Short communication: Lassa fever in Sierra Leone: UN peacekeepers are at risk

Lassa fever is a viral hemorrhagic fever caused by the Lassa virus LASV, which was first isolated in the rodent Mastomys natalensis in 1974 in Kenema, Sierra Leone. As little is known about the abundance and the presence of LASV in rodents living in the Bo area, we carried out a small mammal longitudinal population survey. A standardized trapping session was performed in various habitats and seasons in six villages over two years (2014–2016) and samples collected were tested for arenavirus IgG and LASV. A Bayesian phylogenetic analysis was performed on sequences identified by PCR. A total of 1490 small mammals were collected, and 16 rodent species were identified, with M. natalensis (355, 24%) found to be the most prevalent species. Forty-one (2.8%) samples were IgG positive, and 31 of these were trapped in homes and 10 in surrounding vegetation. Twenty-nine of 41 seropositive rodents were M. natalensis. We detected four LASV by PCR in two villages, all found in M. natalensis. Phylogenetic analysis showed that the sequences were distributed within the Sierra Leonean clade within lineage IV, distinguishing a Bo sub-clade older than a Kenema sub-clade. Compared to other settings, we found a low abundance of M. natalensis and a low circulation of LASV in rodents in villages around Bo district.

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Constraints in the diagnosis and treatment of Lassa Fever and the effect on mortality in hospitalized children and women with obstetric conditions in a rural district hospital in Sierra Leone

Transactions of the Royal Society of Tropical Medicine and Hygiene ◽

10.1093/trstmh/tru009 ◽

2014 ◽

Vol 108 (3) ◽

pp. 126-132 ◽

Cited By ~ 24

Author(s):

A. Dahmane ◽

J. van Griensven ◽

M. Van Herp ◽

R. Van den Bergh ◽

Y. Nzomukunda ◽

...

Keyword(s):

Sierra Leone ◽

District Hospital ◽

Lassa Fever ◽

Rural District ◽

Diagnosis And Treatment ◽

Hospitalized Children

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Determining Ancestry between Rodent- and Human-Derived Virus Sequences in Endemic Foci: Towards a More Integral Molecular Epidemiology of Lassa Fever within West Africa

Biology ◽

10.3390/biology9020026 ◽

2020 ◽

Vol 9 (2) ◽

pp. 26 ◽

Cited By ~ 3

Author(s):

Ayodeji Olayemi ◽

Adetunji Samuel Adesina ◽

Thomas Strecker ◽

N’Faly Magassouba ◽

Elisabeth Fichet-Calvet

Keyword(s):

West Africa ◽

Sierra Leone ◽

Evolutionary History ◽

Epidemiological Studies ◽

Lassa Fever ◽

Clinical Samples ◽

Ecological Studies ◽

Emergence Patterns ◽

Genetic Sequences ◽

Virus Strains

Lassa fever is a viral hemorrhagic illness responsible for thousands of human deaths in West Africa yearly. Rodents are known as natural reservoirs of the causative Lassa mammarenavirus (LASV) while humans are regarded as incidental, spill-over hosts. Analysis of genetic sequences continues to add to our understanding of the evolutionary history, emergence patterns, and the epidemiology of LASV. Hitherto, the source of data in such investigations has mainly comprised human clinical samples. Presently, a rise in the quantity of virus strains accessed through ecological studies over the last 15 years now allows us to explore how LASV sequences obtained from rodents might affect phylogenetic patterns. In this study, we phylogenetically compared LASV sequences obtained from both rodents and humans across West Africa, including those from two localities highly endemic for the disease: Ekpoma in Nigeria and Kenema in Sierra Leone. We performed a time-calibrated phylogeny, using a Bayesian analysis on 198 taxa, including 102 sequences from rodents and 96 from humans. Contrary to expectation, our results show that LASV strains detected in humans within these localities, even those sampled recently, are consistently ancient to those circulating in rodents in the same area. We discuss the possibilities connected to this preliminary outcome. We also propose modalities to guide more comprehensive comparisons of human and rodent data in LASV molecular epidemiological studies.

