Testing a method to improve predictions of disease and mortality risk in western lowland gorillas (gorilla gorilla gorilla) using allostatic load.

Allostatic load is the wear-and-tear organisms accumulate due to senescence and stress; it is measured by combining biomarkers from multiple somatic systems into allostatic load indices (ALIs). Frequently used in human research, ALIs have shown consistent results across samples despite different biomarkers and methods. However, determining optimal models likely is necessary if ALIs are to be feasible research tools in other species. Herein, we build on prior research in western lowland gorillas to explore one potential method for determining which biomarkers may be best for estimating allostatic load. After narrowing down which biomarkers to include using a combination of forward stepwise regression and independent biomarker associations with project variables, we estimated allostatic load using both the traditional one-tailed quartile method as well as a multi-method approach. There was a significant positive association between allostatic load and triglycerides, but not cholesterol, both of which are commonly used as diagnostic markers of poor health. Using binomial generalized linear models, a one-unit increase in allostatic load was associated with increased risk of all-cause morbidity and mortality, but reduced risk of cardiac disease. Although conclusions were similar, compared to our original ALIs, these new ALIs had weaker effect sizes and poorer relative goodness of fit, suggesting this method for identifying the best possible list of biomarkers to include in an index was not effective. This report continues the development of ALIs as a clinical tool in wildlife while systematically testing one possible method for determining an optimal ALI for a particular species.

The first multi-zoo application of an allostatic load index to western lowland gorillas (Gorilla gorilla gorilla).

Vertebrate stress responses are highly adaptive biological functions, maximizing survival probability in life-threatening situations. However, experiencing repeated and/or chronic stressors can generate physiological dysregulation and lead to disease. Because stress responses are multi-systemic and involve a wide range of physiological functions, identifying responses to stressors is best accomplished using integrated biomarker models. Allostatic load, defined as the physiological dysregulation that accumulates over the lifespan due to stressful experiences, is one such model. Allostatic load is measured using allostatic load indices, which are composites of biomarkers from multiple somatic systems. Previously, we reported the use of a 7-biomarker allostatic load index (albumin, CRH, cortisol, DHEA-S, glucose, IL-6, TNF-α) in western lowland gorillas housed at a single zoo. Herein, this index is expanded to examine allostatic load responses to lifetime stressors in gorillas from two additional zoos (n = 63) as well as two pooled samples. The index was created using quartile cut-points for each biomarker. Significant associations were observed between multiple predictor variables and allostatic load, including sex, age, number of stressful events (anesthetic events, zoo transfers, agonistic interactions with wounding, pregnancies), and rearing history (mother-reared, nursery-reared, wild-caught). Additionally, allostatic load was associated with indicators of morbidity (creatinine, cholesterol, triglycerides), age at death, and mortality risk. These results are consistent with those reported in human allostatic load research, suggesting allostatic load indices have potential as an investigative and clinical tool for gorillas and other great apes.

EVALUATING ALLOSTATIC LOAD: A NEW APPROACH TO MEASURING LONG-TERM STRESS IN WILDLIFE.

Animal welfare, conservation, and stress assessment are all critical components of species survival. As organisms experience stressors, they accumulate physiologic dysregulation, leading to multiple negative health outcomes. This brief review suggests measuring the degree of stress-induced damage, known as allostatic load, and then using allostatic load to evaluate changes implemented to improve animal welfare and conservation efforts. Over the past two decades, human clinical research has developed multiple allostatic load indices constructed from composites of neuroendocrine, cardiovascular, metabolic, and immune biomarkers. These indices are designed to estimate allostatic load in hopes of ameliorating or even negating damaging effects of stress. Among humans, allostatic load is associated with a variety of factors such as age, sex, stressful experiences, personality, social position, and early life history. Despite conservation of stress responses throughout mammalian species, reported allostatic load indices for animals are rare. Because many zoo researchers and field scientists already collect data on multiple biomarkers, constructing allostatic load indices may be a relatively affordable, easily implemented, and powerful tool for assessing relative risks of morbidity and mortality within wildlife. As an example, in a study among zoo-housed gorillas, an allostatic load index constructed using seven biomarkers was associated significantly with age, sex, stressful experiences, rearing history, markers of poor health, and mortality risk. Such results evidence that allostatic load is as applicable to animal populations as it is to humans. By using allostatic load as a predictive tool, human caretakers will be better informed of individuals at greatest risk for health declines. Most importantly, allostatic load may provide earlier opportunity for preemptive care while contributing a transformational tool to animal welfare research. Additionally, allostatic load may be compared between individuals and groups within the same population and allow comparisons of health between and across populations, consequently informing habitat and population protection efforts.

