Acute Lassa Virus Encephalitis with Lassa Virus in the Cerebrospinal Fluid but Absent in the Blood: A Case Report with a Positive Outcome

Treatment of highly virulent mammarenavirus infections-status quo and future directions

INTRODUCTION

Mammarenaviruses are negative-sense bisegmented enveloped RNA viruses that are endemic in Africa, the Americas, and Europe. Several are highly virulent, causing acute human diseases associated with high case fatality rates, and are considered to be significant with respect to public health impact or bioterrorism threat.

AREAS COVERED

This review summarizes the status quo of treatment development, starting with drugs that are in advanced stages of evaluation in early clinical trials, followed by promising candidate medical countermeasures emerging from bench analyses and investigational animal research.

EXPERT OPINION

Specific therapeutic treatments for diseases caused by mammarenaviruses remain limited to the off-label use of ribavirin and transfusion of convalescent sera. Progress in identifying novel candidate medical countermeasures against mammarenavirus infection has been slow in part because of the biosafety and biosecurity requirements. However, novel methodologies and tools have enabled increasingly efficient high-throughput molecular screens of regulatory-agency-approved small-molecule drugs and led to the identification of several compounds that could be repurposed for the treatment of infection with several mammarenaviruses. Unfortunately, most of them have not yet been evaluated in vivo. The most promising treatment under development is a monoclonal antibody cocktail that is protective against multiple lineages of the Lassa virus in nonhuman primate disease models.

Lassa Fever Natural History and Clinical Management

Lassa fever is caused by Lassa virus (LASV), an Old World Mammarenavirus that is carried by Mastomys natalensis and other rodents. It is endemic in Sierra Leone, Nigeria, and other countries in West Africa. The clinical presentation of LASV infection is heterogenous varying from an inapparent or mild illness to a fatal hemorrhagic fever. Exposure to LASV is usually through contact with rodent excreta. After an incubation period of 1-3 weeks, initial symptoms such as fever, headache, and fatigue develop that may progress to sore throat, retrosternal chest pain, conjunctival injection, vomiting, diarrhea, and abdominal pain. Severe illness, including hypotension, shock, and multiorgan failure, develops in a minority of patients. Patient demographics and case fatality rates are distinctly different in Sierra Leone and Nigeria. Laboratory diagnosis relies on the detection of LASV antigens or genomic RNA. LASV-specific immunoglobulin G and M assays can also contribute to clinical management. The mainstay of treatment for Lassa fever is supportive care. The nucleoside analog ribavirin is commonly used to treat acute Lassa fever but is considered useful only if treatment is begun early in the disease course. Drugs in development, including a monoclonal antibody cocktail, have the potential to impact the management of Lassa fever.

Two Cases of Lassa Fever Successfully Treated with Ribavirin and Adjunct Dexamethasone for Concomitant Infections

Lassa fever is a viral hemorrhagic fever treated with supportive care and the broad-spectrum antiviral drug ribavirin. The pathophysiology, especially the role of hyperinflammation, of this disease is unknown. We report successful remission of complicated Lassa fever in 2 patients in Nigeria who received the antiinflammatory agent dexamethasone and standard ribavirin.

Lassa Virus Infection: a Summary for Clinicians

OBJECTIVES

This summary on Lassa virus (LASV) infection and Lassa fever disease (LF) was developed from a clinical perspective to provide clinicians a condensed, accessible understanding of the current literature. The information provided highlights pathogenesis, clinical features, and diagnostics with an emphasis on therapies and vaccines that have demonstrated potential value for use in clinical or research environments.

METHODS

An integrative literature review was conducted on the clinical and pathological features, vaccines, and treatments for LASV infection, with a focus on recent studies and in vivo evidence from humans and/or non-human primates (NHPs), when available.

RESULTS

Two antiviral medications with potential benefit for the treatment of LASV infection and one for post-exposure prophylaxis were identified, although a larger number of potential candidates are currently being evaluated. Multiple vaccine platforms are in pre-clinical development for LASV prevention, but data from human clinical trials are not yet available.

CONCLUSION

We provide succinct summaries of medical countermeasures against LASV to give the busy clinician a rapid reference. Although there are no approved drugs or vaccines for LF, we provide condensed information from a literature review for measures that can be taken when faced with a suspected infection, including investigational treatment options and hospital engineering controls.

Clinical characterization of Lassa fever: A systematic review of clinical reports and research to inform clinical trial design

BACKGROUND

Research is urgently needed to reduce the morbidity and mortality of Lassa fever (LF), including clinical trials to test new therapies and to verify the efficacy and safety of the only current treatment recommendation, ribavirin, which has a weak clinical evidence base. To help establish a basis for the development of an adaptable, standardised clinical trial methodology, we conducted a systematic review to identify the clinical characteristics and outcomes of LF and describe how LF has historically been defined and assessed in the scientific literature.

METHODOLOGY

Primary clinical studies and reports of patients with suspected and confirmed diagnosis of LF published in the peer-reviewed literature before 15 April 2021 were included. Publications were selected following a two-stage screening of abstracts, then full-texts, by two independent reviewers at each stage. Data were extracted, verified, and summarised using descriptive statistics.

RESULTS

147 publications were included, primarily case reports (36%), case series (28%), and cohort studies (20%); only 2 quasi-randomised studies (1%) were found. Data are mostly from Nigeria (52% of individuals, 41% of publications) and Sierra Leone (42% of individuals, 31% of publications). The results corroborate the World Health Organisation characterisation of LF presentation. However, a broader spectrum of presenting symptoms is evident, such as gastrointestinal illness and other nervous system and musculoskeletal disorders that are not commonly included as indicators of LF. The overall case fatality ratio was 30% in laboratory-confirmed cases (1896/6373 reported in 109 publications).

