Comparison of flea diversity in the burrows of Richardson's ground squirrels (Urocitellus richardsonii) in urban and rural sites in central Saskatchewan, Canada.

Spatial and temporal differences in the relative abundance of arthropod vectors are important factors that influence the risk of disease for mammalian hosts. Seasonal changes in the diversity and abundance of fleas (Siphonaptera) in Richardson's ground squirrel (Urocitellus richardsonii) burrows were studied at two sites in central Saskatchewan. A total of 225 fleas (151 at an urban site and 74 at a rural site) were collected. Flea prevalence differed among seasons at the urban site but not at the rural site. Of the nine flea species detected (eight at the urban site and six at the rural site), Oropsylla rupestris, O. bruneri, O. labis, O. tuberculata, and Aetheca wagneri are vectors of Yersinia pestis, the causative agent of plague. The presence and abundance of some fleas differed between sites and seasons. Neopsylla inopina and O. rupestris were the most abundant species at the urban site during the spring and summer, respectively, while O. bruneri was the most abundant species at the rural site. Our findings may have implications for the management of the black-tailed prairie dogs (Cynomys ludovicianus) in southwestern Saskatchewan because they coexist with U. richardsonii, are hosts for Oropsylla, and are at great risk of plague exposure/infection.

Fine-scale spatial variation shape fecal microbiome diversity and composition in black-tailed prairie dogs (Cynomys ludovicianus).

BACKGROUND: Host associated gut microbiota are important in understanding the coevolution of host-microbe, and how they may help wildlife populations to adapt to rapid environmental changes. Mammalian gut microbiota composition and diversity may be affected by a variety of factors including geographic variation, seasonal variation in diet, habitat disturbance, environmental conditions, age, and sex. However, there have been few studies that examined how ecological and environmental factors influence gut microbiota composition in animals' natural environments. In this study, we explore how host habitat, geographical location and environmental factors affect the fecal microbiota of Cynomys ludovicianus at a small spatial scale. We collected fecal samples from five geographically distinct locations in the Texas Panhandle classified as urban and rural areas and analyzed them using high throughput 16S rRNA gene amplicon sequencing. RESULTS: The results showed that microbiota of these fecal samples was largely dominated by the phylum Bacteroidetes. Fecal microbiome diversity and composition differed significantly across sampling sites and habitats. Prairie dogs inhabiting urban areas showed reduced fecal diversity due to more homogenous environment and, likely, anthropogenic disturbance. Urban prairie dog colonies displayed greater phylogenetic variation among replicates than those in rural habitats. Differentially abundant analysis revealed that bacterial species pathogenic to humans and animals were highly abundant in urban areas which indicates that host health and fitness might be negatively affected. Random forest models identified Alistipes shahii as the important species driving the changes in fecal microbiome composition. Despite the effects of habitat and geographic location of host, we found a strong correlation with environmental factors and that- average maximum temperature was the best predictor of prairie dog fecal microbial diversity. CONCLUSIONS: Our findings suggest that reduction in alpha diversity in conjunction with greater dispersion in beta diversity could be indicative of declining host health in urban areas; this information may, in turn, help determine future conservation efforts. Moreover, several bacterial species pathogenic to humans and other animals were enriched in prairie dog colonies near urban areas, which may in turn adversely affect host phenotype and fitness.

Post-translocation dynamics of black-tailed prairie dogs (Cynomys ludovicianus): A successful conservation and human-wildlife conflict mitigation tool.

