Japanese Encephalitis Cases Research Articles

Japanese encephalitis virus infection in an endemic area: hospital based study 1998 to 2000

Gampaha Deputy Provincial Director of Health Services division reported a large number of Japanese encephalitis cases during 1996 to 1997. Notified cases included unconfirmed and confirmed cases. A study to determine the true disease burden was considered necessary. Proportion of undifferentiated fever cases due to Japanese encephalitis virus varies in different populations and the Sri Lankan situation is not known. The objectives were to determine the proportion of undifferentiated fever cases and encephalitis cases due to Japanese encephalitis virus; and the case fatality rate and frequency of neurological sequelae in Japanese encephalitis, in a tertiary care hospital in Gampaha. A cross-sectional descriptive study was carried out in the paediatric and medicine units of the North Colombo Teaching Hospital, Ragama during 1998 to 2000. Ninety three randomly selected patients with a diagnosis of undifferentiated fever from whom paired sera could be collected and 32 patients suspected of encephalitis, which were not overtly due to mumps, measles or chicken-pox were included. The Armed Forces Research Institute in Medical Sciences Enzyme linked immunosorbent assay for anti-Japanese encephalitis virus immunoglobulin M and G was used to confirm Japanese encephalitis virus infection. One of 93 (1.08%) undifferentiated fever cases was due to Japanese encephalitis virus infection. Eleven of 32 (34.38%) encephalitis cases had Japanese encephalitis virus infection and 3 (27.3%) had IgM antibodies to Japanese encephalitis virus in cerebrospinal fluid. Case fatality rate and sequelae at discharge were 11.1% each. Japanese encephalitis virus was an important cause of encephalitis in Gampaha during this period. DOI: http://dx.doi.org/10.4038/sljid.v2i1.3321 Sri Lankan Journal of Infectious Diseases Vol.2(1) 2012: 19-27

Influence of socio-economic status and environmental factors on serologically diagnosed Japanese encephalitis cases in the state of West Bengal, India during 2005-2010

Objectives: The main aim of the current study is to examine the influence of socio-economic status and environmental factors on serologically diagnosed Japanese encephalitis cases in the state of West Bengal, India during 2005-2010. Materials and methods: A total of 648 blood/CSF specimens were collected and/or referred from the suspected AES cases, admitted in the different medical colleges and hospitals of the state during the year of 2005-2010. These specimens were subjected to JE Mac ELISA to determine the actual JE case amongst these AES. The association of the socio-economic status and environmental factors with the serologically diagnosed JE positive cases was studied by a statistical analysis through Normal Deviate test or Z test. Result: Out of 648 specimens, only 175 (27.0%) specimens were reactive to JE IgM antibody, of which 60.0% were from the male individuals and 40.0% from the female population. Major cases were observed in the age group of 0 - 10 years; followed by 11 - 20 years. Regarding literacy, only 58.3% cases had no education and 41.7% were from the literate with varying level of education, i.e., from primary level to post gra- duate level. A total of 65.7% cases were from low income group where as only 34.3% cases were from high income group. Regarding house type, 62.3% cases lived in mud house and 37.7% cases lived in the brick house. In most of the cases (74.3%), persons were living in close proximity to rice fields/lakes/ponds. 69.7% cases were found to occur in the monsoon and post-monsoon period whereas 30.3% cases were reported in the pre-monsoon period. Conclusion: Our study concludes that socio-economic status and environmental conditions were statistically significant contextual risk factors for serologically diagnosed JE incidences in West Bengal where JE is proved to be endemic in nature and such study constitutes a new report of this kind in the region.

Japanese Encephalitis in a Danish Short‐Term Traveler to Cambodia

We present a recent case of Japanese encephalitis in a Danish male traveler to Cambodia, who we believe is the second Danish case within the last 15 years. Although both this and a number of other travel-related cases occurred in short-term travelers, change in vaccination recommendations is not recommended.

