A baiting system for delivery of an oral plague vaccine to black-tailed prairie dogs

Laboratory and field studies were conducted between July and October 1999 to identify bait preference, biomarker efficacy, and bait acceptance rates for delivering an oral plague vaccine to black-tailed prairie dogs (Cynomys ludovicianus). Twenty juvenile captive prairie dogs were offered alfalfa baits containing either alfalfa, alfalfa and 5% molasses, or alfalfa, 5% molasses and 4% salt. Based on the results of these trials we selected a bait containing alfalfa, 7% molasses, and 1% salt for field trials to determine bait acceptance rates by free-ranging animals. The biomarkers DuPont Blue dye, iophenoxic acid, and tetracycline hydrochloride were orally administered to captive prairie dogs to determine their efficacy. Only tetracycline proved effective as a biomarker. Two field trials were conducted at separate prairie dog colonies located at the Buffalo Gap National Grassland (Pennington County, South Dakota, USA). In Trial 1, three baits containing tetracycline were distributed around each active burrow entrance and an additional bait was placed inside the burrow (1,276 baits total). In Trial 2, baits were distributed at the same density per burrow as Trial 1, but along transects spaced 10 m apart (1,744 baits total). Trapping began 3 days after bait distribution, and 30 prairie dogs then were captured at each site to determine the percentage of animals marked. In Trial 1, 67% of the prairie dogs captured had tetracycline deposits indicative of bait consumption. In Trial 2, 83% of the prairie dogs had ingested a bait. Approximately 15% of the animals in both trials ate more than one bait. Fleas (Opisocrostis hirsutus) were found on 64 of 70 (91%) of the prairie dogs captured during this study.     

Factors Influencing Uptake of Sylvatic Plague Vaccine Baits by Prairie Dogs

Sylvatic plague vaccine (SPV) is a virally vectored bait-delivered vaccine expressing Yersinia pestis antigens that can protect prairie dogs (Cynomys spp.) from plague and has potential utility as a management tool. In a large-scale 3-year field trial, SPV-laden baits containing the biomarker rhodamine B (used to determine bait consumption) were distributed annually at a rate of approximately 100–125 baits/hectare along transects at 58 plots encompassing the geographic ranges of four species of prairie dogs. We assessed site- and individual-level factors related to bait uptake in prairie dogs to determine which were associated with bait uptake rates. Overall bait uptake for 7820 prairie dogs sampled was 70% (95% C.I. 69.9–72.0). Factors influencing bait uptake rates by prairie dogs varied by species, however, in general, heavier animals had greater bait uptake rates. Vegetation quality and day of baiting influenced this relationship for black-tailed, Gunnison’s, and Utah prairie dogs. For these species, baiting later in the season, when normalized difference vegetation indices (a measure of green vegetation density) are lower, improves bait uptake by smaller animals. Consideration of these factors can aid in the development of species-specific SPV baiting strategies that maximize bait uptake and subsequent immunization of prairie dogs against plague.     

Acceptance of baits for delivery of oral rabies vaccine to raccoons.

During 1993-96 the Ontario Ministry of Natural Resources (Canada) implemented a research project to evaluate the efficacy of three candidate baits to deliver oral rabies vaccine to wild raccoons (Procyon lotor). Extensive field testing revealed that raccoon acceptance of Sugar-Vanilla baits (SV) at densities of 200/km2 and 400/km2, hand-placed in urban habitats of Scarborough (Ontario) during 1993, was 74% and 82%, respectively. Raccoon density in those areas averaged 11/km2. Aerial placement of SV baits in rural habitats in Barrie (Ontario) during 1993 and 1994, yielded raccoon acceptance levels of 58% with a density of 100 baits/km2, 59% at 75 baits/km2, and 47% at 50 baits/km2. Raccoon acceptance of SV baits was significantly lower in areas baited at the density of 50/km2. Acceptance of Cheese baits (CH) at a density of 75 baits/km2 was 52%. During 1996 trials in Barrie, modified SV baits with blister packs protruding through the matrix yielded raccoon acceptance values of 51% at a bait density of 54/km2, whereas acceptance of regular SV baits was 39% at a density of 51 baits/km2. Pooling of bait acceptance data for all years revealed that bait acceptance was highest for adult male raccoons. Raccoon density in rural habitats (Barrie, Ontario) where the studies took place, averaged 11-13/km2. Puncture and impact testing of blister packs in baits suggested that they would adequately serve as a vehicle to contain oral rabies vaccine for delivery to raccoons via baits.     

