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Comparison of two protocols for field immobilization of white-eared opossums (Didelphis albiventris)
Abstract
The aim of this study was to investigate the efficacy of two protocols for field immobilization of white-eared opossums (Didelphis albiventris) and compare their effects on immobilization, cardiopulmonary variables, and recovery times. Twenty one opossums were randomly divided into two groups; G1 received ketamine (15 mg kg−1)-dexmedetomidine (0.15 mg kg−1) intramuscularly (IM) and G2 received the ketamine-dexmedetomidine combination and isoflurane once induction was achieved. Oxygen was delivered by face mask (1.5 L minute−1). Thirty minutes after induction, isoflurane was discontinued (G2) and both groups were administered atipamezole (1.5 mg kg−1) IM. Respiratory (ƒR) and heart rate (HR), oxyhemoglobin saturation (SpO2), and rectal temperature (T) were recorded every 5 min. Induction time, time to first movement (RT1), and time to achieve standing (RT2) were recorded. ANOVA and non-parametric tests were used. Level of immobilization was assessed by observation of movements and evaluation of muscle relaxation. The mean induction time was 4.71 min. RT1 and RT2 were significantly longer in G2. No significant differences were found in SpO2 or ƒR. HR did not vary significantly along time, but was higher in G2. Rectal temperature did not show differences between treatments, but decreased significantly with time in G2. Four of nine animals in G1 showed movements, while no animals in G2 did and muscle relaxation was determined to be better in this latter group. Both protocols were adequate for short-term field immobilization, with minimal alterations of HR and T and relatively short recovery times. Isoflurane provided better immobilization with statistically significant prolongation of recovery times.
... There are different types of works in the bibliography involving analysis of aspects related to Didelphis albiventris. However, most of these studies involve clinical, therapeutic and/or anesthetic aspects, such as the studies by da Silva et al. (2017) on parasite infection in D. albiventris and by Waxman et al. (2018) on immobilization of this species. The few papers more focused on morphology of this species are dedicated to the study of non-fossil structures, such as the work of Schäfer et al. (2017) on the structure of the tongue of this animal. ...
The skeleton of the thoracic limb is one of the key aspects for the understanding of the habits and movement of different mammalian species. Considering the gap about studies related to marsupial osteology, this work proposes to study the aspects inherent to the skeleton of opossums, with emphasis on the detailed anatomical description of the bones that form the thoracic limb. For this purpose, the bones of six specimens of possums of the species Didelphis albiventris were used. These small to medium sized marsupials inhabit a wide range of South America, living in several types of habitats, being commonly described as arboreal omnivores and have anthropic habits. For the execution of this study, the bone accidents perceptible in the specimens were identified by superficial palpation, which were then radiographed. The thoracic limb bones were prepared by boiling and drying in the sun. Finally, from the radiographic images and the prepared bones, a detailed description of the anatomy of the bone components of the thoracic limb of Didelphis albiventris was made, joining the previously obtained data of surface anatomy. These data were compared with data from the literature, discussing the functional significance of the osteological findings of the thoracic limb of Didelphis albiventris.
The efficacy and safety of anesthetic techniques in wildlife have increased greatly, but complications still exist. Some of these complications are predictable but others, such as hyperthermia, acidosis, and capture myopathy may result from the capture event. With anesthesia of domestic animals, it is often possible to titrate induction drugs to minimize adverse effects, but during anesthesia of wildlife, drugs are often delivered at the higher end of the dose range in an attempt to induce anesthesia rapidly. Opioids are administered during the perianesthetic period to provide sedation and preemptive analgesia prior to induction, and are part of balanced anesthesia, reducing minimal anesthetic concentration of the inhalant anesthetic. Both hydromorphone and oxymorphone 0.1‐0.3 mg/kg IM have been used by the authors in lagomorphs as primary analgesics for treatment of moderate to severe pain, but they are also useful for preemptive analgesia and postoperative pain.
