High Seroprevalence of Lawsonia intracellularis in Thoroughbred Farms in Southern Brazil.
Authors: de Souza Rafaela P, Mousquer Mariana A, Müller Vitória, Barbosa Jéssica Carolina Reis, Leite Fábio Pereira Leivas, Guedes Roberto Maurício C, Curcio Bruna da Rosa, Nogueira Carlos E W
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: *Lawsonia intracellularis* Seroprevalence in Brazilian Thoroughbreds Researchers conducted a serological survey across six Thoroughbred breeding farms in southern Rio Grande do Sul, Brazil, to map exposure to *Lawsonia intracellularis*, the causative agent of equine proliferative enteropathy (EPE). Blood samples from 686 horses stratified by age—broodmares (>5 years), two-year-olds, yearlings, and foals aged 0–6 months—were analysed using immunoperoxidase monolayer assay to detect IgG antibodies during 2019–2020. Overall seroprevalence reached 51%, with striking age-related variation: broodmares showed the highest exposure at 86.8% whilst very young foals (0–6 months) demonstrated minimal detection at 5.2%, and farm-level differences ranged from 30.6% to 67.4%. Notably, no clinical signs of EPE were recorded despite this substantial exposure, indicating either subclinical infection or effective management practices mitigating clinical disease. For equine practitioners, these findings underscore endemic circulation of *L. intracellularis* in South American Thoroughbred populations and suggest that age-dependent seroconversion patterns may reflect passive immunity in neonates followed by active exposure as foals integrate into farm environments—a pattern warranting investigation into farm biosecurity practices and vaccination strategies.
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Practical Takeaways
- •High seroprevalence indicates continuous exposure to L. intracellularis on Thoroughbred farms in this region; monitor for clinical signs of EPE even in subclinical populations
- •Age-related antibody patterns suggest young foals (0-6 months) are less exposed or recently weaned from maternal protection; consider biosecurity measures during this vulnerable period
- •Significant farm-to-farm variation (30.6% to 67.4%) suggests management and biosecurity practices differ substantially; investigate higher-prevalence farms for risk factors
Key Findings
- •Overall seroprevalence of L. intracellularis was 51% across 686 Thoroughbred horses in Southern Brazil
- •Broodmares showed highest antibody detection at 86.8%, while foals aged 0-6 months showed lowest at 5.2%
- •Farm 1 had highest seropositivity at 67.4% and Farm 4 had lowest at 30.6%
- •No clinical manifestation of Equine Proliferative Enteropathy was observed despite high seroprevalence, suggesting subclinical exposure