Bait Ingestion by Free-Ranging Raccoons and Nontarget Species in an Oral Rabies Vaccine Field Trial in Florida

Abstract

Oral rabies vaccine-laden baits, with a tetracycline biomarker, were distributed in Pinellas County (Florida, USA) by helicopter drop and from cars from January to April 1997. A total of 130,320 baits was distributed throughout the county, yielding an average bait density of 185 baits per km 2 . Bait ingestion was estimated by microscopic detection of tetracycline in tooth and bone samples from 244 raccoons (Procyon lotor), 33 opossums (Didelphis virginianus), 31 feral cats, and two gray foxes (Urocyon cinereoargenteus) that were trapped during FebruaryApril 1997. Active surveillance consisted of 17 trapping sites that were further categorized by six community descriptors. Passive surveillance consisted of animals that were collected as nuisance animals by Pinellas County Animal Services. The proportion of tetracycline positive raccoons was compared between collection techniques, among trapping sites, vegetation communities, and age and sex categories. Since there was no statistically significant difference in the frequency of tetracycline positive raccoons trapped during active surveillance (59%, 110/187) and passive surveillance (53%, 30/57), the data were pooled, resulting in a tetracycline positive frequency of 57% (140/244). The range in the positive tetracycline frequency established for raccoons from the 17 active surveillance sites was 9% (1/11) to 100% (3/3). The tetracycline positive frequency for raccoons ranged from 25% (3/12) at the dumpster sites to 78% (14/18) at the landfills. Juvenile male raccoons (71%, 34/48) were the most commonly marked age and sex class and adult females (42%, 21/50) were the least commonly marked age and sex class. Eighty-five percent (28/33) of the opossums, 3% (1/31) of the feral cats, and 50% (1/2) of the gray foxes were tetracycline positive.

A New Flavor-Coated Sachet Bait for Delivering Oral Rabies Vaccine to Raccoons and Coyotes

“…Of these, 12 of 13 sachets remained intact within uneaten or partially eaten baits (30%). These results were similar to those reported in Florida by Olson and Werner (1999). We addressed this problem by testing (Trial 8) a different wax sealant having greater tack or adhesive property for holding sachets more securely within polymer baits.…”

“…Dogs, coyotes, and gray foxes were the principal nontarget species taking baits intended for raccoons. These results are more comparable to those reported by Olson and Werner (1999) in Florida, although their nontarget species composition differed from ours.…”

“…A new high tack sachet wax sealant was selected to more securely seal the vaccine sachet within the polymer bait to reduce the likelihood of the sachet being removed from the bait by raccoons (Olson and Werner, 1999). There was no difference in raccoon removal of baits from stations containing either the old or new sealants.…”

“…In the United States, the extruded fish meal polymer bait for raccoons (Procyon lotor) and coyotes (Bait-Tek, Inc., Beaumont, Texas, USA) has evolved as the current bait of choice for both species (Hanlon et al, 1989;Fearneyhough et al, 1998;Olson et al, 2000). This bait is well accepted by free-ranging animals and is very resistant to adverse environmental conditions (Hanlon et al, 1989).…”

Evaluation and Significance of Tetracycline Stability in Rabies Vaccine Baits

“…Tetracyclines are widely used as biomarkers for monitoring vaccine and contraceptive bait consumption in a variety of carnivores and rodents (Linhart and Kennelly, 1967;Crier, 1970;Cowan et al, 1984;Lefebvre et al, 1988;Hanlon et al, 1989;Perry et al, 1989;Bachman et al, 1990;Savarie et al, 1992;Olson et al, 2000;Rosatte and Lawson, 2001). Target species include coyotes (Canis latrans), feral pigs (Sus scrofa), mongoose (Herpestes javanicus), red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), raccoons (Procyon lotor), skunks (Mephitis mephitis, Spilogale putorius), and opossum (Didelphis virginianus).…”