Immunogenicity of the ERA G 333 rabies virus strain in foxes and raccoon dogs.

The immunogenic properties of ERA G 333 attenuated rabies virus strain in foxes and raccoon dogs by the oral route of administration were examined. This strain is a proposed candidate for oral rabies vaccine in Russia. As was previously demonstrated, the advantage of this virus, provided by the US Centers for Disease Control and Prevention in the framework of the Biotechnology Engagement Program, is apathogenicity for 3-week old and adult mice, as well as for other target and non-target species, even when challenged via the intracerebral route. A group of 12, 7-8 month-old foxes and eight wild captured raccoon dogs were given 2.0 ml of ERA G 333 (titre 107.5 FFU) orally on the tongue. Another three foxes and three raccoon dogs were retained as controls. Blood samples were collected before immunization and on day 60 thereafter. The antibody titres were determined by the fluorescent antibody virus neutralization (FAVN) test. Eight foxes and three raccoon dogs showed seroconversion on day 60 postvaccination. Eleven foxes and four raccoon dogs survived challenge with a virulent rabies virus strain. This study has demonstrated the possibility of using ERA G 333 for the oral vaccination of red foxes and raccoon dogs. Further experiments are needed to determine the effective dose, virus stability, and the strength and duration of immunity.