How Central Is the Domestic Pig in the Epidemiological Cycle of Japanese Encephalitis Virus? A Review of Scientific Evidence and Implications for Disease Control

Abstract

Despite the existence of human vaccines, Japanese encephalitis (JE) remains the leading cause of human encephalitis in Asia. Pigs are described as the main amplifying host, but their role in JE epidemiology needs to be reassessed in order to identify and implement efficient control strategies, for both human and animal health. We aimed to provide a systematic review of publications linked to JE in swine, in terms of both individual and population characteristics of JE virus (JEV) infection and circulation, as well as observed epidemiological patterns. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to select and analyze relevant articles from the Scopus database, 127 of which were included in the review. Pigs are central, but the implication of secondary hosts cannot be ruled out and should be further investigated. Although human vaccination cannot eradicate the virus, it is clearly the most important means of preventing human disease. However, a better understanding of the actual involvement of domestic pigs as well as other potential JEV hosts in different JEV epidemiological cycles and patterns could help to identify additional/complementary control measures, either by targeting pigs or not, and in some specific epidemiological contexts, contribute to reduce virus circulation and protect humans from JEV infection.

Host-Feeding Preference and Diel Activity of Mosquito Vectors of the Japanese Encephalitis Virus in Rural Cambodia

“…JE is caused by the Japanese encephalitis virus (JEV) belonging to the Flaviviridae family [ 3 ]. The historically described JEV cycle involves water birds as wild reservoir, pigs as amplifying hosts [ 4 , 5 , 6 ], and mosquito species as vectors [ 7 , 8 ]. Domestic birds are suspected to be secondary reservoir hosts [ 9 , 10 , 11 ].…”

Serological Evidence for Japanese Encephalitis and West Nile Virus Infections in Domestic Birds in Cambodia

“…Humans and horses are generally considered dead-end hosts, as they do not develop a viremia high enough to infect mosquitoes. An exception are pigs, as they serve as amplification hosts for JEV because they develop sufficient viral titers to support further infection of mosquitoes (5)(6)(7). Although the role of ardeid birds as reservoir hosts for JEV is admitted (8,9), the role of domestic birds as potential amplifying hosts has been little investigated so far.…”

Keragaman Spesies Vektor Japanese encephalitis di Sekitar Kandang Babi Kabupaten Tangerang

“…Manusia merupakan dead-end host JEV dan babi merupakan reservoar dan amplifying host utama. 6 Beberapa hewan lain dapat terinfeksi JEV dengan atau tanpa gejala klinis, yaitu kuda, anjing, ayam, bebek, sapi, kucing, ular, katak, domba, kambing, babi hutan, monyet, rakun, burung, dan kerbau. 7 Beberapa faktor risiko dari penularan JE diantaranya migrasi burung dari daerah endemis, jarak terbang nyamuk, peternakan babi dekat pesawahan yang merupakan tempat perindukan vector JE, perubahan iklim, air tergenang, dan introduksi hewan dari wilayah terinfeksi JEV.…”

“…8 Penularan JE di Asia umumnya terjadi di wilayah rural dan suburban dengan wilayah persawahan dan peternakan babi yang berada dalam lokasi yang berdekatan. 3,6 Dari beberapa daerah di Asia, Culex tritaeniorhynchus dianggap sebagai vektor utama penularan JE. 3,9,10 Di Indonesia sendiri, terdapat 10 jenis nyamuk yang telah terkonfirmasi sebagai vektor JE, yaitu Cx.…”