Evaluations of parenteral vaccination and alternative oral vaccine delivery systems as potential management strategies for raccoon rabies

The commensal nature of the raccoon amplifies the biological, economic and social repercussions associated with rabies when the disease becomes established in the population. In the absence of a licensed oral rabies vaccine in the United States, a trap-vaccinate-release effort was tested as a potential method for controlling raccoon rabies. During 1992, 481 individuals (i.e., 167 (35%) juveniles, 308 (64%) adults, and 6 (1%) undetermined) were immunized. In 1993, 376 raccoons (i.e., 163 (43%) juveniles and 213 (57%) adults) were vaccinated. Forty-three percent of 61 vaccinated raccoons demonstrated virus neutralizing antibody titers {dollar}geq{dollar}0.5 IU one year after vaccination. Significantly fewer rabid raccoons were reported from the vaccinated portion of the study area (i.e., 24% of 83), when compared to the unvaccinated portion (i.e., 66% of 106).; A remote-controlled, low-light videography system was used to record raccoon interactions with baits in rural and urban study areas. Rural raccoons accepted and consumed the Ontario fox bait and fishmeal-polymer raccoon bait. Both rabies baits were usually rejected by urban animals. Commercial marshmallow baits were universally accepted by raccoons regardless of site location. Rural raccoons generally consumed all available baits before leaving the study area; no bait preference was observed.; A new raccoon bait was formulated because existing vaccine baits were not readily accepted by raccoons in the urban/suburban environment. The Cornell Vaccine Delivery System was tested at: a density of 200 baits/km{dollar}sp2{dollar} in an urban/suburban raccoon population during the summer of 1993. An iophenoxic acid biomarker was incorporated in the vaccine chamber of each bait. Serum analyses determined that 70% of 69 raccoons were biomarker positive when compared to negative background sera collected during 1992. A final field inspection, completed 17 days after distribution, determined that 71% of 113 baits were consumed or removed from the placement site.; During 1994, the newly-formulated Ontario raccoon bait was evaluated during a similar, urban/suburban summer trial. Biomarker analyses demonstrated that 91% of 46 raccoons were seropositive. After 17 days, 93% of 209 baits were consumed or removed.; A fixed-wing aircraft (Ministry of Natural Resources) was used to distribute Ontario raccoon baits over a 48-km{dollar}sp2{dollar} rural environment (i.e., bait density = 75 baits/km{dollar}sp2{dollar}) during a collaborative effort to effect the first cooperative, international aerial bait delivery in the United States. Thirty-eight (84%) of 45 raccoons were biomarker positive.