Preference among 7 bait flavors delivered to domestic dogs in Arizona: Implications for oral rabies vaccination on the Navajo Nation

Less than 20% of the domestic dogs on tribal lands in the United States are vaccinated against rabies. One method to increase vaccination rates may be the distribution of oral rabies vaccines (ORVs). ONRA (Artemis Technologies, Inc., Ontario, Canada) is the primary ORV used in Canada to vaccinate striped skunks and raccoons. To investigate the potential use of ONRAB ORV baits to vaccinate feral domestic dogs against rabies on tribal lands and beyond, we performed a flavor preference study. A total of 7 bait flavors (bacon, cheese, dog food, hazelnut, sugar-vanilla, peanut butter, and sardine) were offered in pairs to 13 domestic dogs. Each dog was offered all possible combinations of bait pairs over a period of 10 days, with each bait offered 6 times. The proportion of times each bait was consumed first by individual dogs was calculated and comparisons among dogs were conducted using the MIXED procedure in SAS (SAS Institute, Cary, NC). Pairwise comparisons between baits were performed using “contrast” statements with sugar-vanilla flavor as the default for comparison. Type 3 tests of fixed effects showed a significant treatment effect (F6,72 = 9.74, P\u3c 0.0001). Sugar-vanilla was selected first during 14% of the offerings and exhibited the least preference among all bait types (F1,72 = 22.46, P \u3c 0.0001). Dog food was selected first 56% of the time, and more frequently than all other bait types (F1,72 = 13.09, P= 0.0005). domestic dogs. Each dog was offered all possible combinations of bait pairs over a period of 10 days, with each bait offered 6 times. The proportion of times each bait was consumed first by individual dogs was calculated and comparisons among dogs were conducted using the MIXED procedure in SAS (SAS Institute, Cary, NC). Pairwise comparisons between baits were performed using “contrast” statements with sugar-vanilla flavor as the default for comparison. Type 3 tests of fixed effects showed a significant treatment effect (F6,72 = 9.74, P\u3c 0.0001). Sugar-vanilla was selected first during 14% of the offerings and exhibited the least preference among all bait types (F1,72 = 22.46, P \u3c 0.0001). Dog food was selected first 56% of the time, and more frequently than all other bait types (F1,72 = 13.09, P= 0.000

Assessing spatial variation and overall density of aerially broadcast toxic bait during a rat eradication on Palmyra Atoll

Baits containing brodifacoum rodenticide were aerially applied to eradicate invasive black rats from Palmyra Atoll, an important biodiversity center. Bait application must be sufficient to be effective, while minimizing environmental hazards by not exceeding designated label rates, prompting our bait density assessments for two aerial drops. With few physical or human resources on this remote, uninhabited atoll, assessments were particularly challenging, requiring observations within 30 min of aerial application to avoid bait loss to rats, crabs, or elements. We estimated bait density using quadrat sampling within 13 terrestrial sampling areas. We also sampled 10 tidal flat areas to assess inadvertent bait scatter into marine aquatic environments. Of particular value for challenging sampling circumstances, our quadrats had to be lightweight and durable, which we addressed by using widely available PVC hoops (“Hula Hoops”), the size of which was ideal for sampling purposes. At 77.5 and 78.7 kg/ha, overall bait densities were very near to the target densities of 80 and 75 kg/ha, respectively. However, considerable variability in bait densities existed among sampled areas, 8.6–178.2 and 31.4–129.5 kg/ha for the respective drops. Environmental, human, and equipment factors likely accounted for this variability. Tidal flat sampling revealed variable bait scatter into aquatic environments, from 0–46.3 kg/ha across the two drops. No differences were found in average bait densities among 1-, 4-, and 7-m distances from high tide lines. Our methods might broadly assist bait density (and other) surveys under challenging circumstances

Evaluation of the palatability and toxicity of candidate baits and toxicants for mongooses (\u3ci\u3eHerpestes auropunctatus\u3c/i\u3e)

