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Microbial Pathogenesis Nov 2019Japanese encephalitis (JE) has emerged as one of the most important form of viral encephalitis, which accounts for an estimated 70,000 cases each year with approximately... (Review)
Review
Japanese encephalitis (JE) has emerged as one of the most important form of viral encephalitis, which accounts for an estimated 70,000 cases each year with approximately 10,000 fatalities. The clinical presentations and outcome of the infection is dependent upon both virulence of viral determinants and host immune responses. The causative pathogen of JE is a virus known as Japanese encephalitis virus (JEV), which penetrates into the CNS from blood and triggers rapid humoral and cell-mediated immune response. Humoral response is crucial for the control of dissemination of JEV infection and the cytokines produced by cell-mediated immunity during JEV infections serve as potent immune mediators. Till date, JE is only vaccine preventable and no complete antiviral treatment is available so far. Further, vaccine-mediated prevention also has certain limitations. Therefore, an understanding of the pathogenesis of JEV infection can enable the researchers to presume the depth of treatment regime. This review highlights the importance of understanding of the immune mechanisms that are operated in the host during JEV infection and would be helpful in improving future vaccination strategy against JEV.
Topics: Drug Discovery; Encephalitis Virus, Japanese; Encephalitis, Japanese; Humans; Immunity, Cellular; Immunity, Humoral; Japanese Encephalitis Vaccines
PubMed: 31437579
DOI: 10.1016/j.micpath.2019.103678 -
The Indian Journal of Medical Research 2022Japanese encephalitis (JE) is a leading cause of viral encephalitis in Southeast Asia. It is a serious public health issue in India, and cases have been emerging in... (Review)
Review
Japanese encephalitis (JE) is a leading cause of viral encephalitis in Southeast Asia. It is a serious public health issue in India, and cases have been emerging in newer areas of the country. Although vaccination efforts have already been initiated in the country since 2006 and later through the Universal Immunization Programme in 2011, still a significant reduction in the number of cases has to be achieved since an escalating trend of JE incidence has been reported in certain States such as Assam, Uttar Pradesh and West Bengal. Moreover, fresh cases of JE have been reported from certain pockets in Odisha as well. Despite the mass JE vaccination programme implemented in prioritized endemic zones in the country in 2011, a shift in the age group of JE virus (JEV) infection was noticed affecting the adult population in West Bengal. The recent detection of the circulation of genotype I (GI) in Gorakhpur, Uttar Pradesh and the co-circulation of GI and genotype III (GIII) in West Bengal are probably a warning signal for the public health personnel to strengthen the surveillance system in all endemic hotspots in the country. The abrupt emergence of JEV genotype V (GV) in China and Korea in 2009, after its first detection in Malaya in 1952, endemic countries have been cautioned to strengthen their surveillance, because GV has been suspected of getting dispersed efficiently in other parts of Asia. Moreover, the reduced protection efficiency of the JEV GIII-based vaccine against the JEV genotype V further warrants careful evaluation of the ongoing vaccination strategies in the endemic countries, anticipating the possible incursion of GV and its impact on future control strategies. In view of the above facts, the present communication reviews the current knowledge on the molecular epidemiology of JEV in India vis-a-vis the global scenario and discusses the future priorities in JEV research in India for effectively designing control strategies.
Topics: Adult; Humans; Encephalitis Virus, Japanese; Encephalitis, Japanese; India; Asia; Genotype
PubMed: 36926775
DOI: 10.4103/ijmr.IJMR_2606_19 -
Australian Journal of General Practice May 2023Japanese encephalitis virus (JEV) is a mosquito-borne arbovirus endemic to the Asia-Pacific that causes high morbidity and mortality in those who develop symptomatic... (Review)
Review
BACKGROUND
Japanese encephalitis virus (JEV) is a mosquito-borne arbovirus endemic to the Asia-Pacific that causes high morbidity and mortality in those who develop symptomatic disease. Prior to 2021, only five locally acquired cases had been detected in Australia, all in northern Australia. Following a sentinel case in 2021, widespread dissemination of JEV was detected in northern and south-eastern Australia, accompanied by an increase in locally acquired cases, which have been detected as far south as Victoria. This expansion has occurred in the setting of warmer and wetter conditions under the influence of climate change.
