Sub-occipital craniectomy in a lion (Panthera leo) with occipital bone malformation and hypovitaminosis A

Neurologic dysfunction accompanied by malformation of both the skull and the cervical vertebrae has been previously described in lions kept in captivity worldwide, and this dysfunction and malformation were most often related to vitamin A deficiency. Diagnosis of the bone malformation and its effects on the neural tissue was until recently limited to postmortem examination, with characteristic thickening of the bones of the cranial vault, cerebellar herniation, compression of the foramen magnum, and enlargement of the lateral ventricles. For some mildly affected lion cubs with neurologic signs, improvement was reported with excessive vitamin A supplementation. However, definitive diagnosis was only available for those that eventually died or were euthanized. This case documents the antemortem diagnosis of the disease using computed tomographic imaging and liver biopsy. While conservative treatment failed, suboccipital craniectomy removed the thickened occipital bone and was demonstrated to be a successful surgical intervention that can be used to treat more severely affected lions.     

Needle biopsy for hepatic vitamin A levels in lions (Panthera leo)

Hypovitaminosis A (HA)-related skull malformations resulting in neurologic abnormalities and death have been, and still are, reported in captive lions (Panthera leo) worldwide. Liver vitamin A (VA) concentration is the most reliable indicator of animals' VA status, and its assessment is essential in prevention and treatment of HA in lions. A percutaneous needle liver biopsy using high-performance liquid chromatography ultraviolet retinoid analysis for VA concentration measurement was validated. It was first assessed in vitro using chicken liver. Later, the safety and feasibility of ultrasound-guided percutaneous needle liver biopsy was assessed in living lions. Hepatic VA concentrations in lion liver were measured using the above laboratory method. Mean chicken hepatic VA concentration in needle biopsy (NB) and wedge biopsy (WB) of the same liver lobes were 108.66 and 60.89 microg/g wet tissue, respectively, and were significantly (P = 0.03) correlated (r = 0.74). The calculated linear regression for predicting VA concentration in WB using NB VA for chicken liver was 25.194 + 0.3234x NB (microg/g). Four ultrasound-guided percutaneous needle liver biopsies were obtained from each of the four lions under general anesthesia. Mean hepatic VA concentration was 8.25 microg/g wet tissue (range 1.43-25.29 microg/g). Mean serum VA concentration, measured in these four lions was 1,011.1 nmol/L with a standard deviation of 337.91 nmol/L (range 590.26-1,077.2 nmol/L). The lions recovered uneventfully, and no complications were observed during a 4-yr follow-up period. In conclusion, the percutaneous needle liver biopsy technique is a reliable, practical, safe tool for obtaining liver tissue samples antemortem for assessment of the VA status in lions and can be used in future studies.     

Feline asthma syndrome in African lions (Panthera leo).

Feline asthma syndrome, previously recognized only in domestic cats, was diagnosed in three captive African lions (Panthera leo), one of which died as a result of the condition. Two of the lions displayed progressive signs for 7 yr, including severe bouts of coughing, wheezing, dyspnea, rhonchi, and tachypnea that were most severe during the spring and summer, and the third lion displayed acute signs only once. Scattered to diffuse increased interstitial markings, peribronchial cuffing, and focal atelectasis were visible in radiographs. At necropsy, multiple subpleural bullae, 2-3 cm in diameter, were scattered throughout the lung tissue. There were thick-walled bronchi and bronchioles filled with thick grayish mucus, and alveolar spaces were enlarged with severe, diffuse, banded multifocal areas of alveolar wall fibrosis. The lions had significantly elevated IgE type I immediate hypersensitivity responses to recognized aeroallergens. The captive management of lions should address the design and maintenance of allergen-free air supplies. Ventilation systems should be examined routinely and thoroughly cleaned of any residue. The frequency of examination should increase during the summer. Lions and other large cats should be routinely screened for IgE aeroallergen-specific titers, asthma cases should be treated promptly with prednisolone, and investigations of etiology should be initiated.     

Degenerative myelopathy and vitamin A deficiency in a young black-maned lion (Panthera leo).