Rearing history and allostatic load in adult western lowland gorillas (Gorilla gorilla gorilla) in human care.

Disrupted rearing history is a psychological and physical stressor for nonhuman primates, potentially resulting in multiple behavioral and physiological changes. As a chronic, soma-wide stressor, altered rearing may be best assessed using a holistic tool such as allostatic load (AL). In humans, AL estimates outcomes of lifetime stress-induced damage. We predicted mother-reared gorillas would have lower AL than nursery-reared and wild-caught conspecifics. We estimated AL for 27 gorillas housed at the Columbus Zoo and Aquarium between 1956 and 2014. AL estimates were calculated using biomarkers obtained during previous anesthetic events. Biomarkers in the high-risk quartile were counted toward a gorilla's AL. Rearing history was categorized as mother-reared, nursery-reared, and wild-caught. Using ANCOVA, rearing history and AL are significantly associated when age and sex are entered as covariates. Wild-caught gorillas have significantly higher AL than mother-reared gorillas. Neither wild-caught nor mother-reared gorillas are significantly different from nursery-reared gorillas. When examined by sex, males of all rearing histories have significantly lower AL than females. We suggest males face few stressors in human care and ill effects of rearing history do not follow. Wild-caught females have significantly higher AL than mother-reared females, but neither is significantly different from nursery-reared females. Combined with our previous work on AL in this group, wherein females had twofold higher AL than males, we suggest females in human care face more stressors than males. Disrupted rearing history may exacerbate effects of these stressors. Providing opportunities for females to choose their distance from males may help reduce their AL.

Increased inflammation and decreased insulin sensitivity indicate metabolic disturbances in zoo-managed compared to free-ranging black rhinoceros (Diceros bicornis).

Black rhinoceros (rhinos) living in zoos express a host of unusual disease syndromes that are associated with increased morbidity and mortality, including hemolytic anemia, rhabdomyolysis, hepatopathy and ulcerative skin disease, hypophosphatemia and iron overload. We hypothesized that iron overload is a consequence and indicator of disturbances related to inflammation and insulin/glucose metabolism. The objectives of this study were to: (1) generate the first baseline information on biomarkers of inflammation (tumor necrosis factor alpha [TNFα], serum amyloid A [SAA]), insulin sensitivity (insulin, glucose and proxy calculations of insulin sensitivity), phosphate and iron stores (ferritin) using banked serum from free-ranging black rhinos; and (2) then compare serum biomarkers between zoo-managed (n=86 individuals) and free-ranging (n=120) animals. Enzyme immunoassays were validated for serum and then biomarker levels analyzed using mixed models while controlling for sex, age and year of sample collection. Concentrations of TNFα, SAA, insulin and insulin-to glucose ratio were higher (P<0.05) in black rhinos managed in ex situ conditions compared to free-living counterparts. Findings indicate that the captive environment is contributing to increased inflammation and decreased insulin sensitivity in this endangered species.

The effect of fluphenazine decanoate on glucocorticoid production, reproductive cyclicity, and the behavioral stress response in the Persian onager (Equus hemionus onager).

