Vector-free transmission and persistence of Japanese encephalitis virus in pigs

Abstract

Japanese encephalitis virus (JEV), a main cause of severe viral encephalitis in humans, has a complex ecology, composed of a cycle involving primarily waterbirds and mosquitoes, as well as a cycle involving pigs as amplifying hosts. To date, JEV transmission has been exclusively described as being mosquito-mediated. Here we demonstrate that JEV can be transmitted between pigs in the absence of arthropod vectors. Pigs shed virus in oronasal secretions and are highly susceptible to oronasal infection. Clinical symptoms, virus tropism and central nervous system histological lesions are similar in pigs infected through needle, contact or oronasal inoculation. In all cases, a particularly important site of replication are the tonsils, in which JEV is found to persist for at least 25 days despite the presence of high levels of neutralizing antibodies. Our findings could have a major impact on the ecology of JEV in temperate regions with short mosquito seasons.

A Japanese Encephalitis Virus Vaccine Inducing Antibodies Strongly Enhancing In Vitro Infection Is Protective in Pigs

“…and remained positive for viral RNA until 7–8 days p.i. (Figure 3a), comparable to previously published results [23]. …”

“…Furthermore, we have recently shown that, under experimental conditions, the virus can transmit between pigs by contact and is secreted in oronasal fluids for a prolonged period of time [23]. This indicates a potential of JEV to spread and circulate even in areas with a climate unfavorable to the virus transmission by mosquitos.…”

Intensive Circulation of Japanese Encephalitis Virus in Peri-urban Sentinel Pigs near Phnom Penh, Cambodia

“…The MIR of 0.091/ 1,000 for females from all species over our whole study is low compared to MIR in the range of 1–1.2/ 1,000 for a JEV study in Can Tho city [20] and two West Nile studies in Florida and Puerto Rico [28,29] but is similar to previous studies on JEV in rural areas of Can Tho province (MIR of 0.05 / 1,000) and in suburban Bangkok (MIR of 0.046 / 1,000) [30,31]. An actual low infection rate of JEV in mosquitoes despite an intensive circulation in pigs could be consistent with the existence of a direct transmission of JEV between pigs as suggested by the results of a recent experimental study showing that oro-nasal virus excretion could last -5-6 days in pigs [32]. The FOI we are estimating in this study would then result from a combination of a vector-borne and a “within-pen” direct transmission.…”

A Mouse Model of Zika Virus Sexual Transmission and Vaginal Viral Replication

“…Further suspicion is raised by a recent case report of viral transmission between a ZIKV patient and caregiver without sexual contact (Tavernise, 2016). Additionally, the closely related Japanese encephalitis virus can be transmitted without the arthropod vector by oronasal secretions and through the oronasal route in pigs (Ricklin et al, 2016). To begin addressing the question of which types of sex-associated behaviors and contact can result in ZIKV transmission, the current study isolates infection through the vaginal route after administration of exogenous hormones.…”