How Fast Does S. zooepidemicus Invade The Body After Exposure? By Ed Metzger from South West Ontario Veterinary Service

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) has emerged as a significant pathogen in pigs, now ranked as the second most serious bacterial disease on the Swine Health Information Center (SHIC) bacterial disease matrix. Disease outbreaks, while infrequent, can cause high mortality and abortions, with recent severe cases reported in the Netherlands and Germany.

Canadian researchers conducted a study to investigate the early stages of S. zooepidemicus infection in pigs following oronasal inoculation.

Study Details:

• Inoculation: Fourteen pigs were inoculated with live cultures of S. zooepidemicus ST-194.
• Monitoring Intervals: Pigs were monitored at 2, 4, 8, and 24 hours post-inoculation.
• Post Mortems: Performed to assess gross visible lesions and collect samples for bacterial culture and PCR analysis at each time point.

Key Findings:

• Detection in Organs:
  • S. zooepidemicus was detectable in various organs, including the liver and spleen, as early as 2 hours post-inoculation.
• Tonsillar Samples:
  • S. zooepidemicus was consistently identified in tonsillar samples throughout the study.
• Mesenteric Lymph Nodes:
  • S. zooepidemicus was commonly identified within mesenteric (intestinal) lymph nodes.
• Rapid Spread:
  • The spread of S. zooepidemicus to internal organs was quite rapid, consistent with field reports of animals appearing healthy in the morning and becoming critically ill or dead within hours.
• Epidemiological Sampling:
  • Tonsillar samples could be used for epidemiological sampling and diagnostics.
• Persistence and Shedding:
  • Finding S. zooepidemicus within mesenteric lymph nodes suggests persistence of infection, replication, and potential shedding. Further research is needed to confirm these conclusions.

Submitted by Ed Metzger, DVM
Ref: Arthur Nery Finatto, Sulove Koirala, Fernanda Luiza Facioli, Jéssica Aparecida Barbosa, Roman Nosach, Matheus de Oliveira Costa. Organ distribution and early
pathogenesis of Streptococcus equi subsp. zooepidemicus in swine. Comp Immunol Microbiol Infect Dis . 2023 Nov 18:104:102095. doi: 10.1016/j.cimid.2023.102095.
Online ahead of print.