A need to raise the bar - A systematic review of temporal trends in diagnostics for Japanese encephalitis virus infection, and perspectives for future research

Trends in temporal and spatial changes of Japanese encephalitis in Chinese mainland, 2004-2019: A population-based surveillance study

BACKGROUND

Japanese encephalitis (JE) is a serious health concern in China, with approximately 80 % of global infections occurring in China. To develop effective prevention and control strategies, this study explored the epidemiological characteristics of JE in China based on spatiotemporal data, to understand the patterns and trends of JE incidence in different regions and time periods.

METHOD

The incidence and mortality rates of JE were extracted from the Public Health Data Center, the official website of the National Health Commission of the People's Republic of China, and the National Notifiable Infectious Disease Surveillance System from 2004 to 2019. Joinpoint regression was applied to examine the spatiotemporal patterns and annual percentage change in incidence and mortality of the JE.

RESULTS

From 2004 to 2019, a total of 43,569 cases of JE were diagnosed, including 2081 deaths. The annual incidence rate of JE decreased from 0.4171/100,000 in 2004 to 0.0298/100,000 in 2019, with an annual percentage change (APC) of -13.5 % (P < 0.001). The annual mortality rate of JE showed three stages of change, with inflection points in 2006 and 2014. The incidence and mortality rates of JE have declined in all provinces of China, and more cases were reported in 0-14 years of age, accounting for nearly 80 % of all patients.

CONCLUSIONS

The morbidity and mortality rates of JE in China are generally on a downward trend, and emphasis should be placed on strengthening disease surveillance in special areas and populations, popularizing vaccination, and increasing publicity.

The diagnosis of central nervous system infections in resource-limited settings and the use of novel and molecular diagnostic platforms to improve diagnosis

INTRODUCTION

Central nervous system infections (CNSI) disproportionately affect individuals in low-resource settings where diagnosis is challenging; large proportions of patients never receive a confirmed microbiological diagnosis resulting in inadequate management and high mortality. The epidemiology of CNSI varies globally and conventional diagnostics deployed in resource-limited settings have significant limitations, with an urgent need for improved diagnostic strategies.

AREAS COVERED

This review describes molecular platforms and other novel diagnostics used in the diagnosis of CNSI that are applicable to resource-limited settings. An extensive literature search of Medline and PubMed was performed. The emphasis is on investigations targeting infections of relevance to resource-limited settings either due to variation in regional CNSI epidemiology or due to increased prevalence in patients with immunosuppression. This includes commercially available multiplex PCR platforms, mycobacterial PCR platforms, and rapid diagnostics tests. To offer a framework for the optimal implementation in clinical settings, existing evidence highlighting the advantages and limitations of available platforms is reviewed.

EXPERT OPINION

The implementation of molecular platforms and other novel diagnostics has the potential to transform CNSI diagnosis in resource-limited settings, with several examples of successful rollout of novel diagnostics such as Xpert MTB/RIF Ultra and cryptococcal antigen testing.

A CRISPR-Cas12a-Based Diagnostic Method for Japanese Encephalitis Virus Genotypes I, III, and V

The Japanese encephalitis virus (JEV) is prevalent in Asian countries, including Korea, Japan, China, Vietnam, and India. JEV is transmitted to humans by Culex mosquitoes. Despite extensive research efforts, no approved antiviral agents are currently available, although JE can be prevented by vaccination. DNA endonuclease-targeted CRISPR trans reporter (DETECTR) is a newly emerging CRISPR-Cas12a-based molecular diagnostic method combined with isothermal nucleic acid amplification. In this study, DETECTR with reverse transcription-recombinase polymerase amplification (RT-RPA) was effectively utilized for JEV diagnosis and detected down to 10 RNA copies for JEV genotype I (GI) and 1 × 102 copies for both GIII and GV, achieving similar sensitivity to RT-PCR while displaying no cross-reaction with other viruses. A one-tube, one-temperature format of DETECTR was further developed, and its efficiency compared with that of conventional DETECTR.