Exposure time of oral rabies vaccine baits relative to baiting density and raccoon population density

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 a 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/ km2 yielded an average of 3.3 baits consumed per raccoon and the sachet perforated.     

Development of a bait and baiting system for delivery of oral rabies vaccine to free-ranging African wild dogs (Lycaon pictus)

The objective of the study was to develop a bait and baiting system capable of delivering one effective dose of oral rabies vaccine to each member of a free-ranging African wild dog (Lycaon pictus) pack. Trials were conducted between June and October 2000. The results of cafeteria-style bait preference trials testing seven candidate baits in captive wild dogs revealed a significant preference for chicken heads (June trials: P = 0.023, September trials: P = 0.021). Trials using a topical biomarker (rhodamine B) showed that chicken head baits were sufficiently chewed on most occasions to rupture the vaccine container. Free-ranging wild dogs and young pups ingested chicken head baits. Significant dominance of bait intake by a single individual was seen in four of six study packs and in the three packs in which an alpha pair could be distinguished, the dominant feeder was an alpha animal. Pattern of bait distribution and degree of satiation had no effect on pack coverage (proportion of pack ingesting at least one bait). Pack coverage was significantly related to trial number (r = 0.71, P < 0.001), with pack coverage increasing with increased exposure of the pack to the baits. During 46 hr of diurnal observations of free-ranging wild dogs only two baits were lost to non-target species. A baiting system for the oral vaccination of captive and free-ranging wild dogs is proposed.     

Comparison of suburban vaccine distribution strategies to control raccoon rabies

Helicopters and hand baiting are commonly used to distribute vaccine-laden baits to help control raccoon (Procyon lotor) rabies in suburban landscapes, but these techniques may be labor intensive, costly, or unavailable in some areas. We tested conventional baiting strategies against polyvinyl-chloride (PVC) bait stations in Erie County (New York, USA) during July and August 2003-05. Hand, helicopter, and bait station treatments were randomly assigned to six 25-km(2) suburban study sites. To estimate the proportion of raccoons that ingested baits, tooth and blood samples from 954 raccoons were collected and examined for tetracycline biomarker and rabies-neutralizing antibodies, respectively. Overall, 38% (358/954) of the raccoons in Erie County tested positive for tetracycline; 16% (155/954) tested seropositive for rabies virus. Year of study significantly impacted biomarker prevalence; fewer raccoons tested positive for tetracycline in 2004. Probability of seropositivity increased with raccoon age. No statistically significant differences existed between baiting strategies and frequencies of biomarker and antibody-positive raccoons across all years combined. Thus, bait stations could be used as part of an integrated rabies control strategy.     

Control of rabies in Slovenia

Red foxes (Vulpes vulpes) are the main reservoir of rabies in Slovenia, whereas cases of rabies in other wildlife species occur sporadically. In 1995, a program of oral vaccination of wildlife in Slovenia was initiated; baits with oral vaccine were distributed by air at a density of 20 baits/km(2). During 1995, when the oral vaccination program was started, 1,089 cases of rabies (including both wild and domestic animals) were reported. Five years later (1999), only six positive animals were detected among 1,195 tested (0.5%). Despite an increase in bait density (25 baits/km(2)) during the years 2000 and 2001, reported rabies cases increased to 115 and 135, respectively. In 2003, following initiation of a new bait-dropping strategy, which incorporated perpendicular rather than parallel flight lines, the number of rabies cases decreased to eight.     

