A change in epidemiology of Japanese encephalitis in Bankura and Purulia districts of West Bengal.
A case of Acute Encephalitis Syndrome (AES) is defined as a person of any age, at any time of year with the acute onset of fever not more than 5-7 days and a change in mental status (including symptoms such as confusion, disorientation, coma, or inability to talk) and/or new onset of seizures (excluding simple febrile seizures).M Japanese Encephalitis (JE) is presently a major cause of 'Acute Encephalitis Syndrome' (AES). Japanese encephalitis is a viral disease caused by an enveloped single stranded positive sense RNA virus of the genus Flavivirus family Flaviviridae. (2,3) It is a mosquito borne disease transmitted by Culicine mosquitoes, most notably by Culex tritaeniorhynchus & Culex vishnui and occasionally caused by Culexgelidus, Culex fuscocephala, Culex annulus and Culex annulirostris. It is a zoonotic disease i.e. infecting mainly animals and incidentally man. It is transmitted mainly by pig to mosquito to pig cycle or Ardeid bird (herons, egrets) to mosquito to Ardeid bird cycle. Pigs are amplifiers of the virus. Birds are the reservoir of JE virus but are asymptomatic.M JE is reported from different parts of India.
The disease is endemic in 14 states with Assam, Bihar, Haryana, Uttar Pradesh, Karnataka and Tamil Nadu reporting outbreaks every year & contributing about 80% of cases. (5) It has also been reported from West Bengal.M There is continued occurrence of sporadic cases and small outbreaks of JE in Bankura and Purulia districts of West Bengal. However, recent published data regarding the incidence of JE from this part of West Bengal is not available. Hence, our aim was to analyse the Japanese B encephalitis (JE) seropositive cases from various rural, urban and semiurban areas of these two districts of West Bengal.
MATERIALS AND METHODS
The study was undertaken between January 2014 to December 2014 after obtaining ethical clearance from the institutional ethics committee. As isolation of JE virus from clinical specimens is difficult due to low level of viraemia and rapid development of neutralising antibodies against it, (7) the confirmation of a suspected case of JE requires the detection of JEV specific IgM by IgM capture ELISA in clinical samples. This assay distinguishes between JE and Dengue virus, which are serologically cross reactive. (8) CSF and serum samples were collected by lumbar puncture and venepuncture respectively from patients admitted with acute encephalitis syndrome from Paediatric and Medicine wards. All turned out to be unvaccinated. Uncentrifuged CSF and serum samples were analysed for JE specific IgM antibody by IgM antibody capture enzyme linked immunosorbent assay (MAC-ELISA) using kits from NIV (Pune). OD (Optical Density) value was taken by ELISA reader.
During the study period, samples from 287 suspected patients were tested for JE out of which 29(10%) were positive for IgM antibodies. IgM positivity was 16(55%) in males and 13(45%) in females. Out of the 29 reactive cases, 13(45%) were paediatric cases (<12 years) and 16(55%) were adults.
The number of seropositive cases referred from Bankura and Purulia were 13(45%) and 16(55%) respectively. The percentage of IgM positive JE was found to be high during the months of September and October. Among 29 cases, 11 cases occurred in September (38%) and 9 cases occurred in October (31%).
[FIGURE 1 OMITTED]
No death was reported in last year due to JE, but 8 (28%) patients were discharged with sequelae.
DISCUSSION AND CONCLUSION
Among 287 patients, 29(10%) were reactive for JE IgM MAC ELISA, which was corroborative with the findings of the study conducted by Bandyopadhyay et al at Virology laboratory at the Calcutta School of Tropical Medicine and Chakraborty et al at Swasthya Bhawan. (9,10) IgM positivity was 16(55%) in males and 13(45%) in females. So there is no gender predilection which is similar to other studies. (9,10)
Of the 29 reactive cases, 13(45%) were paediatric cases (<12 years) and 16(55%) were adults. The same trend was noticed by Chakraborty et al in West Bengal and Borthakur et al in Assam. (10,11) But in other studies, the number of seropositive JE was more in paediatric population than adult population. (9,12) This change in trend was probably due to vaccination in 1-15 years age group. The Government of India has introduced JE vaccination with SA-14-14-2 vaccine in phased manner starting from 2006. According to IAP immunisation schedule, live attenuated cell culture derived SA 14-14-2 is given in a two dose schedule, first dose at 9 months of age along with measles & second dose at 18 months of age along with DPT booster. Furthermore, all susceptible children up to 15 years of age are to be given 2 doses of the vaccine at 4 weeks interval during outbreaks or anticipated outbreaks. 132 districts have already been brought under JE vaccination as part of Universal Immunization Programme (UIP). (13)
The percentage of IgM positive JE was found to be high during the months of September and October. Bandyopadhyay et al have also reported higher incidence of JE during similar months. The continued occurrence of sporadic cases and small outbreaks during the monsoons is explained by the increased vector burden in the paddy field in this region of West Bengal. No death was reported in this period due to JE and 8 (28%) patients were discharged with sequelae. Whereas other studies showed that approximately 20-30% of JE cases are fatal and 30-50% of survivors have significant neurologic sequelae. (14) In India, case fatality rate ranges from 10-70%. However, with early detection and management of cases, it has come down to an average of approximately 20%. (15)
HOW TO CITE THIS ARTICLE: Das D, Sarkar R, Dey JB, et al. A change in epidemiology of Japanese encephalitis in Bankura and Purulia districts of West Bengal. J. Evolution Med. Dent. Sci. 2016;5(78):5796-5798, DOI: 10.14260/jemds/2016/1308
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Debalina Das , Rehena Sarkar , Jayanta Bikash Dey , Syamal Kundu , Koushik Ghosh 
 Postgraduate Trainee, Department of Microbiology, Bankura Sammilani Medical College, Bankura.
 Postgraduate Trainee, Department of Microbiology, Bankura Sammilani Medical College, Bankura.
 Professor and HOD, Department of Microbiology, Bankura Sammilani Medical College, Bankura.
 Professor and HOD, Department of General Medicine, Bankura Sammilani Medical College, Bankura.
 Demonstrator, Department of Physiology, Calcutta National Medical College, Kolkata.
Financial or Other, Competing Interest: None. Submission 22-08-2016, Peer Review 15-09-2016, Acceptance 21-09-2016, Published 28-09-2016. Corresponding Author: Debalina Das, 95 Santigarh, Graham Road, Kolkata-700040, West Bengal. E-mail: firstname.lastname@example.org DOI: 10.14260/jemds/2016/1308
Table 1: Age Distribution of Patients Reactive for JE N=29 Age Distribution Number Percentage 0-12 years 13 45% >12 years 16 55%
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|Title Annotation:||Original Research Article; Bengal, India|
|Author:||Das, Debalina; Sarkar, Rehena; Dey, Jayanta Bikash; Kundu, Syamal; Ghosh, Koushik|
|Publication:||Journal of Evolution of Medical and Dental Sciences|
|Date:||Sep 29, 2016|
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