Kinetic of rabies antibodies in dogs prime vaccinated

Abstract

Half of the world population (3.5 billion people) occupies areas where there is an increase of dogs, cats and rodents, and zoonosis transmitted by these animals, where rabies is the most worrisome. The protection of humans against urban rabies is achieved mainly by the prophylaxis of dog and cat with vaccines that induce a minimum of antibody titers (≥ 0.5 IU/mL). This study aimed to evaluate the kinetic of antibodies in dogs that were prime vaccinated with Fuenzalida&Palácios modified vaccine during 12 months. Materials and methods: The study was conducted in 2009 during the 41st Annual vaccination campaign against rabies in dogs and cats in the urban area of Botucatu, São Paulo, Brazil. It was considered to determine the sample size at 95% confidence along an estimation error of the order of 10% random contribution associated with the casual participation of the animal. Thus, the study involved 576 dogs over the age of three months, never vaccinated against rabies before, regardless of breed, age or sex randomly selected for blood collection. Samples were collected during five moments at the study period, which are: 0 (first dose of vaccine), 1 [30 days after first vaccination (dafv) and the second dose of vaccine], 2 (60 dafv), 3 (180 dafv) and 4 (360 dafv). Thirty days after the first vaccination (time 1) dogs received the booster vaccination with the same type of vaccine (Fuenzalida&Palácios modified vaccine- Institute of Technology of Paraná – TECPAR®). Serum neutralizing antibodies to rabies was held at the Center for Zoonosis Control of São Paulo trough the rapid fluorescent focus inhibition test (RFFIT). Results: Total (urban and rural) of rabies vaccination coverage reached 81.36% in Botucatu / SP, and 3229 (16.97%) of dogs in urban were first time vaccinated. At 360 days after first vaccination, only 51.5% of the dogs had protective titers throughout over all period of the study (over 5 moments). Discussion and conclusion: In Brazil, by the Control Program, the canine rabies vaccination is annual and mandatory after three months of age. The low concentration of antibodies after vaccination of dogs against rabies has been reported, also the immune response of dogs with prime vaccination (Fuenzalida&Palácios modified vaccine) without booster was evaluated, where the results observed rapid decline of antibody titers, suggesting that many animals cannot be protected between the campaigns. According to the Institute Pasteur in 2000, titers below 0.5 IU/mL do not confer protection against rabies. In addition, rabies can infect the dogs at any period during the campaigns. The coverage of vaccination shows weak protection, since only 51.5% of dogs had protective titers at all time of moments analyzed. Furthermore, it is also known that half of the dogs prime vaccinated are not immunized against rabies virus after 12 months, the results allow us to infer a new vaccination strategy in dogs prime vaccinated should be adopted.