Species-specific visitation and removal of baits for delivery of pharmaceuticals to feral swine

Within the domestic swine industry there is growing trepidation about the role feral swine (Sus scrofa) play in the maintenance and transmission of important swine diseases. Innovative disease management tools for feral swine are needed. We used field trials conducted in southern Texas from February to March 2006 to compare species-specific visitation and removal rates of fish-flavored and vegetable-flavored baits with and without commercially available raccoon (Procyon lotor) repellent (trial 1) and removal rates of baits deployed in a systematic and cluster arrangement (trial 2). During trial 1, 1) cumulative bait removal rates after four nights ranged from 93% to 98%; 2) bait removal rates by feral swine, raccoons, and collared peccaries (Pecari tajacu) did not differ by treatment; and 3) coyotes (Canis latrans) removed more fish-flavored baits without raccoon repellent and white-tailed deer removed more vegetable-flavored baits without raccoon repellent than expected. During trial 2, feral swine removed fish-flavored baits distributed in a cluster arrangement (eight baits within 5 m2) at a rate greater than expected. Our observed bait removal rates illustrate bait attractiveness to feral swine. However, the diverse assemblage of omnivores in the United States compared with Australia where the baits were manufactured adds complexity to the development of a feral swine-specific baiting system for pharmaceutical delivery.     

Proposed field evaluation of a rabies recombinant vaccine for raccoons (Procyon lotor): site selection, target species characteristics, and placebo baiting trials

Prior to a limited field application of an orally-administered vaccinia-rabies glycoprotein (V-RG) recombinant virus vaccine for wildlife, background data were obtained for the proposed site on Parramore Island, Virginia (USA). Mammalian target and nontarget species, potentially at risk for exposure to vaccine were inventoried. Placebo baiting trials with a fishmeal polymer bait resulted in high bait disturbance (88 to 100%), primarily by raccoons (Procyon lotor), with infrequent visitation and no evidence of bait consumption by deer (Odocoileus virginianus), small mammals or avian species. Definitive bait acceptance rates by raccoons (indicative of bait ingestion) were difficult to accurately determine based exclusively on premolar and vibrissae samples collected antemortem from live-trapped raccoons for tetracycline and rhodamine B biomarker analyses, respectively. Bait acceptance rate was more accurately determined during a pilot baiting trial conducted on North Island, South Carolina, when mandibles (postmortem samples) were examined for tetracycline incorporation. Parasitologic findings in raccoons on Parramore Island included Hepatozoan procyonis, Phagicola angrense and Physaloptera rara and a variety of incidental microscopic lesions, and provided baseline pathological data for comparison subsequent to V-RG vaccine application. A population density estimate of one raccoon/2.7 ha was calculated using mark-recapture data for comparison after vaccine deployment. Limited reproductive data, including estimates of pregnancy rates by palpation, the number of live kits/litter live-trapped with previously pregnant raccoons or observed in the dens of radio-collared raccoons, was gathered to assess the effect of proposed oral vaccination with V-RG vaccine. Home ranges were assessed by radio-telemetry of 15 raccoons; all radio-collared raccoons currently reside on Parramore Island.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of non-toxic bait interference for indexing brushtail possum density