Japanese Encephalitis Emergence in Australia: The Potential Population at Risk

In Australia, Japanese encephalitis virus circulated in tropical north Queensland between 1995 and 2005. In 2022, a dramatic range expansion across the southern states has resulted in 30 confirmed human cases and 6 deaths. We discuss the outbreak drivers and estimate the potential size of the human population at risk.

Recent advances to overcome the burden of Japanese encephalitis: A zoonotic infection with problematic early detection

Japanese encephalitis (JE) is a vector-borne neurotropic disease caused by Japanese encephalitis virus (JEV) associated with high mortality rate distributed from Eastern and Southern Asia to Northern Queensland (Australia). The challenges in early detection and lack of point-of-care biomarkers make it the most important Flavivirus causing encephalitis. There is no specific treatment for the disease, although vaccines are licenced. In this review, we focussed on point-of-care biomarkers as early detection tools and developing the effective therapeutic agents that could halt JE. We have also provided molecular details of JEV, disease progression, and its pathogenesis with recent findings which might bring insights to overcome the disease burden.

A review on Japanese Encephalitis virus emergence, pathogenesis and detection: From conventional diagnostics to emerging rapid detection techniques

The virus known as Japanese Encephalitis (JEV) is among the common viral persisting Encephalitis caused by Flavivirus around the Globe, especially in Southeast Asian nations. JEV may be a leading reason for neurological illness in humans, with an estimated 70,000 human cases and 10,000 fatalities per annum. The conventional methods like PRNT (Plaque Reduction Neutralization Test), ELISA (Enzyme-linked immunosorbent assay) RT-PCR (reverse transcription-polymerase chain reaction), and virus isolation are few commercial tests being availed these days, but they have a variety of drawbacks, including being extremely expensive, time-consuming, and requiring expertise. Therefore, researches are being made in the development of improved inexpensive, shorter, sensitive, and time-saving strategies to diagnose the Japanese Encephalitis Virus. A number of these researches encompass the employment of immunosensors, electrochemical sensors and along with the applications of nanotechnology to create highly sensitive detecting device. This review article is based on contemporary breakthroughs in diagnosing Japanese Encephalitis Virus, which are crucial in severing the connection between the propagation of zoonotic disease into the current race, where humans function as dead-end hosts.

A systematic review of brain imaging findings in neurological infection with Japanese encephalitis virus compared with Dengue virus

OBJECTIVES

Japanese encephalitis virus (JEV) and dengue virus (DENV) represent important causes of encephalitis in Asia. Brain imaging may provide diagnostic clues about the etiology of infectious encephalitis. We performed a systematic review of brain imaging findings in Japanese encephalitis (JE) and DENV neurological infection (dengue) to identify characteristic lesions.

METHODOLOGY

Five databases were searched. We included all study types and imaging techniques. Laboratory methods were categorized using diagnostic confidence levels. Imaging data were synthesized, and focal findings are presented as proportions for JE and dengue and for subgroups based on diagnostic confidence.

PRINCIPAL FINDINGS

Thalamic lesions were the most reported magnetic resonance imaging finding in both diseases but appeared to occur more often in JE (74% in 23 studies) than dengue (29.4% in 58 studies). In cases diagnosed with antigen or nucleic acid tests, thalamic lesions were reported frequently in both JE (76.5% in 17 studies) and dengue (65.2% in 23 studies).

SIGNIFICANCE

The results suggest that thalamic lesions frequently occur in both JE and dengue encephalitis. No radiological findings were found to be pathognomonic of either disease. Although brain imaging may support a diagnosis, laboratory confirmation with highly specific tests remains crucial.

Estimates of Japanese Encephalitis mortality and morbidity: A systematic review and modeling analysis

Background

Japanese Encephalitis (JE) is known for its high case fatality ratio (CFR) and long-term neurological sequelae. Over the years, efforts in JE treatment and control might change the JE fatality risk. However, previous estimates were from 10 years ago, using data from cases in the 10 years before this. Estimating JE disease severity is challenging because data come from countries with different JE surveillance systems, diagnostic methods, and study designs. Without precise and timely JE disease severity estimates, there is continued uncertainty about the JE disease burden and the effect of JE vaccination.

