Isolation of an adenovirus from an Arab foal.

The research discusses the discovery of adenovirus strains in horses, more specifically Arab foals. These virus strains were isolate from nasal and ocular swabs of a clinically normal foal from a stud in Queensland.

Research Context

• The research was prompted by previous observations of possible adenovirus infections in horses. Studies conducted in the UK, Iran, Ireland, and Australia showed that horses had antibodies against this virus. There were cases of adenoviruses isolated from horses with respiratory diseases as well.
• As part of a larger investigation on equine herpesviruses, swabs and serum samples were obtained from five mares and two Arab foals.

Research Methodology

• The swabs were stored in a medium, centrifuged to remove bacteria, and the supernatant fluid was stored at -70°C until suitable cell cultures were available.
• The adenoviruses were cultured in equine foetal kidney (EFK) cells at 37°C and were observed over time for changes.
• After a period of time, a cytopathic effect (CPE), indicating a visible change in host cells due to viral infection, was observed. The time until observable CPE decreased and infected all cell types.
• The adenoviruses were resistant to chloroform treatment, suggesting their stability. A haemagglutinin for rat erythrocytes was found in the fluid from disrupted cell cultures.
• Cell changes, including the presence of intranuclear inclusion bodies characteristic of adenoviruses.
• Tissues infected with the virus were stained and changes in the infected cells were examined.
• The cells from the cultures were studied under an electron microscope, which confirmed the presence of adenovirus particles.
• Retesting of the original nasal swab and the testing of an ocular swab from the same foal confirmed the presence of adenovirus.

Results and Interpretation

• The tests confirmed that the adenovirus was present in the secretions of the foal. Strains EAM-1 and EAM-2 were isolated.
• The relationship between adenovirus and Arab foals was called into question, as three of the four isolations of adenovirus have been made from Arab horses. Here the researchers indicate that further work is needed to understand the significance of this finding.
• While the impact of these viruses on equine respiratory infections was not confirmed by this study, the researchers acknowledge that the links drawn in earlier studies between severe respiratory disease in foals and adenovirus infection warrant further exploration.