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ORIGINAL ARTICLE  
Year : 2014  |  Volume : 57  |  Issue : 3  |  Page : 400-406
An appraisal of clinicopathological parameters in Japanese encephalitis and changing epidemiological trends in upper Assam, India


1 Multidisciplinary Research Laboratory (ICMR), Assam Medical College and Hospital, Dibrugarh, Assam, India
2 Department of Microbiology, Silchar Medical College, Ghungur, Silchar, Assam, India
3 Virology Division, Regional Medical Research Centre, Northeast Region (ICMR), Dibrugarh, Assam, India
4 Department of Microbiology, Assam Medical College and Hospital, Dibrugarh, Assam, India
5 Department of Microbiology, DBT Healthcare Molecular Biology Laboratory, Assam Medical College and Hospital, Dibrugarh, Assam, India
6 Biostatistics Division, Regional Medical Research Centre, Northeast Region (ICMR), Dibrugarh, Assam, India

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Date of Web Publication14-Aug-2014
 

   Abstract 

Context: Japanese encephalitis (JE), an acute mosquito-borne viral disease, is one of the leading causes of viral encephalitis in the South-East Asian region. JE is endemic in Assam. The morbidity and mortality due to JE is significant with outbreaks every year during the monsoons. Aims: The aim was to study the clinicopathological profile of JE; to examine their role in predicting disease outcome; and to document the increase in the incidence of JE among the adult population in this region. Materials and Methods: Clinically suspected acute encephalitis syndrome (AES) cases admitted in Assam Medical College and Hospital during the period of May 2011 to April 2012 were tested by JE virus specific Immunoglobulin M capture ELISA. Statistical Analysis Used: Data analysis was performed using SPSS version 16.0. Results: Out of 424 AES cases, 194 were JE positive. The occurrence of JE in adults was higher (P < 0.001) than the pediatric age group. The study recorded a high rate of renal dysfunction in JE cases. A single case of JE induced abortion and two cases of JE-neurocysticercosis co-infections were documented. Regression analysis revealed that adult population, unconsciousness, paresis and elevated cerebrospinal fluid protein level were associated with a worse prognosis in JE cases. Mortality in JE positive cases was higher than the JE negative cases (P = 0.001). Conclusion: The study attempts to highlight the role played by a combination of clinical and laboratory parameters in assessing the severity and outcome in JE and may help in directing the limited medical resources toward those that need it the most.

Keywords: Acute encephalitis syndrome, Enzyme linked immunosorbent assay, Glasgow coma scale, Immunoglobulin M, Japanese encephalitis

How to cite this article:
Patgiri SJ, Borthakur AK, Borkakoty B, Saikia L, Dutta R, Phukan SK. An appraisal of clinicopathological parameters in Japanese encephalitis and changing epidemiological trends in upper Assam, India. Indian J Pathol Microbiol 2014;57:400-6

How to cite this URL:
Patgiri SJ, Borthakur AK, Borkakoty B, Saikia L, Dutta R, Phukan SK. An appraisal of clinicopathological parameters in Japanese encephalitis and changing epidemiological trends in upper Assam, India. Indian J Pathol Microbiol [serial online] 2014 [cited 2020 Aug 8];57:400-6. Available from: http://www.ijpmonline.org/text.asp?2014/57/3/400/138732



   Introduction Top


Encephalitis is an inflammation of the brain parenchyma and is usually a result of viral infection. [1] Acute encephalitis syndrome (AES) has multifactorial etiology with Japanese encephalitis (JE) and Dengue predominating in South-East Asia. [2] JE is endemic in Assam with outbreaks every year during the monsoons. [3] There is significant morbidity and mortality due to JE in Assam with as many as 1343 cases and 229 AES-related deaths in 2012. [4]

This study was carried out to examine the demographical, clinical and laboratory characteristics associated with JE; their role in predicting disease outcome and to document the shifting trend of the disease with reference to the population under study in this region.


   Materials and methods Top


This study was a prospective cross-sectional study of 1 year (May 2011-April2012) duration. The study included patients of all ages admitted in various Clinical Departments of Assam Medical College and Hospital, Dibrugarh satisfying the clinical case definition of AES as per WHO guidelines according to which AES is defined as acute onset of fever and a change in mental status, including symptoms such as confusion, disorientation, or inability to talk and/or new onset of seizures excluding febrile convulsions in a person of any age at any time of year." [5] All AES cases were reported using standard case investigation and laboratory request forms as per guidelines of the National Vector Borne Diseases Control Program (NVBDCP), Ministry of Health and Family Welfare, India. [6] A total of 424 cases were included in the study. Cerebrospinal fluid (CSF) and serum samples were collected from the patients after obtaining informed/written consent from the guardians (in case of minors) and family members (in case of the adults). Only serum samples were collected from patients in whom a lumbar puncture was not possible or was contraindicated. Ethical clearance was obtained from the Institutional Ethics Committee (human).