Methodology

We performed a systematic review to collate age-stratified JE fatality and morbidity data. We used a stepwise model selection with BIC as the selection criteria to identify JE CFR drivers. We used stacked regression, to predict country-specific JE CFR from 1961 to 2030. JE morbidity estimates were grouped from similar study designs to estimate the proportion of JE survivors with long-term neurological sequelae.

Principal findings

We included 82 and 50 peer-reviewed journal articles published as of March 06 2021 for JE fatality and morbidity with 22 articles in both analyses. Results suggested overall JE CFR estimates of 26% (95% CI 22, 30) in 1961–1979, 20% (95% CI 17, 24) in 1980–1999, 14% (95% CI 11, 17) in 2000–2018, and 14% (95% CI 11, 17) in 2019–2030. Holding other variables constant, we found that JE fatality risk decreased over time (OR: 0.965; 95% CI: 0.947–0.983). Younger JE cases had a slightly higher JE fatality risk (OR: 1.012; 95% CI: 1.003–1.021). The odds of JE fatality in countries with JE vaccination is 0.802 (90% CI: 0.653–0.994; 95% CI: 0.62–1.033) times lower than the odds in countries without JE vaccination. Ten percentage increase in the percentage of rural population to the total population was associated with 15.35% (95% CI: 7.71, 22.57) decrease in JE fatality odds. Ten percentage increase in population growth rate is associated with 3.71% (90% CI: 0.23, 7.18; 95% CI: -0.4, 8.15) increase in JE fatality odds. Adjusting for the effect of year, rural population percent, age of JE cases, and population growth rate, we estimated that there was a higher odds of JE fatality in India compared to China. (OR: 5.46, 95% CI: 3.61–8.31). Using the prediction model we found that, in 2000–2018, Brunei, Pakistan, and Timor-Leste were predicted to have the highest JE CFR of 20%. Bangladesh, Guam, Pakistan, Philippines, and Vietnam had projected JE CFR over 20% for after 2018, whereas the projected JE CFRs were below 10% in China, Indonesia, Cambodia, Myanmar, Malaysia, and Thailand. For disability, we estimated that 36% (min-max 0–85) JE patients recovered fully at hospital discharge. One year after hospital discharge, 46% (min-max 0%-97%) JE survivors were estimated to live normally but 49% (min-max 3% - 86%)till had neurological sequelae.

Conclusion

JE CFR estimates were lower than 20% after 2000. Our study provides an updated estimation of CFR and proportion of JE cases with long-term neurological sequelae that could help to refine cost-benefit assessment for JE control and elimination programs.

Japanese Encephalitis (JE) is known for its high case fatality ratio (CFR) and long-term neurological sequelae. Although JE fatality and morbidity risk might change as the characteristics of the population change with the strengthened surveillance scales, expanded immunization coverage, and healthcare improvements, there have not been any updates in the estimates for JE mortality and morbidity estimates for 10 years. In this paper, we made updated estimates of the JE CFR and the proportion of JE survivors with long-term neurological sequelae by performing a systematic review and developing statistical and machine learning models. We estimated JE CFR decreased over time, with estimates of 26% (95% CI 22, 30) in 1961–1979, 20% (95% CI 17, 24) in 1980–1999, 14% (95% CI 11, 17) in 2000–2018, and 14% (95% CI 11, 17) in 2019–2030. countries without JE vaccination, younger JE cases, higher population growth rate, and lower rural population percentage were associated with higher JE CFR. We estimated that 36% (min-max 0–85) JE patients recovered fully at hospital discharge. One year after hospital discharge, 46% (min-max 0%-97%) JE survivors were estimated to live normally but 49% (min-max 3% - 86%) JE patients still had neurological sequelae. The insights gained will be important in evaluating and updating current JE disease burden among all endemic areas and effectively channeling resources to most needed areas.

