Potency of two rabies vaccines in cats as determined by antibody assay and virulent virus challenge

The persistence of immunity induced by a modified live virus rabies vaccine (SAD strain) and an inactivated rabies vaccine combined with panleukopenia vaccine in cats was studied serologically and by virulent rabies virus challenge. The source of challenge virus was a suspension of a dog salivary gland. All 16 cats vaccinated with the inactivated vaccine developed high antibody titres and 15 were protected against the virus challenge. All 8 cats vaccinated with the MLV vaccine produced a serological immune response but 5 cats were not protected against the virus challenge. Some reasons for this phenomenon are discussed.