Percentage non-toxic bait interference is currently used by local authorities to monitor brushtail possum control operations but the validity of the method has not been established. Two models have been proposed to estimate an index of possum density (possums per bait) from a log-transformation of percentage bait interference. In two trials, percentage bait interference and the density index derived from percentage bait interference using the Bamford (1970) model usually increased from night to night. Variation in the number of possums per bait was reduced by dividing the Bamford index by the number of nights baits were put out, as proposed by Jane (1981). The spatial distribution of bait interference along lines of bait stations was random for the first night and usually for at least 5 nights. Rhodomine dye and cyanide poison, alternated at bait stations after at least 5 nights non-toxic baiting, showed that about 83% of possums in one trial and 29% of possums in the other trial interfered with more than one bait on the same night. Increasing the spacing between bait stations reduced the proportion of possums interfering with more than one bait. The number of possums per line killed by cyanide baits after at least 5 nights of non-toxic baiting was strongly correlated with percentage bait interference, with and without logarithmic transformation, on the first night. The possums' apparent ability to remember the location of bait stations from one night to the next means that, in the absence of better advice, the original Bamford (1970) model should be modified as proposed by Jane (1981) to estimate possum density and change in possum density (e.g., from pre- to post-poison).     

Impacts on nontarget avian species from aerial meat baiting for feral pigs

Bait containing sodium fluoroacetate (1080) is widely used for the routine control of feral pigs in Australia. In Queensland, meat baits are popular in western and northern pastoral areas where they are readily accepted by feral pigs and can be distributed aerially. Field studies have indicated some levels of interference and consumption of baits by nontarget species and, based on toxicity data and the 1080 content of baits, many nontarget species (particularly birds and varanids) are potentially at risk through primary poisoning. While occasional deaths of species have been recorded, it remains unclear whether the level of mortality is sufficient to threaten the viability or ecological function of species. A series of field trials at Culgoa National Park in south‐western Queensland was conducted to determine the effect of broadscale aerial baiting (1.7 baits per km²) on the density of nontarget avian species that may consume baits. Counts of susceptible bird species were conducted prior to and following aerial baiting, and on three nearby unbaited properties, in May and November 2011, and May 2012. A sample of baits was monitored with remote cameras in the November 2011 and May 2012 trials. Over the three baiting campaigns, there was no evidence of a population‐level decline among the seven avian nontarget species that were monitored. Thirty per cent and 15% of baits monitored by remote cameras in the November 2011 and May 2012 trials were sampled by birds, varanids or other reptiles. These results support the continued use of 1080 meat baits for feral pig management in western Queensland and similar environs.     

Prevalence of tetracycline and rabies virus antibody in raccoons, skunks, and foxes following aerial distribution of V-RG baits to control raccoon rabies in Ontario, Canada

More than 3.6 million baits containing a recombinant vaccinia virus-rabies glycoprotein (V-RG) oral rabies vaccine were aerially or hand-distributed during 1999-2006 in an approximate 4,000-9,000 km(2) area of eastern Ontario, Canada, as part of a multitactic approach to control the raccoon variant of rabies. The efficacy of the program was assessed through the collection and testing of > 6,900 animals for bait acceptance and rabies virus-specific antibodies. Raccoon acceptance of rabies vaccine baits was significantly greater (71-83% ) in areas baited at a density of 150 baits/km(2) compared to areas baited at 75 baits/km(2) (26-58% ), and more raccoons consumed vaccine baits in areas baited with a flight line spacing of 0.75 km (45.3% [321/708]) than with a spacing of 1.5 km (33.8% [108/320]). In addition, greater numbers of raccoons consumed vaccine baits during a drop in September (52.7% [213/404]) as opposed to a June bait drop (34.6% [216/624]). Seropositivity rates for raccoons ranged between 7% and 28% in areas baited at 75/km(2) and 10% to 27% in areas baited at 150/km(2) with statistical differences varying among years and treatments. The last case of raccoon-variant rabies reported in Ontario was in September 2005. The control of raccoon rabies in Ontario has resulted in an estimated $6M to $10 M Cdn annual savings in rabies-associated costs.     