Field anesthesia is often necessary for both invasive and noninvasive procedures on wild animals. We describe basic principles of safe anesthetic delivery, monitoring, and recovery for application in procedures involving free-ranging wildlife. For invasive procedures, the potential for immediate and lasting pain must be addressed and appropriate analgesia provided. In situations where the minimum standard of safe anesthesia and effective analgesia cannot be provided, the investigator and approving bodies should rigorously evaluate the risk to the patient against the value of the data obtained. This document is intended to serve as a resource for Institutional Animal Care and Use Committees, biologists, veterinarians, and other researchers planning projects that involve free-ranging wildlife in field conditions.
isoflurane is one of many chemical immobilizing agents available for field anesthesia of wildlife. We examined the use of inhaled isoflurane for field immobilization of mesopredators. Five species of mammals were anesthetized in a wetland complex in south-central Nebraska with isoflurane; we developed an induction chamber to use with a portable anesthesia machine to provide anesthesia at the capture location. Sixteen raccoons (Procyon lotor), 20 striped skunks (Mephitis mephitis), 4 Virginia opossums (Didelphis virginiana), 2 American badgers (Taxidea taxus) and 1 mink (Mustela vison) were captured and immobilized; we radio-marked 11 raccoons and 9 skunks. Induction was smooth and uneventful for all species immobilized. Mean induction times for raccoons and skunks were 10.7 min (SD = 1.1) and 11.0 min (SD = 2.4) respectively. Mean handling times (post induction) were 7.1 min (SD = 3.9) for raccoons and 7.3 min (SD = 4.8) for skunks. All animals, with the exception of opossums, were fully recovered within 15 min (raccoon mean recovery: 11.1 min, SD = 3.5; skunk mean recovery: 10.9 min, SD = 3.7). Recovery times for radio-collared animals and uncollared animals did not differ, and individuals with longer handling times did not require longer recovery times. Although isoflurane requires more equipment than injectable anesthesia methods, its short recovery time and wide safety margins deem it practical for use in a variety of field applications.
A four-year longitudinal study of the structure of sylvatic transmission cycles of Trypanosoma cruzi, reservoir host competence and parasite discrete typing units was conducted in a disturbed rural area of the humid Chaco in Argentina. Among 190 mammals examined by xenodiagnosis and polymerase chain reaction amplification, the composite prevalence of infection was substantially higher in Dasypus novemcinctus armadillos (57.7%) and Didelphis albiventris opossums (38.1%) than in Euphractus sexcinctus (20.0%), Tolypeutes matacus (12.5%), and Chaetophractus vellerosus (6.3%) armadillos. Trypanosoma cruzi was detected for the first time in Thylamys pusilla small opossums and in two unidentified small rodents. Infection was spatially aggregated only in armadillos. All Didelphis were infected with T. cruzi I and all armadillo species were infected with T. cruzi III, implying two distinct sylvatic cycles with no inputs from the domestic cycle. Dasypus armadillos and Didelphis opossums were much more infectious to vectors than other armadillos, small opossums, or rodents.
Inhaled isoflurane is one of many chemical immobilizing agents available for field anesthesia of wildlife. We examined the use of inhaled isoflurane for field immobilization of mesopredators. Five species of mammals were anesthetized in a wetland complex in south-central Nebraska with isoflurane; we developed an induction chamber to use with a portable anesthesia machine to provide anesthesia at the capture location. Sixteen raccoons (Procyon lotor), 20 striped skunks (Mephitis mephitis), 4 Virginia opossums (Didelphis virginiana), 2 American badgers (Taxidea taxus) and 1 mink (Mustela vison) were captured and immobilized; we radio-marked 11 raccoons and 9 skunks. Induction was smooth and uneventful for all species immobilized. Mean induction times for raccoons and skunks were 10.7 min (SD = 1.1) and 11.0 min (SD = 2.4) respectively. Mean handling times (post-induction) were 7.1 min (SD = 3.9) for raccoons and 7.3 min (SD = 4.8) for skunks. All animals, with the exception of opossums, were fully recovered within 15 min (raccoon mean recovery: 11.1 min, SD = 3.5; skunk mean recovery: 10.9 min, SD = 3.7). Recovery times for radio-collared animals and uncollared animals did not differ, and individuals with longer handling times did not require longer recovery times. Although isoflurane requires more equipment than injectable anesthesia methods, its short recovery time and wide safety margins deem it practical for use in a variety of field applications.