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Identification of Common CD8+ T Cell Epitopes from Lassa Fever Survivors in Nigeria and Sierra Leone

Journal of Virology ◽

10.1128/jvi.00153-20 ◽

2020 ◽

Vol 94 (12) ◽

Author(s):

Saori Sakabe ◽

Jessica N. Hartnett ◽

Nhi Ngo ◽

Augustine Goba ◽

Mambu Momoh ◽

...

Keyword(s):

T Cell ◽

West Africa ◽

Sierra Leone ◽

T Cell Responses ◽

Lassa Fever ◽

Health Concern ◽

Lassa Virus ◽

T Cell Epitopes ◽

Virus Surface ◽

Cell Responses

ABSTRACT Early and robust T cell responses have been associated with survival from Lassa fever (LF), but the Lassa virus-specific memory responses have not been well characterized. Regions within the virus surface glycoprotein (GPC) and nucleoprotein (NP) are the main targets of the Lassa virus-specific T cell responses, but, to date, only a few T cell epitopes within these proteins have been identified. We identified GPC and NP regions containing T cell epitopes and HLA haplotypes from LF survivors and used predictive HLA-binding algorithms to identify putative epitopes, which were then experimentally tested using autologous survivor samples. We identified 12 CD8-positive (CD8+) T cell epitopes, including epitopes common to both Nigerian and Sierra Leonean survivors. These data should be useful for the identification of dominant Lassa virus-specific T cell responses in Lassa fever survivors and vaccinated individuals as well as for designing vaccines that elicit cell-mediated immunity. IMPORTANCE The high morbidity and mortality associated with clinical cases of Lassa fever, together with the lack of licensed vaccines and limited and partially effective interventions, make Lassa virus (LASV) an important health concern in its regions of endemicity in West Africa. Previous infection with LASV protects from disease after subsequent exposure, providing a framework for designing vaccines to elicit similar protective immunity. Multiple major lineages of LASV circulate in West Africa, and therefore, ideal vaccine candidates should elicit immunity to all lineages. We therefore sought to identify common T cell epitopes between Lassa fever survivors from Sierra Leone and Nigeria, where distinct lineages circulate. We identified three such epitopes derived from highly conserved regions within LASV proteins. In this process, we also identified nine other T cell epitopes. These data should help in the design of an effective pan-LASV vaccine.

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Sierra Leone continues to struggle for relief from Lassa fever

The Lancet ◽

10.1016/s0140-6736(05)64235-3 ◽

1997 ◽

Vol 350 (9089) ◽

pp. 1458

Author(s):

Kelly Morris ◽

Charles Calisher

Keyword(s):

Sierra Leone ◽

Lassa Fever

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Lassa fever in Panguma Hospital, Sierra Leone, 1973-6.

BMJ ◽

10.1136/bmj.1.6073.1399 ◽

1977 ◽

Vol 1 (6073) ◽

pp. 1399-1402 ◽

Cited By ~ 45

Author(s):

E Keane ◽

H M Gilles

Keyword(s):

Sierra Leone ◽

Lassa Fever

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Boosting understanding of Lassa Fever virus epidemiology: Field testing a novel assay to identify past Lassa Fever virus infection in blood and oral fluids of survivors and unexposed controls in Sierra Leone

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0009255 ◽

2021 ◽

Vol 15 (3) ◽

pp. e0009255

Author(s):

Onome Akpogheneta ◽

Steve Dicks ◽

Donald Grant ◽

Zainab Kanneh ◽

Brima Jusu ◽

...

Keyword(s):

