EXPOSURE TIME OF ORAL RABIES VACCINE BAITS RELATIVE TO BAITING DENSITY AND RACCOON POPULATION DENSITY

Authors

Bradley F. Blackwell, USDA/APHIS/WS National Wildlife Research CenterFollow
Thomas W. Seamans, USDA/APHIS/WS National Wildlife Research CenterFollow
Randolph J. White, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services
Zachary J. Patton, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services
Rachel M. Bush, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services
Jonathan D. Cepek, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services

Date of this Version

June 2004

Comments

Published in the Journal of Wildlife Disease 40(2), 2004. pp. 222-229. Copyright Wildlife Disease Association 2004. Permission to use.

Abstract

Oral rabies vaccination (ORV) baiting programs for control of raccoon (Procyon lotor) rabies in the USA have been conducted or are in progress in eight states east of the Mississippi River. However, data specific to the relationship between raccoon population density and the minimum density of baits necessary to significantly elevate rabies immunity are few. We used the 22-km² US National Aeronautics and Space Administration Plum Brook Station (PBS) in Erie County, Ohio, USA, to evaluate the period of exposure for placebo vaccine baits placed at a density of 75 baits/km² relative to raccoon population density. Our objectives were to 1) estimate raccoon population density within the fragmented forest, old-field, and industrial landscape at PBS; and 2) quantify the time that placebo, Merial RABORAL V-RG* vaccine baits were available to raccoons. From August through November 2002 we surveyed raccoon use of PBS along 19.3 km of paved-road transects by using a forward-looking infrared camera mounted inside a vehicle. We used Distance 3.5 software to calculate probability of detection function by which we estimated raccoon population density from transect data. Estimated population density on PBS decreased from August (33.4 raccoons/km²) through November (13.6 raccoons/km²), yielding a monthly mean of 24.5 raccoons/km². We also quantified exposure time for ORV baits placed by hand on five 1-km² grids on PBS from September through October. An average 82.7% (SD=4.6) of baits were removed within 1 wk of placement. Given raccoon population density, estimates of bait removal and sachet condition, and assuming 22.9% nontarget take, the baiting density of 75/ km' yielded an average of 3.3 baits consumed per raccoon anti the sachet perforated.