Immunoglobulin M (IgM) antibody capture ELISA for JE was done for all CSF and serum samples using IgM ELISA kits manufactured by National Institute of Virology, Pune, India and supplied under the NVBDCP. Dengue and Chikungunya viruses were excluded by testing the JE negative serum samples for these viruses using IgM ELISA kits also developed by NIV. Data analysis was done using SPSS, version 16.0 (SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc). P < 0.05 was considered to be statistically significant.


   Results Top


The study population comprised of 424 consecutive nonrepeat clinically diagnosed AES cases. Patients with similar clinical features in which a specific diagnosis was established and which was nonviral in origin were excluded from the study. A total of 406 CSF and 360 serum samples were collected. Based on ELISA test results for CSF and serum samples, 194 cases (45.75%) turned out to be positive for JE virus. If optical density (OD) value of sample tested exceeded the OD of negative control by a factor of 5, the sample was considered as positive.

Of the 230 JE negative cases, serum samples were available for 191 cases, which all tested negative for Dengue and Chikungunya viruses by IgM capture ELISA.

Age specific distribution of Japanese encephalitis cases

The prevalence of JE positive cases was found to vary significantly in the different age groups (P = 0.001). It was lowest in the 0-10 years age group (28.6%) and highest in the >60-70 years group (63.6%). The association of JE with age was tested in the adult (≥15 years) and pediatric age (<15 years) groups and was found to be significant (P < 0.001). The occurrence of JE in persons aged ≥15 years was found to be substantially higher than the pediatric age group [Table 1].
Table 1: Age and sex distribution of JE cases

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Demographical characteristics of Japanese encephalitis cases

The association of JE with geographical location was found to be significant (P < 0.001). The largest number of JE positive cases was reported from Sibsagar District followed by Dibrugarh. Although 89.17 % of the JE positive cases in the study hailed from a rural setup, there was no significant difference in the rural/urban distribution of JE and non-JE AES cases (P = 0.183). The seasonal variation of JE was significant (P < 0.001) with peak incidence in July and August 2011 [Table 2].
Table 2: seasonal and geographical distribution of JE cases

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Clinical and co-morbid features in Japanese encephalitis cases

The JE positive patients had a wide range of clinical features as shown in [Table 3]. The most common presenting symptom at the time of hospitalization was fever which was present in all the cases. Temperatures ranged 100-104°F. A definite change in mental status was also observed. The first neurological manifestation was convulsion, which was recorded in 81 cases (41.6%); of these, 56 cases (69%) had generalized and the rest had focal seizures. Headache was present in 66.5% cases, neck rigidity in 54.6% and unconsciousness in 43.3% cases.
Table 3: Clinical features observed in JE cases

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The mean duration of hospital stay for the JE positive cases that had a favorable outcome (n = 136) was 7.72 days (SD: ±4.09). For the patients who expired (n = 58), the mean interval between hospitalization and death was 3.88 days (SD: ±2.64).

The mean Glasgow coma scale (GCS) score in JE positive cases was lower (8.21 ± 2.78) as compared to non-JE AES cases (9.33 ± 2.75). Among JE positive patients, those who had a fatal outcome had a lower mean GCS score as compared to those who survived (6.71 ± 2.65 vs. 9.07 ± 2.49). In univariate analysis, a lower GCS score was found to be significantly associated with the JE positive cases that had a fatal outcome (P = 0.000202).

The co-morbid conditions that were found to be associated with JE positive cases have been summarized in [Table 4]. As many as 87 cases had features of renal dysfunction as evidenced by a blood urea level of >20 mg/dL and a serum creatinine level of >1.2 mg/dL or both. Out of these, 33 cases (37.9%) had an unfavorable outcome.
Table 4: Comorbid conditions associated with JE cases

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The study population also included one pregnant woman at 30 weeks of gestation presenting with fever, change in mental status and features suggestive of ascending type of paralysis. Cytological and biochemical examination of CSF showed a total cell count of 198 cells/cu. mm with lymphocytic pleocytosis and elevated protein level (64 mg/dL). IgM capture Elisa for JE was positive for both CSF and serum samples. Obstetrical examination revealed intra uterine death of fetus. The patient expired seven days after hospitalization.

Neuroimaging studies revealed cerebral infarct in 12 JE positive cases out of which 8 cases had an unfavorable outcome. Two cases had evidence of old infarcts which may not have been related to the current disease process. Four cases had lacunar infarcts out of which two patients expired. One patient had bilateral thalamic infarct, three had bilateral temporal lobe infarct, one patient had bilateral basal ganglia infarct and one case had sub-acute infarct in the lentiform nucleus. Two cases had diffuse atrophic changes in the brain parenchyma of which one had a fatal outcome; one case had cerebral atrophy and had an unfavorable outcome. Six cases had evidence of healed granulomatous lesions, out of which two cases had signs of neurocysticercosis; all the cases had a favorable outcome. Three cases had evidence of cerebral edema and one case had encephalomalacia (softening of brain matter) changes. One case had features suggestive of residual changes in sub-acute stage of JE on Magnetic resonance imaging (MRI).