Serological and molecular diagnosis of Japanese encephalitis reveals an increasing public health problem in the state of West Bengal, India

Japanese encephalitis (JE), a neurotrophic disease, was first recorded in the state of West Bengal, India in 1973. Since then JE is being reported every year from different districts. With a view to identify the JE cases accurately, a study was undertaken to detect the Japanese encephalitis virus (JEV) as the etiologic agent from the acute encephalitis syndrome (AES) cases and to identify its distribution in different districts. We report the results of 513 blood or cerebrospinal fluid samples referred/collected from the hospitalized AES cases. The samples were initially subjected to Mac-ELISA test followed by reverse transcriptase (RT)-PCR for the detection of IgM antibodies and the JEV genome, specific to E gene, respectively. Out of 513 samples referred/collected, 139 (27.1%) samples were reactive to JE IgM antibody. The remaining 374 samples were screened to select those which had a history of illness with a duration of ≤3 days. Only 147 samples were selected and tested, out of which 36 (24.5%) isolates were achieved and those were RT-PCR positive against the control JEV strain. Detection of IgM antibody to JE and the RT-PCR result confirms the active circulation of JEV in different districts of West Bengal and needs to be monitored carefully.

Estimated global incidence of Japanese encephalitis: a systematic review.

To update the estimated global incidence of Japanese encephalitis (JE) using recent data for the purpose of guiding prevention and control efforts. Thirty-two areas endemic for JE in 24 Asian and Western Pacific countries were sorted into 10 incidence groups on the basis of published data and expert opinion. Population-based surveillance studies using laboratory-confirmed cases were sought for each incidence group by a computerized search of the scientific literature. When no eligible studies existed for a particular incidence group, incidence data were extrapolated from related groups. A total of 12 eligible studies representing 7 of 10 incidence groups in 24 JE-endemic countries were identified. Approximately 67,900 JE cases typically occur annually (overall incidence: 1.8 per 100,000), of which only about 10% are reported to the World Health Organization. Approximately 33,900 (50%) of these cases occur in China (excluding Taiwan) and approximately 51,000 (75%) occur in children aged 0-14 years (incidence: 5.4 per 100,000). Approximately 55,000 (81%) cases occur in areas with well established or developing JE vaccination programmes, while approximately 12,900 (19%) occur in areas with minimal or no JE vaccination programmes. Recent data allowed us to refine the estimate of the global incidence of JE, which remains substantial despite improvements in vaccination coverage. More and better incidence studies in selected countries, particularly China and India, are needed to further refine these estimates.

A Novel Low-Cost Approach to Estimate the Incidence of Japanese Encephalitis in the Catchment Area of Three Hospitals in Bangladesh

Acute meningoencephalitis syndrome surveillance was initiated in three medical college hospitals in Bangladesh in October 2007 to identify Japanese encephalitis (JE) cases. We estimated the population-based incidence of JE in the three hospitals' catchment areas by adjusting the hospital-based crude incidence of JE by the proportion of catchment area meningoencephalitis cases who were admitted to surveillance hospitals. Instead of a traditional house-to-house survey, which is expensive for a disease with low frequency, we attempted a novel approach to identify meningoencephalitis cases in the hospital catchment area through social networks among the community residents. The estimated JE incidence was 2.7/100,000 population in Rajshahi (95% confidence interval [CI] = 1.8-4.9), 1.4 in Khulna (95% CI = 0.9-4.1), and 0.6 in Chittagong (95% CI = 0.4-0.9). Bangladesh should consider a pilot project to introduce JE vaccine in high-incidence areas.

