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Connelly SV, Brazeau NF, Msellem M, Ngasala BE, Aydemir O, Goel V, Niaré K, Giesbrecht DJ, Popkin-Hall ZR, Hennelly C, Park Z, Moormann AM, Ong'echa JM, Verity R, Mohammed S, Shija SJ, Mhamilawa LE, Morris U, Mårtensson A, Lin JT, Björkman A, Juliano JJ, Bailey JA. Strong isolation by distance and evidence of population microstructure reflect ongoing Plasmodium falciparum transmission in Zanzibar. eLife 2024; 12:RP90173. [PMID: 38935423 PMCID: PMC11210957 DOI: 10.7554/elife.90173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2024] Open
Abstract
Background The Zanzibar archipelago of Tanzania has become a low-transmission area for Plasmodium falciparum. Despite being considered an area of pre-elimination for years, achieving elimination has been difficult, likely due to a combination of imported infections from mainland Tanzania and continued local transmission. Methods To shed light on these sources of transmission, we applied highly multiplexed genotyping utilizing molecular inversion probes to characterize the genetic relatedness of 282 P. falciparum isolates collected across Zanzibar and in Bagamoyo district on the coastal mainland from 2016 to 2018. Results Overall, parasite populations on the coastal mainland and Zanzibar archipelago remain highly related. However, parasite isolates from Zanzibar exhibit population microstructure due to the rapid decay of parasite relatedness over very short distances. This, along with highly related pairs within shehias, suggests ongoing low-level local transmission. We also identified highly related parasites across shehias that reflect human mobility on the main island of Unguja and identified a cluster of highly related parasites, suggestive of an outbreak, in the Micheweni district on Pemba island. Parasites in asymptomatic infections demonstrated higher complexity of infection than those in symptomatic infections, but have similar core genomes. Conclusions Our data support importation as a main source of genetic diversity and contribution to the parasite population in Zanzibar, but they also show local outbreak clusters where targeted interventions are essential to block local transmission. These results highlight the need for preventive measures against imported malaria and enhanced control measures in areas that remain receptive to malaria reemergence due to susceptible hosts and competent vectors. Funding This research was funded by the National Institutes of Health, grants R01AI121558, R01AI137395, R01AI155730, F30AI143172, and K24AI134990. Funding was also contributed from the Swedish Research Council, Erling-Persson Family Foundation, and the Yang Fund. RV acknowledges funding from the MRC Centre for Global Infectious Disease Analysis (reference MR/R015600/1), jointly funded by the UK Medical Research Council (MRC) and the UK Foreign, Commonwealth & Development Office (FCDO), under the MRC/FCDO Concordat agreement and is also part of the EDCTP2 program supported by the European Union. RV also acknowledges funding by Community Jameel.
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Affiliation(s)
- Sean V Connelly
- MD-PhD Program, University of North Carolina at Chapel HillChapel HillUnited States
| | - Nicholas F Brazeau
- MD-PhD Program, University of North Carolina at Chapel HillChapel HillUnited States
| | - Mwinyi Msellem
- Research Division, Ministry of HealthZanzibarUnited Republic of Tanzania
| | - Billy E Ngasala
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied SciencesDar es SalaamUnited Republic of Tanzania
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala UniversityUppsalaSweden
| | - Ozkan Aydemir
- Department of Medicine, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Varun Goel
- Carolina Population Center, University of North Carolina at Chapel HillChapel HillUnited States
| | - Karamoko Niaré
- Department of Pathology and Laboratory Medicine, Brown UniversityProvidenceUnited States
| | - David J Giesbrecht
- Department of Pathology and Laboratory Medicine, Brown UniversityProvidenceUnited States
| | - Zachary R Popkin-Hall
- Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Chris Hennelly
- Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Zackary Park
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Ann M Moormann
- Department of Medicine, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - John M Ong'echa
- Center for Global Health Research, Kenya Medical Research InstituteKisumuKenya
