Variations in equid SLC11A1 (NRAMP1) genes and associations with Rhodococcus equi pneumonia in horses.
Authors: Halbert Natalie D, Cohen Noah D, Slovis Nathan M, Faircloth Jay, Martens Ronald J
Journal: Journal of veterinary internal medicine
Summary
# Rhodococcus equi Pneumonia and Equine Genetic Susceptibility Whilst most foals encounter *Rhodococcus equi* in their environment within days of birth, only some develop the chronic suppurative bronchopneumonia characteristic of this disease; understanding why certain animals are inherently resistant remains clinically important for prevention and management strategies. Halbert and colleagues sequenced the SLC11A1 gene—a key regulator of intracellular immune responses—across horses, donkeys and zebras, then examined whether genetic variants correlated with R. equi pneumonia status in age-matched case-control cohorts from three equine breeding farms with endemic disease. A novel -57C/T variant in the gene's promoter region was identified in four horse breeds, and significantly associated with susceptibility to R. equi pneumonia on two of the three farms sampled, suggesting genuine biological significance rather than chance observation. Whilst the mechanistic basis for this association requires further investigation, these findings hint at heritable factors influencing disease resistance that could inform breeding decisions and explain the observed variation in foal morbidity within apparently similar management environments. This work opens possibilities for genetic screening of at-risk populations and represents a foundation for understanding host factors in R. equi and other intracellular bacterial infections affecting equids.
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Practical Takeaways
- •Genetic testing for the -57C/T variant may help identify foals at higher risk for R. equi pneumonia, allowing for targeted preventive management strategies
- •Understanding individual foal genetic susceptibility to R. equi could inform breeding decisions on farms with endemic disease pressure
- •This research suggests that not all foal exposure to environmental R. equi results in clinical disease due to underlying genetic variation in innate immunity
Key Findings
- •Seven novel SLC11A1 gene variants were identified as specific to non-horse equid species (donkey, zebra)
- •A novel horse-specific variant (-57C/T) in the 5' untranslated region was identified across 4 horse breeds
- •The -57C/T variant showed significant allelic and genotypic associations with susceptibility to R. equi pneumonia on 2 of 3 farms with endemic disease
- •SLC11A1 gene variation appears to influence natural resistance to R. equi foal pneumonia, though functional mechanisms remain undetermined