Identification of genomic loci associated with Rhodococcus equi susceptibility in foals.
Authors: McQueen Cole M, Doan Ryan, Dindot Scott V, Bourquin Jessica R, Zlatev Zlatomir Z, Chaffin M Keith, Blodgett Glenn P, Ivanov Ivan, Cohen Noah D
Journal: PloS one
Summary
Rhodococcus equi pneumonia remains a significant cause of mortality and morbidity in foals despite advances in management and treatment, yet the genetic underpinnings of individual susceptibility have remained poorly characterised until now. Cole and colleagues conducted genome-wide association studies using both single nucleotide polymorphism (SNP) and copy number variant (CNV) approaches in 248 Quarter Horse foals stratified into three groups: those with clinical R. equi pneumonia (n=43), foals with subclinical pulmonary lesions on ultrasound but no clinical signs (n=156), and unaffected controls (n=49). A locus on chromosome 26 demonstrated moderate association with disease, harbouring the TRPM2 gene—a critical regulator of neutrophil function and innate immune response—with homozygous carriers showing a 3- to 4-fold increased odds of developing clinical pneumonia compared to either subclinical or unaffected foals. The CNV-based analysis yielded no significant associations, suggesting that structural genomic variants play a minimal role in R. equi susceptibility. These findings indicate that host genetic factors meaningfully influence clinical outcomes in R. equi infection, opening avenues for potential genomic selection in breeding programmes and identifying novel therapeutic targets focused on neutrophil dysfunction in susceptible individuals.
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Practical Takeaways
- •Genetic predisposition influences R. equi pneumonia susceptibility in foals; consider family history and breeding decisions at high-risk farms
- •Some foals develop subclinical pulmonary lesions without clinical signs—ultrasound screening may identify at-risk individuals warranting closer monitoring or preventive management
- •Immune function (neutrophil-related) appears to be a key genetic factor; future management strategies might target immune competence during the critical foal rearing period
Key Findings
- •SNP on chromosome 26 associated with R. equi pneumonia susceptibility in foals, with 3- to 4-fold increased odds of disease for homozygous carriers
- •Associated genomic region contains TRPM2 gene, which is involved in neutrophil function and immune response
- •Subclinical pulmonary lesions detected ultrasonographically in 156 foals (63% of cohort) without clinical signs, indicating variable disease expression
- •No copy number variants associated with R. equi pneumonia susceptibility identified in this population