Japanese encephalitis (JE) part II: 14 Years’ follow-up of survivors

Japanese encephalitis, the commonest Arbovirus encephalitis, has been endemic in many parts of Asia, the Pacific Islands, and India; also, there have been many epidemics. Most of the post JE cases have been associated with neurological and neuropsychiatric deficits but have not been properly classified and followed. Practically all the previous studies were in children or young adults. The aim of this study, involving only adult cases, the largest ever being reported, has been to follow the 688/1,199 survivors of JE patients out of 1,282 of acute cases admitted during four epidemics for a period of 14 years after properly classifying the sequelae. This prospective study was conducted in B.R.D. Medical College Gorakhpur (India), involving 665/688 post JE cases with neuropsychiatric deficits from four epidemics of 1978, 1980, 1988 and 1989 which were properly classified in nine groups. While the first epidemic of 1978 was being studied, more disastrous episodes flared up and the patients were subsequently added. Hence, the total duration of this prospective study was from November 1978 to December 2003. There were 14 defaulted initially from 688 followed (23/688 without sequelae and 665/688 with neuropsychiatric deficits), and later 130 were lost from time to time at various stages of follow up. Four out of 23/688 discharged without any deficit had to be readmitted for bizarre movements, assaultative behaviour and euphoria without fever and altered sensorium. All of them improved by symptomatic treatment. Progressive improvement occurred in all the parameters consisting of psychological disturbances, higher cerebral dysfunction, speech disorders (dysphonia, dysarthria, dysphasias, apraxia and agnosia), extra pyramidal, pyramidal features, and hypothalamic disturbances, cranial nerves including pupils and fundi and seizures. Maximum cases improved between 6 months (55%) to 1 year (78%). Only some features improved between 5 to 14 years. Four patients of hemiplegia remained bed ridden. Some non disabling features like dysarthria and corticospinal features without paralysis persisted in 5% (95% improved) and 74% (26% improved) respectively. One patient with bizarre movement and nine with marked tremors could not regain normalcy. A large number of patients of JE are left with several minor or gross residual neuropsychiatric and neurological features after the acute phase. In this series also the discharged patients with neurological deficits who were quite disabled initially and needed constant care by family members and also those who required some help intermittently improved with passage of time and eventually returned to normal life. Some of them were left with non-disabling residual neurological signs even after 14 years. Fourteen of 544 (3%) could not return to their livelihood.

Japanese encephalitis epidemiology in Arunachal Pradesh, a hilly state in northeast India

ObjectiveTo confirm Japanese encephalitis (JE) cases from the state of Arunachal Pradesh (AP), India for the first time. MethodsSuspected acute encephalitis syndrome (AES) cases were screened from 2005-2010. The cases were initially tested for antibodies against JE by using IgM MAC ELISA kits (National Institute of Virology, Pune). RNA was extracted from the cerebrospinal fluid (CSF) samples followed by molecular amplification of JE virus specific gene primer. The data obtained were used to calculate relative risks between the age groups and between the genders. Epi info 6.0 was used for the statistical analysis. ResultsPresence of JE cases in the state of AP, India was established. JE cases from 10 out of 16 districts were recorded. As part of control and preventive measures, mass vaccination for children (0-15 years) by SA-14-14-2 JE vaccine was taken up in 2010 in the district of Lohit. Vaccination coverage of 83.09% among the target population was achieved. ConclusionsThe study presents the first report of confirmed JE cases from the state of AP, India. This finding attracts attention as JE cases are rarely seen to occur in hilly places.

On-site assessment on the definition and classification of suspected cases in the manual of WHO Japanese Encephalitis Surveillance Standards

To assess the new edition of WHO Japanese Encephalitis (JE) Surveillance Standards (WHO Standards) based on syndrome surveillance data and to provide field evidence regarding the standards. Based on syndrome surveillance data, acute encephalitis syndrome (AES) case was categorized, according to the WHO Standards. A cohort study was applied to estimate the AES definition set in the Standard and relative risk was computed to estimate the existence and intensity of statistical correlation between AES and JE cases. Percentage of attributable risk was counted to describe the coverage of AES for JE cases in the studied population. Sensitivity, specificity, Youden index and positive predictive value of AES components were calculated for the purpose of identifying the clinical values under the screening program. 1424 suspected cases were evaluated in the surveillance program and 1396 cases with ELISA result, of which 109 positive cases were detected. According to the "standardized" classification, a total of 706 cases in line with AES case definition, were categorized into 83 cases of JE, 425 cases of AES unknown and 198 cases of AES other agent. In the cohort study, a relative risk of 4.62 (95%CI: 2.80 - 7.63) and the percentage of attributable risk as 78.35% (95%CI: 64.25% - 86.89%) were observed. The AES definition for JE was significantly effecting on the screening programs and a strong correlation strength was observed in the study. AES syndrome could cover most of the JE cases. "Convulsions", with appreciative screening value, was recommended to be involved into the new version of the WHO Standards.

Full Genome Sequence and Virulence Analyses of the Recent Equine Isolate of Japanese Encephalitis Virus

In the past 25 years, there has been only one case of Japanese encephalitis in horses in Japan. We determined the full genome sequence of the Japanese encephalitis virus (JEV) strain JEV/eq/Tottori/2003 isolated from an afflicted horse and also analyzed its virulence in mice. The sequence analysis showed that the genome of JEV/eq/Tottori/2003 is similar to that of genotype I, a dominant genotype of JEV presently circulating in Japan. Its neurovirulence, but not neuroinvasiveness, was still as high as it was for genotype III, thus indicating the necessity for continuation of a vaccination program of horses against JEV.

