Endoscopic and virological observations on respiratory disease in a group of young Thoroughbred horses in training.

This study investigates respiratory diseases in racehorses through endoscopic examination and monitoring for viral infection. Primarily, equine herpes virus-2 (EHV-2) was detected. The study reveals that all horses had Pharyngeal Lymphoid Hyperplasia (PLH), yet there was no correlation found between PLH’s severity and EHV-1 antibodies or EHV-2 isolation. Racing performance wasn’t affected by PLH’s severity. Furthermore, they noticed Exercise Induced Pulmonary Haemorrhage (EIPH) in a notable proportion of horses after intense training; its occurrence, however, was unpredictable.

Scope of the Research

• The research centered around examining respiratory diseases in a group of Thoroughbred racehorses in training.
• The primary method of investigation was through detailed examination using a fibreoptic endoscope and monitoring for possible viral infection.

Main Findings

• The only virus detected throughout the study was equine herpes virus-2 (EHV-2).
• All inspected horses were found to be dealing with the presence of Pharyngeal Lymphoid Hyperplasia (PLH), a condition that causes enlargement of the pharyngeal lymphoid tissue. The severity of this condition appeared to decline as the racehorses aged.
• There was no discovered association between PLH and the measures of antibodies produced against EHV-1, nor any association between PLH and the isolation of EHV-2, indicating that the herpes virus did not directly influence the prevalence or severity of PLH.
• Performance in races was not affected by the severity of PLH, suggesting that while PLH was present in all horses, it did not negatively impact their competitive performance.

Additional Observations

• One other notable observation was the presence of Exercise Induced Pulmonary Haemorrhage (EIPH) in 47% of the horses after they had undergone strenuous exercise or training. EIPH was defined by the presence of blood in the horse’s airways following physical exertion.
• Despite the high incidence of EIPH, the occurrence was not predictable, and 95% of the horses examined on more than one occasion experienced EIPH.
• Further findings showed the presence of observable mucoid or mucopurulent exudate (a form of mucus or pus) in the trachea in half of the total examinations. The observation of this exudate was seen to increase following exercise.