Presence of African horse sickness virus in equine tissues, as determined by in situ hybridization.

The research examines the presence of the African horse sickness virus (AHSV) in the tissues of horses at the terminal stages of infection, traced using a specific RNA probe. It highlights that the virus spreads extensively in lung and heart tissues.

Study Design and Subject Matter

• The retrospective study involved sixteen horses, fifteen infected with AHSV and one non-infected to serve as a control. The infected ponies presented a variety of clinical signs and had been infected with different serotypes of the AHSV – thirteen with serotype 4, one with serotype 1, and one with serotype 2.
• The focus of the research was to track the prevalence of AHSV in the body tissues of the infected horses. The team used a negative-sense digoxigenin-labeled RNA probe that corresponded to the gene responsible for encoding the nonstructural protein-1 of AHSV serotype 4.
• The research involved horses that were terminally ill from the virus, and they were euthanized when their illness became severe. The tissues studied included the lung, heart, spleen, neck muscle, and supraorbital fat from each pony.

Findings of the Study

• The study found that the virus had spread widely and was present in significant amounts in the sections of the lung and hearts examined. However, it was found in relatively less quantity in other tissues like the spleen, neck muscle, and supraorbital fat.
• The histological examination implied that the most noticeable changes due to the presence of the virus were found in the forms of pulmonary edema and in some cases, acute myocardial necrosis.
• The in situ hybridization technique revealed that the virus localized to cells resembling endothelium in all organs except the spleen, where the virus was present in both endothelium-like cells and large mononuclear cells.

Conclusion

• This study provides valuable insight into the spread and localization of the African horse sickness virus within the tissues of infected horses.
• The findings highlight the organ-specific tissue distribution of the virus, revealing that the lungs and heart are significantly affected, reflecting the clinical signs seen in infected horses.