Arterial oxygenation and acid-base status before and during oxygen supplementation in captive European bison (Bison bonasus) immobilized with etorphine-acepromazine-xylazine.

Chemical immobilization of captive European bison (Bison bonasus) is often required for veterinary care, transportation, or husbandry practices playing an important role in conservation breeding and reintroduction of the species. We evaluated the efficiency and physiological effects of an etorphine-acepromazine-xylazine combination with supplemental oxygen in 39 captive European bison. Animals were darted with a combination of 1.4 mg of etorphine, 4.5 mg of acepromazine, and 20 mg of xylazine per 100 kg based on estimated body mass. Arterial blood was sampled on average 20 min after recumbency and again 19 min later and analyzed immediately with a portable i-STAT analyzer. Simultaneously, heart rate, respiratory rate, and rectal temperature were recorded. Intranasal oxygen was started after the first sampling at a flow rate of 10 mL.kg-1.min-1 of estimated body mass until the end of the procedure. The initial mean partial pressure of oxygen (PaO2) was 49.7 mmHg with 32 out of 35 sampled bison presenting with hypoxemia. We observed decreased respiratory rates and pH and mild hypercapnia consistent with a mild respiratory acidosis. After oxygen supplementation hypoxemia was resolved in 21 out of 32 bison, but respiratory acidosis was accentuated. Bison immobilized with a lower initial drug dose required supplementary injections during the procedure. We observed that lower mean rectal temperatures during the immobilization event were significantly associated with longer recovery times. For three bison, minor regurgitation was documented. No mortality or morbidity related to the immobilizations were reported for at least 2 months following the procedure. Based on our findings, we recommend a dose of 0.015 mg.kg-1 etorphine, 0.049 mg.kg-1 acepromazine, and 0.22 mg.kg-1 xylazine. This dose reduced the need for supplemental injections to obtain a sufficient level of immobilization for routine management and husbandry procedures in captive European bison. Nevertheless, this drug combination is associated with development of marked hypoxemia, mild respiratory acidosis, and a small risk of regurgitation. Oxygen supplementation is strongly recommended when using this protocol.

Interactions between the rabies virus and nicotinic acetylcholine receptors: A potential role in rabies virus induced behavior modifications.

Rabies causes approximately 60,000 casualties annually and has a case fatality rate approaching 100% once clinical signs occur. The glycoprotein on the surface of the virion is important for the host immune response and facilitates interaction of the virion with host cell receptors. Nicotinic acetylcholine receptors were the first receptors identified as a molecular target for the rabies virus. Additional targets, including neural cell adhesion molecule, p75 neurotrophin receptor, metabotropic glutamate receptor subtype 2, and integrin ß1, have been added to the list, all of which can mediate viral entry into the cell. Multiple receptors and different subtypes of nicotinic acetylcholine receptors result in a complex picture of virus-receptor interactions. In addition, some data suggest that the rabies virus glycoprotein inhibits cell signaling events mediated by various nicotinic receptor subtypes that have been implicated in altering behavior in unaffected animals. This review focuses on interactions between the rabies virus glycoprotein and nicotinic receptors and proposes possible functional consequences, including behavioral modifications and therapeutic approaches for future research.

Retention and loss of PIT tags and surgically implanted devices in the Eurasian beaver.

BACKGROUND: Passive integrated transponder devices (PIT tags) are a valuable tool for individual identification of animals. Similarly, the surgical implantation of transmitters and bio-loggers can provide useful data on animal location, physiology and behavior. However, to avoid unnecessary recapture and related stress of study animals, PIT tags and bio-loggers should function reliably for long periods of time. Here, we evaluated the retention of PIT tags, and of very high frequency (VHF) transmitters and bio-loggers that were either implanted subcutaneously or into the peritoneal cavity of Eurasian beavers (Castor fiber). RESULTS: Over a 21-year period, we implanted PIT tags in 456 individuals and failed to detect a PIT tag at recapture in 30 cases, consisting of 26 individuals (6% of individuals). In all instances, we were still able to identify the individual due to the presence of unique ear tag numbers and tail scars. Moreover, we implanted 6 VHFs, 36 body temperature loggers and 21 heart rate loggers in 28 individuals, and experienced frequent loss of temperature loggers (at least 6 of 23 recaptured beavers) and heart rate loggers (10 of 18 recaptured beavers). No VHFs were lost in 2 recaptured beavers. CONCLUSIONS: Possible causes for PIT tag loss (or non-detection) were incorrect implantation, migration of the tag within the body, a foreign body reaction leading to ejection, or malfunctioning of the tag. We speculate that logger loss was related to a foreign body reaction, and that loggers were either rejected through the incision wound or, in the case of temperature loggers, possibly adhered and encapsulated to intestines, and then engulfed by the gastro-intestinal tract and ejected. We discuss animal welfare implications and give recommendations for future studies implanting bio-loggers into wildlife.