Prairie dogs have declined by 98% throughout their range in the grasslands of North America. Translocations have been used as a conservation tool to reestablish colonies of this keystone species and to mitigate human-wildlife conflict. Understanding the behavioral responses of prairie dogs to translocation is of utmost importance to enhance the persistence of the species and for species that depend on them, including the critically endangered black-footed ferret. In 2017 and 2018, we translocated 658 black-tailed prairie dogs on the Lower Brule Indian Reservation in central South Dakota, USA, a black-footed ferret recovery site. Here, we describe and evaluate the effectiveness of translocating prairie dogs into augered burrows and soft-released within presumed coteries to reestablish colonies in previously occupied habitat. We released prairie dogs implanted with passive integrated transponders (PIT tags) and conducted recapture events approximately 1-month and 1-year post-release. We hypothesized that these methods would result in a successful translocation and that prairie dogs released as coteries would remain close to where they were released because of their highly social structure. In support of these methods leading to a successful translocation, 69% of marked individuals was captured 1-month post-release, and 39% was captured 1-year post-release. Furthermore, considerable recruitment was observed with 495 unmarked juveniles captured during the 1-year post-release trapping event, and the reestablished colony had more than doubled in the area by 2021. Contrary to our hypothesis, yet to our knowledge a novel finding, there was greater initial movement within the colony 1-month post-release than expected based on recapture locations compared with the published average territory size; however, 1 year after release, most recaptured individuals were captured within the expected territory size when compared to capture locations 1-month post-release. This research demonstrates that while translocating prairie dogs may be socially disruptive initially, it is an important conservation tool.

Evaluation of stress response in black-tailed prairie dogs (Cynomys ludovicianus) in arid regions from colonies in Chihuahua Mexico.

Among all the regulatory homeostatic networks in vertebrates, the activation of the hypothalamic-pituitaryadrenal axis during the stress response, has gained considerable attention, and the measurement of fecal glucocorticoids (FGC) has become an invaluable tool to assess adrenocortical activity related to stressful events in wild and captive animals. However, the use of FGC requires the validation of measurement techniques and the proper selection of the specific hormone according to the study species. The main objective of this study was to identify the dominant glucocorticoid (GC) hormone in the stress response of black-tailed prairie dogs (Cynomys ludovicianus) in an arid grassland of Chihuahua, Mexico. A capture stress challenge in the field was developed to determine if the levels of glucocorticoids (cortisol and corticosterone) both in serum and fecal samples could be attributed to stress in Cynomys ludovicianus. The samples were analysed with the technique of liquid phase radioimmunoassay , and this study showed that both cortisol and corticosterone are present at measurable levels in serum and fecal samples of black-tailed prairie dogs. We found that both GCs were present in similar concentrations in serum, however, corticosterone concentration in fecal samples was higher than cortisol. Likewise, biochemical validations performed in this study to test the assay reached acceptable levels of reliability. Therefore, we confirm that fecal analysis can be implemented as a method to measure stress responses in wild prairie dogs.

Perceived predation risk predicts glucocorticoid hormones, but not reproductive success in a colonial rodent.

The Cort-Adaptation hypothesis suggests that elevated glucocorticoids (GCs) can facilitate an adaptive response to environmental and physiological challenges. Most previous studies have focused on avian species, which may limit their generalizability to mammals, where lactation is known to be a major physiological challenge. Furthermore, the effect of predation risk on GC levels has not been tested in the Cort-Adaptation hypothesis. We sought to test this hypothesis in a colonial prey species, black-tailed prairie dogs (Cynomys ludovicianus). We predicted that individuals located near fewer neighboring conspecifics would perceive an increased risk of predation and, in turn, have increased GCs (measured through hair cortisol concentration (HCC)) and reduced annual reproductive success compared to more centrally located individuals. We also investigated other putative influences on HCC: age, lactation status, body condition, and season of hair growth. Levels of vigilance behavior were higher for those with fewer neighboring conspecifics, suggesting variation in perceived risk of predation. Further, the risk of predation appeared to represent a chronic, detrimental stressor as evidenced by a significant increase in HCC for prairie dogs with fewer neighbors. Lactation status and season also influenced HCC. We found support for the Cort-Adaptation hypothesis where increased HCC during the reproductive season correlated with whether a female produced a litter, but not litter size, suggesting a minimum threshold of GCs is required for successful reproduction in this species. Our work illustrates that HCC may operate as an indicator of perceived predation risk, but care should be taken to consider the variety of factors influencing GC homeostasis, in particular lactation, when drawing conclusions using HCC as a marker of long-term stress.

Characterization of faecal and caecal microbiota of free-ranging black-tailed prairie dogs (Cynomys ludovicianus) using high-throughput sequencing of the V4 region of the 16S rRNA gene.

