN: 1873-0329
The recent identification of Pseudamphistomum truncatum, (Rudolphi, 1819) (Trematoda: Opisthorchiidae) and Metorchis bilis (Braun, 1790) Odening, 1962 (synonymous with Metorchis albidus (Braun, 1893) Loos, 1899 and Metorchis crassiusculus (Rudolphi, 1809) Looss, 1899 (Trematoda: Opisthorchiidae)) in otters from Britain caused concern because of associated biliary damage, coupled with speculation over their alien status. Here, we investigate the presence, intensity and phylogeny of these trematodes in mustelids (principally otters) across Europe (Czech Republic, Denmark, France, Germany, Norway, Poland and Sweden and Britain). The trematodes were identified to species using the internal transcribed spacer II (ITS2) locus. Both parasites were found across Europe but at unequal frequency. In the German state of Saxony, eight out of eleven (73%) otters examined were infected with P. truncatum whilst this parasite was not found in either mink from Scotland (n = 40) or otters from Norway (n = 21). Differences in the phylogenies between the two species suggest divergent demographic histories possibly reflecting contrasting host diet or competitive exclusion, with M. bilis exhibiting greater mitochondrial diversity than P. truncatum. Shared haplotypes within the ranges of both parasite species probably reflect relatively unrestricted movements (both natural and anthropogenic) of intermediate and definitive hosts across Europe.
Sherrard-Smith E, Upton L, Zakutansky S, et al., 2015, THE COMBINED IMPACT OF TRANSMISSION-BLOCKING DRUGS AND RTS, S VACCINES IS SYNERGISTIC?, Publisher: AMER SOC TROP MED & HYGIENE, Pages: 503-503, ISSN: 0002-9637
Harding-Esch E, Sherrard-Smith E, Dangerfield C, et al., 2015, WEB-TOOL TO ASSESS THE COST-EFFECTIVENESS OF CHLAMYDIA POINT-OF-CARE TESTS AT THE LOCAL LEVEL, Publisher: BMJ PUBLISHING GROUP, Pages: A143-A143, ISSN: 1368-4973
Dangerfield CE, Sherrard-Smith E, Green N, et al., 2015, IMPACT AND COST-EFFECTIVENESS OF POINT-OF-CARE TESTING FOR CHLAMYDIA: ACCOUNTING FOR GEOGRAPHIC VARIATION IN INFECTION BURDEN AND TESTING RATES, HEALTH SERVICE CONFIGURATION, AND IMPLEMENTATION STRATEGY, Publisher: BMJ PUBLISHING GROUP, Pages: A152-A153, ISSN: 1368-4973
Harding-Esch E, Sherrard-Smith E, Fuller SS, et al., 2015, SEXUAL BEHAVIOUR IN THE TIME PERIOD BETWEEN BEING TESTED FOR CHLAMYDIA AND RECEIVING TEST RESULT AND TREATMENT, Publisher: BMJ PUBLISHING GROUP, Pages: A37-A37, ISSN: 1368-4973
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- Citations: 4
Sherrard-Smith E, Chadwick EA, Cable J, 2015, The impact of introduced hosts on parasite transmission: opisthorchiid infections in American mink (<i>Neovison vison</i>), BIOLOGICAL INVASIONS, Vol: 17, Pages: 115-122, ISSN: 1387-3547
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- Citations: 10
Sherrard-Smith E, Perkins SE, Chadwick EA, et al., 2015, Spatial and seasonal factors are key determinants in the aggregation of helminths in their definitive hosts: <i>Pseudamphistomum truncatum</i> in otters (<i>Lutra lutra</i>), INTERNATIONAL JOURNAL FOR PARASITOLOGY, Vol: 45, Pages: 75-83, ISSN: 0020-7519
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- Citations: 14
Lowndes CM, Sherrard-Smith E, Dangerfield C, et al., 2014, Point-of-care testing versus standard practice for chlamydia: a new approach to assessing the public health effect of rapid testing and treatment at local level, European Public Health Science Conference, Publisher: ELSEVIER SCIENCE INC, Pages: 47-47, ISSN: 0140-6736
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- Citations: 1
Bluemel JK, Derlink M, Pavlovcic P, et al., 2014, Integrating vibrational signals, mitochondrial DNA andmorphology for species determination in the genus <i>Aphrodes</i> (Hemiptera: Cicadellidae), SYSTEMATIC ENTOMOLOGY, Vol: 39, Pages: 304-324, ISSN: 0307-6970
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- Citations: 21
Sherrard-Smith E, Chadwick EA, Cable J, 2013, Climatic variables are associated with the prevalence of biliary trematodes in otters, INTERNATIONAL JOURNAL FOR PARASITOLOGY, Vol: 43, Pages: 729-737, ISSN: 0020-7519
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- Citations: 8
