Rethinking Japanese Encephalitis Virus Transmission: A Framework for Implicating Host and Vector Species
Year: 2015
Type: review
Abstract: UnderstandingJapanese encephalitis virus (JEV) is an important cause of viral encephalitis in Asia, with an estimated 67,900 cases annually [1].Mosquito-borne zoonoses, including JEV, present some of the most complex disease systems, often involving multiple mosquito and vertebrate species.The first investigations of JEV transmission ecology were undertaken in the 1950s in Saitama Prefecture, Japan (Fig 1A) [2][3][4][5][6][7][8][9][10].As a result of these studies, Culex tritaeniorhynchus was implicated as the primary vector and pigs as the amplifying hosts, with a minor role described for ardeid birds [10].Scherer et al. [3] justified the intensive investigation of pigs and birds in Japan by emphasizing that, within this context, only these animals and wild rodents underwent population turnover high enough to provide the continuous supply of susceptible individuals necessary to explain the occurrence of annual epidemics.Research was focused on these species, in preference to other animals, including cattle, whose total and susceptible populations were smaller.Among potential bird hosts, ardeid birds in particular were studied because they possessed anti-JEV antibodies, were numerous, colonial, could be caught in large numbers, and were large enough to withstand repeated bleedings adequate for testing.Their selection was not meant to imply that other birds were not potentially important in JEV ecology [3].The transmission cycle proposed from this initial research in Japan arose from careful study of the transmission context in that location, at that time.Vertebrate population density (Fig 2), life span, and JEV viremia were considered when implicating primary hosts [6][7][8].Baited mosquito traps were used to determine numbers of mosquitoes attracted to a variety of bird species, pigs, and humans [5].The relative abundance of each mosquito species caught in baited traps and their JEV infection status were compared when implicating vectors in transmission [4].Cx. tritaeniorhynchus was found to be most abundant in traps baited with hosts able to produce JEV viremia [2,4], providing circumstantial evidence for this species' role in transmission, which was strengthened by laboratory experiments demonstrating this mosquito's competence for JEV replication and transmission [2].As highlighted by numerous review articles, the initial investigations in Japan have formed the basis for describing the JEV transmission cycle, primarily involving Cx. tritaeniorhynchus, pigs, and, to a lesser extent, ardeid birds [11][12][13][14][15].
Source: PLoS neglected tropical diseases
Language: English
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,670
OpenAlex ID: W2190896587