Degenerative myelopathy and vitamin A deficiency were diagnosed in a 1-year-old, female, black-maned lion (Panthera leo). Diffuse white matter degeneration characterized by dilated myelin sheaths, Wallerian degeneration, and reactive astrocytosis was present at all levels of the spinal cord. With luxol fast blue-resyl echt violet stain, bilaterally symmetrical demyelination was observed in the fasciculus cuneatus of the cervical spinal cord and in peripheral white matter of cervical, thoracic, and lumbar segments. Additionally, the ventral gray columns and brain stem nuclei contained rare chromatolytic neurons with abnormal neurofilament accumulation. Leptomeninges of the cervical spinal cord were focally adhered to the dura and thickened by fibrosis and osseous metaplasia. Vitamin A deficiency was diagnosed based on hepatic vitamin A concentration of 1.71 microg/g dry weight. Adequate hepatic vitamin A concentration for yearling to adult domestic animals ranges between 150 and 1000 microg/g dry weight. Lesions were distinct from those previously described in young captive lions with vitamin A deficiency, which had thickened skull bones and cerebellar herniation. The pathogenesis of vitamin A-associated myelopathy in this lion may be similar to that described in adult cattle, which is believed to result from spinal cord compression secondary to elevated pressure of cerebrospinal fluid.     

Comparison of radiography and magnetic resonance imaging for evaluating the extent of nasal neoplasia in dogs

OBJECTIVES: Magnetic resonance imaging (MRI) is increasingly used in veterinary practice and, in some centres, is part of the diagnostic work-up of small animals with nasal disease. However, there are no published studies which critically evaluate the use of magnetic resonance imaging for this purpose. The purpose of this work was to assess the changes seen using magnetic resonance imaging and to compare them with radiography. METHODS: The study included 12 dogs that had undergone both radiography and magnetic resonance imaging of the nasal cavity and had a histopathological diagnosis of malignant nasal neoplasia. Two pairs of board-certified radiologists scored the radiographs and the MRI scans, evaluating 10 signs of abnormality using a simple scoring system. Magnetic resonance imaging features were described in detail, and radiographic and magnetic resonance imaging scores for each sign as well as total scores were compared. RESULTS: Magnetic resonance imaging often showed that the tumour was more extensive than it had appeared on radiography but occasionally showed that radiographs had overestimated its size. Although radiography was reliable for assessment of the presence and size of a mass and for the extent of turbinate destruction, it usually failed to show occlusion of the major airway passages that were evident on magnetic resonance imaging. Extension of the tumour into the opposite nasal cavity, frontal sinus, orbit and cranial cavity was shown much better on magnetic resonance imaging. CLINICAL SIGNIFICANCE: Minor but significant extension beyond the nasal cavity, which is important for treatment planning and prognosis, requires magnetic resonance imaging for demonstration, although radiography shows major changes reliably.     

Reversible anaesthesia of free-ranging lions (Panthera leo) in Zimbabwe

The combination of medetomidine-zolazepam-tiletamine with subsequent antagonism by atipamezole was evaluated for reversible anaesthesia of free-ranging lions (Panthera leo). Twenty-one anaesthetic events of 17 free-ranging lions (5 males and 12 females, body weight 105-211 kg) were studied in Zimbabwe. Medetomidine at 0.027-0.055 mg/kg (total dose 4-11 mg) and zolazepam-tiletamine at 0.38-1.32 mg/kg (total dose 50-275 mg) were administered i.m. by dart injection. The doses were gradually decreased to improve recovery. Respiratory and heart rates, rectal temperature and relative haemoglobin oxygen saturation (SpO2) were recorded every 15 min. Arterial blood samples were collected from 5 lions for analysis of blood gases and acid-base status. For anaesthetic reversal, atipamezole was administered i.m. at 2.5 or 5 times the medetomidine dose. Induction was smooth and all lions were anaesthetised with good muscle relaxation within 3.4-9.5 min after darting. The predictable working time was a minimum of 1 h and no additional drug doses were needed. Respiratory and heart rates and SpO2 were stable throughout anaesthesia, whereas rectal temperature changed significantly over time. Atipamezole at 2.5 times the medetomidine dose was sufficient for reversal and recoveries were smooth and calm in all lions independent of the atipamezole dose. First sign of recovery was observed 3-27 min after reversal. The animals were up walking 8-26 min after reversal when zolazepam-tiletamine doses < 1 mg/kg were used. In practice, a total dose of 6 mg medetomidine and 80 mg zolazepam-tiletamine and reversal with 15 mg atipamezole can be used for either sex of an adult or subadult lion. The drugs and doses used in this study provided a reliable, safe and reversible anaesthesia protocol for free-ranging lions.     

Seroprevalence of Toxoplasma gondii in mainland and sub-Antarctic New Zealand sea lion (Phocarctos hookeri) populations

AIMS: To investigate the seroprevalence of antibodies to Toxoplasma gondii in New Zealand sea lions (Phocarctos hookeri), as a potential contributor to reproductive failure.

