Persistence of antibody titres in adult dogs and puppies following anti-rabies immunization

In Sri Lanka, the first dose of pre-exposure antirabies vaccine is given to puppies at the age of 3 months with annual boosters. There have been many instances where puppies of less than 3 months have been affected with rabies. Antirabies vaccination failures have also been reported. Therefore, it is important to know the duration of protection in dogs following antirabies immunization. Animals for this study were divided into two main groups (adult dogs and puppies) and further subdivided into 4 groups (adult dogs with a past immunization history against rabies, adult dogs without a past immunization history, puppies of immunized bitches and puppies of unimmunized bitches). In this study, neutralizing antibody titres in puppies and adult dogs following pre and post anti-rabies immunization were determined by the rapid fluorescent focus inhibition test. All animals were bled on days 0 (D0 preimmunization), 30 (DJ 0), 180 ( D | g 0 ) and 360 (t>3 J . Titres were less than 0.5 IU/mL (protective antibody titre against rabies) in DQ samples of all puppies recruited for this study, in 26.7% of DJ 0 samples of puppies of unimmunized bitches, in 89.5% of D| 8 0 samples of puppies and in all DJ 60 samples of puppies. Antibody titres in 50% of DJ 6 0 samples of adult dogs without a previous immunization history were also less than 0.5 IU/ mL. Antibody titres of all dogs with a past immunization history against rabies, were maintained above the protective level 1 year after immunization. Based on the results of this study, it is recommended that puppies should be immunized against rabies before the age of 3 months with a booster at a suitable interval. Thereafter, annual revaccination should be done. Adult dogs without a past immunization history also should be given two anti-rabies vaccines in the first year at a suitable interval in order to maintain a protective antibody titre until the annual booster.