Incidence of Japanese Encephalitis among Children is associated with the Presence of Pigs in Bali, Indonesia

Japanese encephalitis (JE) is an encephalitic arboviral disease transmitted by mosquitoes with pigs as one of its amplifying hosts. JE is still endemic in Bali and affects mostly children. People in Bali still rear pigs and live in close proximity to irrigated rice fields which is a perfect habitat for mosquitoes. However, few studies have examined the seroprevalence of JE virus (JEV) in pigs as a risk factor for JE in children in Bali together with pigpen location from houses and irrigated rice fields. Therefore, blood samples were collected from pigs in 5 regencies in Bali where JE cases were reported. Indirect enzyme-linked immunosorbent assays were performed on the sera to detect IgM and IgG antibodies against JEV. A total of 80 pig sera were assayed, 60% of which were positive for antibody against JEV. The seroprevalence of JEV-IgM and JEV-IgG was 20% and 40%, respectively. There were three risk factors that had significant associations (p < 0.05) with JE in children such as JEV-IgG-positive pigs, pigpen location <10 meters from the household, and distance of <500 meters between irrigated rice field and pigpen with an IgG-positive pig. In conclusion, the presence of pigs still plays an important role in the JEV transmission cycle in Bali, as demonstrated by the high seroprevalence of JEV-IgG in pigs, and that pigs kept close to households and irrigated rice fields were risk factors for JE in Bali.