OBJECTIVE
To provide Australian general practitioners (GPs) an overview of JEV, given its recent expansion, and the potential for sustained endemicity.
DISCUSSION
As the distribution of JEV expands under the influence of climate change, Australian GPs need to be familiar with this condition, especially those practicing in rural areas and where detections have occurred.
Topics: Animals; Humans; Climate Change; Encephalitis Virus, Japanese; Encephalitis, Japanese; Victoria
PubMed: 37149766
DOI: 10.31128/AJGP-07-22-6484 -
Japanese Encephalitis Virus: The Emergence of Genotype IV in Australia and Its Potential Endemicity.Viruses Nov 2022A fatal case of Japanese encephalitis (JE) occurred in northern Australia in early 2021. Sequence studies showed that the virus belonged to genotype IV (GIV), a genotype... (Review)
Review
A fatal case of Japanese encephalitis (JE) occurred in northern Australia in early 2021. Sequence studies showed that the virus belonged to genotype IV (GIV), a genotype previously believed to be restricted to the Indonesian archipelago. This was the first locally acquired case of Japanese encephalitis virus (JEV) GIV to occur outside Indonesia, and the second confirmed fatal human case caused by a GIV virus. A closely related GIV JEV strain subsequently caused a widespread outbreak in eastern Australia in 2022 that was first detected by fetal death and abnormalities in commercial piggeries. Forty-two human cases also occurred with seven fatalities. This has been the first major outbreak of JEV in mainland Australia, and geographically the largest virgin soil outbreak recorded for JEV. This outbreak provides an opportunity to discuss and document the factors involved in the virus' spread and its ecology in a novel ecological milieu in which other flaviviruses, including members of the JE serological complex, also occur. The probable vertebrate hosts and mosquito vectors are discussed with respect to virus spread and its possible endemicity in Australia, and the need to develop a One Health approach to develop improved surveillance methods to rapidly detect future outbreak activity across a large geographical area containing a sparse human population. Understanding the spread of JEV in a novel ecological environment is relevant to the possible threat that JEV may pose in the future to other receptive geographic areas, such as the west coast of the United States, southern Europe or Africa.
Topics: Animals; Humans; Encephalitis Virus, Japanese; Encephalitis, Japanese; Genotype; Mosquito Vectors; Vertebrates; Culex
PubMed: 36366578
DOI: 10.3390/v14112480 -
Viruses Jun 2021Japanese encephalitis virus (JEV) is a zoonotic pathogen mainly found in East and Southeast Asia and transmitted by mosquitoes. The objective of this review is to... (Meta-Analysis)
Meta-Analysis Review
Japanese encephalitis virus (JEV) is a zoonotic pathogen mainly found in East and Southeast Asia and transmitted by mosquitoes. The objective of this review is to summarize the knowledge on the diversity of JEV mosquito vector species. Therefore, we systematically analyzed reports of JEV found in field-caught mosquitoes as well as experimental vector competence studies. Based on the investigated publications, we classified 14 species as confirmed vectors for JEV due to their documented experimental vector competence and evidence of JEV found in wild mosquitoes. Additionally, we identified 11 mosquito species, belonging to five genera, with an experimentally confirmed vector competence for JEV but lacking evidence on their JEV transmission capacity from field-caught mosquitoes. Our study highlights the diversity of confirmed and potential JEV vector species. We also emphasize the variety in the study design of vector competence investigations. To account for the diversity of the vector species and regional circumstances, JEV vector competence should be studied in the local context, using local mosquitoes with local virus strains under local climate conditions to achieve reliable data. In addition, harmonization of the design of vector competence experiments would lead to better comparable data, informing vector and disease control measures.
Topics: Animals; Disease Vectors; Encephalitis Virus, Japanese; Encephalitis, Japanese; Geography, Medical; Global Health; Humans; Mosquito Vectors; Population Surveillance
PubMed: 34208737
DOI: 10.3390/v13061154 -
PLoS Neglected Tropical Diseases Aug 2022Thailand has introduced a nationwide vaccination against Japanese encephalitis virus (JEV) into National Immunization Programme since the 1990's. To improve the...