Chadwick EA, Cable J, Chinchen A, et al., 2013, Seroprevalence of toxoplasma gondii in the Eurasian otter (lutra lutra) in England and Wales, Parasites & Vectors, Vol: 6, ISSN: 1756-3305
BackgroundToxoplasma gondii is found on all continents and can infect all endothermic vertebrates. Toxoplasmosis is a globally important zoonosis with potentially devastating health impacts both for humans and a range of domestic and wild species. The World Health Organisation have repeatedly recommended the collection of accurate epidemiological data for T. gondii, yet despite recognised links between infection of wildlife, domestic animals and humans, seroprevalence in wild species is rarely monitored. Here, serological investigation using the Gold Standard Sabin-Feldman Dye Test was used to test for T. gondii in Eurasian otters (Lutra lutra) found dead, mainly as road-kill, in England and Wales. This is the first spatially widespread study of T. gondii in UK wildlife, and the first extensive survey of T. gondii in Eurasian otters, a sentinel species of fresh waters.FindingsInfection was both common (39.5% prevalence, n = 271) and widespread, with significantly more infection in the east than the west of the UK. There was an increase in seroprevalence with age, but no sex bias.ConclusionsThe relatively high prevalence of T. gondii in a predominantly piscivorous freshwater mammal suggests widespread faecal contamination of freshwater ecosystems with oocysts. Continued surveillance of the Eurasian otter for T. gondii is valuable because of conservation concerns due to the otter’s ‘near threatened’ status on the IUCN Red List and because of the host’s role as a sentinel for freshwater health.
Sherrard-Smith E, Chadwick E, Cable J, 2012, Abiotic and biotic factors associated with tick population dynamics on a mammalian host: Ixodes hexagonus infesting otters, lutra iutra, PLoS One, Vol: 7, Pages: 1-7, ISSN: 1932-6203
The Eurasian otter, Lutra lutra, hosts several parasites with zoonotic potential. As this semiaquatic mammal has large ranges across terrestrial, freshwater and marine habitats, it has the capacity for wide dispersion of pathogens. Despite this, parasites of otters have received relatively little attention. Here, we examine their ectoparasite load and assess whether this is influenced by abiotic or biotic variables. Climatic phenomena such as the North Atlantic Oscillation (NAO) affect weather conditions in northern Europe. Consequently parasite distributions, particularly species with life stages exposed to the external environment, can be affected. We assessed the extent to which inter-annual variations in large-scale weather patterns (specifically the NAO and Central England (CE) temperatures) and host characteristics influenced tick prevalence and intensity. Ectoparasites consisted of a single species, the nidiculous tick Ixodes hexagonus (prevalence = 24.3%; mean intensity = 7.2; range = 1–122; on n = 820 otter hosts). The prevalence, but not intensity of infestation, was associated with high CE temperatures, while both prevalence and intensity were associated with positive phases of the NAO. Such associations indicate that I. hexagonus are most abundant when weather conditions are warmer and wetter. Ticks were more prevalent on juvenile than sub-adult or adult otters, which probably reflects the length of time the hosts spend in the holt where these ticks quest. High tick number was associated with poor host condition, so either poor condition hosts are more susceptible to ticks, or tick infestations negatively impact on host condition. Otters are clearly an important and common host for I. hexagonus, which has implications for vector-borne diseases. This work is the first to consider the impacts of long-term weather patterns on I. hexagonus and uses wild-animal cadavers to illustrate the importance of abiotic and biotic pressures impacting parasitic
Sherrard-Smith E, Cable J, Chadwick EA, 2009, Distribution of Eurasian otter biliary parasites, <i>Pseudamphistomum truncatum</i> and <i>Metorchis albidus</i> (Family Opisthorchiidae), in England and Wales, PARASITOLOGY, Vol: 136, Pages: 1015-1022, ISSN: 0031-1820
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- Citations: 20
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