Post-Natal Persistent Infection With Classical Swine Fever Virus in Wild Boar: A Strategy for Viral Maintenance?

Area of Science:

• Veterinary Virology
• Infectious Diseases
• Immunology

Background:

• Classical swine fever virus (CSFV) poses a significant threat to swine populations globally.
• Understanding the pathogenesis of CSFV in wild boar is crucial for disease control in endemic regions.
• Post-natal persistent infection can lead to prolonged viral shedding and transmission.

Purpose of the Study:

• To investigate the potential for post-natal persistent infection with a moderately virulent CSFV strain in wild boar piglets.
• To evaluate the innate and specific immune responses in persistently infected wild boars.
• To determine the age window for susceptibility to persistent CSFV infection in wild boar.

Main Methods:

• Intranasal inoculation of wild boar piglets with CSFV strain Catalonia 01 within 10 hours of birth.
• Contact exposure of naive piglets (within 48 hours of birth) to infected animals.
• Monitoring viral replication, humoral and cellular immune responses, and type I and II interferon levels.

Main Results:

• 46.67% of directly inoculated piglets developed persistent CSFV infection, remaining asymptomatic with high viral loads.
• Contact-exposed piglets also developed persistent infection (33.33%), extending the susceptible age window to 48 hours post-birth.
• Persistently infected animals showed largely unimpaired type I interferon-alpha responses but a decrease in interferon-gamma producing cells.

Conclusions:

• Moderately virulent CSFV strains can establish persistent infections in wild boar piglets exposed shortly after birth.
• The susceptible window for developing persistent infection extends to at least 48 hours post-birth.
• The immune evasion strategies employed by the virus in persistently infected animals, coupled with increasing wild swine populations, highlight a potential epidemiological challenge.