Modeling the distribution of Culex tritaeniorhynchus to predict Japanese encephalitis distribution in the Republic of Korea

Over 35,000 cases of Japanese encephalitis (JE) are reported worldwide each year. Culex tritaeniorhynchus is the primary vector of the JE virus, while wading birds are natural reservoirs and swine amplifying hosts. As part of a JE risk analysis, the ecological niche modeling programme, Maxent, was used to develop a predictive model for the distribution of Cx. tritaeniorhynchus in the Republic of Korea, using mosquito collection data, temperature, precipitation, elevation, land cover and the normalized difference vegetation index (NDVI). The resulting probability maps from the model were consistent with the known environmental limitations of the mosquito with low probabilities predicted for forest covered mountains. July minimum temperature and land cover were the most important variables in the model. Elevation, summer NDVI (July-September), precipitation in July, summer minimum temperature (May-August) and maximum temperature for fall and winter months also contributed to the model. Comparison of the Cx. tritaeniorhynchus model to the distribution of JE cases in the Republic of Korea from 2001 to 2009 showed that cases among a highly vaccinated Korean population were located in high-probability areas for Cx. tritaeniorhynchus. No recent JE cases were reported from the eastern coastline, where higher probabilities of mosquitoes were predicted, but where only small numbers of pigs are raised. The geographical distribution of reported JE cases corresponded closely with the predicted high-probability areas for Cx. tritaeniorhynchus, making the map a useful tool for health risk analysis that could be used for planning preventive public health measures.

Japanese Encephalitis Disease Burden and Clinical Features of Japanese Encephalitis in Four Cities in the People's Republic of China

The incidence rate of Japanese encephalitis (JE) in the People's Republic of China has decreased substantially with the wide use of JE vaccine, but the accuracy of JE reporting is uncertain. We established active surveillance for acute meningitis and encephalitis syndrome (AMES) in four prefectures in China during 2006-2008 and performed JE laboratory testing on AMES cases identified from six sentinel hospitals in each prefecture. We estimated JE incidence for each prefecture by applying age-adjusted and season-adjusted JE positivity rates from sentinel hospitals to the total AMES resident cases. We identified 4,513 AMES cases, including 3,561 (79%) among residents of four prefectures. Among 2,294 AMES cases from sentinel hospitals, we identified 213 (9.2%) laboratory-confirmed JE cases. Adjusted estimates of JE incidence per 100,000 persons ranged from 0.08 in Shijiazhuang to 1.58 in Guigang. Active surveillance and laboratory confirmation provides a better estimate of the actual JE disease burden and should be used to further refine JE prevention strategies.

Japanese encephalitis virus remains an important cause of encephalitis in Thailand

Japanese encephalitis virus (JEV) is endemic in Thailand and prevention strategies include vaccination, vector control, and health education. Between July 2003 and August 2005, we conducted hospital-based surveillance for encephalitis at seven hospitals in Bangkok and Hat Yai. Serum and cerebrospinal (CSF) specimens were tested for evidence of recent JEV infection by immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) and a plaque reduction neutralization test (PRNT). Of the 147 patients enrolled and tested, 24 (16%) had evidence of acute flavivirus infection: 22 (15%) with JEV and two (1%) with dengue virus. Of the 22 Japanese encephalitis (JE) cases, 10 (46%) were aged ≤ 15 years. The median length of hospital stay was 13 days; one 13-year-old child died. Ten percent of encephalitis patients enrolled in Bangkok hospitals were found to have JEV infection compared to 28% of patients enrolled in hospitals in southern Thailand (p < 0.01). Four (40%) of the 10 children with JE were reported as being vaccinated. JEV remains an important cause of encephalitis among hospitalized patients in Thailand. The high proportion of JE among encephalitis cases is concerning and additional public health prevention efforts or expanded vaccination may be needed.

Japanese encephalitis in travelers from non-endemic countries, 1973-2008.