Simple Field Anesthesia for Free-Ranging Microtines.

Although physical restraint without anesthesia is a common way to immobilize microtines in field settings, tagging can cause pain and stress, and escape-response movements may reduce marking quality. To evaluate if inhaled isoflurane may be a tool to minimize these issues, we anesthetized free-ranging voles (Microtus and Myodes spp.) undergoing subcutaneous injection of a passive integrated transponder tag and dorsal fur clipping. We anesthetized 24 voles for short-duration anesthesia using two 0.2-mL isoflurane doses in a simple drop-chamber system. We used the first dose to induce unconsciousness and the second dose to immediately restore unconsciousness after the vole regained consciousness from the first dose. Median induction times were 54 s for the first dose (interquartile range [IQR], 47-61) and 50 s for the second dose (IQR, 38-55). Median recovery times were 33 s for the first dose (IQR, 26-60) and 62 s for the second dose (IQR, 35-104). No mortalities occurred during the holding period. The technique was simple, inexpensive, and effective. We therefore recommend using isoflurane delivered in a drop chamber when tagging or marking microtines in the field to improve handling.

Regional variations and relationships among cytokine profiles, white blood cell counts, and blood mercury concentrations in Steller sea lion (Eumetopias jubatus) pups.

The Steller sea lion (SSL) population west of 144°W longitude experienced a significant population decline. While there appears to be a stable or increasing population trend in rookeries in the Gulf of Alaska (GOA) and Southeast Alaska (SEA), some rookeries within the Aleutian Islands (AI) have failed to recover. Previous studies found regional differences in whole blood total mercury concentrations ([THg]) showing more than 20% of AI pups had [THg] above critical thresholds for increased risk of immunological effects and other adverse outcomes. Measurements of immune cell-signaling proteins can be used to evaluate the immune status of marine mammals in relation to [THg]. We compared serum cytokine and chemokine concentrations in pups among regions (AI, eastern GOA, SEA), and examined associations among cytokines, chemokines, white blood cell (WBC) counts, and [THg]. Considering liver is an important target organ for mercury and immune protein synthesis we additionally examined the relationship of [THg] with liver-related enzymes serum aspartate (AST) and alanine aminotransferase (ALT). We observed regional differences in cytokine and chemokine measurements and immune protein associations. There was a positive association between total WBC counts and [THg] in AI pups, whereas a negative association between lymphocytes and [THg] in SEA pups. These findings may indicate regional variation in proliferation and differentiation of hematopoietic cells, differences in immune system development, and/or a difference in antigenic stimuli. No associations between [THg] and cytokines, chemokines, AST or ALT were found. Observed regional differences in cytokine and chemokine milieu during gestational and early development in SSL pups could lead to an imbalance in cell differentiation that could impact immunological resiliency in juvenile and adult life stages. We report concentration ranges of a suite of cytokines and chemokines which may prove to be a useful metric for ecotoxicology and risk assessment studies in SSLs and other wildlife.

Assessment of clinical outcomes associated with mercury concentrations in harbor seal pups (Phoca vitulina richardii) in central California.