Artificial insemination, performed to maximize genetic diversity in populations of zoo-housed animals, requires intensive management and has been associated with low success rates in fractious species. In these species, stressors, such as frequent handling, may impact fertility. Long-acting neuroleptic pharmaceuticals (LANs) can attenuate the stress response to handling, but may also disrupt ovulation in some species, compromising their use for artificial insemination. Therefore, the goal of this study was to determine whether LANs may be used to mitigate stress during reproductive management in wild equids without inhibiting ovulation. Six female Persian onagers (Equus hemionus onager) were treated with fluphenazine decanoate (FD; 0.1 mg/kg IM) or saline control in a random crossover design study. Urinary cortisol, progesterone, estrogen metabolites and behavior were monitored, and follicular dynamics were examined using ultrasonography until ovulation. Onagers demonstrated significantly lower cortisol concentrations (P = 0.03) when treated with FD (6.61 ± 3.26 ng/mg creatinine) compared to saline (9.73 ± 3.19 ng/mg creatinine). Overall, there were no differences in peak estrogen (P = 0.51) or progesterone (P = 0.38) concentrations between the two groups, and all animals ovulated within the expected time frame following FD treatment. However, some onagers exhibited only minor reductions in cortisol secretion and one treated female demonstrated a suppressed luteal progesterone peak, indicating a possible reproductive cost to FD administration. While FD may be useful for highly fractious equids for which the stress of handling delays or inhibits ovulation, these results warrant further investigation of dosing.

Improved sperm cryosurvival in diluents containing amides versus glycerol in the Przewalski's horse (Equus ferus przewalskii).

Two studies were conducted to understand sperm cryosensitivity in an endangered equid, the Przewalski's horse (Equus ferus przewalski), while testing the cryoprotectant ability of formamides. The first assessed the toxicity of permeating cryoprotectants (glycerol, methylformamide [MF] and dimethylformamide [DMF]) to Przewalski's horse spermatozoa during liquid storage at 4°C. The second examined the comparative influence of three diluents (with or without formamides) on cryosurvival of sperm from the Przewalski's versus domestic horse. When Przewalski's horse spermatozoa were incubated at 4°C in INRA 96 with differing concentrations of glycerol, MF or DMF or a combination of these amides, cells tolerated all but the highest concentration (10% v/v) of MF alone or in combination with DMF, both of which decreased (P<0.05) motility traits. There was no effect of cryoprotectants on sperm acrosomal integrity. In the cryosurvival study, average sperm motility and proportion of cells with intact acrosomes in fresh ejaculates were similar (P>0.05) between the Przewalski's (67%, 84%, respectively) and domestic (66%, 76%) horse donors. Sperm from both species were diluted in lactose-EDTA-glycerol (EQ), Botu-Crio (BOTU; a proprietary product containing glycerol and MF) or SM (INRA 96 plus 2% [v/v] egg yolk and 2.5% [v/v] MF and DMF) and then frozen over liquid nitrogen vapor. After thawing, the highest values recovered for total and progressive sperm motility, acrosomal integrity and mitochondrial membrane potential were 42.4%, 21.8%, 88.7% and 25.4CN (CN=mean JC-1 fluorescence intensity/cell on a channel number scale), respectively, in the Przewalski's and 49.3%, 24.6%, 88.9% and 25.8CN, respectively, in the domestic horse. Although sperm progressive motility and acrosome integrity did not differ (P>0.05) among treatments across species, mitochondrial membrane potential was higher (P<0.05) in both species using EQ compared to BOTU or SM media. Additionally, Przewalski's stallion sperm expressed higher (P<0.05) post-thaw total motility in BOTU and SM compared to EQ, whereas there were no differences among freezing diluents in the domestic horse. In summary, Przewalski's stallion sperm benefit from exposure to either MF or DMF as an alternative cryoprotectant to glycerol. Overt sperm quality appears similar between the Przewalski's and domestic horse, although the total motility of cells from the former appears more sensitive to certain freezing diluents. Nonetheless, post-thaw motility and acrosomal integrity values for Przewalski's horse spermatozoa mimic findings in the domestic horse in the presence of INRA 96 supplemented with 2% (v/v) egg yolk and a combined 2.5% concentration of MF and DMF.

Evaluation of season-related dietary changes on the serum profiles of fat-soluble vitamins, mineral, fatty acids, and lipids in the captive greater one-horned rhinoceros (Rhinoceros unicornis).

