Serological and molecular epidemiology of Japanese Encephalitis in Zhejiang, China, 2015-2018

Japanese Encephalitis Virus and Schizophyllum commune Co-Infection in a Harbor Seal in Japan

The Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, has a wide host range, extending from pigs and ardeid birds to opportunistic dead-end hosts, such as humans and horses. However, JEV encephalitis infections in aquatic mammals are rare, with only two cases in seals reported to date. Here, we report a lethal case of JEV and Schizophyllum commune co-infection in an aquarium-housed harbor seal in Japan. We isolated JEV from the brain of the dead seal and characterized its phylogeny and pathogenicity in mice. The virus isolate from the seal was classified as genotype GIb, which aligns with recent Japanese human and mosquito isolates as well as other seal viruses detected in China and Korea, and does not exhibit a unique sequence trait distinct from that of human and mosquito strains. We demonstrated that the seal isolate is pathogenic to mice and causes neuronal symptoms. These data suggest that seals should be considered a susceptible dead-end host for circulating JEV in natural settings.

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.

Development of Colloidal Gold-Based Immunochromatographic Strips for Rapid Detection and Surveillance of Japanese Encephalitis Virus in Dogs across Shanghai, China

Japanese encephalitis virus (JEV) causes acute encephalitis in humans and is of major public health concern in most Asian regions. Dogs are suitable sentinels for assessing the risk of JEV infection in humans. A neutralization test (NT) or an enzyme-linked immunosorbent assay (ELISA) is used for the serological detection of JEV in dogs; however, these tests have several limitations, and, thus, a more convenient and reliable alternative test is needed. In this study, a colloidal gold immunochromatographic strip (ICS), using a purified recombinant EDIII protein, was established for the serological survey of JEV infection in dogs. The results show that the ICSs could specifically detect JEV antibodies within 10 min without cross-reactions with antibodies against other canine viruses. The test strips could detect anti-JEV in serum with dilution up to 640 times, showing high sensitivity. The coincidence rate with the NT test was higher than 96.6%. Among 586 serum samples from dogs in Shanghai examined using the ICS test, 179 (29.98%) were found to be positive for JEV antibodies, and the high seropositivity of JEV in dogs in China was significantly correlated with the season and living environment. In summary, we developed an accurate and economical ICS for the rapid detection of anti-JEV in dog serum samples with great potential for the surveillance of JEV in dogs.

Genotype Change in Circulating JEV Strains in Fujian Province, China

Japanese encephalitis (JE), found in pigs, is a serious mosquito-borne zoonotic infectious disease caused by the Japanese encephalitis virus (JEV). JEV is maintained in an enzootic cycle between mosquitoes and amplifying vertebrate hosts, mainly pigs and wading birds. It is transmitted to humans through the bite of an infected mosquito, allowing the pathogen to spread and cause disease epidemics. However, there is little research on JEV genotype variation in mosquitoes and pigs in Fujian province. Previous studies have shown that the main epidemic strain of JEV in Fujian Province is genotype III. In this study, a survey of mosquito species diversity in pig farms and molecular evolutionary analyses of JEV were conducted in Fujian, China, in the summer of 2019. A total of 19,177 mosquitoes were collected at four sites by UV trap. Four genera were identified, of which the Culex tritaeniorhynchus was the most common mosquito species, accounting for 76.4% of the total (14,651/19,177). Anopheles sinensi (19.25%, 3691/19,177) was the second largest species. High mosquito infection rateswere an important factor in the outbreak. The captured mosquito samples were milled and screened with JEV-specific primers. Five viruses were isolated, FJ1901, FJ1902, FJ1903, FJ1904, and FJ1905. Genetic affinity was determined by analyzing the envelope (E) gene variants. The results showed that they are JEV gene type I and most closely related to the strains SH-53 and SD0810. In this study, it was found through genetic evolution analysis that the main epidemic strain of JE in pig farms changed from gene type III to gene type I. Compared with the SH-53 and SD0810 strains, we found no change in key sites related to antigenic activity and neurovirulence of JEV in Fujian JEV and pig mosquito strains, respectively. The results of the study provide basic data for analyzing the genotypic shift of JEV in Fujian Province and support the prevention and control of JEV.

Adults in Northwest China experienced the largest outbreak of Japanese encephalitis in history 10 years after the Japanese encephalitis vaccine was included in the national immunization program: A retrospective epidemiological study

Mainland China included Japanese encephalitis (JE) vaccine in the national immunization program in 2008 to control the JE epidemic. However, Gansu province in Western China experienced the largest JE outbreak since 1958 in 2018. We conducted a retrospective epidemiological study to explore the causes of this outbreak. We found that adults aged ≥20 years (especially those in rural areas) were the main JE cases in Gansu Province, with a significant increase in the JE incidence in older adults aged ≥60 years in 2017 and 2018. In addition, JE outbreaks in Gansu Province were mainly located in the southeastern region, while the temperature and precipitation in Gansu Province were gradually increasing in recent years, which made the JE epidemic areas in Gansu Province gradually spread to the western of Gansu Province. We also found that adults aged ≥20 years in Gansu Province had lower JE antibody positivity than children and infants, and the antibody positivity rate decreased with age. In the summer of 2017 and 2018, the density of mosquitoes (mainly the Culex tritaeniorhynchus) in Gansu Province was significantly higher than in other years, and the genotype of JEV was mainly Genotype-G1. Therefore, in the future JE control in Gansu Province, we need to strengthen JE vaccination for adults. Moreover, strengthening mosquito surveillance can provide early warning of JE outbreaks and the spread of epidemic areas in Gansu Province. At the same time, strengthening JE antibody surveillance is also necessary for JE control.

