Japanese encephalitis in north Queensland, Australia, 1998

Abstract

Objective To describe the circumstances of two cases of Japanese encephalitis (JE) in north Queensland in 1998, including one acquired on the Australian mainland. Design Serological surveillance of sentinel pigs for JE virus activity; serological surveys of humans and pigs and viral cultures of mosquito collections. Setting Islands in the Torres Strait and communities in the Northern Peninsula Area (NPA) and near the mouth of the Mitchell River in Cape York, Queensland, In the 1998 wet season (December 1997‐May 1998). Results Sentinel pigs in the Torres Strait began to seroconvert to JE virus in February 1998, just before onset of JE in an unvaccinated 12‐year‐old boy on Badu island. By mid‐April, most sentinel pigs had seroconverted. Numerous JE viruses were isolated from Culex annulirostris mosquitoes collected on Badu. In early March, a person working at the mouth of the Mitchell River developed JE. Serological surveys showed recent JE virus infection in 13 young pigs on a nearby farm, but not in 488 nearby residents. In NPA communities, sentinel pigs seroconverted slowly and JE viruses were isolated from three, but none of 604 residents showed evidence of recent infection. Nucleotide sequencing showed that 1998 JE virus isolates from the Torres Strait were virtually identical not only to the 1998 isolate from an NPA pig, but also to previous (1995) Badu isolates. Conclusions JE virus activity was more widespread in north Queensland in the 1998 wet season than in the three previous wet seasons, but ecological circumstances (eg, less intensive pig husbandry, fewer mosquitoes) appear to have limited transmission on the mainland. Nucleotide sequencing indicated a common source for the 1995 and 1998 JE viruses. Circumstantial evidence suggests that cyclonic winds carried infected mosquitoes from Papua New Guinea.

Two laboratory-confirmed cases of Japanese encephalitis imported to Germany by travelers returning from Southeast Asia

“…1 An estimated 3 billion people are at risk for JEV infection, 3 and JE has extended its geographical range from Asia to the South Pacific and Northern Australia. 4,5 Based on the viral envelope (E) gene, JEV is divided into 5 genotypes which have a different geographical distribution. 6 It has been suggested, however, that all known genotypes originated in the Indonesia-Malaysia region.…”

Infections inapparentes chez l’Homme : un cheval de Troie pour l’introduction et la diffusion des arbovirus transmis par des moustiques dans les régions non endémiques ?

“…Ainsi, à partir de 1995, le JEV a été introduit à plusieurs reprises en Australie, à partir de la Papouasie-Nouvelle-Guinée. On ne pense pas que ces introductions aient été réalisées par des malades virémiques, mais plus vraisemblablement par des moustiques infectés portés par les vents [28,29,53,65,66].…”

Japanese encephalitis and vaccines: past and future prospects

“…By the age of 15 years almost all people living in endemic regions have been infected with the JEV [10]. The disease occurs in almost all regions of Asia [10], and recently has also emerged to the North of the Australian subcontinent, especially to the islands of Torres strait [13]. One main reason for the expansion of the JEV is the enhanced agricultural cultivation such as rice cultivation and consecutively growing habitats for the mosquitoes [4,11].…”

“…The risk of an infection with JEV is present in many regions of Asia, and the North of the Australian subcontinent [4,10,13,24]. Routine JE immunizations were performed in Japan, China, South Korea and Vietnam [15].…”