Black-tailed prairie dogs (Cynomys ludovicianus) are keystone species within their grassland ecosystems; their population stability affects a multitude of other species. The goals of this study were to explore, describe and compare the bacterial communities in caecal and hard faecal samples from free-ranging black-tailed prairie dogs (n = 36) from KS, USA, using high-throughput sequencing of the V4 region of the 16S rRNA gene and to compare sex and geographic locations. A total of 22 paired faecal and caecal samples were collected post-mortem from free-ranging black-tailed prairie dogs from 5 different geographical locations. The results revealed that the microbiota of both faecal and caecal samples were dominated by the phylum Firmicutes (genera belonging to the Clostridiales order). There was significantly greater richness in faecal compared with caecal samples. There were significant differences between the 5 different geographic regions (P < 0.001), specifically in the relative abundances of genera. There were differences in rare members of the microbiome between faecal samples from male and female prairie dogs but with no significant impact on overall community structure. This study provides novel data and expands our knowledge about the gastrointestinal microbiome composition of free-ranging black-tailed prairie dogs, which has potential to inform conservation efforts and improve their captive management.

No evidence for enzootic plague within black-tailed prairie dog (Cynomys ludovicianus) populations.

Yersinia pestis, causative agent of plague, occurs throughout the western United States in rodent populations and periodically causes epizootics in susceptible species, including black-tailed prairie dogs (Cynomys ludovicianus). How Y. pestis persists long-term in the environment between these epizootics is poorly understood but multiple mechanisms have been proposed, including, among others, a separate enzootic transmission cycle that maintains Y. pestis without involvement of epizootic hosts and persistence of Y. pestis within epizootic host populations without causing high mortality within those populations. We live-trapped and collected fleas from black-tailed prairie dogs and other mammal species from sites with and without black-tailed prairie dogs in 2004 and 2005 and tested all fleas for presence of Y. pestis. Y. pestis was not detected in 2126 fleas collected in 2004 but was detected in 294 fleas collected from multiple sites in 2005, before and during a widespread epizootic that drastically reduced black-tailed prairie dog populations in the affected colonies. Temporal and spatial patterns of Y. pestis occurrence in fleas and genotyping of Y. pestis present in some infected fleas suggest Y. pestis was introduced multiple times from sources outside the study area and once introduced, was dispersed between several sites. We conclude Y. pestis likely was not present in these black-tailed prairie dog colonies prior to epizootic activity in these colonies. Although we did not identify likely enzootic hosts, we found evidence that deer mice (Peromyscus maniculatus) may serve as bridging hosts for Y. pestis between unknown enzootic hosts and black-tailed prairie dogs.

Evaluating the use of a low dose fipronil bait in reducing black-tailed prairie dog (Cynomys ludovicianus) fleas at reduced application rates.

Plague is a virulent zoonosis, vectored by fleas, posing danger to black-tailed prairie dogs (BTPDs) (Cynomys ludovicianus), black-footed ferrets (Mustela nigripes), and humans in North America. During prior research, a fipronil grain bait (0.005%) applied at rates of 1-½ cup/burrow, reduced flea abundance by > 95-100% when applied three times February-March in northern Colorado. The objective of the current study was to determine the efficacy of fipronil bait against fleas in northern Colorado at reduced application rates (½ cup/burrow) and frequencies (1-2 applications). The field study was conducted in Larimer county, Colorado USA between June-November 2018. Three test plots were selected: two treatment plots (1 vs. 2 fipronil bait applications) and one untreated control. Fipronil was applied at a rate of ½ cup (~95 g)/burrow. Fleas were collected from captured BTPDs and swabs of active burrows prior to bait application and up to 134-days post-treatment. A total of 203 BTPDs and 210 active burrows were sampled. Within the treatment plots, no fleas were collected from BTPDs up to 134-days post-treatment (100% efficacy). Five fleas were recovered from burrows within the one-application plot (<40-days post-application) with efficacy ranging from 97.1 to 100%. No fleas were recovered from burrows within the two-application plot. We caution that while fleas were present within the control plot throughout the study, abundances were low. The efficacy results are supported by those of prior field research conducted in South Dakota and suggest that fipronil bait may be applied at lower rates and frequencies than initially proposed, with potential to sustain flea removal >4-months.

Dialects in the alarm calls of black- tailed prairie dogs (Cynomys ludovicianus): A case of cultural diffusion?

