Haematological changes in two thoroughbred horses in training with confirmed equine herpesvirus 1 infections.

The research looks into the cause and effect relationship between an outbreak of respiratory disease among thoroughbred horses and the equine herpesvirus 1 (EHV-1), specifically noting how its presence changed the tested horses’ haematological (blood) values over a period of time.

Context and Rationale of the Study

• The study was primarily driven by an outbreak of respiratory disease seen among thoroughbred horses in training in Hong Kong.
• The researchers identified the cause of the outbreak as equine herpesvirus 1 (EHV-1), a common virus among horses, especially subtype 1, also known as the “abortion strain” because it is known to cause abortions in pregnant mares.
• To understand the effects of this virus on infected horses, the researchers chose two of the affected horses and closely monitored them over several weeks.

Methodology

• The researchers collected blood samples from two horses infected with EHV-1 over an extended period.
• These samples were used to measure their haematological values, focusing particularly on the changes observed.
• The primary marker that the researchers chose for their study was the monocyte count in the blood samples. Monocytes are a kind of white blood cells that help the body fight off viruses and infections.

Findings

• The results showed a significant increase in the monocyte count in the first few days after the horses were infected with the virus.
• In one horse, the monocyte count steadily declined after the initial peak which is consistent with the body’s usual response to a viral attack.
• However, the other horse showed a second peak in monocyte count after a period of exercise. This second peak illustrates that the horse’s body had to fight off the virus harder due to the added physical stress from the exercise, hence emphasizing the importance of resting animals in the early stages of a disease.