Circulating concentrations of fat-soluble vitamins A, D, and E, minerals, fatty acids, and lipids were quantified in five captive greater one-horned rhinoceroses (Rhinoceros unicornis) throughout two time periods, during which two diets were offered. Animals were fed mixed-grass hay and concentrate pellets while managed in barns for winter housing (April sampling, winter diet). During the spring and summer, animals were fed the same amount of concentrate pellet but had free access to North American browse and grasses instead of dried forage (November sampling, summer diet). Levels of 25-hydroxyvitamin D and α-tocopherol were statistically higher in summer diet samples than in winter diet samples. Retinol was not statistically different between seasons, and ß-carotene concentrations were undetectable at both time periods. Cholesterol, triglycerides, and non-esterified fatty acids were all significantly elevated following access to unlimited fresh forages in summer. Serum electrolytes were not different between the two time periods but differences in circulating minerals were noted (cobalt, inorganic iodine, and magnesium elevated in winter diet samples; selenium and zinc elevated in summer diet). Access to non-native fresh green forages resulted in improvement of several nutritional parameters in greater one-horned rhinoceroses, implying a benefit when fresh browse and access to grass is provided.

Long-acting neuroleptic use for reproductive management of non-domestic ungulates using the domestic goat (Capra hircus) as a model.

Fluphenazine decanoate is a long-acting phenothiazine neuroleptic that attenuates the stress response and may be useful during intensive handling for reproductive procedures in non-domestic ungulates. However, phenothiazines are also associated with elevated serum prolactin, which can suppress fertility in some species. For this study, 10 female domestic goats were used as a model for non-domestic caprids to test effects of fluphenazine decanoate on serum cortisol and reproductive cyclicity following estrus synchronization. Two identical trials were conducted during the breeding season, employing a random crossover design. First, females underwent estrus synchronization using a 14-day treatment with progesterone (330 mg; CIDR). After 7 days of CIDR exposure, the treatment group (n = 5) received fluphenazine decanoate (1.0 mg/kg IM) and controls (n = 5) received an equivalent volume of 0.9% saline IM. At CIDR withdrawal (Day 14), animals received 125 mg cloprostenol sodium to lyse any luteal tissue and synchronize estrus. Blood was collected every 2 hr from 36 hr after CIDR withdrawal until 24 hr after standing estrus, or up to 5 days to monitor stress and reproductive hormones. Serum cortisol, prolactin, luteinizing hormone (LH) and progesterone concentrations were determined by enzyme immunoassay. While treatment with fluphenazine was associated with lower cortisol concentrations compared to controls (P = 0.001), 4 of the 10 treated animals experienced elevated serum prolactin, suppression of the LH surge and inhibition of ovulation. These findings suggest that long-acting neuroleptic drugs reduce the adrenal stress response, but may interfere with reproductive responses and negatively influence breeding success.

Baseline assessment of ophthalmic parameters in the greater one-horned rhinoceros (Rhinoceros unicornis).

Five healthy captive greater one-horned rhinoceroses (Rhinoceros unicornis) were evaluated with standing sedation (detomidine hydrochloride 20-30 mg and butorphanol tartrate 50-60 mg per animal) to determine baseline values for tear production, intraocular pressure (IOP), conjunctival flora, and ocular anatomy using brightness mode transpalpebral ultrasonography with a 4- to 7-MHz broadband curvilinear transducer. The mean Schirmer tear test I value was 18.2 ± 3.49 mm/min. The mean IOP measured using applantation tonometry was 31.2 ± 6.62 mm Hg. Ocular biometry measurements were the following: axial length 2.61 ± 0.11 cm; corneal thickness 0.13 ± 0.01 cm; anterior segment depth 0.28 ± 0.06 cm; lens depth 0.70 ± 0.11 cm; and posterior segment depth 1.46 ± 0.13 cm. These values indicate that the globe is smaller than that of the domestic horse. All eight conjunctival swabs cultured bacterial and fungal microorganisms, with the most common being Staphylococcus spp. (57%). All bacterial isolates were considered to be commensal organisms due to the presence of mixed bacterial populations and lack of clinical signs of ocular disease. The data collected in this study should provide veterinarians with baseline information to assist in the diagnosis of ophthalmic conditions in the greater one-horned rhinoceros.