| | - Robert Verity
- MRC Centre for Global Infectious Disease Analysis, Imperial College LondonLondonUnited Kingdom
| | - Safia Mohammed
- Zanzibar Malaria Elimination Program (ZAMEP)ZanzibarUnited Republic of Tanzania
| | - Shija J Shija
- Zanzibar Malaria Elimination Program (ZAMEP)ZanzibarUnited Republic of Tanzania
| | - Lwidiko E Mhamilawa
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied SciencesDar es SalaamUnited Republic of Tanzania
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala UniversityUppsalaSweden
| | - Ulrika Morris
- Department of Microbiology, Tumor and Cell Biology, Karolinska InstitutetStockholmSweden
| | - Andreas Mårtensson
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala UniversityUppsalaSweden
| | - Jessica T Lin
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska InstitutetStockholmSweden
- Department of Global Public Health, Karolinska InstituteStockholmSweden
| | - Jonathan J Juliano
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel HillChapel HillUnited States
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel HillChapel HillUnited States
| | - Jeffrey A Bailey
- Department of Pathology and Laboratory Medicine, Brown UniversityProvidenceUnited States
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Zhan Q, Tiedje KE, Day KP, Pascual M. From multiplicity of infection to force of infection for sparsely sampled Plasmodium falciparum populations at high transmission. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.02.12.24302148. [PMID: 38853963 PMCID: PMC11160831 DOI: 10.1101/2024.02.12.24302148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
High multiplicity of infection or MOI, the number of genetically distinct parasite strains co-infecting a single human host, characterizes infectious diseases including falciparum malaria at high transmission. It accompanies high asymptomatic Plasmodium falciparum prevalence despite high exposure, creating a large transmission reservoir challenging intervention. High MOI and asymptomatic prevalence are enabled by immune evasion of the parasite achieved via vast antigenic diversity. Force of infection or FOI, the number of new infections acquired by an individual host over a given time interval, is the dynamic sister quantity of MOI, and a key epidemiological parameter for monitoring the impact of antimalarial interventions and assessing vaccine or drug efficacy in clinical trials. FOI remains difficult, expensive, and labor-intensive to accurately measure, especially in high-transmission regions, whether directly via cohort studies or indirectly via the fitting of epidemiological models to repeated cross-sectional surveys. We propose here the application of queuing theory to obtain FOI on the basis of MOI, in the form of either a two-moment approximation method or Little's law. We illustrate these methods with MOI estimates obtained under sparse sampling schemes with the recently proposed " v a r coding" method, based on sequences of the v a r multigene family encoding for the major variant surface antigen of the blood stage of malaria infection. The methods are evaluated with simulation output from a stochastic agent-based model, and are applied to an interrupted time-series study from Bongo District in northern Ghana before and immediately after a three-round transient indoor residual spraying (IRS) intervention. We incorporate into the sampling of the simulation output, limitations representative of those encountered in the collection of field data, including under-sampling of v a r genes, missing data, and usage of antimalarial drug treatment. We address these limitations in MOI estimates with a Bayesian framework and an imputation bootstrap approach. We demonstrate that both proposed methods give good and consistent FOI estimates across various simulated scenarios. Their application to the field surveys shows a pronounced reduction in annual FOI during intervention, of more than 70%. The proposed approach should be applicable to the many geographical locations where cohort or cross-sectional studies with regular and frequent sampling are lacking but single-time-point surveys under sparse sampling schemes are available, and for MOI estimates obtained in different ways. They should also be relevant to other pathogens of humans, wildlife and livestock whose immune evasion strategies are based on large antigenic variation resulting in high multiplicity of infection.