The small Indian mongoose (Herpestes auropunctatus) is an invasive pest species responsible for damage to native avian, reptile, and amphibian species on Hawaii, Croatia, Mauritius, and several Caribbean Islands, among other regions.Mongoose control has been pursued through a variety of means, with varying success. One toxicant, diphacinone, has been shown to be effective in mongooses and is co-labeled in a rodenticide bait for mongoose control in Hawaii; however, preliminary observations indicate low performance as a mongoose toxicant due likely to poor consumption. We evaluated the efficacy and palatability of 10 commercial rodenticide baits, technical diphacinone powder, and two alternative acute toxicants against mongooses in laboratory feeding trials. We observed poor acceptance and subsequent low overall mortality, of the hard grain-based pellets or block formulations typical of most of the commercial rodenticide baits. The exception was Tomcat® bait blocks containing 0.1% bromethalin, an acute neurotoxin, which achieved up to 100% mortality. Mortality among all other commercial rodenticide formulations ranged from 10 to 50%. Three-day feedings of 0.005% technical diphacinone formulated in fresh minced chicken achieved 100% mortality. One-day feedings of para-aminopropiophenone (PAPP), a chemical that reduces the oxygen-carrying capacity of the blood, achieved 100% mortality at concentrations of 0.10 to 0.15%. Bait acceptance of two sodium nitrite formulations (similar toxic mode of action as PAPP) was relatively poor, and mortality averaged 20%. In general, commercially produced rodenticide baits were not preferred by mongooses and had lower mortality rates compared to freshly prepared meat bait formulations. More palatable baits had higher consumption and achieved higher mortality rates. The diphacinone bait registered for rat and mongoose control in Hawaii achieved 20% mortality and was less effective than some of the other commercial or candidate fresh bait products evaluated in this study

Longevity of Rodenticide Bait Pellets in a Tropical Environment Following a Rat Eradication Program

Invasive rodents (primarily Rattus spp.) are responsible for loss of biodiversity in island ecosystems worldwide. Large-scale rodenticide applications are typically used to eradicate rats and restore ecological communities. In tropical ecosystems, environmental conditions rapidly degrade baits and competition for baits by non-target animals can result in eradication failure. Our objective was to evaluate persistence of rodenticide baits during a rat eradication program on Palmyra Atoll; a remote tropical atoll with intense competition for resources by land crabs. Following aerial application, bait condition was monitored in four terrestrial environments and in the canopy foliage of coconut palms. Ten circular PVC hoops were fixed in place in each of Palmyra\u27s four primary terrestrial habitats and five rodenticide pellets were placed in each hoop. Five coconut palms were selected in three distinct regions of the atoll. One rodenticide pellet was placed on each of five palm fronds in each coconut palm. Fresh baits were placed in all monitoring locations after each broadcast bait application. Bait condition and survival was monitored for 7 days after the first bait application and 6 days after second application. Bait survival curves differed between applications at most monitoring sites, suggesting a decrease in overall rat activity as a result of rodenticide treatment. One terrestrial site showed near 100%bait survival after both applications, likely due to low localized rat and crab densities. Median days to pellet disappearance were one and two days for the first and second application, respectively. Differences in survival curves were not detected in canopy sites between bait applications. Median days to pellet disappearance in canopy sites were 2 and 4 days for the first and second application, respectively. Frequent rainfall likely contributed to rapid degradation of bait pellets in coconut palm fronds

Assessing spatial variation and overall density of aerially broadcast toxic bait during a rat eradication on Palmyra Atoll

Baits containing brodifacoum rodenticide were aerially applied to eradicate invasive black rats from Palmyra Atoll, an important biodiversity center. Bait application must be sufficient to be effective, while minimizing environmental hazards by not exceeding designated label rates, prompting our bait density assessments for two aerial drops. With few physical or human resources on this remote, uninhabited atoll, assessments were particularly challenging, requiring observations within 30 min of aerial application to avoid bait loss to rats, crabs, or elements. We estimated bait density using quadrat sampling within 13 terrestrial sampling areas. We also sampled 10 tidal flat areas to assess inadvertent bait scatter into marine aquatic environments. Of particular value for challenging sampling circumstances, our quadrats had to be lightweight and durable, which we addressed by using widely available PVC hoops (“Hula Hoops”), the size of which was ideal for sampling purposes. At 77.5 and 78.7 kg/ha, overall bait densities were very near to the target densities of 80 and 75 kg/ha, respectively. However, considerable variability in bait densities existed among sampled areas, 8.6–178.2 and 31.4–129.5 kg/ha for the respective drops. Environmental, human, and equipment factors likely accounted for this variability. Tidal flat sampling revealed variable bait scatter into aquatic environments, from 0–46.3 kg/ha across the two drops. No differences were found in average bait densities among 1-, 4-, and 7-m distances from high tide lines. Our methods might broadly assist bait density (and other) surveys under challenging circumstances