Comparison of butorphanol-detomidine versus butorphanol-azaperone for the standing sedation of captive greater one-horned rhinoceroses (Rhinoceros unicornis).

Three adult and two subadult greater one-horned rhinoceroses (Rhinoceros unicornis) were sedated a total of nine times using two different intramuscular sedative combinations in order to compare the effectiveness of these combinations in inducing consistent standing sedation in this species. The sedation protocols compared were butorphanol tartrate (50-60 mg) and detomidine hydrochloride (20-30 mg; BD) versus butorphanol tartrate (80-120 mg) and azaperone (80-120 mg; BA). Specific doses were adjusted according to age and sex class, and based on previous experience. Parameters compared included time to achieve defined levels of sedation, time to recovery following antagonism, physiological parameters including heart rate, respiratory rate, indirect arterial blood pressure, and venous blood gas values. A hydraulic restraint chute was utilized to mechanically restrain animals during the procedures, and blood collection and ophthalmic examinations were conducted on all animals. Both protocols resulted in standing sedation for > or = 22.3 +/- 2.9 min or until antagonists were administered. The BD protocol resulted in deeper and more consistent sedation, compared to the BA protocol. Naltrexone hydrochloride (250-300 mg) and tolazoline hydrochloride (1,500-2,000 mg) were administered intramuscularly to antagonize protocol BD, whereas naltrexone alone (200-500 mg) was used to antagonize BA. Time to full antagonism, defined as normal mentation and ambulation following administration of antagonists, was prolonged in the BD protocol (132.3 +/- 17.2 min) compared with the BA protocol (7.5 +/- 2.5 min). Venous blood gas analysis did not reveal any significant blood gas deviations during sedation when compared with either conscious equine or white rhinoceros (Ceratotherium simum) venous reference ranges. In summary, both combinations resulted in adequate standing sedation for minimally invasive procedures, although BD resulted in more profound and consistent sedation.

Fundamental studies of the reproductive biology of the endangered persian onager (Equus hemionus onager) result in first wild equid offspring from artificial insemination.

We studied the Persian onager (Equus hemionus onager), an endangered equid subspecies. The objective was to characterize endocrine patterns and ovarian follicular dynamics of females as well as seminal traits and sperm sensitivity to cryopreservation in males as a prerequisite to testing the feasibility of artificial insemination (AI). Urinary progesterone and estrogen metabolite profiles were determined by enzyme immunoassay in 11 females. Serial ultrasonography of ovarian activity was performed for 2 mo in a subset of four females. Females were seasonally polyestrous (June-November). Ovarian morphometry via ultrasonography and urinary progesterone profiles were more reflective of reproductive events than urinary estrogen patterns, and preovulatory follicle size was smaller than reported for other equid species. There was evidence for lactational suppression of estrus for up to 1.5 yr in nursing dams. Electroejaculation allowed recovery of highly motile sperm from 7, anesthetized males on 57% of occasions. Spermatozoa, including motility and acrosomal integrity, were resilient to freeze-thawing. Artificial insemination was successful in 2 of 3 females following detection of a dominant follicle and deslorelin administration, resulting in births of a healthy female and male foal by using fresh/chilled and frozen/thawed sperm, respectively.

Twenty-five metagenome-assembled genomes recovered from the gut microbiome of the domestic ferret, Mustela putorius.

With the advent of metagenomics has come an increased appreciation for the gut microbiome's role in overall health of mammalian organisms. Even so, studies characterizing taxonomic and functional diversity of the ferret gut microbiome remain limited. Here, we present 25 metagenome-assembled genomes recovered from the gut microbiome of domestic ferrets.

Abnormal reproductive patterns in Przewalski's mares are associated with a loss in gene diversity.