Prairie dogs (Cynomys spp.) produce an alarm call when a predator appears. Gunnison's prairie dogs (Cynomys gunnisoni) produce calls that vary in spectral structure according to predator type and specific characteristics unique to the individual predator, such as color and shape. These calls vary depending on geographic location and have been characterized as dialects. Black-tailed prairie dogs (Cynomys ludovicianus) also encode information about terrestrial predators in their alarm calls. However, nothing is known about whether there are dialects in these alarm calls, and if so, why these dialects might have arisen. We studied the alarm calls and habitat characteristics of eight different black-tailed prairie dog colonies within the Southwestern USA: Maxwell National Wildlife Refuge, NM, Vermejo Park Ranch, NM, Kiowa National Grasslands, NM, Rita Blanca National Grasslands, TX, and Comanche National Grasslands, CO. An analysis of time and frequency changes in alarm calls showed that colony sites that were located within 30 km each other did not have significant differences in alarm call structure, but sites that were more distant were significantly different from the other sites, consistent with the existence of dialects as well as with genetic models of isolation by distance. The acoustic structure of the alarm calls was not explained by differences in habitat characteristics at each site. A comparison of Squared Euclidian Distances (D2) of alarm calls versus linear distances between sites showed a significant positive correlation, implying that alarm call dialect differences increase the farther one site is from another. This relationship is consistent with a cultural diffusion model of dialects, and is similar to that observed in human dialects.

Wildlife Refuges Support High Bee Diversity on the Southern Great Plains.

The native prairie of the southern Great Plains has been especially modified by two related forces: conversion of native prairie to agricultural forms of land use and removal of black-tailed prairie dogs (Rodentia: Sciuridae, Cynomys ludovicianus (Ord, 1815)) that act as ecosystem engineers via their burrowing and grazing activities. It is unknown how these changes have affected the native bee community. We surveyed the bee communities in relatively intact native prairie at two National Wildlife Refuges in Texas, quantifying bee community structure as a function of the presence/absence of grazing by prairie dogs. Over a 5-mo sampling period in spring-summer 2013, we found high overall bee diversity (180 species, mostly solitary ground-nesters), with differences detected in diversity between Muleshoe and Buffalo Lake National Wildlife Refuges as well as on and off prairie dog colonies. Although the same three species dominated the bee community at both refuges, most species were represented by relatively few individuals, leading to overall differences in diversity (richness, evenness, and effective number of species) by refuge. Bee diversity differed between sites on and off prairie dog colonies, but in trends that differed by refuge and by index, suggesting that location was more important than prairie dog presence. These results represent a reference fauna against which other regional bee communities in other land-cover types can be compared, but the high spatial heterogeneity we found indicates that detecting effects of landscape change on native bees will be challenging.

Investigation of the utility of feces and hair as non-invasive measures of glucocorticoids in wild black-tailed prairie dogs (Cynomys ludovicianus).

Non-invasive measures of glucocorticoid (GC) hormones and their metabolites, particularly in feces and hair, are gaining popularity as wildlife management tools, but species-specific validations of these tools remain rare. We report the results of a validation on black-tailed prairie dogs (Cynomys ludovicianus), a highly social engineer of the grasslands ecosystem that has experienced recent population declines. We captured adult female prairie dogs and brought them into temporary captivity to conduct an adrenocorticotropic hormone (ACTH) stimulation test, assessing the relationship between plasma GC and fecal glucocorticoid metabolite (FGM) levels following a single injection of a low (4 IU/kg) or high dose (12 IU/kg) of ACTH, compared to a single injection of saline. We also gave repeated injections of ACTH to adult females to assess whether this would result in an increase of hair cortisol concentrations, compared with control individuals repeatedly injected with saline. A single injection of ACTH at either low or high dose peaked plasma cortisol levels after 30 min, and thereafter the cortisol levels declined until 120 min, where they returned to pre-treatment levels comparable to those of the saline injected group. Despite the significant elevation of plasma cortisol in the treatment groups following ACTH injection, the elevation of FGM levels in the treatment groups were not significantly different from those in the control group over the following 12 h. Repeated injection of a high dose of ACTH failed to increase hair cortisol concentration in treatment animals. Instead, hair cortisol levels remained comparable to the pre-treatment mean, despite an increase in post-treatment hair cortisol levels seen in the saline-injected group. The magnitude of increase in the saline control group was comparable to natural seasonal variation seen in unmanipulated individuals. These results highlight that while measurement of GCs and their metabolites in feces and hair are potentially valuable conservation tools for black-tailed prairie dogs, further validation work is required before these matrices can be to real-world conservation applications.

