Study of the duration and distribution of equine influenza virus subtype 2 (H3N8) antigens in experimentally infected ponies in vivo.

This research investigates how equine influenza virus subtype 2 (H3N8) behaves in ponies, including its duration and distribution. Through experimental infection, the virus was found to not only affect the upper respiratory tract but also the bronchial system, with the viral antigen present up to three weeks after initial infection.

Research Methodology

• For the purpose of the experiment, 6-8-month-old pony foals were experimentally infected with equine influenza subtype-2 virus. The virus was delivered through a face mask into the ponies’ respiratory systems using an ultrasonic nebulizer.
• Successful infection was indicated by each pony developing a high temperature, a deep hacking cough, and a mucus-purulent nasal discharge that lasted for 7 to 10 days.
• Virus samples were taken from various parts of the pony’s respiratory system, including the nasopharynx, the mid-trachea, and the mainstem bronchus. An endoscope equipped with cytology brushes was used for this purpose. Samples were also taken from bronchoalveolar lavage fluid.

Findings from the Research

• On the 3rd and 5th day after infection, virus samples were successfully extracted from nasopharyngeal swabs of all pony subjects.
• From the 3rd to the 7th day after infection, a condition known as ciliacytophtorea, or the detachment of cilia from columner epithelial cells, was noticed on routine cytological stain.
• Using an indirect immunoperoxidase staining technique, scientists detected the viral antigen in both intact and fragmented ciliated epithelial cells, as well as in fragments of the ciliated plates.
• The presence of infected cells and cell fragments were particularly evident on the 3rd and 5th day after infection in the nasopharynx, mid-trachea, and mainstem bronchus. In the bronchoalveolar lavage samples, infected cell and cell fragment presence was noticed from the 3rd to the 7th day after infection.
• On the 7th and 21st day post-infection, the viral antigen was identified within vacuoles of alveolar macrophage-like cells. These cells were collected using bronchoalveolar lavage.

Conclusion

• Based on the findings of the research, it was concluded that the equine influenza virus can infect not only the upper airways of ponies but also their bronchial epithelium.
• Furthermore, evidence showed that the viral antigen could be present in the infected pony’s system for up to 21 days after initial infection.