Clinical profiles and some associated factors of Japanese encephalitis in Bali

Background Japanese Encephalitis (JE) is a mosquito-borne viral disease that can affect the central nervous system and cause several complications and death. In Indonesia, particularly in Bali, studies of JE in humans are still very limited. Objective To assess the clinical manifestations and outcome of JE in Bali and to identify some possible associated factors and monthly distribution of admission to the hospitals. Methods A cross-sectional study was conducted in 8 district hospitals, army hospital, and Sanglah central hospital, as surveillance centers in Bali, from July 2001 through January 2003. Subjects less than 12 years of age and residences of Bali province who were suspected of having acute viral encephalitis, aseptic meningitis, and acute flaccid paralysis referred from all health facilities were included in this study. The diagnosis of JE was established by detection of virus-specific IgM in CSF and serum, with IgM capture enzyme-linked immunosorbent assay (MAC ELISA) Results During the study, 158 subjects with encephalitis were included; 55 (34.8%) were caused by JE and 103 (65.2%) were caused by non-JE. It showed that pig owning and rice farming were significantly associated with JE (PR= 3.02, 95% CI 1.29; 7.10; P= 0.009 and PR= 2.86, 95% CI 1.30; 6,31, P= 0.008, respectively). Most subjects (46.2%) were under 2 years old with mean age of 37.24 (SD 32.24) months. Forty-two (26.6%) subjects had nuchal rigidity, and all of them had aseptic meningitis. Denpasar had the highest prevalence of non-JE cases. Bangli and Klungkung had the lowest prevalence of JE and non-JE. The highest prevalence of JE was in Gianyar. Peak prevalences of JE were in April and May 2002. Peak prevalences of non-JE were during August-October 2001 and in March-April 2002. Four (7.3%) subjects of JE group and 25 (24.3%) subjects of non-JE died. There were 25 (45.5%) out of 55 subjects who survived with disability. Twenty-four (43.6%) JE subjects and 34 (33.0%) non-JE subjects had good outcome. Conclusions Around one third of the subjects were positively diagnosed as JE. The highest prevalence of JE was found in Gianyar. Peak prevalences of JE are in April and May 2002. Pig owning and rice farming are associated factors. Almost half of JE subjects survived with disability