CONCLUSION

Systematic review is an important tool in the clinical characterisation of diseases with limited publications. The results herein provide a more complete understanding of the spectrum of disease which is relevant to clinical trial design. This review demonstrates the need for coordination across the LF research community to generate harmonised research methods that can contribute to building a strong evidence base for new treatments and foster confidence in their integration into clinical care.

Insights into the Pathogenesis of Viral Haemorrhagic Fever Based on Virus Tropism and Tissue Lesions of Natural Rift Valley Fever

Rift Valley fever phlebovirus (RVFV) infects humans and a wide range of ungulates and historically has caused devastating epidemics in Africa and the Arabian Peninsula. Lesions of naturally infected cases of Rift Valley fever (RVF) have only been described in detail in sheep with a few reports concerning cattle and humans. The most frequently observed lesion in both ruminants and humans is randomly distributed necrosis, particularly in the liver. Lesions supportive of vascular endothelial injury are also present and include mild hydropericardium, hydrothorax and ascites; marked pulmonary congestion and oedema; lymph node congestion and oedema; and haemorrhages in many tissues. Although a complete understanding of RVF pathogenesis is still lacking, antigen-presenting cells in the skin are likely the early targets of the virus. Following suppression of type I IFN production and necrosis of dermal cells, RVFV spreads systemically, resulting in infection and necrosis of other cells in a variety of organs. Failure of both the innate and adaptive immune responses to control infection is exacerbated by apoptosis of lymphocytes. An excessive pro-inflammatory cytokine and chemokine response leads to microcirculatory dysfunction. Additionally, impairment of the coagulation system results in widespread haemorrhages. Fatal outcomes result from multiorgan failure, oedema in many organs (including the lungs and brain), hypotension, and circulatory shock. Here, we summarize current understanding of RVF cellular tropism as informed by lesions caused by natural infections. We specifically examine how extant knowledge informs current understanding regarding pathogenesis of the haemorrhagic fever form of RVF, identifying opportunities for future research.

One-Year Retrospective Review of Psychiatric Consultations in Lassa Fever, Southern Nigeria

We conducted a retrospective review of psychiatric consultations for hospitalized patients with Lassa fever in southern Nigeria. Ten (8.8%) of 113 patients had psychiatric consultations. Delirium was the most common psychiatric manifestation complicating Lassa fever. Findings suggest that psychiatric intervention could improve overall outcomes of Lassa fever.

Delayed-onset paraparesis in Lassa fever: A case report

Lassa fever (LF) is an endemic viral hemorrhagic fever in West Africa. Among the serious complications of the disease are neurological manifestations whose spectrum is incompletely known. Here we report the case of a 61-year-old man who developed a delayed-onset paraparesis a few weeks after getting infected with Lassa virus, thereby suggesting a possible association between LF and spinal cord disorders.

Diagnostics for Lassa fever virus: a genetically diverse pathogen found in low-resource settings

Lassa fever virus (LASV) causes acute viral haemorrhagic fever with symptoms similar to those seen with Ebola virus infections. LASV is endemic to West Africa and is transmitted through contact with excretions of infected Mastomys natalensis rodents and other rodent species. Due to a high fatality rate, lack of treatment options and difficulties with prevention and control, LASV is one of the high-priority pathogens included in the WHO R&D Blueprint. The WHO LASV vaccine strategy relies on availability of effective diagnostic tests. Current diagnostics for LASV include in-house and commercial (primarily research-only) laboratory-based serological and nucleic acid amplification tests. There are two commercially available (for research use only) rapid diagnostic tests (RDTs), and a number of multiplex panels for differential detection of LASV infection from other endemic diseases with similar symptoms have been evaluated. However, a number of diagnostic gaps remain. Lineage detection is a challenge due to the genomic diversity of LASV, as pan-lineage sensitivity for both molecular and immunological detection is necessary for surveillance and outbreak response. While pan-lineage ELISA and RDTs are commercially available (for research use only), validation and external quality assessment (EQA) is needed to confirm detection sensitivity for all known or relevant strains. Variable sensitivity of LASV PCR tests also highlights the need for improved validation and EQA. Given that LASV outbreaks typically occur in low-resource settings, more options for point-of-care testing would be valuable. These requirements should be taken into account in target product profiles for improved LASV diagnostics.

Diagnostic approach to encephalitis and meningoencephalitis in adult returning travellers

BACKGROUND

Encephalitis and meningoencephalitis are severe, sometime life-threatening infections of the central nervous system. Travellers may be exposed to a variety of neurotropic pathogens.

AIMS

We propose to review known infectious causes of encephalitis in adults acquired outside Europe, and how to identify them.

SOURCES

We used Pubmed and Embase, to search the most relevant publications over the last years.

CONTENT

Microbiologic tests and radiological tools to best identify the causative pathogen in travellers presenting with encephalitis and ME are presented in this narrative review, as well as a diagnostic approach tailored to the visited area and types of exposures.

IMPLICATIONS

This review highlights the diagnostic difficulties inherent to exotic causes of central nervous system infections, and attempts to guide clinicians with respect to which microbiological tests to consider, in addition to brain MRI, when approaching a returning traveller presenting with encephalitis.