The ex situ population of the Przewalski's horse (Equus ferus przewalskii) is not self-sustaining (20% foaling rate), and the demography is skewed toward aging individuals with low gene diversity. We designed the present study to gain a better understanding of the reproductive biology of the Przewalski's mare and to determine whether age and gene diversity influenced reproductive function. Urine samples were collected 3-7 days/wk from 19 mares from May to September, and ultrasound examinations of follicular structures were performed 3 days/wk for 5 wk from May through July in nine individuals. A high proportion of mares exhibited abnormal (endocrine, 5 [26.3%] of 19; follicular, 2 [22.2%] of 9) or acyclic (endocrine, 4 [21.1%] of 19; follicular, 3 [33.3%] of 9) reproductive patterns. In four cyclic mares, estrous cycle length was 25.1 ± 1.2 days, with 12.2 ± 0.9 days of diestrus. Follicles in cyclic mares grew 1.2 ± 0.6 mm per day and ovulated after reaching 40.4 ± 8.9 mm. Mares with a high coefficient of inbreeding excreted reduced levels of mean urinary estrogens (r(2) = 0.476, P < 0.05), but age had no significant impact on reproductive patterns in this population. Overall, these data suggest that long-term genetic management of this population is necessary to maintain reproductive fitness.

Glucocorticoid response to changes in enclosure size and human proximity in the Persian onager (Equus hemionus onager).

This study investigated glucocorticoid (GC) responses to season and changes in enclosure size and human proximity in the Persian onager (Equus hemionus onager). Enzyme immunoassays were validated to measure GC metabolites in urine and feces (fGCM). Fecal samples were collected from 10 female onagers while in a large pasture, after transport to smaller yards (in greater proximity to people), and 2 months thereafter. Urine samples were collected for 1 year while females were in smaller yards to examine seasonal GC activity. Approximately, 2-fold increases (P < 0.05) were observed in fGCM levels after transport from pasture to yards with increased human exposure, followed by a rapid decline (within -17 days) to baseline (pasture) values. However, responses varied among onagers during the 30 days after translocation, with one female failing to acclimate. Mean fGCM concentrations in smaller yards 2 months after transport were comparable to those in pasture. Seasonal GC concentrations were lowest (P < 0.05) during winter, indicating modest seasonal variability. Results demonstrate an acute increase in GC secretion in Persian onagers that moved from large to small enclosures coincident with increased human activities. Most animals acclimated within 3 weeks, suggesting that this rare equid has retained mechanisms to acclimate to marked alterations in an ex situ environment.

Use of thermography and fluorescein angiography in the management of a Chilean flamingo with avascular necrosis of the wing.

A Chilean flamingo (Phoenicopterus chilensis) was presented to the veterinary clinic at the North Carolina Zoological Park for evaluation of acute weakness of the right wing. Results of a physical examination revealed a lack of a palpable pulse in the radial artery, which suggested occlusion or obstruction of the vessel. Radiography, thermography, and fluorescein angiography confirmed right wing injury and vascular compromise. Based on the poor prognosis for return to function associated with irreversible vascular damage, the wing was amputated. After a period of observation and treatment, the bird was returned to public exhibit.

Allostatic Load Indices With Cholesterol and Triglycerides Predict Disease and Mortality Risk in Zoo-Housed Western Lowland Gorillas (Gorilla gorilla gorilla).

Allostatic load, or the physiological dysregulation accumulated due to senescence and stress, is an established predictor of human morbidity and mortality and has been proposed as a tool for monitoring health and welfare in captive wildlife. It is estimated by combining biomarkers from multiple somatic systems into allostatic load indices (ALIs), providing a score representing overall physiological dysregulation. Such ALIs have been shown to predict disease and mortality risk in western lowland gorillas. In these prior analyses, we were unable to include lipid markers, a potential limitation as they are key biomarkers in human models. Recently, we were able to assay serum cholesterol and triglycerides and add them to our previous ALI. We then re-examined associations with health outcomes using binomial generalized linear models. We constructed ALIs using 2 pooling strategies and 2 methods. By itself, a 1-unit increase in allostatic load was associated with higher odds of all-cause morbidity and mortality, but results were mixed for cardiac disease. However, the best fit models for all-cause morbidity and cardiac disease included only age and sex. Allostatic load was retained alongside age in the best fit models for mortality, with a 1-unit increase associated with 23% to 45% higher odds of death. Compared with previous results, ALIs containing cholesterol and triglycerides better predict disease risk in zoo-housed western lowland gorillas, as evidenced by larger effect sizes for some models and better goodness of fit for all ALIs. Based on these results, we address methodology for future allostatic load research on wildlife.