BACKGROUND
Thailand has introduced a nationwide vaccination against Japanese encephalitis virus (JEV) into National Immunization Programme since the 1990's. To improve the understanding of immunity and susceptibility of the population after 28 years of a vaccination programme, we conducted a JEV seroepidemiological study in a JEV-endemic area of Thailand.
METHODS
An age-stratified, population-based, seroepidemiological study was conducted in Chiang Mai, Thailand-a northern Thai province where is an endemic area of Japanese encephalitis. Nine districts were chosen based on administrative definition: rural (n = 3); urban (n = 3); and peri-urban (n = 3). Within each district, eligible participants were randomly selected from 3 age groups: adolescents (10-20 years); adults (21-50 years); and older adults/elderly (≥51 years) by computer randomization. Plaque reduction neutralization tests (PRNT50 and PRNT90) were performed to measure neutralizing antibodies to JEV. To account for the cross-reactivity of JEV and other flaviviruses, JEV seroprotection was defined according to age, previous history of JEV vaccination, and PRNT50/PRNT90 levels of study participants.
RESULTS
Overall, 279 adolescents, 297 adults, and 297 older adults/elderly were enrolled from nine districts. Age-stratified, protocol-defined, cluster-adjusted JEV seroprotection rates were 61% (95% CI: 48-73%), 43% (95% CI: 31-57%), and 52% (95% CI: 37-67%) for adolescents, adults, and older adults/elderly, respectively. Living in peri-urban districts, having a history of prior dengue virus infection, and previously receiving mouse brain-derived JEV vaccine were significantly associated with seroprotection to JEV in adolescents. Older age and male sex were associated with seroprotection for adults; and only male sex was the associated factor for older adults/elderly (P <0.05).
CONCLUSIONS
Approximately half of population living in a JEV-endemic area demonstrated seroprotection to JEV. Ongoing nationwide surveillance on JEV seropepidemiology is an important strategy to understand the evolving population-level immunity to JEV, and to help formulating the appropriate recommendations on JE immunization.
Topics: Animals; Antibodies, Neutralizing; Antibodies, Viral; Encephalitis Virus, Japanese; Encephalitis, Japanese; Humans; Japanese Encephalitis Vaccines; Male; Mice; Seroepidemiologic Studies; Vaccination
PubMed: 35913983
DOI: 10.1371/journal.pntd.0010674 -
Medical and Veterinary Entomology Dec 2023In Southeast Asia, despite the use of Japanese encephalitis vaccines and vaccination coverage, Japanese encephalitis (JE) transmission is still a major public health...
In Southeast Asia, despite the use of Japanese encephalitis vaccines and vaccination coverage, Japanese encephalitis (JE) transmission is still a major public health issue. The main vectors of this virus are mosquitoes from the genus Culex, which diversity and density are important in Southeast Asia. The main vector species of Japanese encephalitis virus (JEV) in Cambodia belong to the Vishnui subgroup. However, their morphological identification solely based on the adult stage remains challenging, making their segregation and detection difficult. In order to identify and describe the distribution of the three main JEV vector species in Cambodia, namely Culex vishnui, Cx. pseudovishnui and Cx. tritaeniorhynchus, mosquito samplings were carried out throughout the country in different environments. Phylogenetic analysis of the cytochrome c oxidase subunit I (coI) gene using maximum-likelihood tree with ultrafast bootstrap and phylogeographic analysis were performed. The three main Culex species are phylogenetically separated, and represent two distinct clades, one with Cx. tritaeniorhynchus and the second with Cx. vishnui and Cx. pseudovishnui, the latter appearing as a subgroup of Cx. vishnui. The phylogeographic analysis shows a distribution of the Vishnui subgroup on the entire Cambodian territory with an overlapped distribution areas leading to a sympatric distribution of these species. The three JEV vector species are geographically well-defined with a strong presence of Cx. pseudovishnui in the forest. Combined with the presence of Cx. tritaeniorhynchus and Cx. vishnui in rural, peri-urban, and urban areas, the presence of JEV-competent vectors is widespread in Cambodia.
Topics: Animals; Encephalitis Virus, Japanese; Phylogeny; Cambodia; Encephalitis, Japanese; Culicidae; Culex; Mosquito Vectors
PubMed: 37404158
DOI: 10.1111/mve.12678 -
Journal of Microbiology and... Sep 2022Japanese encephalitis virus (JEV), the causative agent of Japanese encephalitis (JE), is an importantly zoonotic, vector-borne virus widely prevalent in Asia. Although...