Specificity and success of oral-bait delivery to Eurasian wild boar in Mediterranean woodland habitats

Eurasian wild boar (Sus scrofa) is an important reservoir host for pathogens affecting humans and domestic animals. The eradication of these diseases may require the development of control strategies that reduce pathogen transmission between wildlife and domestic animals. Baiting for oral vaccine delivery is often considered for wildlife disease control. The effective and efficient field vaccination of wildlife requires species-specific baits as delivery vehicles for oral vaccines and designing appropriate baiting strategies. The objective of this study was to determine the proportion of young and adult wild boar and non-target animals that consumed baits containing a chemical marker, iophenoxic acid (IPA), in delivery trials conducted in summer in four different sites in the Mediterranean region of Spain where wild boar are abundant. The proportion of wild boar showing IPA markers in serum in autumn ranged from 11.5% to 56.4%. When attending to age classes, 12.6% to 72.7% of young individuals presented IPA. The results evidenced that the percent of wild boar that ingested the baits varied among study sites and age classes. Placing baits inside selective cages (for juveniles) and under heavy pavel stones (for adults) contributed to improve age specificity in bait consumption. We suggest ways for improving the age specificity of bait delivery systems used for young and adult wild boar.     

A new flavor-coated sachet bait for delivering oral rabies vaccine to raccoons and coyotes

Research was conducted during 1996-2000 to develop baits for delivering an oral rabies vaccine to raccoons (Procyon lotor) and coyotes (Canis latrans). A bait was sought that: (1) was attractive to the target species, (2) could be distributed by aircraft, (3) was as effective (or more so) than the currently used fish meal polymer bait, and (4) could be produced in large numbers by automated procedures and could be purchased by user groups at substantially lower cost. Ten field trials were conducted to document raccoons' bait flavor preferences, evaluate a new vaccine sachet bait coated with various attractants, and determine if the sachet bait would effectively deliver Raboral V-RG oral rabies vaccine (Merial Limited, Athens, Georgia, USA) to this species. Raccoons preferred fish and crustacean-based flavors over those derived from plant materials. Raccoon visits to tracking stations, frequency of bait removals, and percent of sachets discarded by this species that were emptied of placebo vaccine indicated efficacy of the new bait was equal or superior to the currently used fish meal polymer bait. A field trial conducted in fall 1998 compared aerially distributed vaccine-laden sachet and polymer baits and showed there was no difference between the percent of raccoons from the test and reference areas subsequently found positive for rabies antibody. Four bait trials to determine coyote response to sachet baits were conducted in 1997-98. The propensity for canids to gulp or bolt smaller food items is well known. Thus, a first trial involved offering fish-flavored sachet baits of different sizes to 30 captive coyotes to determine if smaller size baits were more frequently swallowed intact. Two field trials were also conducted in fall 1997 to determine if free-ranging coyotes discriminated among sachet baits coated with different attractants. Finally, Raboral V-RG-laden poultry-flavored sachet baits were aerially dropped and the percent of seropositive coyotes was compared with coyotes from surrounding areas where fish meal polymer vaccine baits had been distributed. Captive coyotes did not swallow sachet baits intact, regardless of size. Bait preference field trials indicated that coyotes preferred poultry, cheese/beef tallow, and fish-flavored sachet baits and that such baits were taken at the same rate as polymer baits. A sample of coyotes from the area baited with vaccine-laden sachet baits had a markedly higher (P = 0.01) seropositivity rate than coyotes from areas where vaccine was distributed in polymer baits. Sachet bait production could be facilitated by automated technology and sachet baits used either as an alternative vaccine delivery device or in combination with the fish meal polymer bait.     