Seventeen recently trapped opossum, Didelphis virginiana, (median weight 2.45 kg; range = 1.6-5.0 kg; quartiles = 1.8-3.3 kg) were immobilized with either telazol (15 or 30 mg/kg) or a mixture of medetomidine (100 micrograms/kg), butorphanol (0.2 mg/kg), and ketamine HCl (10 mg/kg) based on estimated weights. Anesthetized animals were subjected to cardiac puncture for blood withdrawal and toe pinch. Euthanasia was accomplished by intracardiac administration of 1 ml of concentrated pentobarbital sodium/phenytoin solution. Weights were underestimated for 14 of 17 animals, but were within 0.5 kg of the actual weight. Both drug combinations provided rapid and calm immobilization. Median time to recumbency for the medetomidine-butorphanol-ketamine group (n = 5) was 6 min (range = 4-10 min; quartiles = 6 and 8 min). The median time to recumbency was not statistically different for the low (n = 6) and high dose (n = 6) telazol groups, 3 and 3.5 min respectively (quartiles 3; 3.5 and 4; 5.5 min). The stronger heart beat with telazol immobilization facilitated cardiac puncture. All five animals administered the medetomidine-butorphanol-ketamine mixture and three of six animals given the low telazol dose reacted to cardiac puncture. Only one of six animals given the estimated 30 mg/kg dose of telazol reacted slightly to cardiac puncture. We conclude that 30 mg/kg telazol provides sufficient immobilization and analgesia to allow accurate cardiac puncture of the opossum if the procedure is performed within 5 to 10 min of recumbency. Intracardiac administration of concentrated pentobarbital sodium/phenytoin solution followed by bilateral thoracotomy provides appropriate euthanasia suitable for field situations.
Establishing the putative links between sylvatic and domestic transmission cycles of
Trypanosoma cruzi
, the etiological agent of Chagas disease, is of public health relevance. We conducted three surveys to assess
T. cruzi
infection in wild mammals from a rural and a preserved area in Misiones Province, Northeastern Argentina, which had recently been declared free of vector- and blood-borne transmission of human
T. cruzi
infection. A total of 200 wild mammals were examined by xenodiagnosis (XD) and/or polymerase chain reaction (PCR) amplification of the hyper-variable region of kinetoplast DNA minicircles of
T. cruzi
(kDNA-PCR). The overall prevalence of
T. cruzi
infection was 8%. Nine (16%) of 57
Didelphis albiventris
opossums and two (7%) of 29
Desmodus rotundus
vampire bats were positive by both XD and kDNA-PCR. Additionally, one
D. rotundus
positive for
T. cruzi
by kDNA-PCR tested positive by satellite-DNA-PCR (SAT-DNA-PCR). The
T. cruzi
-infected bats were captured indoors and in the yard of a vacant dwelling. All
D. albiventris
were infected with TcI and both XD-positive
D. rotundus
by TcII. Fifty-five opossum cubs within the marsupium were negative by XD. The mean infectiousness to the vector was 62% in
D. albiventris
and 50% in
D. rotundus
. Mice experimentally infected with a parasite isolate from a vampire bat displayed lesions typically caused by
T. cruzi
. Our study documents the presence of the genotype TcII in a sylvatic host for the first time in Argentina, and the occurrence of two transmission cycles of
T. cruzi
in a district free of domestic vector-borne transmission.
SUMMARY A combination of tiletamine hydrochloride and zolazepam hydrochloride in a 1:1 ratio by weight was used successfully to sedate mountain brushtail possums, Trichosurus caninus, in the field. A standard total dose of 50 to 60 mg provided adequate sedation for the completion of a range of handling procedures. We describe the induction time, dose rate and side-effects associated with the use of tiletamine and zolazepam in T caninus.
