Field and laboratory studies of equine influenza viruses isolated in 1979.

The study investigates the effects and characteristics of equine influenza viruses, particularly strain A/England 1/79, noting the development of disease in ponies post intranasal instillation and the virus recovery timeline from nasopharynx. Comparison of this strain with prototype A/Miami 1/63 virus reveals no significant antigenic difference.

Experimentation and Observations

• The research initially delves into the experimental procedure where ponies were made to develop disease symptoms by introducing the A/England 1/79 equine influenza virus intranasally. Observable symptoms started to manifest on the fourth day post instillation.
• The virus was found to be present in the nasopharynx of the infected ponies, ranging from day two to day nine post exposure. The nasopharynx is the upper part of the throat behind the nose which connects with the nasal cavity – a typical location for detection of respiratory infections like influenza.

Antigenic Analysis and Comparison

• The study further investigated any antigenic differences or variations between the A/England 1/79 virus and the prototype A/Miami 1/63 virus. Antigens are substances that evoke an immune response, in this case, from the virus. To ascertain this, post infection ferret and chicken sera and post vaccination pony sera were used.
• The findings showed no significant antigenic difference between the A/England 1/79 virus and the prototype A/Miami 1/63 virus. This could imply a level of conserved immunological response between the two influenza viruses based on the cross-reactivity of the sera used in the study.

Antigenic Homogeneity and Hemagglutination Inhibiting (HI) Ability

• Four virus isolates, identified between January and July 1979, were compared for any antigenic differences, findings indicated no significant variances.
• Even though the viruses were antigenically similar, differences were observed in the ability of the strains to detect haemagglutination inhibiting antibody in convalescent horse sera.
• This suggests the variable effectiveness of hemagglutination (the clumping of red blood cells in response to a viral antigen), inhibition which is often employed as an indirect measure to evaluate the presence of antibodies in the blood against a particular virus.