An Automatic System to Evaluate Bait Station Visitation by Brown Treesnakes and Mongooses

Understanding the temporal, spatial, and behavioral patterns of the free-ranging target species in response to candidate baits and baiting strategies is important to ensure control success. This information can also assist in the development and deployment of feeding stations and can exclude non-target species while constituting effective bait delivery and control strategies for certain invasive animals, especially at environmentally sensitive sites. We used passive integrated transponder (PIT) tags in conjunction with very-high frequency radio-telemetry to remotely record bait station visitations and evaluate bait attractiveness in separate field research studies of brown treesnakes (Boiga irregularis) on Andersen Air Force Base, Guam, Northern Mariana Islands, between 1999 and 2000 and in 2007, for small Indian mongooses (Urva auropunctata: Syn. Herpestes auropunctatus) on Hilo, Hawaiʻi Island, Hawaiʻi. USA. This system allowed us to document visitation rates to bait stations by brown treesnakes and mongooses. In Guam, we determined that 75% of medium to large brown treesnakes (\u3e850 mm snout-vent length [SVL]) attracted to the bait stations consumed toxic bait, while smaller snakes (SVL) were not attracted to the bait stations. On Hawai‘i Island, we learned mongooses foraged over large areas (range = 6.0–70.2 ha), traveled up to 598 m to select baits, had restricted centers of activity, and displayed fidelity to newly discovered food sources. We recorded discrete group feeding activity not previously documented for mongooses. We found that anterior and posterior double-PIT tagging improved detectability of both target species. The complimentary monitoring system we used can be easily adapted for monitoring small mammals, birds, reptiles, or amphibian species and various activities of interest

Capture-Recapture Reveals Heterogeneity in Habitat-Specific Mongoose Densities and Spatiotemporal Variability in Trapping Success in St. Kitts, West Indies

The small Indian mongoose (Urva auropunctata) is a non-native invasive species across the Caribbean and a rabies reservoir on at least four islands in the region. Although previous studies reported mongoose density estimates in their non-native range, the variability in trapping designs, study seasonality, and analytical methods among studies precludes direct comparisons. This study is the first to report mongoose densities for the island of St. Kitts, West Indies. Our objective was to quantify mongoose densities across four habitats characteristic for the island. High capture and recapture rates in this study resulted in detailed estimates of spatial heterogeneity in mongoose densities, ranging from 0.53 (CI95: 0.46–0.61) mongooses/ha in suburban habitat to 5.85 (CI95: 4.42–7.76) mongooses/ha in nearby dry forest. Estimates were robust to the estimation method used (correlation among methods, r \u3e 0.9). Female-biased sex ratios estimated from fall season versus mostly unbiased sex ratios estimated from summer season suggests seasonality in capture success resulting from differences in sex-specific activity patterns of mongooses. We found no effect of habitat characteristics, at the scale of trap placements, associated with mongoose capture success

Modeling Mongoose Rabies in the Caribbean: A Model-Guided Fieldwork Approach to Identify Research Priorities

We applied the model-guided fieldwork framework to the Caribbean mongoose rabies system by parametrizing a spatially-explicit, individual-based model, and by performing an uncertainty analysis designed to identify parameters for which additional empirical data are most needed. Our analysis revealed important variation in output variables characterizing rabies dynamics, namely rabies persistence, exposure level, spatiotemporal distribution, and prevalence. Among epidemiological parameters, rabies transmission rate was the most influential, followed by rabies mortality and location, and size of the initial infection. The most influential landscape parameters included habitat-specific carrying capacities, landscape heterogeneity, and the level of resistance to dispersal associated with topography. Movement variables, including juvenile dispersal, adult fine-scale movement distances, and home range size, as well as life history traits such as age of independence, birth seasonality, and age- and sex-specific mortality were other important drivers of rabies dynamics. We discuss results in the context of mongoose ecology and its influence on disease transmission dynamics. Finally, we suggest empirical approaches and study design specificities that would provide optimal contributing data addressing the knowledge gaps identified by our approach, and would increase our potential to use epidemiological models to guide mongoose rabies control and management in the Caribbean

Bait flavor preference and immunogenicity of ONRAB baits in domestic dogs on the Navajo Nation, Arizona