MAMMALIAN HOSTS, VECTORS, AND BACTERIAL PATHOGENS IN COMMUNITIES WITH AND WITHOUT BLACK-TAILED PRAIRIE DOGS ( CYNOMYS LUDOVICIANUS) IN NORTHWESTERN MEXICO.

: The presence of keystone species can influence disease dynamics through changes in species diversity and composition of vector and host communities. In this study, we compared 1) the diversity of small mammals; 2) the prevalence, abundance, and intensity of arthropod vectors; and 3) the prevalence of Yersinia pestis, Francisella tularensis, and Bartonella spp. in vectors, between two grassland communities of northern Sonora, Mexico, one with (La Mesa [LM]) and one without (Los Fresnos [LF]) black-tailed prairie dogs ( Cynomys ludovicianus). The mammal community in LF exhibited higher species richness and diversity than LM, and species composition was different between the two communities. Flea species richness, prevalence, abundance, and intensity, were higher in LM than in LF. The most abundant fleas were Oropsylla hirsuta and Pulex simulans, and C. ludovicianus was the host with the highest flea intensity and richness. There was no serologic evidence for the presence of Y. pestis and F. tularensis in any community, but Bartonella spp. was present in 18% of the total samples. Some specificity was observed between Bartonella species, flea species, and mammal species. Although prairie dogs can indirectly affect the diversity and abundance of hosts and vectors, dynamics of vector-borne diseases at these spatial and temporal scales may be more dependent on the vector and pathogen specificity.

Climate change impacts on the conservation outlook of populations on the poleward periphery of species ranges: A case study of Canadian black-tailed prairie dogs (Cynomys ludovicianus).

Given climate change, species' climatically suitable habitats are increasingly expected to shift poleward. Some imperilled populations towards the poleward edge of their species' range might therefore conceivably benefit from climate change. Interactions between climate and population dynamics may be complex, however, with climate exerting effects both indirectly via influence over food availability and more directly, via effects on physiology and its implications for survival and reproduction. A thorough understanding of these interactions is critical for effective conservation management. We therefore examine the relationship between climate, survival and reproduction in Canadian black-tailed prairie dogs, a threatened keystone species in an imperilled ecosystem at the northern edge of the species' range. Our analyses considered 8 years of annual mark-recapture data (2007-2014) in relation to growing degree days, precipitation, drought status and winter severity, as well as year, sex, age and body mass. Survival was strongly influenced by the interaction of drought and body mass class, and winter temperature severity. Female reproductive status was associated with the interaction of growing degree days and growing season precipitation, with spring precipitation and with winter temperature severity. Results related to body mass suggested that climatic variables exerted their effects via regulation of food availability with potential linked effects of food quality, immunological and behavioural implications, and predation risk. Predictions of future increases in drought conditions in North America's grassland ecosystems have raised concerns for the outlook of Canadian black-tailed prairie dogs. Insights gained from the analyses, however, point to mitigating species management options targeted at decoupling the mechanisms by which climate exerts its negative influence. Our approach highlights the importance of understanding the interaction between climate and population dynamics in peripheral populations whose viability might ultimately determine their species' ability to track climatically suitable space.

Suspected Hepadnavirus Association with a Hepatocellular Carcinoma in a Black-Tailed Prairie Dog (Cynomys ludovicianus).

Hepatocellular carcinomas are the most commonly reported neoplasm of black-tailed prairie dogs (Cynomys ludovicianus). In several other closely related Sciuridae species, infection with species-specific hepadnaviruses is associated with the development of these tumours, but such a hepadnavirus has not yet been identified in any prairie dog species, although its presence has been hypothesized previously. An adult prairie dog was humanely destroyed due to progressive illness and the identification of a cranial abdominal mass that was determined on histopathology to be a hepatocellular carcinoma. Deep sequencing of the tumour tissue identified the presence of a hepadnavirus, similar in its genetic structure to woodchuck hepatitis virus. Electron microscopy showed the presence of viral particles similar in structure to other hepadnaviral particles. This report suggests that a hepadnavirus may be associated with the development of hepatocellular carcinomas in the prairie dog.

