Retrospective analysis of post-mortem findings in Thoroughbreds aged from birth to 18 months presented to a UK pathology laboratory.
Authors: Mouncey R, Arango-Sabogal J C, de Mestre A M, Foote A K, Verheyen K L
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Congenital defects—predominantly conformational manifestations of developmental orthopaedic disease (DOD)—accounted for one-fifth of mortality in Thoroughbreds under 18 months presented to a UK pathology laboratory between 2006 and 2020, with odds of these defects 56-fold higher in neonates aged 0–2 days compared to older foals. Pneumonia emerged as the second most significant cause of death overall (14% of cases), with Rhodococcus equi identified in half of pneumonia cases and a striking 4.3-fold increased odds during the pre-weaning period (1–4 months of age). This retrospective analysis of 137 post-mortem reports demonstrates clear age-related patterns in mortality aetiology, highlighting that early perinatal deaths are predominantly driven by conformational defects, whilst respiratory infections become increasingly problematic as foals progress through the pre-weaning phase. For breeders, stud veterinarians and those involved in foal management, these findings underscore the importance of rigorous neonatal assessment for structural abnormalities and targeted biosecurity protocols during early rearing, particularly regarding R. equi exposure and management on yards with infected premises. The prominence of DOD-related mortality also warrants consideration of maternal nutrition, genetics and breeding strategies to reduce the incidence of these devastating conformational problems in the earliest critical weeks of life.
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Practical Takeaways
- •Conformational manifestations of DOD represent a significant perinatal mortality risk; farriers and vets should anticipate potential congenital limb alignment issues in young Thoroughbreds presenting with clinical signs
- •Rhodococcus equi pneumonia is the primary infectious cause of death in pre-weaning foals; early recognition of respiratory signs and environmental management (dust, aerosol control) are critical during the 1-4 month window
- •Mortality patterns shift dramatically with age, suggesting different preventive strategies are needed for neonates versus weaners—perinatal defects require management at birth, while infectious disease prevention focuses on the pre-weaning period
Key Findings
- •Congenital defects were most common overall (20%), with 69% being conformational manifestations of DOD
- •Pneumonia occurred in 14% of cases, predominantly in pre-weaning foals (1-4 months), with Rhodococcus equi identified in 50% of pneumonia cases
- •Odds of congenital defects were 56.6 times greater in foals aged 0-2 days compared to 4-18 months (P<0.001)
- •Odds of pneumonia were 4.3 times greater in foals aged 1-4 months compared to 0-2 days (P=0.04)