Sampling subterranean termite species diversity and activity in tropical savannas: an assessment of different bait choices

Abstract.  1. Cellulose baits are commonly used for semi-quantitative sampling of subterranean wood-feeding termites, with a single food choice sampling programme implemented most often. In most situations, however, the composition and feeding preferences of the subterranean termite assemblage remain unknown.
2. The diversity, frequency, foraging activity, and intensity of attack of termites were assessed regularly at 144 baits representing 12 different bait choices over 8.5 months, in two northern Australian tropical savanna sites that differed in vegetation structure (closed vs open). Baits differed in type (paper rolls, cardboard, wooden stakes), position (surface, buried), and moisture status at installation (wet, dry).
3. Sixteen species were recorded, including 11 wood-feeders. Average species diversity, foraging activity, and bait consumption were greater at buried baits than at surface baits. Wooden baits were most attractive early in the experiment, and paper baits more attractive later. Mean species diversity was greatest at wooden stakes in the closed site. Species frequency of occurrence varied across bait choices.
4. A composite bait sampling protocol of stakes and paper rolls installed above and below ground gave an accurate assessment of the activity, diversity, and structure of the termite guild sampled across all baits over 8.5 months.
5. The choice of bait, its presentation, and time of examination are critical to the success of a termite baiting programme. If the aim is to characterise the structure and foraging activity of the subterranean termite assemblages that are attracted to baits, composite baiting protocols should be implemented.     

Oral rabies vaccination of a northern Ohio raccoon population: relevance of population density and prebait serology

Ohio's oral rabies vaccination (ORV) program was established to prevent the westward spread of the raccoon (Procyon lotor) rabies virus (Lyssavirus, Rhabdoviridae) in Ohio, USA. The program, which targets raccoons, distributes vaccine-bait units (VBU) at a target density of 75 units/km2. Few studies have examined the relationship of VBU density and target population density to the prevalence of rabies virus-neutralizing antibodies (RVNA). We conducted experimental VBU distributions in August 2003 and August 2004, 150 km west of the ORV zone where there was no history of raccoon rabies. We measured change in RVNA titers in blood collected from live-trapped raccoons before and after VBU distributions. A closed population mark-recapture estimate of the size of the target population was 91 raccoons/km2, compared to the realized VBU distribution density of 70 units/km2. Surprisingly, 41% of 37 serum samples were RVNA-positive (>or=0.05 IU/ml) before VBU distribution in 2003, but all titers were <0.25 IU/ml. Although viable VBUs were distributed in August 2003, only 21% of 315 samples were RVNA-positive before VBU distribution in 2004, but 9% had titers>or=0.25 IU/ml. Tetracycline (biomarker in bait) prevalence in teeth indicated that 57% of raccoons ingested VBUs after distribution in 2003, and 54% ingested VBUs after distribution in 2004. However, only 8% and 11% of sera were positive for RVNA (>or=0.05 IU/ml) after VBU distribution in 2003 and 2004, respectively. Only 4-5% of sera collected after bait distribution had titers>or=0.25 IU/ml each year. The standard distribution density of 75 VBUs/km2 was insufficient to produce a population-wide immunoprotective response against rabies infection in our high-density target population. Presence of RVNA in a presumed na?ve population before baiting demonstrates that estimating prevalence of RVNA after oral rabies vaccination can be problematic without knowledge of background titers and seasonal changes in prevalence of RVNA before and after baiting.     

Prerequisites for oral immunization of free-ranging raccoons (Procyon lotor) with a recombinant rabies virus vaccine: study site ecology and bait system development.