Prevalence and Genetic Characteristics of Japanese Encephalitis Virus among Mosquitoes and Pigs in Hunan Province, China from 2019 to 2021

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 (p < 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.

Prevalence of Japanese encephalitis (JE) virus in mosquitoes and animals of the Asian continent: A systematic review and meta-analysis

BACKGROUND

Japanese encephalitis (JE) is a viral zoonotic disease that has been found in several countries of Asia and is responsible for high mortality and morbidity of men and animals in rural and sub-urban endemic areas due to the virus re-circulation among diverse hosts and vectors. The present study estimates the prevalence of the JE virus in the vector and animal population of the Asian continent using a systematic review and meta-analysis.

METHODS

The Cochran collaborators' Preferred Reporting Items for Systematic Reviews and Meta-Analysis [PRISMA] guidelines were used for systematic review and meta-analysis. The heterogeneity was observed in meta-regression analysis due to several factors including region, species, and different diagnostic assays used in various studies. Thus we did sensitivity and subgroup analysis.

RESULTS

The prevalence of the JE virus was calculated using a total sample size of 47,391. Subgroup analysis revealed the JE virus prevalence of 39% in the Southeast Asia region, followed by East Asia with 35% and South Asia with 15% prevalence. Hence, the overall pooled prevalence of the JE virus was 26% in the Asian continent.

CONCLUSIONS

The highest proportion of infection was found in pigs amongst all animals, reinforcing the fact that they can be used as sentinels to predict outbreaks in humans. The findings of this study will enable researchers and policymakers in better understanding the disease's spatial and temporal distribution, as well as in creating and implementing location-specific JE prevention and control measures.

The Comparison of Inflammatory Cytokines (IL-6 and IL-18) and Immune Cells in Japanese Encephalitis Patients With Different Progression

Background

Japanese encephalitis virus (JEV) is the main cause of viral encephalitis in Asia. Nowadays, no effective and specific therapy for JE patients is available except supportive treatment. The fatality rate of JE patients is still about 30%, and more than half of survivors suffered from various neuropsychiatric sequelae. Thus, more attention should be paid to JE.

Methods

In this study, a retrospective cohort of JE patients was collected and the general features of JE patients admitted into the Department of Infectious Diseases were analyzed. Meanwhile, the dynamic change of plasma cytokines and immune cells in JE patients with divergent prognosis was detected and analyzed.

Results

We found a mounted proportion of adult/old patients in JE cases. The level of IL-6 and IL-18 increased in JE patients especially in fatal individuals. There was a continuous decreased percentage of CD4⁺ T and B cells in severe JE patients with fatal outcome compared with the surviving JE patients.

Conclusions

The consistent high level of IL-6 and IL-18 in the plasma and low proportion of CD4⁺ T and B cells in the PBMCs might be the indicators of poor prognosis.

Economic and disease burden of Japanese encephalitis in Zhejiang Province, 2013-2018

BACKGROUND

Japanese encephalitis (JE) is a mosquito-borne disease and associated with high mortality and disability rate among symptomatic cases. In the absence of local data, this study estimated the economic burden and the disability-adjusted life years (DALYs) due to JE in Zhejiang Province, China during 2013-2018, to increase disease awareness and provide evidence for effective health policy.

METHODOLOGY/PRINCIPLE FINDINGS

We merged multiple data sources, including National Notifiable Disease Registry System (NNDRS), patient interviews and medical records from corresponding hospitals for JE cases which occurred during 2013-2018 in Zhejiang Province. Direct costs were extracted from hospitals' billing systems and patient interviews. Indirect costs and disease burden were calculated based on questionnaire survey from patient interviews and follow-up assessment by general practitioners. Given under-reporting, an expansion factor (EF) was applied to extrapolate the JE burden to the provincial level. The total economic burden of JE during 2013-2018 was estimated at US $12.01 million with an EF = 3. Of this, $8.32 million was due to direct economic cost and $3.69 million to indirect cost. The disease burden of JE was 42.75 DALYs per million population (28.44 YLD, 14.28 YLL) according to the 1990 Global Burden of Disease (GBD 1990) methodology and 80.01 DALYs (53.67YLD, 26.34YLL) according to the GBD 2010 methodology. Sensitivity analysis demonstrated that the overall economic burden varied from US$ 1.73-36.42 million. The greatest variation was due to the prognosis of illness (-85.57%-203.17%), followed by occupation (-34.07%-134.12%) and age (-72.97%-47.69%).

CONCLUSIONS/SIGNIFICANCE

JE imposes a heavy burden for families and society in Zhejiang Province. This study provides comprehensive empirical estimates of JE burden to increase awareness and strengthen knowledge of the public. These data may support provincial level public health decision making for prevention and control of JE. Ongoing surveillance for acute meningitis and encephalitis syndrome (AEMS) in sentinel hospitals, is needed to further refine estimates of JE burden.