Ecologic Studies of Japanese Encephalitis Virus in Japan

Age-Related Susceptibility to Japanese Encephalitis Virus in Domestic Ducklings and Chicks

“…10 In a series of studies conducted in Japan during the 1950s, Culex tritaeniorhynchus was implicated as the major arthropod vector of JEV and ardeid birds (egrets and herons) or pigs as the principle vertebrate amplifying hosts. [11][12][13][14][15] Subsequent studies established that mosquitoes transmit JEV from a number of different species and reinforced the concept that JEV transmission is especially prevalent in areas where humans live near water birds or domestic pigs, and during the seasons when mosquito vector populations are high. [15][16][17] Birds from a variety of different species have been shown to be susceptible to infection with JEV, but are considered to play a minor role in virus transmission in comparison to egrets, herons, and pigs.…”

“…[15][16][17] Birds from a variety of different species have been shown to be susceptible to infection with JEV, but are considered to play a minor role in virus transmission in comparison to egrets, herons, and pigs. 11,13,18 Adult ducks and chickens are among birds that develop a low magnitude viremia, unlikely to result in substantial transmission to feeding mosquitoes. 19,20 However, it has been reported that recently hatched chicks develop much higher viremia than adult birds, 21 and in JEV-endemic regions, large numbers of free-ranging chickens and ducks live and breed near humans, providing an abundant pool of potential amplifying hosts for JEV.…”

Product review on the JE vaccine IXIARO

“…Humans usually do not develop a level or duration of viremia sufficient to infect mosquitoes. 5,14 Therefore, humans are dead-end hosts, and human JE cases imported into nonendemic areas represent a minimal risk for subsequent transmission of the virus. 13 In endemic areas, most Japanese encephalitis infections occur in children younger than 10 years, 6,7 but non-immune adults who live in or visit endemic areas can also be affected.…”

Variation in Arbovirus Infection Rates in Species of Birds Sampled in a Serological Survey During an Encephalitis Epidemic in the Murray Valley of South‐eastern Australia, February 1974

“…The two viruses are closely related, and there is a "gross morphologic and biologic resemblance" between the two primary vectors, Cx annulirostris and Cx tritaeniorhynchus (Reeves et al, 1954). The domestic pig has been shown to be crucially involved in epidemics of Japanese encephalitis (Scherer, Moyer, Izumi, Gresser and McCown, 1959;Detels et al, 1976) and there is serological evidence of frequent infection of feral pigs with MVE virus in northern New South Wales (Gard et al, 1976). However, the most intriguing potential parallel is the relationship between the two viruses and the black-crowned night heron (Nycticorax nycticorax) and the rufous or nankeen night heron (Nycticorax calcndonicus).…”

“…He attributed these findings to the longevity of the herons compared with that of passerines, and to the tolerance of night herons to mosquito attack. The black-crowned night heron {Nycticorax nycticorax) is preferentially involved in the ecology of Japanese encephalitis in Japan (Scherer, Buescher and McClure, 1959) and the suspected involvement of species of Ciconiiformes, including the black-crowned night heron, in the primary cycle of St Louis encephalitis in Florida led to investigations of host-vector relationships between local Ciconiiform species and Culex nigripalpus, a proven vector of the virus. It was demonstrated that with species of Ciconiiformes it is the behavioural response of the birds to mosquito attack rather than host preference per se that mainly determines the success rate of feeding.…”