METHODS: Archived sera were sourced from New Zealand sea lions from two recolonising mainland populations in the Otago Peninsula (n=15) and Stewart Island (n=12), as well as a declining population at Enderby Island (n=28) in the New Zealand sub-Antarctic. Sera were tested for antibodies to T. gondii using a commercially available ELISA (with samples considered positive if the sample to positive ratio was?>30%), and latex agglutination test (LAT; with titres ≥1:32 considered positive). Western blot analysis was used to validate the results of a subset of 14 samples.

RESULTS: Five samples from sea lions in mainland locations were confirmed positive for antibodies to T. gondii. Two adult females exhibited high LAT antibody titres (min 1:2048, max 1:4096) on both occasions when sampled 1 and 2 years apart, respectively. No animals from Enderby Island were seropositive.

CONCLUSIONS: Toxoplasma gondii infection is unlikely to be a major contributor to poor reproductive success in New Zealand sea lions. However, continued surveillance is pertinent to assess subclinical and clinical impacts of the parasite on these threatened populations. The commercial tests evaluated here, with further species-specific threshold refinement could provide a fast, inexpensive and reliable indicator of T. gondii exposure in New Zealand sea lions.     

COMPUTED TOMOGRAPHIC ANALYSIS OF CALVARIAL HYPEROSTOSIS IN CAPTIVE LIONS

Osseous malformations in the skull and cervical vertebrae of lions in captivity are believed to be caused by hypovitaminosis A. These often lead to severe neurologic abnormalities and may result in death. We describe the characterization of these abnormalities based on computed tomography (CT). CT images of two affected and three healthy lions were compared with define the normal anatomy of the skull and cervical vertebrae and provide information regarding the aforementioned osseous malformations. Because bone structure is influenced by various factors other than the aforementioned disease, all values were divided by the skull width that was not affected. The calculated ratios were compared and the most pronounced abnormalities in the affected lions were, narrowing of the foramen magnum, thickening of the tentorium osseus cerebelli and thickening of the dorsal arch of the atlas. CT is useful for detection of the calvarial abnormalities in lions and may be useful in further defining this syndrome.     

RADIOLOGIC ABNORMALITIES OF THE APPENDICULAR SKELETON OF THE LION (PANTHERA LEO): INCIDENTAL FINDINGS AND MYCOBACTERIUM BOVIS-INDUCED CHANGES

Thoracic and pelvic limbs from 15 euthanized free-ranging lions (Panthera leo), ranging in age from 16 to 144 months, underwent standard radiographic evaluation. All lions had tested positive for Mycobacterium bovis by means of a modified intradermal tuberculn test. The radiographs of six lions were normal and nine had incidental findings of which six had more than one lesion. Seven lions had lesions suspected to be associated with tuberculosis, which was confirmed in specific joints in two lions. Incidental pathology was classified as traumatic injuries and degenerative or trauma-associated joint disease. The traumatic lesions were fractures of which the most remarkable was a femur malunion. Four lions had fibula and another three lions had metacarpal/tarsal and phalangeal fractures. Joint lesions included glenoid, humeral head, and accessory carpal bone osteophytes. There was evidence of a cranial cruciate ligament rupture in an 8-year-old male. Trauma induced joint lesions were seen in four stifles (fragmented or displaced sesamoid bones, fragmented meniscal ossicle, or mineralized fragments). Radiological abnormalities believed to be caused by M. bovis were present in one stifle, one radiocarpal three tibiotarsal, and one tarsometatarsal joints. These had evidence of septic arthritis with extensive bone formation and capsular mineralization. In one 20-month-old lion, changes typical of a bone abscess were found in a proximal tibia. Radiologic evidence of elbow hygromas were seen in three elbows, all believed to be caused by M. bovis. Lions appeared to cope fairly well with a variety of traumatic injuries and were also susceptible to some of the aging/incidental radiologic findings seen in dogs and cats. The suspected M. bovis osseous lesions were more likely to involve the joints, particularly the tarsal joint and were mainly proliferative.     