Acquired arteriovenous fistula in a grizzly bear (Ursus arctos horribilis).

A captive adult male grizzly bear (Ursus arctos horribilis) was evaluated due to multifocal wounds of the skin and subcutaneous tissues sustained as a result of trauma from another grizzly bear. On presentation, one lesion that was located in the perineal region seemed to be a deep puncture with purple tissue protruding from it. This perineal wound did not heal in the same manner or rate as did the other wounds. Twenty-five days after initial detection, substantial active hemorrhage from the lesion occurred and necessitated anesthesia for examination of the bear. The entire lesion was surgically excised, which later proved curative. An acquired arteriovenous fistula was diagnosed via histopathology. Arteriovenous fistulas can develop after traumatic injury and should be considered as a potential complication in bears with nonhealing wounds.

Clinical Parelaphostrongylus tenuis infection in two captive American bison (Bison bison).

CASE DESCRIPTION: 2 juvenile (17 and 19 months of age) male American bison (Bison bison) were examined because of acute bilateral hind limb weakness and ataxia; 1 animal also had urinary incontinence. TREATMENT AND OUTCOME: Given the clinical signs and rapid deterioration in the condition of these 2 animals, obtaining a definitive diagnosis was considered essential to minimizing the risk of disease in the remaining bison herd and among other animals at the facility. Therefore, both affected animals were euthanized. At necropsy, no gross abnormalities were seen. Histologic examination of sections of the brains from both animals revealed mild to moderate multifocal aggregates of eosinophils and mononuclear cells in perivascular regions of the meninges and gray matter of the cerebrum, cerebellum, and brainstem. Systematic examination of multiple sections of brain and spinal cord revealed evidence of nematode sections and aberrant parasite migration. CLINICAL RELEVANCE: Findings suggested that CNS migration of Parelaphostrongylus tenuis in American bison may cause clinical signs. These findings have implications for the management of captive bison and free-ranging bison sharing ranges with white-tailed deer (Odocoileus virginianus), the definitive host, and elk (Cervus elaphus canadensis).

Serologic response to West Nile virus vaccination in the greater one-horned rhinoceros (Rhinoceros unicornis).

Vaccination has been an important component of preventative health care programs of North American zoologic institutions in their protection of valuable species against West Nile virus (WNV) infection since its detection in 1999. Although approved only for horses, commercial WNV vaccine has been used for the purpose of protection of nondomestic species, including avian, equid, and rhinoceros species. Currently, there are two commercial equine vaccines available, a killed vaccine and a recombinant viral-vectored vaccine. Both products have been used for the vaccination of Greater One-horned rhinoceroses (Rhinoceros unicornis) held in North American zoologic institutions. In this study, the efficacy of these vaccines was evaluated in Greater One-horned rhinoceroses based on the humoral immune response stimulated by vaccine administration. Five rhinoceroses were vaccinated in 2005 by using the killed equine vaccine and four received boosters in 2006 by using the recombinant vaccine. Rhinoceroses were evaluated for differences in pre- and postvaccination neutralizing antibody titer and gamma and beta globulins on serum protein electrophoresis. No changes were observed after administration of the killed vaccine; however, antibody titers were observed in two of four rhinoceroses after administration of the recombinant vaccine. No significant changes were observed in the serum protein electrophoresis after either vaccine. Based on these findings, the WNV recombinant vaccine appeared to induce a more measurable humoral immune response than the killed product in the Greater One-horned rhinoceros. However, further investigation of both vaccines is warranted to evaluate whether changes in the frequency of administration, dosage, or adjuvant might stimulate an improved humoral response in these animals.