Japanese encephalitis virus (JEV), the causative agent of Japanese encephalitis (JE), is an importantly zoonotic, vector-borne virus widely prevalent in Asia. Although JE has been well controlled in China, its prevalence remains a huge threat to the pig industry as well as human health. Herein, we report on our molecular and serological investigations of JEV among pigs from different regions in Hunan Province of China from 2019 to 2021. Collectively, 19.27% (583/3026, 95% Confidential Interval (CI) 17.86-20.68) of sampled pigs were positive for JEV IgG antibody as revealed by indirect enzyme-linked immunosorbent assay, and the seroprevalence of JEV among pigs was significantly associated with the development stage and breeding scale ( < 0.01). Meanwhile, 10.99% (42/382, 95% CI 7.86-14.13) of tissue samples of pigs with suspected clinical symptoms of JE and 23.44% (15/64, 95% CI 13.06-33.82) of mosquito batches were JEV-positive via reverse polymerase chain reaction. In addition, the complete E gene sequences of 14 JEV strains identified in this study were amplified and sequenced. Phylogenetic analysis showed that all 14 JEV strains belonged to genotype I-b and displayed a distinct genetic relationship to the present JEV vaccine strain (SA14-14-2). In conclusion, our results revealed not only the severe prevalence of JEV in Hunan Province, but also that JEV I-b might be the predominant genotype in Hunan Province, suggesting therefore that effective measures for JE control are urgently needed.
Topics: Animals; Antibodies, Viral; China; Culicidae; Encephalitis Virus, Japanese; Encephalitis, Japanese; Genotype; Humans; Immunoglobulin G; Mosquito Vectors; Phylogeny; Prevalence; Seroepidemiologic Studies; Swine
PubMed: 36116917
DOI: 10.4014/jmb.2207.07068 -
Interdisciplinary Topics in Gerontology... 2020People who travel to countries where they are at risk of contracting specific infections often need specific vaccines. To make correct recommendations in this respect... (Review)
Review
People who travel to countries where they are at risk of contracting specific infections often need specific vaccines. To make correct recommendations in this respect several points have to be considered. The state of health of the traveler should be known as well as his or her destination and travel style. Very important, however, is the age of the traveler. As advancing age leads to changes in the immune system, in older individuals many infections are more severe. On the other hand, most vaccines are less immunogenic in the elderly. In this chapter, we will discuss which vaccines are necessary for older travelers visiting (mainly) tropical and subtropical countries, how these vaccines have to be used, and if perhaps their use has to be altered in older individuals. First, standard vaccinations will be addressed. When the immunization state of the individual is incomplete because certain vaccinations are expired or missing, it has to be updated. Vaccinations against tetanus, diphtheria, influenza, pneumococcal diseases, measles, and poliomyelitis have to be considered in this respect, because the risk of getting infected with these diseases in tropical and subtropical regions or in regions with poor hygienic conditions is often higher or at least the same as in industrialized countries. The second and main part of this chapter contains the typical travel vaccines. We will deal with vaccinations against cholera, hepatitis A and B, Japanese encephalitis, invasive meningococcal diseases, rabies, typhoid fever, and yellow fever. Clinical courses and epidemiology of the different infections are presented. The respective vaccines are discussed in detail, especially their efficiency in older individuals as far as data are available in this respect. Finally, recommendations for their use in older travelers will be given.
Topics: Aged; Cholera; Diphtheria; Encephalitis, Japanese; Encephalitis, Tick-Borne; Hepatitis A; Hepatitis B; Humans; Immunologic Factors; Influenza, Human; Meningococcal Infections; Poliomyelitis; Rabies; Tetanus; Travel; Typhoid Fever; Vaccination; Vaccines; Yellow Fever
PubMed: 32305985
DOI: 10.1159/000504492 -
PLoS Neglected Tropical Diseases May 2022Japanese 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...
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.
Topics: China; Encephalitis, Japanese; Humans; Japanese Encephalitis Vaccines; Morbidity; Philippines; Thailand
PubMed: 35613183
DOI: 10.1371/journal.pntd.0010361