Experimental vesicular stomatitis virus infection in horses: effect of route of inoculation and virus serotype.
Authors: Howerth E W, Mead D G, Mueller P O, Duncan L, Murphy M D, Stallknecht D E
Journal: Veterinary pathology
Summary
# Editorial Summary Vesicular stomatitis (VS) remains a significant concern for equine practitioners, yet understanding its transmission routes and tissue involvement remains incomplete. Howerth and colleagues experimentally infected horses with both New Jersey and Indiana serotypes via multiple routes simulating natural transmission (contact and vector-borne), then systematically tracked clinical signs, viral shedding patterns, antibody responses, and tissue involvement over a 12–15 day period. Oral cavity secretions yielded the highest and most consistent viral titres, followed by nasal shedding, whilst viraemia was absent and faecal shedding never detected—findings that clarify why VS is primarily an oronasal disease and why contact transmission occurs predominantly through saliva rather than systemic infection. Notably, neutralising antibodies appeared between days 6–12 post-inoculation coinciding with lesion resolution, and post-mortem examination revealed viral RNA persisting in tonsillar and lymph node tissues even after lesions had healed and become non-vesicular, suggesting these tissues warrant investigation as sites for confirming infection during convalescence when traditional isolation techniques fail. These results have direct implications for biosecurity protocols during outbreaks (emphasising control of saliva-contaminated environments), for interpreting diagnostic results in horses with healing lesions, and for developing more targeted surveillance methods—particularly molecular techniques examining lymphoid tissues—to identify persistently infected animals during disease resolution.
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Practical Takeaways
- •VSV transmission in horses occurs primarily through oral contact and vectors; monitor salivary shedding as the main transmission risk rather than fecal or blood routes
- •Clinical recovery and antibody development occur within 2 weeks post-exposure, but viral RNA persistence in lymphoid tissues means infected horses may remain epidemiologically relevant longer than clinical signs suggest
- •Multiple transmission routes during outbreaks mean prevention strategies should address both direct contact (saliva) and vector-mediated spread rather than single-route assumptions
Key Findings
- •Both VSV-NJ and VSV-IN caused clinical infection in horses via contact and vector transmission routes, confirmed by seroconversion
- •Oral cavity was the primary site of viral shedding with highest titers, followed by nasal cavity; conjunctival and fecal shedding rare/absent
- •Neutralizing antibody development (days 6-12 post-inoculation) coincided with cessation of lesion development and viral clearance
- •Lymph nodes and tonsils retained detectable viral RNA at necropsy (days 12-15) despite clinical resolution, suggesting local immunity role in healing