Location: Foreign Arthropod Borne Animal Disease Research
Project Number: 3022-32000-025-038-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2026
End Date: Jul 31, 2029
Objective:
Objective: To improve the understanding of JEV transmission.
Japanese encephalitis virus (JEV) is an emerging threat to livestock, particularly swine, which serve as amplifying hosts for the virus. The primary mode of JEV transmission is through mosquitoes. In the United States (U.S.), several mosquito species with the potential to act as JEV vectors are present and widely distributed. Although JEV is compatible with multiple mosquito species, transmission efficiency likely varies among competent species and among strains within the same species. Thus, one aim is to characterize variation in JEV transmission across Culex species and JEV strains.
In addition to vector transmission, direct pig-to-pig transmission through oronasal exposure. In addition to the reproductive disease that occurs in sow/gilts, JEV can also infect boars and was found in the semen of boars. The second aim of this study will examine sexual transmission of JEV by investigating viral infection of the swine reproductive tract.
Approach:
Aim 1. Characterize variation in JEV transmission across Culex species and strains.
Distinct Culex spp., including Cx. tarsalis and Cx. pipiens, will be collected from the field and reared under standard mosquito rearing conditions. Adult females will exposed to JEV spiked swine blood via artificial membrane feeding system. Groups of 20 mosquitoes from each species or strain will be collected at defined timepoints. To assess infection, dissemination, and transmission rates of these mosquitoes various tissues and saliva will be processed for quantification of virus and viral RNA. In addition, saliva will be collected from 100 JEV-exposed mosquitoes per mosquito species and strain to examine changes and selective pressures. The saliva will be assessed for phenotypic differences in the virus by examining growth kinetics, plaque morphology, virus titers and genomic sequences. Two independent experimental replicates will be conducted for each mosquito species or strain.
Aim 2. Evaluate JEV presence and associated pathology in the lower reproductive tract of swine following infection by needle or mosquito bite.
Swine will be infected either subcutaneously with needle inoculation, or by bite from JEV exposed mosquitoes. Infected pigs will be monitored according to established protocols, and necropsies will be performed at defined timepoints post-exposure. At necropsy, the reproductive tract will be collected from male and female animals, with a focus on the lower tract. In females, this will include the vagina and cervix, along with vaginal swabs. In males, tissues will include penis and urethra. In addition, semen-associated samples, including epididymal fluid and vas deferens contents, will be collected when possible. Samples will be divided for virological and histopathological analyses. For virological analyses, homogenized tissues will be used for detection of viral RNA and infectious virus. Histopathological analyses will be conducted on fixed tissues to assess structural alterations and evidence of tissue damage or inflammation associated with JEV infection. In addition, immunohistochemistry will be conducted to detect JEV antigen within tissues and to help identify infected cell types. Control (uninfected) animals will be included for comparison in the pathology analyses.