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Affiliation(s)
- Qi Zhan
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL, USA
| | - Kathryn E. Tiedje
- Department of Microbiology and Immunology, Bio21 Institute and Peter Doherty Institute, The University of Melbourne, Melbourne, Australia
| | - Karen P. Day
- Department of Microbiology and Immunology, Bio21 Institute and Peter Doherty Institute, The University of Melbourne, Melbourne, Australia
| | - Mercedes Pascual
- Department of Biology, New York University, New York, NY, USA
- Department of Environmental Studies, New York University, New York, NY, USA
- Santa Fe Institute, Santa Fe, NM, USA
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3
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Akoniyon OP, Akiibinu M, Adeleke MA, Maharaj R, Okpeku M. A Comparative Study of Genetic Diversity and Multiplicity of Infection in Uncomplicated Plasmodium falciparum Infections in Selected Regions of Pre-Elimination and High Transmission Settings Using MSP1 and MSP2 Genes. Pathogens 2024; 13:172. [PMID: 38392910 PMCID: PMC10891941 DOI: 10.3390/pathogens13020172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/22/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
BACKGROUND Understanding the genetic structure of P. falciparum population in different regions is pivotal to malaria elimination. Genetic diversity and the multiplicity of infection are indicators used for measuring malaria endemicity across different transmission settings. Therefore, this study characterized P. falciparum infections from selected areas constituting pre-elimination and high transmission settings in South Africa and Nigeria, respectively. METHODS Parasite genomic DNA was extracted from 129 participants with uncomplicated P. falciparum infections. Isolates were collected from 78 participants in South Africa (southern Africa) and 51 in Nigeria (western Africa). Allelic typing of the msp1 and msp2 genes was carried out using nested PCR. RESULTS In msp1, the K1 allele (39.7%) was the most common allele among the South African isolates, while the RO33 allele (90.2%) was the most common allele among the Nigerian isolates. In the msp2 gene, FC27 and IC3D7 showed almost the same percentage distribution (44.9% and 43.6%) in the South African isolates, whereas FC27 had the highest percentage distribution (60.8%) in the Nigerian isolates. The msp2 gene showed highly distinctive genotypes, indicating high genetic diversity in the South African isolates, whereas msp1 showed high genetic diversity in the Nigerian isolates. The RO33 allelic family displayed an inverse relationship with participants' age in the Nigerian isolates. The overall multiplicity of infection (MOI) was significantly higher in Nigeria (2.87) than in South Africa (2.44) (p < 0.000 *). In addition, heterozygosity was moderately higher in South Africa (1.46) than in Nigeria (1.13). CONCLUSIONS The high genetic diversity and MOI in P. falciparum that were observed in this study could provide surveillance data, on the basis of which appropriate control strategies should be adopted.
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Affiliation(s)
- Olusegun Philip Akoniyon
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4041, South Africa; (O.P.A.); (M.A.A.)
| | - Moses Akiibinu
- Department of Biochemistry and Chemistry, Caleb University, Lagos 11379, Nigeria;
| | - Matthew A. Adeleke
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4041, South Africa; (O.P.A.); (M.A.A.)
| | - Rajendra Maharaj
- Office of Malaria Research, South African Medical Research Council, Cape Town 7505, South Africa;
| | - Moses Okpeku
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4041, South Africa; (O.P.A.); (M.A.A.)
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Tsoungui Obama HCJ, Schneider KA. A maximum-likelihood method to estimate haplotype frequencies and prevalence alongside multiplicity of infection from SNP data. FRONTIERS IN EPIDEMIOLOGY 2022; 2:943625. [PMID: 38455338 PMCID: PMC10911023 DOI: 10.3389/fepid.2022.943625] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/26/2022] [Indexed: 03/09/2024]
Abstract
The introduction of genomic methods facilitated standardized molecular disease surveillance. For instance, SNP barcodes in Plasmodium vivax and Plasmodium falciparum malaria allows the characterization of haplotypes, their frequencies and prevalence to reveal temporal and spatial transmission patterns. A confounding factor is the presence of multiple genetically distinct pathogen variants within the same infection, known as multiplicity of infection (MOI). Disregarding ambiguous information, as usually done in ad-hoc approaches, leads to less confident and biased estimates. We introduce a statistical framework to obtain maximum-likelihood estimates (MLE) of haplotype frequencies and prevalence alongside MOI from malaria SNP data, i.e., multiple biallelic marker loci. The number of model parameters increases geometrically with the number of genetic markers considered and no closed-form solution exists for the MLE. Therefore, the MLE needs to be derived numerically. We use the Expectation-Maximization (EM) algorithm to derive the maximum-likelihood estimates, an efficient and easy-to-implement algorithm that yields a numerically stable solution. We also derive expressions for haplotype prevalence based on either all or just the unambiguous genetic information and compare both approaches. The latter corresponds to a biased ad-hoc estimate of prevalence. We assess the performance of our estimator by systematic numerical simulations assuming realistic sample sizes and various scenarios of transmission intensity. For reasonable sample sizes, and number of loci, the method has little bias. As an example, we apply the method to a dataset from Cameroon on sulfadoxine-pyrimethamine resistance in P. falciparum malaria. The method is not confined to malaria and can be applied to any infectious disease with similar transmission behavior. An easy-to-use implementation of the method as an R-script is provided.