Japanese encephalitis (JE) is a severe disease and a risk for travelers who visit JE-endemic countries. We reviewed all published JE cases in travelers from non-endemic areas from 1973 through 2008, and assessed factors related to risk of infection. There were 55 cases that occurred in citizens of 17 countries. Age range of case-patients was 1-91 years (median = 34 years). Ten (18%) persons died and 24 (44%) had mild to severe sequelae. In a detailed risk assessment of 37 case-patients, 24 (65%) had spent > or = 1 month in JE-endemic areas, and most had factors identified that may have increased infection risk. The estimate of overall JE risk was low, < 1 case/1 million travelers to JE-endemic countries. Nonetheless, for each traveler, a careful assessment of itinerary and activities, a decision on vaccination, and information on mosquito precautions are needed to reduce the risk of this disease.

Temporal Variation in the Susceptibility of Culex tritaeniorhynchus (Diptera: Culicidae) to Japanese Encephalitis Virus in an Endemic Area of Tamil Nadu, South India

The study area, Cuddalore, is one of the endemic districts for Japanese encephalitis (JE) in southern India and there is a strong seasonality in JE case incidence, as well as JE virus (JEV) infection in the principal vector Culex (Culex) tritaeniorhynchus Giles. In a longitudinal 3-year study (July 2003 to June 2006), we determined the susceptibility of wild-caught female Cx. tritaeniorhynchus for JEV infection over several seasons from several villages. The susceptibility varied in all four seasons with the lowest value (4.82 geometric mean [GM]) in hot and wet seasons and highest (13.22 GM) in cool and wet seasons. Infection rate was significant between seasons (7.08-11.85 GM) and years (4.82-13.22 GM). Although the vector was abundant throughout the year, with an average per man-hour density ranging from 58 to 652, the JEV infection rates showed no correlation with vector abundance during different seasons in the index villages. The temporal and spatial changes in the competency of the vector appeared to influence the JEV infection rate in vector, which may at least partially explain the seasonality in JEV human cases in the study area.

Etiological Spectrum of Clinically Diagnosed Japanese Encephalitis Cases Reported in Guizhou Province, China, in 2006

The proportion of laboratory-confirmed Japanese encephalitis (JE) virus (JEV) infections was compared to the number of JE cases reported on the basis of seasonality and the clinical symptoms of hospitalized patients in Guizhou Province, China, between April and November 2006. Of the 1,837 patients with reported JE, 1,382 patients in nine prefectures were investigated. JE was confirmed in 1,210 of 1,382 (87.6%) patients by a JEV-specific immunoglobulin M (IgM) antibody-capture enzyme-linked immunosorbent assay (MAC-ELISA), heminested reverse transcriptase PCR, and virus isolation. Two strains of JEV belonging to genotype 1 were isolated. Other viral pathogens responsible for encephalitis, including echovirus, mumps virus, herpes simplex virus, and cytomegalovirus, were identified in 67 of 172 (38.9%) JE-negative cases. On the basis of the distribution of the laboratory-confirmed JE cases from different hospitals according to the Chinese administrative division, which included hospitals at the provincial, city, county, and township levels, county hospitals detected the highest number of JE cases (81.8%), whereas township hospitals detected the smallest number of JE cases (1.4%). Provincial and city hospitals had the highest and lowest rates of accuracy of providing a clinical diagnosis of JE, as confirmed by laboratory testing (91.8% and 76.7%, respectively). This study demonstrates that laboratory confirmation improves the accuracy of diagnosis of JE and that an enhanced laboratory capacity is critical for JE surveillance as well as the identification of other pathogens that cause encephalitic syndromes with clinical symptoms similar to those caused by JEV infection.

Epidemiology and burden of disease from Japanese encephalitis in Cambodia: results from two years of sentinel surveillance

To describe the results from two years of Japanese encephalitis (JE) sentinel surveillance in Cambodia. Sentinel site surveillance for JE in children aged 15 years and under was implemented in Cambodia in mid-2006. It was integrated into the routine meningoencephalitis surveillance system. Six hospitals were selected as sentinel sites. Epidemiological information and diagnostic specimens were collected from each patient presenting with meningoencephalitis. Cerebrospinal fluid and sera were tested for presence of immunoglobulin M antibodies against JE and dengue viruses by an ELISA. Surveillance data from 2006 to 2008 were analysed. Of 586 patients presenting with meningoencephalitis, 110 (19%) were confirmed to have JE. The percentage of confirmed JE cases at individual sentinel sites ranged from 13% to 35% of all meningoencephalitis cases. Mean age was 6.2 years, with 95% of JE cases in children aged 12 years and under. Cases occurred year-round in both 12-month reporting periods. JE is an important cause of meningoencephalitis in Cambodian children. As JE is a vaccine-preventable disease, an immunization programme could result in a considerable reduction in morbidity and mortality from JE among children in Cambodia.