Monomethyl mercury (MeHg+) from the diet can cause mild to severe neurotoxicosis in fish-eating mammals. Chronic and low-level in utero exposure also can be neurotoxic, as documented in laboratory animal studies and epidemiologic investigations. In free-ranging animals, it is challenging to study low-level exposure related neurotoxicosis, and few studies have investigated the relationship between mercury (Hg) and adverse outcomes in wild populations. Relative to Hg concentrations on admission we evaluated different types of behaviors for 267 Pacific harbor seal (HS; Phoca vitulina richardii) pups at The Marine Mammal Center from 2015 to 2019 during rehabilitation after stranding and maternal separation. Admitted HS pups underwent a clinical exam; including sex and weight determination, and hair (partly lanugo grown in utero) and blood samples were collected for total Hg concentration ([THg]) determination. All pups were monitored weekly (behavior assessments included response to tactile stimulation, movement, swimming, interactions with other seals, hand feeding, and feeding independently), and days in rehabilitation and survival were recorded. There was a significant negative correlation between [THg] and responses to tactile stimulation and movements, measured in both hair and whole blood (p < 0.05). This relationship was found both during the intensive care unit (ICU) stage, and during the pool stage of rehabilitation. Additionally, there was a significant association between greater [THg] and number of days spent in rehabilitation, although there was no relationship between [THg] and survival. There was a significant sex difference, with greater [THg] in female pups, which contrasts with previously published findings in juvenile and adult harbor seals. Our findings support small, but significant associations between gestational THg exposure and clinical effects for tactile sensory response and movement, and longer rehabilitation durations for HS pups, although there was considerable variability among animals.

Assessing oxidative stress in Steller sea lions (Eumetopias jubatus): Associations with mercury and selenium concentrations.

Selenium (Se) bioavailability is required for synthesis and function of essential Se-dependent antioxidants, including the enzyme glutathione peroxidase (GPx). Strong interactions between monomethyl mercury and Se impair the critical antioxidant role of Se. Approximately 20% of Steller sea lion (Eumetopias jubatus, SSL) pups sampled in the western Aleutian Islands, Alaska, had total Hg concentrations ([THg]) measured in hair and whole blood above thresholds of concern for adverse physiologic effects in pinnipeds. Importantly, low molar ratios of TSe:THg, in some cases < 1 in several tissues (hair, liver, pelt, muscle, spleen, intestine, heart, lungs, brain) were documented for one SSL pup with [THg] above threshold of concern, which may lead to antioxidant deficiency. Our aim with this study was to evaluate the relationship between circulating [THg], [MeHg+], [TSe] and TSe:THg molar ratio status relative to oxidative stress and antioxidants measured during general anesthesia in free-ranging SSL. We captured, anesthetized and sampled newborn SSL pups at rookeries located in the Aleutian Islands or Gulf of Alaska. Biomarkers analyzed for oxidative stress included 4-hydroxynenonal and thiobarbituric acid reactive substances (4-HNE and TBARS, respectively, lipid peroxidation), protein carbonyl content (PCC, protein oxidation), and GPx activity as a key indicator for Se-dependent antioxidant defense levels. We found a negative association between TBARS and [TSe], and SSL with low [TSe] had higher concentrations of 4-HNE than those with intermediate [TSe]. These results suggest that SSL with lower [TSe] experience increased lipid peroxidation potentially associated with [THg] status.

Severe Hypoxemia in Muskoxen ( Ovibos moschatus ) Immobilized with Etorphine and Xylazine Corrected with Supplemental Nasal Oxygen.

Twenty-three muskoxen ( Ovibos moschatus ) housed in a captive facility for rewilding in Sweden were chemically immobilized for annual health evaluations and hoof trimming. The muskoxen were darted in May to September (2012-15) in their holding pen with etorphine (0.015 mg/kg) and xylazine (0.1 mg/kg) intramuscularly. Twenty-two of the 23 animals were immobilized with a single dart injection. The mean (SD) induction time was 4 (2) min. Arterial blood gases were collected from 18 animals. All animals were severely hypoxemic with varying degrees of respiratory acidosis. The hypoxemia resolved in 17 of 18 animals with intranasal oxygen supplementation at 1 L/min per 100 kg. Relative arterial oxygen saturation (SpO2) measured by pulse oximetry was significantly higher than the arterial oxygen saturation calculated from the partial pressure of arterial oxygen (SaO2) obtained by a blood gas analyzer. Based on these findings, muskox can be immobilized successfully with etorphine (0.015 mg/kg) and xylazine (0.1 mg/kg) but should receive supplemental oxygen.