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5
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Brashear AM, Cui L. Population genomics in neglected malaria parasites. Front Microbiol 2022; 13:984394. [PMID: 36160257 PMCID: PMC9493318 DOI: 10.3389/fmicb.2022.984394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 08/22/2022] [Indexed: 11/13/2022] Open
Abstract
Malaria elimination includes neglected human malaria parasites Plasmodium vivax, Plasmodium ovale spp., and Plasmodium malariae. Biological features such as association with low-density infection and the formation of hypnozoites responsible for relapse make their elimination challenging. Studies on these parasites rely primarily on clinical samples due to the lack of long-term culture techniques. With improved methods to enrich parasite DNA from clinical samples, whole-genome sequencing of the neglected malaria parasites has gained increasing popularity. Population genomics of more than 2200 P. vivax global isolates has improved our knowledge of parasite biology and host-parasite interactions, identified vaccine targets and potential drug resistance markers, and provided a new way to track parasite migration and introduction and monitor the evolutionary response of local populations to elimination efforts. Here, we review advances in population genomics for neglected malaria parasites, discuss how the rich genomic information is being used to understand parasite biology and epidemiology, and explore opportunities for the applications of malaria genomic data in malaria elimination practice.
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Stanley CC, Mukaka M, Kazembe LN, Buchwald AG, Mathanga DP, Laufer MK, Chirwa TF. Analysis of Recurrent Times-to-Clinical Malaria Episodes and Plasmodium falciparum Parasitemia: A Joint Modeling Approach Applied to a Cohort Data. FRONTIERS IN EPIDEMIOLOGY 2022; 2:924783. [PMID: 38455327 PMCID: PMC10911024 DOI: 10.3389/fepid.2022.924783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 06/08/2022] [Indexed: 03/09/2024]
Abstract
Background Recurrent clinical malaria episodes due to Plasmodium falciparum parasite infection are common in endemic regions. With each infection, acquired immunity develops, making subsequent disease episodes less likely. To capture the effect of acquired immunity to malaria, it may be necessary to model recurrent clinical disease episodes jointly with P. falciparum parasitemia data. A joint model of longitudinal parasitemia and time-to-first clinical malaria episode (single-event joint model) may be inaccurate because acquired immunity is lost when subsequent episodes are excluded. This study's informativeness assessed whether joint modeling of recurrent clinical malaria episodes and parasitemia is more accurate than a single-event joint model where the subsequent episodes are ignored. Methods The single event joint model comprised Cox Proportional Hazards (PH) sub-model for time-to-first clinical malaria episode and Negative Binomial (NB) mixed-effects sub-model for the longitudinal parasitemia. The recurrent events joint model extends the survival sub-model to a Gamma shared frailty model to include all recurrent clinical episodes. The models were applied to cohort data from Malawi. Simulations were also conducted to assess the performance of the model under different conditions. Results The recurrent events joint model, which yielded higher hazard ratios of clinical malaria, was more precise and in most cases produced smaller standard errors than the single-event joint model; hazard ratio (HR) = 1.42, [95% confidence interval [CI]: 1.22, 2.03] vs. HR = 1.29, [95% CI:1.60, 2.45] among participants who reported not to use LLINs every night compared to those who used the nets every night; HR = 0.96, [ 95% CI: 0.94, 0.98] vs. HR = 0.81, [95% CI: 0.75, 0.88] for each 1-year increase in participants' age; and HR = 1.36, [95% CI: 1.05, 1.75] vs. HR = 1.10, [95% CI: 0.83, 4.11] for observations during the rainy season compared to the dry season. Conclusion The recurrent events joint model in this study provides a way of estimating the risk of recurrent clinical malaria in a cohort where the effect of immunity on malaria disease acquired due to P. falciparum parasitemia with aging is captured. The simulation study has shown that if correctly specified, the recurrent events joint model can give risk estimates with low bias.
