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      High prevalence of asymptomatic malaria infections in adults, Ashanti Region, Ghana, 2018

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          Abstract

          Background

          Ghana is among the high-burden countries for malaria infections and recently reported a notable increase in malaria cases. While asymptomatic parasitaemia is increasingly recognized as a hurdle for malaria elimination, studies on asymptomatic malaria are scarce, and usually focus on children and on non-falciparum species. The present study aims to assess the prevalence of asymptomatic Plasmodium falciparum and non-falciparum infections in Ghanaian adults in the Ashanti region during the high transmission season.

          Methods

          Asymptomatic adult residents from five villages in the Ashanti Region, Ghana, were screened for Plasmodium species by rapid diagnostic test (RDT) and polymerase chain reaction (PCR) during the rainy season. Samples tested positive were subtyped using species-specific real-time PCR. For all Plasmodium ovale infections additional sub-species identification was performed.

          Results

          Molecular prevalence of asymptomatic Plasmodium infection was 284/391 (73%); only 126 (32%) infections were detected by RDT. While 266 (68%) participants were infected with Plasmodium falciparum, 33 (8%) were infected with Plasmodium malariae and 34 (9%) with P. ovale. The sub-species P. ovale curtisi and P. ovale wallikeri were identified to similar proportions. Non-falciparum infections usually presented as mixed infections with P. falciparum.

          Conclusions

          Most adult residents in the Ghanaian forest zone are asymptomatic Plasmodium carriers. The high Plasmodium prevalence not detected by RDT in adults highlights that malaria eradication efforts must target all members of the population. Beneath Plasmodium falciparum, screening and treatment must also include infections with P. malariae, P. o. curtisi and P. o. wallikeri.

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          Most cited references18

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          Asymptomatic malaria infections: detectability, transmissibility and public health relevance.

          Most Plasmodium falciparum infections that are detected in community surveys are characterized by low-density parasitaemia and the absence of clinical symptoms. Molecular diagnostics have shown that this asymptomatic parasitic reservoir is more widespread than previously thought, even in low-endemic areas. In this Opinion article, we describe the detectability of asymptomatic malaria infections and the relevance of submicroscopic infections for parasite transmission to mosquitoes and for community interventions that aim at reducing transmission. We argue that wider deployment of molecular diagnostic tools is needed to provide adequate insight into the epidemiology of malaria and infection dynamics to aid elimination efforts.
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            Mass screening and treatment on the basis of results of a Plasmodium falciparum-specific rapid diagnostic test did not reduce malaria incidence in Zanzibar.

            Seasonal increases in malaria continue in hot spots in Zanzibar. Mass screening and treatment (MSAT) may help reduce the reservoir of infection; however, it is unclear whether rapid diagnostic tests (RDTs) detect a sufficient proportion of low-density infections to influence subsequent transmission.
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              Probing the composition of Plasmodium species contained in malaria infections in the Eastern region of Ghana

              Background Asymptomatic falciparum and non-falciparum malaria infections are major challenges to malaria control interventions, as they remain a source of continual infection in the community. This becomes even more important as the debate moves towards elimination and eradication. This study sought to quantify the burden of Plasmodium malaria infection in seven communities in the Eastern Region of Ghana. Methods The cross-sectional study recruited 729 participants aged 85 years old and below from 7 closely linked communities. Finger pricked blood was used to prepare thick and thin blood smears as well as spot filter paper and an histidine rich protein 2 (HRP2) rapid diagnostic test kit (RDT). Genomic DNA was extracted from the filter paper dry blood spot (DBS) and used in PCR to amplify the Plasmodium 18S rRNA gene using species specific PCR. Results 96.6% of the participants were identified as afebrile, with axillary temperatures below 37.5 °C. PCR identified 66% of the participants to harbor malaria parasites, with 9 P. malariae and 7 P. ovale mono-infections accounting for 2.2% and P. falciparum combined with either 36 P. malariae or 25 P. ovale infections, accounting for 13.3%. Parasite prevalence by microscopy (32%) was similar to the RDT positivity rate (33%). False positive RDT results ranged from 64.6% in children aged between 5 and 9 years to 10% in adults aged 20 years and above. No significant differences were observed in falciparum and non-falciparum parasite carriage at the community level, however young adults aged between 15 and 19 years had the highest prevalence (34.8% (16/46)) of P. falciparum and P. malariae parasite carriage whilst children aged between 5 and 9 years had the highest level (11.4% (14/123)) of P. ovale carriage. Conclusion The high rate of misidentification of non-falciparum parasites and the total absence of detection of P. ovale by microscopy suggests that more sensitive malaria diagnostic tools including molecular assays are required to accurately determine the prevalence of carriers of non-falciparum parasites and low density P. falciparum infections, especially during national surveillance exercises. Additionally, malaria control interventions targeting the non-falciparum species P. malariae and P. ovale parasites are needed.
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                Author and article information