EVALUATION OF THE EFFECTS OF STERNAL VERSUS LATERAL RECUMBENCY ON TRENDS OF SELECTED PHYSIOLOGIC PARAMETERS DURING ISOFLURANE ANESTHESIA IN ZOO-HOUSED BLACK-TAILED PRAIRIE DOGS (CYNOMYS LUDOVICIANUS).

Isoflurane gas anesthesia is often used for immobilization of prairie dogs in field studies, laboratory research, and veterinary clinical purposes. The goals of this prospective study were to evaluate the effects of sternal versus right lateral recumbency on trends of selected physiologic parameters during isoflurane anesthesia in black-tailed prairie dogs ( Cynomys ludovicianus ). Fourteen adult, zoo-housed black-tailed prairie dogs were tested during the study. Animals were anesthetized using isoflurane and randomly placed in either sternal or right lateral recumbency to evaluate changes in trends of physiologic parameters, measured selectively every 30 min throughout a 60-min anesthesia period. Results were analyzed using linear mixed modeling. Right lateral recumbency resulted in a decrease in anion gap of about 4.6 mEq/L (95% confidence interval [95% CI]: 3.1-6.0, P < 0.001), whereas sternal recumbency resulted in a lower decrease of 2.1 mEq/L (95% CI: 0.7-3.6, P = 0.02). However, the absolute values at the beginning and at the end of the anesthesia time were not significantly different between the right lateral and sternal recumbency (all P > 0.57). Body position did not have any effect on any other variables, and most of the observed physiologic changes were due to the duration of anesthesia. Our results indicate no significant effect on trends of selected physiologic parameters between sternal recumbency and right lateral recumbency during 1 hr of isoflurane anesthesia in black-tailed prairie dogs.

Burrow Dusting or Oral Vaccination Prevents Plague-Associated Prairie Dog Colony Collapse.

Plague impacts prairie dogs (Cynomys spp.), the endangered black-footed ferret (Mustela nigripes) and other sensitive wildlife species. We compared efficacy of prophylactic treatments (burrow dusting with deltamethrin or oral vaccination with recombinant "sylvatic plague vaccine" [RCN-F1/V307]) to placebo treatment in black-tailed prairie dog (C. ludovicianus) colonies. Between 2013 and 2015, we measured prairie dog apparent survival, burrow activity and flea abundance on triplicate plots ("blocks") receiving dust, vaccine or placebo treatment. Epizootic plague affected all three blocks but emerged asynchronously. Dust plots had fewer fleas per burrow (P < 0.0001), and prairie dogs captured on dust plots had fewer fleas (P < 0.0001) than those on vaccine or placebo plots. Burrow activity and prairie dog density declined sharply in placebo plots when epizootic plague emerged. Patterns in corresponding dust and vaccine plots were less consistent and appeared strongly influenced by timing of treatment applications relative to plague emergence. Deltamethrin or oral vaccination enhanced apparent survival within two blocks. Applying insecticide or vaccine prior to epizootic emergence blunted effects of plague on prairie dog survival and abundance, thereby preventing colony collapse. Successful plague mitigation will likely entail strategic combined uses of burrow dusting and oral vaccination within large colonies or colony complexes.

Responses of Juvenile Black-tailed Prairie Dogs ( Cynomys ludovicianus ) to a Commercially Produced Oral Plague Vaccine Delivered at Two Doses.

