A modified bait for oral delivery of biological agents to raccoons and feral swine.

A field study was conducted on Ossabaw Island (Georgia, USA) in March 1994 to evaluate four different types of bait for delivering orally effective biological agents to raccoons (Procyon lotor) and feral swine (Sus scrofa). A deep-fried corndog batter bait, which was previously shown to be ingested by both captive and free-ranging raccoons, and a polymer fishmeal bait which had been shown effective for both raccoons and feral swine were compared with a grain-based dog food meal polymer bait topically coated with corn oil and cornmeal or with fish oil and fishmeal. Tracking stations were used to determine the number of each bait type visited and removed by animals visiting stations. We found no significant differences in the numbers of different baits removed by either species. These data support the results of earlier studies which also indicated that an inexpensive grain-based matrix bait surface-coated with attractive flavors can be used to deliver oral biologics to problem species.

Acceptance of candidate baits by domestic dogs for delivery of oral rabies vaccines.

Protocols for evaluating oral rabies vaccine baits for domestic dogs were field tested in central Mexico, after which dog-food manufacturers and suppliers to the pet-food industry were advised as to potential ingredients for use in prototype dog baits. Bait-preference trials in which confined dogs were used were then undertaken, followed by field tests of free-ranging farmer-owned dogs in three towns in the Nile River Delta region of Egypt. Both confined and free-ranging dogs showed strong preferences for certain baits or bait coatings (poultry, beef tallow, cheese, egg and a proprietary product). Fish-meal polymer baits, widely used for wildlife species, were less preferred. In Egypt, a commercial dog-food-meal bait coated with beef tallow and dry cheese, was consumed at a rate approaching that of a chicken-head bait. The percentage baits that were actually eaten after they had been offered to dogs, ranged from 71-96% for household dogs tested in Mexico, 65-91% for confined dogs (beagles and mixed breeds) tested in the United States, and 32-88% for farmer-owned dogs tested in Egypt.

Oral rabies vaccination of red foxes and golden jackals in Israel: preliminary bait evaluation.

Field trials were conducted in late April to early May of 1995 and 1996 in central Israel to assess the potential for controlling rabies in red foxes (Vulpes vulpes) and golden jackals (Canis aureus) by using vaccine-laden baits. Of the bait types which were field tested, polymer fish meal baits were selected as the most suitable for both species. Fish meal baits containing tetracycline hydrochloride, an oral biomarker, were distributed by four-wheel-drive vehicle at a density of approximately 30 baits/km2 in two test areas of 35 km2. Of the animals which were trapped and euthanized seven to ten days after treatment, 65% of foxes and 56% of jackals gave positive results when tested for the biomarker. These results indicate the potential effectiveness of oral rabies vaccination of these species in Israel and possibly elsewhere in the Middle East, where rabies is a problem in wild canids.

Immunogenicity, efficacy and safety of an oral rabies vaccine (SAG-2) in dogs.

A study of immunogenicity and efficacy of Street Alabama Gif (SAG-2) attenuated rabies virus vaccine in laboratory beagles was conducted. Four groups of ten dogs each received either 1.0 ml of SAG-2 orally on the tongue or 1.5 ml in baits. On day 180 postvaccination, all dogs were challenged with a street rabies virus. The antibody response in groups that received the vaccine directly on the tongue was higher than in those vaccinated with baits, but the difference between groups was not statistically significant. All vaccinated dogs survived, whereas 80% of controls died of rabies. Our findings demonstrate that the SAG-2 is a safe and effective vaccine for oral immunization of canines.

Field evaluation of baits and baiting strategies for delivering oral vaccine to mongooses in Antigua, West Indies.

A field study was conducted on Antigua, West Indies, to determine the feasibility of delivering an oral rabies vaccine or population control agent to free-ranging mongooses (Herpestes javanicus). Two biomarkers (tetracycline hydrochloride [THCL] and DuPont Oil Blue A dye) and two bait types (DuPont polymer fish meal and polyurethane foam) were used to bait three study sites. Four hundred polymer baits containing both biomarkers were distributed at 36 central point bait stations (11 baits/station) on an 80 ha study site (5 baits/ha); 69% of the mongoose population consumed one or more baits. Two thousand baits containing THCL and 400 baits containing DuPont dye were distributed on two additional 100 ha study sites (24 baits/ha). Polymer fish meal baits were used on the first site and polyurethane baits on the second site. Based on the presence of biomarkers in bone or soft tissue, 96 to 97% of the mongooses at both sites consumed at least one bait. We conclude that oral baiting of mongooses is a feasible method for delivery of vaccines for the control of rabies in this species.

Field evaluation of baits and baiting strategies for delivering oral vaccine to mongooses in Antigua, West Indies

A field of study was conducted on Antigua, West Indies to determine the feasibility of delivering an oral rabies vaccine or population control agent to free-ranging mongooses (Herpestes javanicua). Two biomarkers (tetracycline hydrochloride [THCL] and Dupoint Oil Blue A dye) and two bait types (Dupont polymer fish meal and polyurethane foam) were used to bait three study sites. Four hundred polymer baits containing both biomarkers were distributed at 36 central point bait stations (11 baits/station) on an 80 ha study site (5 baits/ha); 69 percent of the mongoose population consumed one or more baits. Two thousand baits containing THCL and 400 baits containing DuPont dye were distributed on two additional 100 ha study sites (24 baits/ha). Polymer fish meal baits were used on the first site and polyurethane baits on the second site. Based on the presence of biomarkers in bone or soft tissue, 96 to 97 percent of the mongooses at both sites consumed at least one bait. We conclude that oral baiting of mongooses is a feasible method for delivery of vaccines for the control of rabies in this species (AU)

A field evaluation of baits for delivering oral rabies vaccines to raccoons (Procyon lotor).