Cerebrospinal fluid findings in Japanese encephalitis positive cases

Cerebrospinal fluid cell count data was available for 152 out of 194 JE positive cases. Analysis revealed that 137 cases (90.1%) had evidence of CSF pleocytosis (cell count >5/cu.mm) out of which 95% had lymphocytosis. One hundred and four cases had CSF counts in the range >5-50; 20 cases had CSF counts in the range >50-100 and the remaining 13 cases had CSF counts >100 cells/cu mm.

Data regarding CSF sugar levels was available for 157 JE positive cases. Analysis revealed that CSF glucose level was lowered in 82 cases (52.3%). Total CSF protein was found to be elevated in 105 cases (66.9%, n = 157).

The mean difference of three CSF parameters (CSF cell count, total protein and glucose) was tested in the two age groups using the independent samples t-test [Table 5]. Data showed a significant difference in the total CSF protein levels between the pediatric and adult age groups (55 mg/dL vs. 79 mg/dL, P = 0.011).
Table 5: Comparison of means of CSF parameters with pediatric and adult age group amongst JE positive cases (using independent sample t-test)

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Japanese encephalitis specific Immunoglobulin M antibody detection in cerebrospinal fluid and serum samples

Out of the 424 cases included in the study period, CSF samples were obtained from 406 cases and serum samples were obtained from 360 cases. One hundred and ninety-two (47.3%) CSF samples and 120 (33.3%) serum samples tested positive for JE specific IgM antibody.

The association between the duration of illness and rate of JE positivity was studied and was found to be significant (P = 0.002). One hundred and sixty (37.7%) AES cases were reported within 3days of onset of disease of which 67(41.9%) were JE positive. The largest number of AES cases (179, 42.2%) was reported within 4-6 days of onset with a positivity of 54.2% for JE specific IgM antibody. Out of the 31 cases with duration of illness >10 days, only six turned out JE positive.

Univariate logistic regression analysis of clinical and laboratory parameters with disease outcome

A combination of 15 factors including age, sex, nine clinical (duration of illness, seizures, headache, unconsciousness, paralysis, neck rigidity, diarrhea, pain abdomen and vomiting) and four laboratory parameters (CSF cell count, protein, sugar and IgM OD values) were selected to predict the outcome of disease in the JE positive cases. The analysis was carried out considering disease outcome as the dependent variable and each of the parameters as independent variables having a possible bearing on the outcome of disease [Supplementary Table 1]. [Additional file 1]

In univariate logistic regression analysis, the factors found to be significantly associated with an increasing trend for expired category as compared to their respective references were: Age ≥15 years; Presence of Unconsciousness; Presence of paralysis/paresis and CSF protein >50 mg/dL.

In the multiple regression analysis, after controlling for all the significant factors in univariate analysis, age group ≥15 years (OR: 8.30, CI: 1.81-38.12, P = 0.007), unconsciousness (OR: 2.99, CI: 1.41-6.34, P = 0.004) and paralysis/paresis (OR: 9.65, CI: 1.08-85.88, P = 0.042) were found to be significantly associated with the expired category. Though statistically not significant, the odds of having a fatal outcome was 1.66 times higher for those who had CSF protein >50 mg/dL.

Association of clinical features, laboratory parameters and disease outcome in relation to age group

The association of age group was tested against six clinical (seizures, headache, unconsciousness, paralysis, neck rigidity, and disease outcome) and three CSF parameters (cell count, sugar, protein) using Chi-square test [Supplementary Table 2]. [Additional file 2] Compared to the adult group, respondents of pediatric age group were significantly more likely to have seizure (P < 0.001), unconsciousness (P = 0.027) and a normal CSF sugar (<40 mg/dL, P < 0.001) level. Significantly, a higher proportion of adult respondents had headache (P < 0.001), CSF protein >50 mg/dL (P = 0.018) and unfavorable outcome (P = 0.005) as compared to the pediatric respondent.

Mortality in Japanese encephalitis cases

This study recorded an overall mortality of 29.9 % (58 deaths in 194 cases) in JE positive cases. The mortality rate was found to be 34.6% (53 deaths in 153 cases) in adults and 12.2% (5 out of 41 cases) in the pediatric age group, the difference being significant (P = 0.005). The mortality was also higher in the JE positive cases when compared to non-JE AES cases (29.9% vs. 16.52%, P = 0.001).