                Contributors
                rollingt@mskcc.org
                Journal
                Malar J
                Malar J
                Malaria Journal
                BioMed Central (London )
                1475-2875
                12 October 2020
                12 October 2020
                2020
                : 19
                : 366
                Affiliations
                [1 ]GRID grid.13648.38, ISNI 0000 0001 2180 3484, Division of Infectious Diseases, I. Department of Medicine, , University Medical Centre Hamburg-Eppendorf, ; Hamburg, Germany
                [2 ]GRID grid.424065.1, ISNI 0000 0001 0701 3136, Department of Tropical Medicine, , Bernhard Nocht Institute for Tropical Medicine, ; Hamburg, Germany
                [3 ]Kumasi Center for Collaborative Research in Tropical Medicine, Kumasi, Ghana
                [4 ]GRID grid.13648.38, ISNI 0000 0001 2180 3484, Department of Medicine, , University Medical Centre Hamburg-Eppendorf, ; Hamburg, Germany
                [5 ]GRID grid.424065.1, ISNI 0000 0001 0701 3136, National Reference Centre for Tropical Pathogens, Bernhard Nocht Institute for Tropical Medicine, ; Hamburg, Germany
                [6 ]GRID grid.452463.2, German Centre for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems, ; Hamburg, Germany
                [7 ]GRID grid.424065.1, ISNI 0000 0001 0701 3136, Department of Clinical Immunology of Infectious Diseases, , Bernhard Nocht Institute for Tropical Medicine, ; Hamburg, Germany
                [8 ]GRID grid.13992.30, ISNI 0000 0004 0604 7563, Present Address: Weizmann Institute of Science, ; Rehovot, Israel
                [9 ]GRID grid.240324.3, ISNI 0000 0001 2109 4251, Present Address: NYU Langone Medical Center, ; New York, NY USA
                [10 ]GRID grid.51462.34, ISNI 0000 0001 2171 9952, Present Address: Infectious Disease Service, Department of Medicine, , Memorial Sloan Kettering Cancer Center, ; New York, NY USA
                Author information
                http://orcid.org/0000-0002-0277-5067
                Article
                3441
                10.1186/s12936-020-03441-z
                7552528
                33046056
                bfff2181-5572-46d5-bc5e-bc9d37917cec
                © The Author(s) 2020

                Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

                History
                : 3 April 2020
                : 6 October 2020
                Funding
                Funded by: Bayer AG
                Funded by: FundRef http://dx.doi.org/10.13039/100009139, Deutsches Zentrum für Infektionsforschung;
                Award ID: 80095CLTHR
                Award Recipient :
                Funded by: Projekt DEAL
                Categories
                Research
                Custom metadata
                © The Author(s) 2020

                Infectious disease & Microbiology
                asymptomatic malaria,plasmodium falciparum,plasmodium malariae,plasmodium ovale curtisi,plasmodium ovale wallikeri,ghana,sub-saharan africa,rapid diagnostic test,polymerase chain reaction,molecular prevalence

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