Exertional heat illness: a review of the syndrome affecting racing Thoroughbreds in hot and humid climates.

The research article discusses the lethal effects of exertional heat illness (EHI) on racing Thoroughbreds, triggered by the combination of intense physical effort and hot, humid conditions. It provides an understanding of EHI, its progression, and current approaches to treatment based on the existing literature.

Syndrome Overview

• The study focuses on exertional heat illness (EHI), a syndrome affecting racing Thoroughbreds in hot and humid environments. This condition is caused by the rapid elevation of the horse’s body temperature due to intense physical exertion coupled with unfavorable environmental conditions.
• Heat accumulation in horses can reach a crucial threshold of around 42°C, which can trigger a pathophysiological cascade leading to potentially fatal consequences.
• Although EHI is well-documented in humans, information about its effects on Thoroughbred racehorses is limited.

Progression of Clinical Signs

• The research article describes the progression of clinical signs related to EHI affecting the central nervous system (CNS) and gastrointestinal systems of horses, which appear to mirror the underlying physiological changes seen in humans affected by the same condition.
• Early indicators include mild irritability, such as agitation and random kicking. The horse may then progress to unmanageable states involving disorientation, severe uncoordinated movement, and eventually convulsions, coma, and death.
• The clinical signs also include manifestations of endotoxaemia, a condition characterized by the presence of endotoxins in the blood, suggesting systemic infection.

Current Treatment Approaches

• At present, the treatment protocols for EHI in racehorses are primarily empirical, which means they are based on practical experience rather than scientific data or theory.
• The typical treatment approach involves rapid and efficient cooling of the horse to reduce body temperature, administration of sedatives to control agitation and restlessness, administration of non-steroidal anti-inflammatory drugs (NSAIDs) to alleviate the effects of endotoxaemia, and glucocorticoids to stabilize cell membranes and curb the inflammatory effects on the CNS.

Conclusion

• The research article offers a comprehensive overview of EHI in racehorses and suggests the proposed pathophysiology based on the existing literature and understanding of both equine and human heat illness.
• It also provides insights into current treatment strategies, though emphasizing the need for further targeted investigation to improve the prevention, detection, and treatment of EHI in Thoroughbred racehorses.