Immunoglobulin M seroneutralization for improved confirmation of Japanese encephalitis virus infection in a flavivirus-endemic area

BACKGROUND

The mainstay of diagnostic confirmation of acute Japanese encephalitis (JE) involves detection of anti-JE virus (JEV) immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA). Limitations in the specificity of this test are increasingly apparent with the introduction of JEV vaccinations and the endemicity of other cross-reactive flaviviruses. Virus neutralization testing (VNT) is considered the gold standard, but it is challenging to implement and interpret. We performed a pilot study to assess IgG depletion prior to VNT for detection of anti-JEV IgM neutralizing antibodies (IgM-VNT) as compared with standard VNT.

METHODS

We evaluated IgM-VNT in paired sera from anti-JEV IgM ELISA-positive patients (JE n=35) and negative controls of healthy flavivirus-naïve (n=10) as well as confirmed dengue (n=12) and Zika virus (n=4) patient sera. IgM-VNT was subsequently performed on single sera from additional JE patients (n=76).

RESULTS

Anti-JEV IgG was detectable in admission serum of 58% of JE patients. The positive, negative and overall percentage agreement of IgM-VNT as compared with standard VNT was 100%. A total of 12/14 (86%) patient samples were unclassified by VNT and, with sufficient sample available for IgG depletion and IgG ELISA confirming depletion, were classified by IgM-VNT. IgM-VNT enabled JE case classification in 72/76 (95%) patients for whom only a single sample was available.

CONCLUSIONS

The novel approach has been readily adapted for high-throughput testing of single patient samples and it holds promise for incorporation into algorithms for use in reference centres.

Mouse models of Japanese encephalitis virus infection: A systematic review and meta-analysis using a meta-regression approach

BACKGROUND

Japanese encephalitis (JE) virus (JEV) remains a leading cause of neurological infection across Asia. The high lethality of disease and absence of effective therapies mean that standardised animal models will be crucial in developing therapeutics. However, published mouse models are heterogeneous. We performed a systematic review, meta-analysis and meta-regression of published JEV mouse experiments to investigate the variation in model parameters, assess homogeneity and test the relationship of key variables against mortality.

METHODOLOGY/ PRINCIPAL FINDINGS

A PubMed search was performed up to August 2020. 1991 publications were identified, of which 127 met inclusion criteria, with data for 5026 individual mice across 487 experimental groups. Quality assessment was performed using a modified CAMARADES criteria and demonstrated incomplete reporting with a median quality score of 10/17. The pooled estimate of mortality in mice after JEV challenge was 64.7% (95% confidence interval 60.9 to 68.3) with substantial heterogeneity between experimental groups (I^2 70.1%, df 486). Using meta-regression to identify key moderators, a refined dataset was used to model outcome dependent on five variables: mouse age, mouse strain, virus strain, virus dose (in log10PFU) and route of inoculation. The final model reduced the heterogeneity substantially (I^2 38.9, df 265), explaining 54% of the variability.

CONCLUSION/ SIGNIFICANCE

This is the first systematic review of mouse models of JEV infection. Better adherence to CAMARADES guidelines may reduce bias and variability of reporting. In particular, sample size calculations were notably absent. We report that mouse age, mouse strain, virus strain, virus dose and route of inoculation account for much, though not all, of the variation in mortality. This dataset is available for researchers to access and use as a guideline for JEV mouse experiments.

Childhood encephalitis hospitalizations associated with virus agents in medium-endemic states in India

BACKGROUND

Japanese encephalitis (JE) is the leading cause of childhood acute encephalitis syndrome (AES) in India. We enhanced the AES surveillance in sentinel hospitals to determine trends and virus etiologies in central India.

METHODS

The neurological hospitalizations among children ≤15 years were tracked by using the AES case definition implemented by the national program. Acute and convalescent sera along with cerebrospinal fluid (CSF) specimens were collected and tested at the strengthened site hospital laboratories for anti-JE, anti-Dengue and anti-Chikungunya virus by IgM ELISA; along with Chandipura virus RT-PCR. Herpes simplex and enterovirus testing was undertaken at the reference laboratory.