   Discussion Top


Historically, JE has been described as a disease affecting predominantly the pediatric age group. Most of the Indian studies on JE also reiterate this fact. [7],[8],[9],[10],[11] However, the present study found the occurrence of JE in adults to be substantially higher than the pediatric age group. As many as 54.6% of the cases belonging to the ≥15 years age group turned out to JE positive as compared to 28.5% in the pediatric age group. A likely explanation for this changing trend may be the JE mass vaccination campaigns undertaken in several Upper Assam districts since 2006. In these campaigns, only children aged 1-15 years of age were included, which might account for the shift in age specific distribution of JE in the region.

Considering the large number of adults infected with JEV and the increasing mortality in this group, the JE vaccination campaign was re-launched in Assam in October 2011 and included the adult population as well. This is the first instance of an adult vaccination campaign against JE anywhere in India. Live attenuated JE virus (virus strain: SA-14-14-2) vaccine was administered free of cost by the state government.

This study found the majority of cases being reported during the monsoon season which is similar to that observed by Phukan et al. in Assam. [11] The present study also recorded a case of JE induced abortion in a pregnant female at 30 weeks of gestation. In India, four miscarriages were reported among nine JE infected pregnant women in a study conducted by Chaturvedi et al. [12] However, this is the first documented case of JE in a pregnant woman from Assam.

Renal dysfunction characterized by an elevated blood urea and serum creatinine levels is not very common with arboviral diseases. Hemorrhagic fever with renal syndrome has been described in literature to be associated with Bunyavirus diseases. [13] Misra et al. however reported renal dysfunction in ten laboratory confirmed JE cases with renal failure in two cases. [14] The current study found abnormal renal functions in 87 cases out of which 33 cases expired. In a study conducted in Malaysia, the authors found that features of shock were associated with poor outcome of JE at hospital discharge. [15] In this study, inadequate rehydration may have accounted for the renal dysfunction and high mortality associated with these cases.

In this study, fever was the commonest symptom and was present in all the cases. Similar observations were made by Parida et al. in Gorakhpur, Phukan et al. in Assam and Sengupta et al. [10],[11],[16] Altered sensorium was also a common feature of all the cases in the study. This compares favorably to the observations made by Sengupta et al. and Kumar et al. [16],[17] Convulsions were recorded in 41.6 % cases which is slightly higher than that observed by Phukan et al. in Assam. [11] The present study could not assess the long term sequelae in JE patients due to problems in follow-up.

The present study found that adult age group and elevated CSF protein levels were associated with a fatal outcome in JE cases. This is in contrast to a study conducted by Burke et al. where age, CSF protein content and CSF leukocyte count were not found to be significant risk factors for a fatal outcome in JE patients. [18] However, elevated concentration of CSF protein and depressed levels of consciousness were found to be significantly associated with a fatal outcome in JE positive pediatric patients in Thailand. [19] The presence of seizures, headache and neck rigidity were not found to have a significant association with disease outcome in JE cases. Neuroimaging studies suggestive of Cerebrovascular accident were found to be associated with higher fatalities.

Japanese encephalitis related morbidity and mortality still remains high. The present study recorded an overall mortality of 29.9%. Similar findings have been reported by Desai et al. and Baruah et al. [20],[21] And contrary to popular belief, it is the adult population that has a significantly higher mortality rate as compared to the pediatric age group.

The study highlights the role played by a combination of clinical and laboratory parameters in assessing the severity and outcome in JE patients in this region. This when combined with other well-known indices like GCS may help in directing the somewhat limited medical resources toward those that need it the most and reduce the overall morbidity and mortality associated with JE in the region. The large number of non-JE AES cases also presents a challenge and call for newer diagnostic facilities for detection of other viral, bacterial and parasitic causes of AES.


   Acknowledgments Top


This study was funded by the Department of Biotechnology, Govt. of India (DBT Sanction NO. BT/Med/15/Vision-NER/2011, Date: November 2nd 2011). The authors are also grateful to National Vector Borne Disease Control Program (NVBDCP), Directorate General of Health Services, Ministry of Health and Family Welfare, Govt. of India and National Institute of Virology (NIV), Pune, India for supply of ELISA kits. The authors also offer their sincere thanks to Dr. Mithu Medhi, Dr. Vicky Lahkar, Mr. Charitra Saikia and Mr. Chandan Sarmah for their assistance during the course of the study.

 
   References Top

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Correspondence Address:
Saurav Jyoti Patgiri
Research Scientist II, Multidisciplinary Research Laboratory (ICMR), Assam Medical College and Hospital, Dibrugarh - 786 002
India
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Source of Support: Financial support from the Department of Biotechnology (DBT), Govt. of India (DBT Sanction NO. BT/Med/15/ Vision-NER/2011, Date: November 2nd 2011), Conflict of Interest: None


DOI: 10.4103/0377-4929.138732

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