Factors influencing the antibody response of dogs vaccinated against rabies

Since 2000, there has been a legal requirement in the UK that dogs and cats should have an effective rabies vaccination with demonstrable sero-conversion if their owners wish to avoid quarantine on re-entry to the UK. In 2002, 10,483 rabies titres were determined on dogs at the VLA. Statistical analyses assessed the efficacy of each vaccine within different dog breeds. Animal size, age, breed, sampling time and vaccine had significant effects on pass rates and median titres. Our data suggests that a general relationship between animal size and level of antibody response exists and smaller sized dogs elicited higher antibody levels than larger breeds of dog. It was not however, only the magnitude of response immediately following vaccination but also the duration of immunity that varied between breeds of dog. Another observation was that young animals, less than 1-year of age, generated a lower antibody response to rabies vaccination than adults. Considerably higher failure rates were also observed for different vaccines tested. Regression analysis revealed that two vaccines performed equally well, and significantly better than the others tested. The variation in antibody response relating to length of interval of sampling following vaccination is not unexpected and presumably relates to the response kinetics for primary vaccination. These data need to be placed in perspective in order to minimise the risk of rabies being re-introduced into a rabies-free country, especially in the consideration of removing the requirement for serological testing for rabies vaccinated dogs that participate in pet travel schemes.