Changes in Rice and Livestock Production and the Potential Emergence of Japanese Encephalitis in Africa

The known distribution of Japanese encephalitis (JE) is limited to Asia and Australasia. However, autochthonous transmission of Japanese encephalitis virus was reported in Africa for the first time in 2016. Reasons for the current geographic restriction of JE and the circumstances that may permit emergence in non-endemic areas are not well known. Here, I assess potential changes in vector breeding habitat and livestock production in Africa that are conducive to JEV transmission, using open-source data available from the Food and Agriculture Organization between 1961 and 2019. For 16 of 57 countries in Africa, there was evidence of existing, or an increase in, conditions potentially suitable for JE emergence. This comprised the area used for rice production and the predicted proportion of blood meals on pigs. Angola, where autochthonous transmission was reported, was one of these 16 countries. Studies to better quantify the role of alternative hosts, including domestic birds in transmission in endemic regions, would help to determine the potential for emergence elsewhere. In Africa, surveillance programs for arboviruses should not rule out the possibility of Japanese encephalitis virus (JEV) circulation in areas with high pig or bird density coincident with Culicine breeding habitats.

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Japanese Encephalitis Virus in Australia: From Known Known to Known Unknown

Tropical Medicine and Infectious Disease ◽

10.3390/tropicalmed4010038 ◽

2019 ◽

Vol 4 (1) ◽

pp. 38 ◽

Cited By ~ 4

Author(s):

Andrew F. van den Hurk ◽

Alyssa T. Pyke ◽

John S. Mackenzie ◽

Sonja Hall-Mendelin ◽

Scott A. Ritchie

Keyword(s):

Japanese Encephalitis Virus ◽

Japanese Encephalitis ◽

Vector Competence ◽

Encephalitis Virus ◽

Surveillance Systems ◽

Northern Australia ◽

The Status ◽

Surveillance Programs ◽

Torres Strait ◽

Transmission Cycles

Japanese encephalitis virus (JEV) is a major cause of neurological disease in Asia. It is a zoonotic flavivirus transmitted between water birds and/or pigs by Culex mosquitoes; humans are dead-end hosts. In 1995, JEV emerged for the first time in northern Australia causing an unprecedented outbreak in the Torres Strait. In this article, we revisit the history of JEV in Australia and describe investigations of JEV transmission cycles in the Australian context. Public health responses to the incipient outbreak included vaccination and sentinel pig surveillance programs. Virus isolation and vector competence experiments incriminated Culex annulirostris as the likely regional vector. The role this species plays in transmission cycles depends on the availability of domestic pigs as a blood source. Experimental evidence suggests that native animals are relatively poor amplifying hosts of JEV. The persistence and predominantly annual virus activity between 1995 and 2005 suggested that JEV had become endemic in the Torres Strait. However, active surveillance was discontinued at the end of 2005, so the status of JEV in northern Australia is unknown. Novel mosquito-based surveillance systems provide a means to investigate whether JEV still occurs in the Torres Strait or is no longer a risk to Australia.

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