RESULTS

Among 1619 pediatric neurological hospitalizations reported during 2015-16, AES case definition was fulfilled in 332 (20.5%) cases. After excluding 52 non-AES cases, 280 AES cases resident from study districts were considered eligible for study. The treating physicians diagnosed non-viral causes in 90 cases, therefore 190 (67.9%) of 280 AES cases were suspected with viral etiologies. We enrolled 140 (73.7%) of 190 eligible AES cases. Viral etiologies were confirmed in 31 (22.1%) of 140 enrolled AES cases. JE (n = 22) was the leading cause. Additional non-JE viral agents included Chikungunya (5), Dengue (2) and Chandipura (2). However, only 21 (9.4%) of 222 additional AES cases referred from peripheral hospitals were confirmed as JE.

CONCLUSIONS

Japanese encephalitis virus continues to be the leading cause of childhood acute encephalitis syndrome in central India despite vaccination program. Surveillance needs to be intensified for assessing the true disease burden of Japanese encephalitis following vaccination program implementation.

Aptamers isolated against mosquito-borne pathogens

Mosquito-borne diseases are a major threat to public health. The shortcomings of diagnostic tools, especially those that are antibody-based, have been blamed in part for the rising annual morbidity and mortality caused by these diseases. Antibodies harbor a number of disadvantages that can be clearly addressed by aptamers as the more promising molecular recognition elements. Aptamers are defined as single-stranded DNA or RNA oligonucleotides generated by SELEX that exhibit high binding affinity and specificity against a wide variety of target molecules based on their unique structural conformations. A number of aptamers were developed against mosquito-borne pathogens such as Dengue virus, Zika virus, Chikungunya virus, Plasmodium parasite, Francisella tularensis, Japanese encephalitis virus, Venezuelan equine encephalitis virus, Rift Valley fever virus and Yellow fever virus. Intrigued by these achievements, we carry out a comprehensive overview of the aptamers developed against these mosquito-borne infectious agents. Characteristics of the aptamers and their roles in diagnostic, therapeutic as well as other applications are emphasized.

Investigation of Japanese encephalitis virus as a cause of acute encephalitis in southern Pakistan, April 2015-January 2018

Background

Japanese encephalitis (JE) occurs in fewer than 1% of JE virus (JEV) infections, often with catastrophic sequelae including death and neuropsychiatric disability. JEV transmission in Pakistan was documented in 1980s and 1990s, but recent evidence is lacking. Our objective was to investigate JEV as a cause of acute encephalitis in Pakistan.

Methods

Persons aged ≥1 month with possible JE admitted to two acute care hospitals in Karachi, Pakistan from April 2015 to January 2018 were enrolled. Cerebrospinal fluid (CSF) or serum samples were tested for JEV immunoglobulin M (IgM) using the InBios JE Detect^TM assay. Positive or equivocal samples had confirmatory testing using plaque reduction neutralization tests.

Results

Among 227 patients, testing was performed on CSF in 174 (77%) and on serum in 53 (23%) patients. Six of eight patient samples positive or equivocal for JEV IgM had sufficient volume for confirmatory testing. One patient had evidence of recent West Nile virus (WNV) neurologic infection based on CSF testing. One patient each had recent dengue virus (DENV) infection and WNV infection based on serum results. Recent flavivirus infections were identified in two persons, one each based on CSF and serum results. Specific flaviviruses could not be identified due to serologic cross-reactivity. For the sixth person, JEV neutralizing antibodies were confirmed in CSF but there was insufficient volume for further testing.

Conclusions

Hospital-based JE surveillance in Karachi, Pakistan could not confirm or exclude local JEV transmission. Nonetheless, Pakistan remains at risk for JE due to presence of the mosquito vector, amplifying hosts, and rice irrigation. Laboratory surveillance for JE should continue among persons with acute encephalitis. However, in view of serological cross-reactivity, confirmatory testing of JE IgM positive samples at a reference laboratory is essential.