Serosurveillance for Japanese encephalitis in children in several districts of West Bengal, India

Abstract

Aim: To evaluate the prevalence of antibodies to flaviviruses, particularly Japanese encephalitis (JE) in children. Methods: Virological and serological investigations were conducted into JE, along with dengue 2 (Den2) and West Nile viruses, in the Flavivirus group. The paediatric age group (up to 10 y), in the districts of Burdwan, Bankura, Midnapore and Purulia of West Bengal, India, was assessed for recent activity of these viruses, for 4 consecutive years from 1996 to 1999. In total, 2260 sera samples were collected, of which 204 were from acute fever cases; only 72 paired sera were available. There was a significantly higher incidence of fever cases in children belonging to the schedule caste and schedule tribes. These communities occupy the lowest level in the society and are closely associated with pigs. Results: No virus could be isolated from the sera collected from fever cases. The results of the serological survey showed the presence of antibodies to JE virus in only 13.3% of the contact sera, 33.3% of acute sera and 22.1% of convalescent sera investigated. Only 3.1% of the contact sera had antibodies to Den2 and no antibodies were found against West Nile virus. This indicates that the JE virus is in recent circulation in the population of these four districts, and as the majority of children lack substantial immunity to JE virus, they may be affected by an epidemic. Conclusion: Children up to 10 y of age in the four districts of West Bengal are mostly non-immune to JE virus. If an outbreak occurs, the majority of these populations may be affected.