We confirmed safety and immunogenicity of mass-produced vaccine baits carrying an experimental, commercial-source plague vaccine (RCN-F1/V307) expressing Yersinia pestis V and F1 antigens. Forty-five juvenile black-tailed prairie dogs ( Cynomys ludovicianus ) were randomly divided into three treatment groups (n=15 animals/group). Animals in the first group received one standard-dose vaccine bait (5×107 plaque-forming units [pfu]; STD). The second group received a lower-dose bait (1×107 pfu; LOW). In the third group, five animals received two standard-dose baits and 10 were left untreated but in contact. Two vaccine-treated and one untreated prairie dogs died during the study, but laboratory analyses ruled out vaccine involvement. Overall, 17 of 33 (52%; 95% confidence interval for binomial proportion [bCI] 34-69%) prairie dogs receiving vaccine-laden bait showed a positive anti-V antibody response on at least one sampling occasion after bait consumption, and eight (24%; bCI 11-42%) showed sustained antibody responses. The STD and LOW groups did not differ (P≥0.78) in their proportions of overall or sustained antibody responses after vaccine bait consumption. Serum from one of the nine (11%; bCI 0.3-48%) surviving untreated, in-contact prairie dogs also had detectable antibody on one sampling occasion. We did not observe any adverse effects related to oral vaccination.

Efficacy of a fipronil bait in reducing the number of fleas (Oropsylla spp.) infesting wild black-tailed prairie dogs.

Bubonic plague (Yersinia pestis) is a deadly zoonosis with black-tailed prairie dogs (Cynomys ludovicianus) as a reservoir host in the United States. Systemic insecticides are a promising means of controlling the vectors, Oropsylla spp. fleas, infesting these prairie dogs, subsequently disrupting the Y. pestis cycle. The objective of this study was to conduct a field trial evaluating the efficacy of a grain rodent bait containing fipronil (0.005%) against fleas infesting prairie dogs. The study was performed in Larimer County, CO, where bait was applied to a treatment area containing a dense prairie dog population, three times over a three-week period. Prairie dogs were captured and combed for fleas during four study periods (pre-, mid-, 1st post-, and 2nd post-treatment). Results indicated the use of bait containing fipronil significantly reduced flea burden. The bait containing fipronil was determined to reduce the mean number of fleas per prairie dog >95% for a minimum of 52 days post-initial treatment application and 31 days post-final treatment application. These results suggest the potential for this form of treatment to reduce flea population density on prairie dogs, and subsequently plague transmission, among mammalian hosts across the United States and beyond.

PLASMA THYROXINE (T4) CONCENTRATION IN ZOO-KEPT BLACK-TAILED PRAIRIE DOGS (CYNOMYS LUDOVICIANUS).

This study was conducted to determine plasma thyroxine (T4) concentrations in zoo-kept black-tailed prairie dogs ( Cynomys ludovicianus ). Thirty-one healthy prairie dogs of both sexes were studied as part of their annual clinical health evaluation, performed under general isoflurane anesthesia. Each animal underwent a complete physical examination, complete blood count, plasma biochemistry, and venous blood gas analysis. Heparinized venous blood samples were collected individually and processed for plasma T4 analysis using a veterinary biochemistry analyzer. The median plasma T4 concentration for the prairie dogs in this study was 4.1 µg/dl (minimum = 0.6 µg/dl; maximum = 8.0 µg/dl). The mean ± standard deviation plasma T4 concentration was 4.49 ± 2.39 µg/dl. No significant differences were found for varying ages, sexes, weights, or housing systems. The data presented in this report can promote better physiologic understanding and improve clinical management of this rodent species.

Detections of Yersinia pestis East of the Known Distribution of Active Plague in the United States.

We examined fleas collected from black-tailed prairie dog (Cynomys ludovicianus) burrows from 2009 through 2011 in five national park units east of the known distribution of active plague across the northern Great Plains for the presence of Yersinia pestis. Across all national park units, Oropsylla tuberculata and Oropsylla hirsuta were the most common fleas collected from prairie dog burrows, 42.4% and 56.9%, respectively, of the 3964 fleas collected from burrow swabbing. Using a nested PCR assay, we detected 200 Y. pestis-positive fleas from 3117 assays. In total, 6.4% of assayed fleas were Y. pestis positive and 13.9% of prairie dog burrows swabbed contained Y. pestis-positive fleas. Evidence of the presence of Y. pestis was observed at all national park units except Devils Tower National Monument in Wyoming. We detected the presence of Y. pestis without large die-offs, i.e., enzootic sylvatic plague, east of the known distribution of active plague and near the eastern edge of the present distribution of black-tailed prairie dogs. This study, in combination with previous work suggests that sylvatic plague likely occurs across the range of black-tailed prairie dogs and should now be treated as endemic across this range.