A model baiting system suitable for the delivery of an oral rabies vaccine to free-ranging raccoons (Procyon lotor) was developed and tested on barrier islands in South Carolina (USA). Features of barrier island physiography and ecology were studied relative to selective bait deployment and site biosecurity. Capture-mark-recapture data were obtained from 228 raccoons. Raccoon density estimates, using a modified census assessment technique, were one raccoon per 1.8 to 2.7 ha. Mean (+/- SE) and range home area estimates of radio-collared raccoons were 84 (+/- 15.6) ha (27 to 176 ha) by a minimum convex polygon method and 138 (+/- 22.8) ha (43 to 241 ha), by a harmonic mean transformation method. Habitat utilization determinations of radio-collared raccoons were conducted to identify study areas to potentially maximize selectivity of bait towards raccoons and to reduce the absolute number of baits deployed. Island raccoons showed a habitat preference for maritime forest, maritime shrub and marsh areas. Additionally, there was no evidence of inter-island or mainland exchange of ear-tagged or radio-collared raccoons. A disease and mortality survey was conducted to identify baseline pathology and incidental lesions in the target raccoon population, prior to actual vaccination initiation. Thirty-eight percent of 30 clinically suspect raccoons sampled had intracytoplasmic eosinophilic inclusions diagnostic of canine distemper; no other lesions suggestive of viral etiologies were found. Serological surveys for raccoon poxvirus and rabies virus antibodies were negative. Antibody titers to canine adenovirus 1 and 2 indicated a moderate level of exposure (approximately 10 to 16%) in the raccoon population. Overall, 93 to 100% of placebo baits were consistently disturbed by 7 days post-bait deployment, and bait acceptance rates by raccoons ranged from 49 to 85%, by using a modular systems approach to select the optimum combination of bait attractant, biomarker, matrix, density, and distribution. These results suggest that a large proportion (up to 85%) of a free-ranging island raccoon population can be selectively and safely targeted, marked and monitored utilizing a proposed oral bait delivery system for recombinant or other rabies vaccines.     

Comparing ONRAB® AND RABORAL V-RG® oral rabies vaccine field performance in raccoons and striped skunks, New Brunswick, Canada, and Maine, USA

Control of rabies in mesocarnivore reservoirs through oral rabies vaccination (ORV) requires an effective vaccine bait. Oral rabies vaccine performance in the field may be affected by a variety of factors, including vaccine bait density and distribution pattern, habitat, target species population density, and the availability of competing foods. A field study in which these covariates were restricted as much as possible was conducted along the international border of the state of Maine (ME), USA, and the province of New Brunswick (NB), Canada, to compare the performance of two oral rabies vaccines in raccoons (Procyon lotor) and striped skunks (Mephitis mephitis). RABORAL V-RG(?) (vaccinia-rabies glycoprotein recombinant oral vaccine in fishmeal-coated sachet) or ONRAB(?) (adenovirus-rabies glycoprotein recombinant oral vaccine in Ultralite bait matrix) were distributed in ME and NB, respectively, by fixed-wing aircraft at a density of 75 baits/km(2) along parallel flight lines spaced 1.0 km apart. Sera were collected from live-trapped raccoons and skunks 5-7 wk post-ORV and assayed to determine antibody prevalence in each area. Duplicate serum samples were provided blind to two different laboratories for analyses by rabies virus serum neutralization assays (at both laboratories) and a competitive enzyme-linked immunosorbent assay (at one laboratory). There was no significant difference in the proportion of antibody-positive animals determined by the three serologic methods, nor was there a significant difference between ONRAB and RABORAL V-RG in the proportion of antibody-positive striped skunks observed post-ORV. In contrast, the proportion of antibody-positive raccoons was significantly higher in the ONRAB- versus the RABORAL V-RG-baited areas (74% vs. 30%; χ(2)=89.977, df=5, P<0.0001). These data support that ONRAB may serve as an effective tool for raccoon rabies control.     

Response of feral cats to a track‐based baiting programme using Eradicat® baits

The feral Cat (Felis catus) is a significant threat to Australian fauna, and reducing their impacts is considered an essential action for threatened species conservation. Poison baiting is increasingly being used for the broad scale control of feral cats. In this study, we measured the population response of feral cats to a track‐based baiting programme using Eradicat^® baits in the semi‐arid northern wheatbelt region of Western Australia. Over two years, 1500 baits were laid once annually and the response of feral cats was measured using remote cameras in a before–after, control–impact design. There was a significant reduction in feral cat activity in the second year, but not the first. During bait uptake trials, corvids removed the most number of baits, followed by cats and varanids. The lack of a response to baiting in the first year may be due to existing low cat numbers in the baited area and/or the timing of the baiting. We provide a list of key recommendations to help inform future cat baiting programmes and research.