Japanese Encephalitis in Mainland China

Japanese encephalitis (JE) is a seasonal epidemic disease with a 50-year recorded history in China. Its characteristics can be summarized as follows: (i) it is a seasonal epidemic disease; approximately 90% of cases are recorded in July, August, and September each year. The peak of JE onset is 1 month earlier in South China than in the north of the country; (ii) the disease is highly sporadic. It is rare for more than two cases to appear simultaneously in one family; (iii) most affected children are under 15 years old; (iv) the disease is widely distributed in all areas of the nation except Qinghai Province, Xinjiang Uygur Autonomous, and Tibet. Due to widespread application of the JE vaccine, the number of JE cases has decreased significantly nationwide, from 174,932 cases of morbidity in 1971 to 5,097 cases in 2005.

Japanese Encephalitis in Travelers: Review of Cases and Seasonal Risk

Japanese encephalitis (JE) is a leading cause of viral meningoencephalitis transmitted by Aedes mosquitoes in large parts of Asia. Travelers are at risk for JE, the main risk factors being outdoor evening and nighttime exposure in rural areas during the transmission period. Among travelers and expatriates visiting Asia since 1992, an increasing number, also after short‐term visit, has contracted JE. 1–4 This increase has coincided with a huge expansion of tourism to endemic areas in Southeast Asia (SEA) during this period. Of the survivors, more than half experience neurological sequelae. The aim of this review was to describe and summarize published and anecdotal non indexed reports of cases of JE among travelers, with a special emphasis on travelers from Scandinavian countries. JE infections are most often asymptomatic 5 but lead to overt encephalitis in 1 to 20 cases per 1,000 infected. 1,6,7 Although no seroprevalence study on travelers has been published, it is reasonable to assume that for each of the few clinical cases reported, several mild or inapparent cases have occurred. A higher probability of clinical disease has been seen in nonimmune adults as exemplified by the ratio subclinical to clinical disease of 1 of 25 US servicemen stationed in SEA. 8 Since the mean age of travelers in many Western countries is well over 50 years, an increased proportion of clinical cases as well as increased severity of illness by age have practical implications for prophylactic measures in travelers. Limited data indicate that JE acquired during the first or second trimesters of pregnancy causes intrauterine infection and miscarriage, but to our knowledge, no pregnancy‐associated cases have been seen in travelers. 9 Risk figures for travelers at risk are a crude estimate, based on the number of …

Japanese Encephalitis: Defining Risk Incidence for Travelers to Endemic Countries and Vaccine Prescribing From the UK and Switzerland: Table 1

Large numbers of Western travelers visit countries endemic for Japanese encephalitis (JE). The risk of infection is unknown. This study attempts at estimating a risk incidence for visitors from two European countries with the available data. Using the total number of case reports between 1978 and 2008, the number of visits made by European tourists to endemic regions, and total doses of vaccines sold in the two study countries, the risk incidence of JE in travelers was estimated. The proportion of vaccinated visitors to endemic regions was retrieved from the data of two travel clinics (in London and Basel) and related to vaccine prescribing in UK and Swiss travelers. In 2004, an estimated 0.16% to 0.3% of UK and Swiss travelers were vaccinated against JE, with no surveillance reports of JE cases. Between 116,000 and 152,000 European travelers would receive vaccination. More than 99% travel to endemic countries without vaccination. Only 40 cases of JE infection have been reported in travelers for the past 30 years. The risk incidence is thus 1.3 per year in 7.1 million visits of the 17 million European travelers who are at a potential risk of JE infection. This study and the analysis of the existing literature support the recommendation that all travelers should be informed about the risk of JE infection but also suggest that there is no evidence for justifying a general recommendation for JE vaccination in travelers to endemic areas.