Acute Phase Protein Response in Native and Imported Horses After Routine Combination Vaccination Protocol.
Authors: Smith Meagan A, Kristula Michaela A, Aceto Helen, Levine David G
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Smith and colleagues conducted a prospective cohort study comparing acute phase protein responses to routine combination vaccination in native and imported horses, measuring serum amyloid A (SAA), fibrinogen and rectal temperature at baseline, 24, 48, 72, 96 and 168 hours post-vaccination. Whilst both groups mounted an acute phase response characterised by elevated SAA and fibrinogen concentrations within 24 hours, imported horses demonstrated a substantially greater and more sustained inflammatory reaction: SAA remained significantly elevated throughout the observation period (averaging 358 mg/L higher than natives; P = 0.03), whereas native horses returned to baseline by day seven. Imported horses also exhibited consistently higher baseline rectal temperatures (median 37.8°C versus 37.3°C; P = 0.002) and a greater proportional temperature increase at 24 hours post-vaccination. Fibrinogen responses did not differ significantly between groups, despite both showing marked elevation sustained through 168 hours. These findings highlight that recently imported horses mount a more pronounced systemic inflammatory response to vaccination than previously vaccinated natives—a clinically relevant distinction for practitioners evaluating post-vaccination clinical signs, as the more vigorous SAA elevation in imports could easily be misinterpreted as infection or illness rather than a robust (if exaggerated) vaccine response.
Read the full abstract on PubMed
Practical Takeaways
- •Recently imported horses show a stronger and more prolonged acute phase response to routine vaccinations compared to native previously-vaccinated horses; clinicians should expect elevated SAA and temperature in imports for up to 1 week post-vaccination
- •When evaluating recently vaccinated imported horses for illness, distinguish between normal post-vaccination inflammation and true disease, as SAA elevation alone may not indicate pathology in this population
- •Native horses typically resolve acute phase markers within 7 days of vaccination, providing a useful clinical timeline for expected normalization
Key Findings
- •Both native and imported horses showed elevated SAA and fibrinogen within 24 hours of combination vaccination
- •Imported horses maintained significantly elevated SAA from 24-168 hours (coefficient 358 mg/L, P=0.03), while native horses returned to baseline by 168 hours
- •Imported horses had significantly higher baseline and post-vaccination rectal temperatures than native horses (P=0.002)
- •Fibrinogen increased significantly in both groups 24-168 hours post-vaccination with no significant difference between native and imported horses (P=0.5)