Experimental Infections of Pigs with Japanese Encephalitis Virus Genotype 4

Area of Science:

• Veterinary Virology
• Pathogen Discovery
• Public Health Entomology

Background:

• Japanese encephalitis virus (JEV) emerged in Australia in 2022, posing a significant threat to pig reproductive health and public safety.
• Experimental infection studies are crucial for understanding JEV pathogenesis and developing control strategies.

Purpose of the Study:

• To establish an in vivo infection model for the Australian JEV outbreak strain (genotype 4) in pigs.
• To evaluate different inoculation routes and doses for experimental JEV infection.
• To characterize the clinical, virological, and pathological outcomes of JEV infection in pigs.

Main Methods:

• Weaned piglets were experimentally infected with JEV (genotype 4) via intradermal injection or intranasal instillation at different ages and doses.
• Infection was confirmed by qRT-PCR of blood, oral/nasal swabs, and saliva.
• Viremia, antibody development, JEV presence in tonsils, clinical signs, and histopathological changes in nervous tissues were assessed.

Main Results:

• Intradermal JEV injection successfully infected pigs at 5 and 11 weeks of age, with viremia peaking at 3-4 days post-challenge.
• JEV was consistently detected in tonsils, while detection in swabs and saliva was inconsistent.
• Infected pigs exhibited pyrexia and histopathological evidence of meningitis, encephalitis, and gliosis in nervous tissues.

Conclusions:

• The established in vivo pig model effectively replicates JEV infection, demonstrating viremia and neurological pathology.
• This model is valuable for assessing the efficacy of JEV vaccines and conducting comparative pathogenesis studies with different JEV genotypes.
• Understanding JEV transmission and pathogenesis in pigs is critical for public health protection in Australia.