Rabies is responsible for an estimated 59,000 human deaths worldwide, and domestic dogs are the primary reservoir and vector of the disease. Among some nations, widespread vaccination has led to elimination of rabies in domestic dogs, yet dogs are still susceptible to rabies infection from interactions with wildlife reservoirs. On Tribal lands in the United States, less than 20% of domestic dogs are vaccinated for rabies, and parenteral vaccination is often unfeasible. Oral rabies vaccination may provide a solution, but a suitable bait flavor and vaccine must be identified. We evaluated 5 bait flavors (bacon, cheese, egg, fish, and sweet) in pairwise flavor-preference trials using placebo Ultralite baits in 26 domestic dogs on the Navajo Nation, Arizona. Each bait flavor was offered a total of 104 times. In all paired comparisons, bacon was more frequently preferred to the alternative. The sweet flavor (the flavor used operationally for oral rabies vaccine (ORV) distribution in Canada) was least preferred. Forty domestic dogs were offered baits containing ONRAB ORV: 14 received the sweet-flavored bait packet and 26 received bacon-flavored baits. Serum was collected from dogs before vaccination and at day 14 and 30 or 37 days after vaccination. Thirty-seven dogs consumed the baits, 2 baits (both sweet flavored) were chewed and spit out, and 1 (sweet flavored) was swallowed without apparent chewing (gulped). Eight dogs had preexisting rabies virus neutralizing antibody (RVNA) titers and 13 naïve dogs failed to seroconvert during the study period. Overall, 27 dogs (67.5%) showed increased RVNA titers after vaccination, including 1 dog who chewed and spit out the bait and all dogs with positive baseline RVNA titers. Geometric mean titers for all dogs that seroconverted during the study period peaked at day 14 (1.2 IU/ mL; n = 24) and decreased slightly by the final sampling day (0.8 IU/mL; n = 27).We conclude that bacon flavor may be a suitable bait flavor for ORV distribution in loosely kept or free-roaming domestic dogs. Seroconversion among dogs who ingested ONRAB-filled baits was variable. Why 13 dogs who consumed ORV baits failed to seroconvert remains unknown. Additional research to improve seroconversion rates in domestic dogs after vaccination with ONRAB is recommended

Bait flavor preference and immunogenicity of ONRAB baits in domestic dogs on the Navajo Nation, Arizona

Rabies is responsible for an estimated 59,000 human deaths worldwide, and domestic dogs are the primary reservoir and vector of the disease. Among some nations, widespread vaccination has led to elimination of rabies in domestic dogs, yet dogs are still susceptible to rabies infection from interactions with wildlife reservoirs. On Tribal lands in the United States, less than 20% of domestic dogs are vaccinated for rabies, and parenteral vaccination is often unfeasible. Oral rabies vaccination may provide a solution, but a suitable bait flavor and vaccine must be identified. We evaluated 5 bait flavors (bacon, cheese, egg, fish, and sweet) in pairwise flavor-preference trials using placebo Ultralite baits in 26 domestic dogs on the Navajo Nation, Arizona. Each bait flavor was offered a total of 104 times. In all paired comparisons, bacon was more frequently preferred to the alternative. The sweet flavor (the flavor used operationally for oral rabies vaccine (ORV) distribution in Canada) was least preferred. Forty domestic dogs were offered baits containing ONRAB ORV: 14 received the sweet-flavored bait packet and 26 received bacon-flavored baits. Serum was collected from dogs before vaccination and at day 14 and 30 or 37 days after vaccination. Thirty-seven dogs consumed the baits, 2 baits (both sweet flavored) were chewed and spit out, and 1 (sweet flavored) was swallowed without apparent chewing (gulped). Eight dogs had preexisting rabies virus neutralizing antibody (RVNA) titers and 13 naïve dogs failed to seroconvert during the study period. Overall, 27 dogs (67.5%) showed increased RVNA titers after vaccination, including 1 dog who chewed and spit out the bait and all dogs with positive baseline RVNA titers. Geometric mean titers for all dogs that seroconverted during the study period peaked at day 14 (1.2 IU/ mL; n = 24) and decreased slightly by the final sampling day (0.8 IU/mL; n = 27).We conclude that bacon flavor may be a suitable bait flavor for ORV distribution in loosely kept or free-roaming domestic dogs. Seroconversion among dogs who ingested ONRAB-filled baits was variable. Why 13 dogs who consumed ORV baits failed to seroconvert remains unknown. Additional research to improve seroconversion rates in domestic dogs after vaccination with ONRAB is recommended