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Affiliation(s)
- Christopher C. Stanley
- Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Mavuto Mukaka
- Oxford Centre for Tropical Medicine and Global Health, Oxford, United Kingdom
- Mahidol-Oxford Tropical Medicine Research Unit, Bangkok, Thailand
| | | | - Andrea G. Buchwald
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Don P. Mathanga
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Miriam K. Laufer
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Tobias F. Chirwa
- Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
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7
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Lagnika HO, Moussiliou A, Agonhossou R, Sovegnon P, Djihinto OY, Medjigbodo AA, Djossou L, Amoah LE, Ogouyemi-Hounto A, Djogbenou LS. Plasmodium falciparum msp1 and msp2 genetic diversity in parasites isolated from symptomatic and asymptomatic malaria subjects in the South of Benin. Parasitol Res 2022; 121:167-175. [PMID: 34993632 DOI: 10.1007/s00436-021-07399-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 11/29/2021] [Indexed: 10/19/2022]
Abstract
Symptomatic and asymptomatic malaria patients are considered as the reservoirs of human Plasmodium. In the present study, we have evaluated the Plasmodium falciparum merozoite surface protein-1 (Pfmsp1) and protein-2 (Pfmsp2) genetic diversity among the symptomatic and asymptomatic malaria infection from health facilities in Cotonou, Benin Republic. A cross-sectional study recruited 158 individuals, including 77 from the asymptomatic and 81 from the symptomatic groups. The parasites were genotyped using Nested Polymerase Chain Reaction. Samples identified as Plasmodium falciparum were genotyped for their genetic diversity. No significant difference was observed in the overall multiplicity of infection (MOI) between the asymptomatic and symptomatic groups. In the symptomatic group, the overall frequency of K1, MAD20, and RO33 allelic family was more predominant (98.5%) followed by 3D7 (87.3%) and FC27 (83.1%). However, in asymptomatic group, the K1 alleles were the most prevalent (100%) followed by FC27 (89.9%), 3D7 (76.8%), MAD20 (60.5%), and RO33 (35.5%). The frequency of multiple allelic types (K1+MAD20+RO33) at the Pfmsp1 loci in the symptomatic infections was significantly higher when compared to that of the asymptomatic ones (97% vs. 34%, p < 0.05), whereas no difference was observed in the frequency of multiple allelic types (3D7 and FC27) at the Pfmsp2 loci between the two groups. The high presence of msp1 multiple infections in the symptomatic group compared to asymptomatic ones suggests an association between the genetic diversity and the onset of malaria symptoms. These data can provide valuable information in the development of a vaccine that could reduce the symptomatic disease.
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Affiliation(s)
- Hamirath Odée Lagnika
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Azizath Moussiliou
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Romuald Agonhossou
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Pierre Sovegnon
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Oswald Yédjinnavênan Djihinto
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Adandé Assogba Medjigbodo
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Laurette Djossou
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin
| | - Linda Eva Amoah
- Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | | | - Luc Salako Djogbenou
- Tropical Infectious Diseases Research Centre, University of Abomey-Calavi, 01BP 526, Cotonou, Benin.
- Laboratory of Infectious Vector-Borne Diseases, Regional Institute of Public Health/University of Abomey-Calavi, BP 384, Ouidah, Benin.
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