Haematological measurements as an aid to early diagnosis and prognosis of respiratory viral infections in thoroughbred horses.

The research presents early detection techniques and prognosis methods for respiratory viral infections in thoroughbred horses, especially the equine herpes virus 1 (EHV1). The study used hematological examination and endoscopic changes to spot the onset of the disease before the confirmation of the virus could be made through isolation or serology.

Research Background and Aim

• In 1988, a significant rise in respiratory disease among thoroughbred horses was noticed in Hong Kong. The researchers aimed at devising methods for early detection and predicting the progression of these diseases based on hematological measurements.

Methodology

• Ten horses from different stables were chosen for the study. These horses developed high temperatures within three days of each other and then seroconverted to EHV1.
• Serial blood samples were taken from these horses for hematological examination.
• The researchers also used endoscopic examination on the horses to monitor visible mucopus development after the initial infection.

Findings

• All ten horses showed an absolute monocyte count of more than 0.5 x 10(9)/litre within the first five days. This indicates an immune response, as monocytes are a type of white blood cell that can transform into macrophages and contribute to the immune system’s response against viruses or bacteria.
• Nine of the horses showed a high neutrophil/lymphocyte (N/L) ratio on the first day which decreased and reversed within four or five days. A high N/L ratio is typically a sign of an ongoing acute infection or inflammation.
• Five of the horses exhibited high plasma viscosity and a large difference in the viscosity between plasma and serum. This returned to normal within ten days for three of these horses. High plasma viscosity indicates altered flow properties of blood, often associated with infections or inflammations.

Implications

• Following the initial infection, six of the nine horses developed visible mucopus as observed through endoscopy. This included the five horses with large differences in plasma and serum viscosity.
• The researchers suggest that these hematological and endoscopic changes can be helpful in identifying horses in the acute stages of EHV1 infection. They can also help in tracking the progress of the disease before a definitive diagnosis (through virus isolation or serology) can be confirmed.