Variations in equid SLC11A1 (NRAMP1) genes and associations with Rhodococcus equi pneumonia in horses.

The research study investigates genetic variations in horses, zebras, and donkeys that potentially influence the susceptibility or resistance against Rhodococcus equi pneumonia, which predominantly affects young foals. Specifically, the study focuses on the SLC11A1 gene and the discovery of a novel variant, namely -57C/T.

Study Purpose and Background

• The main aim of the research was to identify genetic factors in equid species (horses, donkeys, zebras) that could explain the variance in susceptibility to Rhodococcus equi pneumonia, a significant bacterial infection predominantly impacting foals.
• R. equi is an intracellular pathogen that results in chronic bronchopneumonia, but not all foals exposed to the bacteria develop the disease. The underlying causes for this selective susceptibility were previously unknown, spurring this genetic investigation.

Research Methodology

• The study examined the solute carrier family 11 member 1 (SLC11A1) gene sequences specifically in the 5′ untranslated region, exon 1, and part of intron 1 for variations.
• Comparisons were drawn among genetic variations in three separate horse breeding farms via an age-matched case-control design.

Findings

• Seven unique variants in the 5’untranslated region were identified, determined to be specific to either or both of the non-horse equid species (donkey, zebra).
• A unique horse variant referred to as -57C/T present in the 5′ untranslated region was found in four different breeds.
• The -57C/T variant was discovered in two out of the three farms that had a high incidence of R. equi pneumonia, affecting two distinct horse breeds.
• The -57C/T variant showed significant allelic and genotypic associations with susceptibility to R. equi pneumonia in foals from these farms.

Implications

• The practical implications of the -57C/T variant in disease resistance are not fully understood yet. Nevertheless, the study marks an important milestone towards understanding the natural genetic resistance to R. equi pneumonia in foals and potentially other intracellular bacterial diseases affecting equid species.
• The findings may guide future research and breeding practices and pave the way for developing preventative approaches or treatments for R. equi pneumonia in foals.