THIAFENTANIL-AZAPERONE-XYLAZINE AND CARFENTANIL-XYLAZINE IMMOBILIZATIONS OF FREE-RANGING CARIBOU (RANGIFER TARANDUS GRANTI) IN ALASKA, USA.

Carfentanil-xylazine (CX) has been the primary drug combination used for immobilizing free-ranging ungulates in Alaska, US since 1986. We investigated the efficacy of a potential new drug of choice, thiafentanil (Investigational New Animal Drug A-3080). Captive trials indicated that thiafentanil-azaperone-medetomidine could provide good levels of immobilization. However, field trials conducted in October 2013 on free-ranging caribou ( Rangifer tarandus granti) calves showed the combination too potent, causing three respiratory arrests and one mortality. The protocol was revised to thiafentanil-azaperone-xylazine (TAX), with good results. The induction time was not significantly different between the two combinations. However, the recovery time was significantly shorter for the TAX group than for the CX group. A physiologic evaluation was performed on 12 animals immobilized on CX and 15 animals on TAX. Arterial blood was collected after induction and again after 10 min of intranasal oxygen supplements (1 L/min). Both groups had significant increases in partial pressure of arterial oxygen after oxygen treatment. There was a concurrent significant increase in partial pressure of arterial carbon dioxide in both groups. Rectal temperature increased significantly in both groups during the downtime, which is consistent with other studies of potent opioids in ungulates. On the basis of our results, we found TAX to be a potential alternative for the current CX protocol for immobilizing free-ranging caribou calves via helicopter darting.

Improvement of arterial oxygenation in free-ranging moose (Alces alces) immobilized with etorphine-acepromazine-xylazine.

BACKGROUND: The effect of intranasal oxygen and/or early reversal of xylazine with atipamezole on arterial oxygenation in free-ranging moose (Alces alces) immobilized with etorphine-acepromazine-xylazine with a cross-sectional clinical study on 33 adult moose was evaluated. RESULTS: Before treatment the mean±SD (range) partial pressure of arterial oxygen (PaO2) was 62±17 (26-99) mmHg. Twenty-six animals had a PaO2<80 mmHg. Ten had a PaO2 of 40-60 mmHg and three animals had a PaO2<40 mmHg. Intranasal oxygen and intravenous administration of atipamezole significantly increased the mean PaO2, as did the combination of the two. In contrast, atipamezole administered intramuscularly at the evaluated dose had no significant effect on arterial oxygenation. CONCLUSIONS: This study shows that intranasal oxygen effectively improved arterial oxygenation in immobilized moose, and that early intravenous reversal of the sedative component, in this case xylazine, in an opioid-based immobilization drug-protocol significantly improves arterial oxygenation.

Physiologic evaluation of medetomidine-ketamine anesthesia in free-ranging Svalbard (Rangifer tarandus platyrhynchus) and wild Norwegian reindeer (Rangifer tarandus tarandus).

Previously published studies indicated that combinations of medetomidine and ketamine were effective for both Svalbard (Rangifer tarandus platyrhynchus) and wild Norwegian reindeer (Rangifer tarandus tarandus). Both previous studies indicated that reindeer were hypoxemic on the basis of pulse oximetry. We conducted a physiologic evaluation of these two protocols using arterial blood gases. Medetomidine (10 mg) and ketamine (200 mg) were administered by dart from the ground in Svalbard reindeer (October 2010) and from a helicopter for wild reindeer (March 2012). Of tested animals, all seven wild reindeer and five of seven Svalbard reindeer were hypoxemic before oxygen administration. Nasal oxygen insufflation (1 L/min for five Svalbard reindeer and one wild reindeer and 2 L/min for four wild reindeer) corrected hypoxemia in all cases evaluated. For reversal, all animals received 5 mg atipamezole per mg medetomidine intramuscularly.