Sierra Leone ◽

Sensitivity And Specificity ◽

Large Scale ◽

Oral Fluid ◽

Field Testing ◽

Lassa Fever ◽

Fever Virus ◽

World Health ◽

Hospitalised Patients ◽

Lassa Fever Virus

Background Despite identification 50 years ago, the true burden of Lassa Fever (LF) across Africa remains undefined for reasons including research focus on hospitalised patients, lack of validated field-feasible tools which reliably identify past infection, and the fact that all assays require blood samples making large-scale surveys difficult. Designated a priority pathogen of epidemic potential requiring urgent research by the World Health Organisation, a better understanding of LF sero-epidemiology is essential to developing and evaluating new interventions including vaccines. We describe the first field testing of a novel species-neutral Double Antigen Binding Assay (DABA) designed to detect antibodies to LF in plasma and oral fluid. Methodology/Principal findings Paired plasma and oral fluid were collected in Sierra Leone from survivors discharged from Kenema Government Hospital Lassa Fever Unit between 1980 and 2018, and from controls recruited in Freetown in 2019. Epidemiological sensitivity and specificity of the DABA measured against historical diagnosis in survivors and self-declared non-exposed controls was 81.7% (95% CI 70.7%– 89.9%) and 83.3% (72.7%- 91.1%) respectively in plasma, and 71.8% (60.0%– 81.9%) and 83.3% (72.7%– 91.1%) respectively in oral fluid. Antibodies were identified in people infected up to 15 years and, in one case, 40 years previously. Participants found oral fluid collection easy and painless with 80% happy to give an oral fluid sample regularly. Conclusions/Significance Given the difficulties of assay validation in a resource-limited setting, including unexpected exposures and diagnostics of varying accuracy, the new assay performed well in both plasma and oral fluid. Sensitivity and specificity are expected to be higher when case/control ascertainment is more definitive and further work is planned to investigate this. Even at the performance levels achieved, the species-neutral DABA has the potential to facilitate the large-scale seroprevalence surveys needed to underpin essential developments in LF control, as well as support zoonotic investigations.

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Public health response to two imported, epidemiologically related cases of Lassa fever in the Netherlands (ex Sierra Leone), November 2019

Eurosurveillance ◽

10.2807/1560-7917.es.2020.25.15.2000265 ◽

2020 ◽

Vol 25 (15) ◽

Author(s):

Femke Overbosch ◽

Mark de Boer ◽

Karin Ellen Veldkamp ◽

Pauline Ellerbroek ◽

Chantal P Bleeker-Rovers ◽

...

Keyword(s):

Public Health ◽

The Netherlands ◽

Sierra Leone ◽

Healthcare Facility ◽

Lassa Fever ◽

Low Risk ◽

Lassa Virus ◽

Public Health Response ◽

Health Response

On 20 November 2019, Lassa fever was diagnosed in a physician repatriated from Sierra Leone to the Netherlands. A second physician with suspected Lassa fever, repatriated a few days later from the same healthcare facility, was confirmed infected with Lassa virus on 21 November. Comprehensive contact monitoring involving high- and low-risk contacts proved to be feasible and follow-up of the contacts did not reveal any case of secondary transmission in the Netherlands.

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A Sporadic and Lethal Lassa Fever Case in Forest Guinea, 2019

Viruses ◽

10.3390/v12101062 ◽

2020 ◽

Vol 12 (10) ◽

pp. 1062

Author(s):

N’Faly Magassouba ◽

Enogo Koivogui ◽

Sory Conde ◽

Moussa Kone ◽

Michel Koropogui ◽

...

Keyword(s):

Sierra Leone ◽

Lassa Fever ◽

Regional Hospital ◽

Health Centers ◽

Lassa Virus ◽

Fever Case ◽

Internal Bleeding ◽

Facial Edema ◽

Frequent Vomiting ◽

Generation Sequencing

Lassa fever is a rodent-borne disease caused by Lassa virus (LASV). It causes fever, dizziness, vertigo, fatigue, coughing, diarrhea, internal bleeding and facial edema. The disease has been known in Guinea since 1960 but only anectodical acute cases have been reported to date. In January 2019, a 35-year-old man, a wood merchant from Kissidougou, Forest Guinea, presented himself at several health centers with persistent fever, frequent vomiting and joint pain. He was repeatedly treated for severe malaria, and died three weeks later in Mamou regional hospital. Differential diagnosis identified LASV as the cause of death. No secondary cases were reported. The complete LASV genome was obtained using next-generation sequencing. Phylogenetic analysis showed that this strain, namely the Kissidougou strain, belongs to the clade IV circulating in Guinea and Sierra Leone, and is thought to have emerged some 150 years ago. Due to the similarity of symptoms with malaria, Lassa fever is still a disease that is difficult to recognize and that may remain undiagnosed in health centers in Guinea.

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