There are approximately 75 species of American opossums (didelphids). Systematic behavioral research has been reported for only a small number of species, namely, Monodelphis domestica and Didelphis virginiana. Observational studies and field reports on several other didelphid species have also been published. The current review covers behavioral studies on didelphids including research on territoriality, reproductive behaviors, parturition, maternal behaviors, nest-building, vocalizations, scent-marking, circadian rhythms, swimming, locomotion, discrimination learning, maze learning, operant learning, problem box learning, exploration, death-feigning, predatory behavior, and prey manipulation. Didelphid behavior is compared in several contexts with eutherian mammals. Other than death-feigning, which has only been reported for one or two didelphid species, the behaviors observed in didelphids are qualitatively similar to those of eutherian mammals. Nevertheless, differences can be seen in prey manipulation and spatial maze behavior. Social interactions appear to be sparser in opossums than in most eutherian mammals. However, the scarcity of systematic research on didelphid behavior still prevents firm conclusions regarding these ancient and interesting mammals. Futher research on didelphids is warranted, particularly since they provide a natural comparison group for small generalist eutherians.
A combination of tiletamine hydrochloride and zolazepam hydrochloride in a 1:1 ration by weight was used successfully to sedate mountain brushtail possums, Trichosurus caninus, in the field. A standard total dose of 50 to 60 mg provided adequate sedation for the completion of a range of handling procedures. We describe the induction time, dose rate and side-effects associated with the use of tiletamine and zolazepam in T caninus.
Background:
Desflurane decreases the vasoconstriction and shivering thresholds disproportionately at high anesthetic concentrations. This result contrasts with the authors' previous report that isoflurane decreases the vasoconstriction threshold linearly. It is surprising that the basic shape of the concentration-response curve should differ with these two otherwise similar anesthetics. Therefore, the hypothesis that isoflurane produces a nonlinear reduction in the vasoconstriction threshold was tested. Because the effect of isoflurane on shivering remains unknown, the extent to which isoflurane reduces the shivering threshold also was determined.
Methods:
Eight men volunteered to be studied on four randomly ordered days: (1) a target end-tidal isoflurane concentration of 0.55%, (2) a target concentration of 0.7%, (3) control (no anesthesia) and a target end-tidal concentration of 0.85%, and (4) a target end-tidal concentration of 1.0%. Volunteers were surface-cooled until peripheral vasoconstriction and shivering were observed. We arithmetically compensated for changes in skin temperature using the established linear cutaneous contributions to control for each response. From the calculated thresholds (core temperatures triggering responses at a designated skin temperature of 34 degrees C), the concentration-response relation was determined.
Results:
Isoflurane administration produced a dose-dependent reduction in the vasoconstriction and shivering thresholds, decreasing each approximately 4.6 degrees C at an end-tidal concentration of 1%. Residual analysis indicated that the vasoconstriction and shivering thresholds were decreased in a nonlinear fashion during isoflurane administration. The vasoconstriction-to-shivering range was 1.5 +/- 0.8 degree C without isoflurane, and did not change significantly during isoflurane administration.
Conclusions:
The vasoconstriction-to-shivering range remained unchanged by isoflurane administration. In this regard, the effects of isoflurane are similar to those of desflurane, propofol, and alfentanil. The current data differ from the authors' previous report, in that the dose-dependence for vasoconstriction was nonlinear, with isoflurane reducing the threshold disproportionately at higher anesthetic concentrations. Differing dose-dependence in the two studies may result either because the current study's volunteers were not exposed to surgical stimulation and were given less isoflurane, or because of design limitations in the previous protocol.
Chemical immobilization and physiological evaluation of wild white eared opossums
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Tarragona EL, Zurvera D, Manzoli DE et al (2014) Chemical immobilization and physiological evaluation of wild white eared opossums,
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Isoflurane produced marked and nonlinear decreases in the vasoconstriction and shivering thresholds
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Chemical immobilization and physiological evaluation of wild white eared opossums, Didelphis albiventris (Lund 1841) of Santa Fe province, Argentina
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Steffey EP, Mama KR, Brosnan RJ (2015) Inhalation anesthetics. In:
Grimm KA, Lamont LA, Tranquilli WJ et al (eds) Veterinary anesthesia and analgesia, 5th edn. Wiley Blackwell, UK, pp 297-331
First finding of Trypanosoma cruzi II in vampire bats from a district free of domestic vector-borne transmission in Northeastern Argentina
- H D Argibay
- M M Orozco
- M V Cardinal
- HD Argibay