A new competitive enzyme-linked immunosorbent assay demonstrates adequate immune levels to rabies virus in compulsorily vaccinated Japanese domestic dogs.

A competitive enzyme-linked immunosorbent assay (c-ELISA) was developed as an alternative to the viral neutralization (VN) test for rapid and simple detection of antibodies to rabies virus. The competitor antibody in the c-ELISA was a biotinylated monoclonal antibody to the nucleoprotein of rabies virus. Initial comparisons showed a high correlation between titers obtained with the VN test and the c-ELISA (n = 88, r = 0.90), indicating that the c-ELISA could be used as a reliable substitute for the VN test. To evaluate the immune status of Japanese dogs to rabies virus, a total of 1,019 serum samples were collected from domestic dogs in 1994 and tested for antibodies with the c-ELISA. Overall, 84.8% of the dogs had antibodies against rabies virus, indicating that the vaccination strategy for preventing rabies outbreaks in domestic dogs is probably sufficient in Japan. Dogs receiving final vaccinations a year or more previously were 48.3 and 90.3% positive for antibodies when vaccinated once only or two or more times, respectively. This suggests that almost all dogs vaccinated twice or more remain seropositive for over 1 year in Japan.