Eight field trials were conducted in 1989 and 1990 in Georgia (USA) and Maryland (USA) to evaluate baits and baiting strategies for delivering oral rabies vaccines to raccoons (Procyon lotor). Bait packets consisting of corn meal and egg batter-based baits enclosed in plastic bags were placed at 1.0-m diameter, raked tracking stations and checked daily. Packets were well accepted by raccoons; they visited 31 to 44% of the tracking stations where they removed 69 to 90% of the packets within 4 to 5 days. All or nearly all baits were removed from plastic bags and less than 1% of the baits were found only partially eaten. No rejection of water-filled paraffin ampules in baits was observed. The use of an odor attractant on bait packets did not appear to enhance bait discovery when packets were placed on raccoon travel routes. An attractant did enhance discovery when baits were placed off-road in a simulated aerial baiting test. Nontarget species comprised 31 to 53% of all visits to the stations; they took 28 to 55% of the baits but did not appear to adversely affect bait availability for raccoons. A total of 2,300 baits, each containing a wax ampule holding 10 mg of a physiological marker (iophenoxic acid), were distributed at a rate of 82 baits/km2 on 2,800 ha of Sapelo Island, Georgia. Thirty-five (65%) of 54 raccoons collected following bait placement had eaten one or more baits as indicated by elevated levels of iodine in the blood serum.

Bait formulation and distribution for oral rabies vaccination of domestic dogs: an overview.

Current efforts to develop oral rabies vaccine baits for domestic dogs are reviewed and new materials (bait matrices, additives, vaccine containers, vaccine modification) for improving bait acceptance and vaccine delivery are suggested. Methods that have been used to evaluate the food or bait preferences of confined and free-ranging animals are summarized, as are the guidelines for bait distribution compiled by the World Health Organization.

Evaluation of baits for oral rabies vaccination of mongooses: pilot field trials in Antigua, West Indies.

A field study was conducted on the island of Antigua, West Indies, to evaluate baits for delivering an oral rabies vaccine to the small Indian mongoose (Herpestes auropunctatus). Tracking tiles were used to determine that mongooses were nonselective and took both egg-flavored polyurethane baits and fish-flavored polymer baits containing several different food materials. A high proportion of baits were taken the day of placement with minimal disturbance by nontarget species. DuPont Oil Blue A dye was an effective short-term biomarker for use in baits; based on its subsequent detection in mongooses, some of the population had consumed and not cached or discarded baits. Central point baiting stations showed promise as an alternative delivery technique.

Evaluation of baits for oral rabies vaccination of mongooses: pilot field trials in Antigua, West Indies

A field study was conducted on the island of Antigua, West Indies, to evaluated baits for delivering an oral rabies vaccine to the small mongoose (Herpestes auropunctatus). Tracking tiles were used to determine that mongooses were nonselective and took both egg-flavored polyurethane baits and fish-flavored polymer baits containing several different food materials. A high proportion of baits were taken the day of placement with minimal disturbance by nontarget species. DuPont Oil Blue A dye was an effective short-term biomarker for use in baits;based on its subsequent detection in mongooses, some of the population had consumed and not cached or discarded baits. Central point baiting stations showed promise as an alternative delivery technique (AU)

Some factors affecting the oral rabies vaccination of free-ranging carnivores.

Conditions which affect the outcome of oral rabies vaccination programs include environmental factors, and the behaviour, population densities and dynamics of target and non-target species. Examples are given from recent research and the literature.

A field evaluation in Mexico of four baits for oral rabies vaccination of dogs.

We evaluated four baits for the delivery of oral rabies vaccines to dogs. In a controlled study in a town in rural Mexico, 177 randomly selected dogs were assigned to receive one of four experimental baits (two of which were developed by the Denver Wildlife Research Center [DWRC]): one of two cylindrical polyurethane sponges with a corn meal coating (one fried in corn oil [DWRC-corn], the other in fish oil [DWRC-fish]), a fish-flavored polymer bait, or a wax bait. Each dog was also offered a commercial dog biscuit. We recorded whether or not the bait was completely consumed, and used the following measures to estimate the amount of oropharyngeal contact with each bait: total chewing time, presence of pieces of bait on the ground following administration, the total area of ground surrounding the location of ingestion that was covered with green dye contained in each bait, and condition of ampules that contained the dye. The dog biscuits were completely consumed significantly more often than the baits (155 of 176 [88%] for the biscuits versus 89 of 176 [50.5%] for the four baits; P less than 10(-6)), but were chewed for a significantly shorter time than the baits (mean time 34 sec for the biscuit versus 60-82 sec for the four baits: P less than 0.001). The ideal bait would probably combine the attractiveness of the commercial biscuit and the ability of the sponge baits to promote contact with the mucous membranes.

Formulation and evaluation of baits for oral rabies vaccination of raccoons (Procyon lotor).

Captive raccoons were offered a variety of vaccine containers and bait components in a series of three-choice tests. Paraffin wax ampules were the most readily accepted vaccine container. Preferred bait components included corn and shellfish oils, deep fried corn meal batter, and egg, apple and buttermilk flavorings. These results, together with factors including ease of bait formulation, cost, and suitability for field use, were used to develop an experimental delivery system for an oral rabies vaccine. The developed system was composed of a polyurethane sleeve (1.5 x 5.5 cm) dipped in a commercial food batter mix together with corn meal, milk and egg. The sleeve was deep fried in corn oil and a 2.0 ml ampule containing a recombinant rabies vaccine was then inserted into the sleeve bait. These baits were presented to 10 captive raccoons. Nine of the 10 animals developed high levels of rabies virus neutralizing antibodies. Field tests are needed to determine if the delivery system developed also is effective for wild raccoons.