Knowledge Obtained from an Elderly Case of Japanese Encephalitis

Abstract

The nationwide introduction of a Japanese encephalitis (JE) vaccine has contributed to a reduction in the annual infection rate of JE in Japan. However, the current neutralizing antibody prevalence ratio in Japan is approximately 20% in children 3-4 years of age and in people in their forties and fifties. We herein report a man with JE who was definitively diagnosed by multi-virus real-time polymerase chain reaction employing biopsied brain tissue and serological examinations. JE should be kept in mind when a patient has severe encephalitis of unknown etiology. In order to protect the susceptible population from JE, vaccination is recommended, especially for children and middle-aged people.

Tick-borne encephalitis in Japan, Republic of Korea and China

“…In Japan, a nationwide vaccination program against JEV started in 1954, which successfully provided protection to the public and significantly reduced the incidence of JEV infections. 72 In ROK, an inactive vaccine derived from the mouse brain was first used between the late 1960s and the early 1970s, in 1985 the nationwide vaccination coverage for JEV reached ~90%, and the estimated rate of immunization was ~80% in 2008. 73 Considering the presence of Flavivirus-induced antibody cross-reactivity, 74 particularly that cross protection of JEV vaccines against other mosquito-borne flaviviruses, such as the West Nile virus, 75 has been established and that people with pre-existing anti-JEV antibodies have shown low immune responses against TBEV, 42 the populations in Japan and ROK (with their high vaccination rates for JEV) might have also been protected against TBEV because of an undiscovered cross-protection effect.…”

“… 73 Considering the presence of Flavivirus-induced antibody cross-reactivity, 74 particularly that cross protection of JEV vaccines against other mosquito-borne flaviviruses, such as the West Nile virus, 75 has been established and that people with pre-existing anti-JEV antibodies have shown low immune responses against TBEV, 42 the populations in Japan and ROK (with their high vaccination rates for JEV) might have also been protected against TBEV because of an undiscovered cross-protection effect. Nevertheless, in 2013 among Japanese subjects aged 40–60 years, only <20% were reported to have anti-JEV antibodies, 72 indicating a lack of potential cross protection of JEV vaccination against TBEV for the majority of this age group. In China, anti-JEV antibodies have been detected in the healthy population in Heilongjiang Province, where TBE is a notifiable disease, 76 but whether anti-JEV antibody is prevalent in TBEV endemic regions is unclear.…”