Field studies of an attenuated Venezuelan equine encephalomyelitis vaccine (strain TC-83).

The research investigates the effectiveness and safety of a strain TC-83 attenuated Venezuelan equine encephalomyelitis vaccine used in horses, looking specifically at the rate of immune response, the level of the virus detected in the blood after vaccination, and any potential adverse reactions.

Research Objective

• The research aimed to determine the effectiveness of the strain TC-83 attenuated Venezuelan equine encephalomyelitis vaccine in horses. This was evaluated by studying the rate of seroconversions, post-vaccination viremia, and any potential adverse reactions to the vaccine.

Seroconversion

• Seroconversion is the period of time during which a specific antibody develops and becomes detectable in the blood. It generally represents the point of immune response to an infection or vaccination.
• The rate of seroconversion indicates how many of the vaccinated horses developed an immune response. This rate varied across different studies, with the lowest being 50% in one study and the highest reaching 100% in others.

Post-vaccination Viremia

• Viremia refers to the presence of viruses in the blood. In this context, post-vaccination viremia is the measurement of the virus after administering the vaccine.
• The peak level of viremia recorded was between 7 x 10(3) and 8 x 10(3) plaque-forming units per ml. This level helps assess the immune response generated by the vaccine and how well it helped in controlling the virus.

Adverse Reactions

• The study also focused on identifying any potential adverse reactions to the vaccine. This is pivotal in assessing the safety aspect of the vaccine.
• The study found no adverse reactions in any of the vaccinated horses, which included 42 pregnant mares and their resulting foals. This demonstrates the vaccine’s safety and tolerance in different demographic groups among horses.