Duration of serum antibody response to rabies vaccination in horses.

This research studied the duration of the antibody response to rabies vaccination in horses, examining how age and previous vaccination history might impact the lasting effectiveness of the vaccine. Researchers found that previously vaccinated horses maintained an adequate response for 2-3 years, meaning a longer vaccination interval might be possible for these animals. Horses vaccinated for the first time did not show such long-lasting responses, suggesting more frequent vaccinations might be necessary.

Research Objective

• The study aimed to understand how age and inferred prior vaccination history affect the longevity of vaccine-induced protection against rabies in horses. This was accomplished by tracking the horses’ serological response to the rabies vaccination over several years.

Design and Procedures

• The research involved 48 horses with an unknown vaccination history. The horses were given a single rabies vaccine, and blood samples were taken at various intervals before and after vaccination to assess their serum rabies virus-neutralizing antibody (RVNA) levels.
• The recommended protective immune response defined by the World Health Organization for humans, which equates to an RVNA value of ≥ 0.5 U/mL, was used as a benchmark for the horses.
• The RVNA levels were compared between younger (<20 years) and older (≥20 years) horses, as well as those assumed to be previously vaccinated and those thought to be immunologically naive based on pre-vaccination RVNA values.

Results

• It was found that horses presumed to be previously vaccinated maintained a protective RVNA value for 2-3 years.
• The age of the horses did not significantly affect the response/duration of protective RVNA values to rabies vaccination.
• There were seven horses that exhibited poor responses to vaccination. Significant differences in RVNA levels were found between horses assumed to have been previously vaccinated and horses thought to be naive before the study.

Conclusions and Clinical Relevance

• The study concludes that horses that had previously been vaccinated against rabies might be able to go longer than a year between vaccinations.
• However, this was not the case for horses receiving their first rabies vaccination, who might need more frequent inoculations.
• This conclusion warrants further research to verify the findings and refine the optimal primary dose series for rabies vaccination in horses.