Comparison of Antibody Responses after Vaccination with Two Inactivated Rabies Vaccines in Thimphu Dogs

Abstract

We compared the antibody responses after vaccination with two commercially available inactivated rabies vaccines – Rabisin (Merial, France) and Raksharab (Indian Immunologicals) in dogs in Thimphu city, Bhutan. Fifty puppies were randomly assigned to two groups of 25 each and one group was subcutaneously vaccinated with a single dose of Rabisin and other group with Raksharab rabies vaccines as primary vaccination on day 0. Similarly, 50 adult dogs were also randomly assigned to two groups of 25 each and each group wassubcutaneously vaccinated with a single dose of Rabisin and Raksharab vaccines as booster vaccination. Serum samples were collected on day 0 (prior to vaccination), 14 and 28 from all the dogs. Rabies antibodies were measured over a period of 28 days using SERELISA® Rabies Ab Mono Indirect enzyme-linked immunosorbent assay (ELISA). A total of 198 blood samples from 66 dogs (3 sample each on day 0, 14 and 28) were collected and analyzed. Eight puppies (8/35; 22.86% belonging to Raksharab (n=7) and Rabisin vaccination group (n=1) demonstrated a minimum protective antibody titre (≥0.5 IU/ml) ranging from 0.6 to 2.75 IU/ml while the remaining puppies (n=27) demonstrated an antibody titre ranging from 0.1 to 0.45 IU/ml on day 0 (prior to primary vaccination). The antibody titre level increased after primary vaccination ranging from 0.21 to 4.78 IU/ml and 0.16 to 7.38 IU/ml under Rabisin group on day 14 and 28, respectively, and from 0.59 to 5.80 IU/ml and 1.19 to 6.76 IU/ml under Raksharab group on day 14 and 28, respectively. In adult dogs under Rabisin booster vaccination group, 56% (9/16) of the dogs had ≥0.5 IU/ml of antibody titre (ranges: 0.25 to 6.45 IU/ml) on day 0 (before vaccination) and all dogs attained protective titre on day 14 (ranges: 1.07 to 6.46 IU/ml) and on day 28 (ranges: 2.22 to 10.26 IU/ml). Similarly, under Raksharab booster vaccination group, 56% (9/16) of the dogs had ≥0.5 IU/ml of antibody titre (ranges: 0.27 to 5.39 IU/ml) on day 0 (before vaccination). Excepting one adult male dog, all other dogs attained protective titre (≥0.5 IU/ml) on day 14 (ranges: 0.62 to 5.59 IU/ml) and on day 28 (ranges: 1.86 to 6.66 IU/ml). The findings showed that both the inactivated vaccines have elicited minimum threshold level for protection (≥0.50 IU/ml) responses as per the recommendation of the World Animal Health Organization (OIE) and World Health Organization (WHO), indicating that the vaccines used in Bhutan are potent and efficient and thus, acceptable for primary and booster vaccination against rabies in dogs.