Clinical, serological and virological characteristics of an outbreak of paresis and neonatal foal disease due to equine herpesvirus-1 on a stud farm.

The study explores an outbreak of the equine herpesvirus-1 (EHV-1) on a large stud farm, detailing its clinical, serological and virological properties while providing valuable recommendations for the management of future such outbreaks.

Overview of the Study

• The study revolves around an outbreak of equine herpesvirus-1 (EHV-1) on a large stud farm. The outbreak infected around 85 mares, 22 foals and three stallions among a population of 133 mares, 54 foals and four stallions.
• Overall, the outbreak manifested clinical disease in 16 mares, two stallions and 13 foals. The virus presented different symptoms in different classes of the horse population.

Clinical Signs and Symptoms

• In stallions, the visible signs of EHV-1 infection were scrotal oedema, ataxia and loss of libido.
• Mares expressed symptoms such as ataxia and recumbency or inability to rise from laying position.
• Foals had uveitis (inflammation of the eye’s middle layer or uvea) and nasal discharge, although pneumonia and colic with intussusception (a condition in which one segment of intestine invaginates within another, causing an intestinal blockage) were also established at autopsy.
• Mares nursing foals were more susceptible to the neurological disease caused by the virus, with 12 out of 38 infected, compared to barren mares, of whom only one of 46 contracted the disease.
• The outbreak caused the death of three mares, with those who had been recumbent failing to breed again.

Serological and Virological Characteristics

• Control procedures relied on virological and serological testing, in addition to stringent management practices to curtail the spread of the infection within and outside of the stud farm.
• There was a noteworthy antibody response in adult horses, indicative of the body’s immune response to the virus. However, this response was generally poor in foals, suggesting a weaker immune response; three of the nine viraemic (actively carrying the live virus in the bloodstream) foals did not develop any significant increases in the levels of circulating antibody.

Management Recommendations

• The study concludes with recommendations for the management of future EHV-1 outbreaks. Although it does not detail these recommendations, it implies the necessity to devise resilient strategies to curtail the spread and impact of the virus.