Clinical relevance of novel Otarine herpesvirus-3 in California sea lions (Zalophus californianus): lymphoma,esophageal ulcers,and strandings

Herpesviruses have been recognized in marine mammals, but their clinical relevance is not always easy to assess. A novel otarine herpesvirus-3 (OtHV3) was detected in a geriatric California sea lion (Zalophus californianus), and using a newly developed quantitative PCR assay paired with histology, OtHV3 was associated with esophageal ulcers and B cell lymphoblastic lymphoma in this animal. The prevalence and quantities of OtHV3 were then determined among buffy coats from 87 stranded and managed collection sea lions. Stranded sea lions had a higher prevalence of OtHV3 compared to managed collection sea lions (34.9% versus 12.5%; p = 0.04), and among the stranded sea lions, yearlings were most likely to be positive. Future epidemiological studies comparing the presence and viral loads of OtHV3 among a larger population of California sea lions with and without lymphoid neoplasia or esophageal ulcers would help elucidate the relevance of OtHV3-associated pathologies to these groups.     

Risk factors associated with development of poxvirus lesions in hospitalized California sea lions

OBJECTIVE: To identify risk factors that may predispose California sea lions (Zalophus californianus) to development of cutaneous poxvirus nodules during hospitalization in a rehabilitation center. DESIGN: Retrospective case-control study. ANIMALS: 90 California sea lions admitted to a rehabilitation center. PROCEDURE: Hospital records of 275 stranded California sea lions admitted to the rehabilitation center between January 1 and December 31, 2002, were reviewed. All California sea lions (n = 18) that developed > or = 1 cutaneous poxvirus nodule during hospitalization were classified as cases. Seventy-two California sea lions that did not develop poxvirus lesions during hospitalization were randomly selected (control group). The frequencies of various exposure factors prior to admission, at admission, and during hospitalization for cases and control sea lions were compared by use of logistic regression. RESULTS: California sea lions that had previously been admitted to the rehabilitation center were 43 times as likely to develop poxvirus lesions as sea lions admitted for the first time; those with high band neutrophil counts (> 0.69 X 10(3) bands/microL) at admission were 20 times less likely to develop poxvirus lesions than sea lions with counts within reference limits. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that sea lions with a history of prior hospitalization or band neutrophil counts within reference limits at admission were more likely to develop poxvirus lesions during hospitalization. Sea lions with histories of hospitalization should be kept in quarantine and infection control measures implemented to help prevent disease transmission to attending personnel and other hospitalized animals.     

Comparison between magnetic resonance imaging,computed tomography,and arthrography to identify artificially induced cartilage defects of the equine carpal joints

While articular cartilage changes are considered to be one of the initial events in the pathological cascade leading to osteoarthritis, these changes remain difficult to detect using conventional diagnostic imaging modalities such as plain radiography. The aim of this prospective, experimental, methods comparison study was to compare the sensitivity of magnetic resonance imaging (MRI), magnetic resonance arthrography, computed tomography (CT), and CT arthrography in the detection of artificially induced articular cartilage defects in the equine carpal joints. Defects were created in the antebrachiocarpal and middle carpal joint using curettage by a board‐certified equine surgeon. Normal articular cartilage thickness varied from a maximum of 1.22 mm at the level of the distal aspect of the radius to a minimum of 0.17 mm in the proximal articular surface of the third carpal bone. Regarding cartilaginous defect measurements the remaining cartilaginous bed range from a maximum of 0.776 mm in the partial thickness defects, and 0 mm (defect reaches the subchondral bone) when total thickness defect were made. Computed tomography and magnetic resonance imaging were performed followed by CT arthrography and magnetic resonance arthrography after antebrachiocarpal and middle carpal intraarticular contrast administration. All images were reviewed by two board‐certified veterinary radiologists, both of whom were blinded to the location, presence of, and thickness of the cartilage defects. A total number of 72 lesions in nine limbs were created. Mean sensitivity for localizing cartilage defects varied between imaging modalities with CT arthrography showing the best sensitivity (69.9%), followed by magnetic resonance arthrography (53.5%), MRI (33.3%), and CT (18.1%) respectively. The addition of contrast arthrography in both magnetic resonance and CT improved the rate of cartilage lesion detection although no statistical significance was found. Computed tomographic arthrography displayed the best sensitivity for detecting articular cartilage defects in the equine antebrachiocarpal and middle‐carpal joints, compared to magnetic resonance arthrography, MRI, and CT.     

Serologic and molecular characterization of tickborne pathogens in lions (Panthera leo) from the Fasano Safari Park, Italy.

Lions (Panthera leo) are an endangered species threatened by illegal hunting, habitat loss, and infectious diseases. Little is known about the tick-borne pathogens that infect lions and could contribute to population declines. The objective of this study was to characterize Rickettsia spp., Anaplasma phagocytophilum, and Coxiella burnetii infections in 10 lions from the Fasano Safari Park in Italy by serology, polymerase chain reaction, and sequence analysis. Although animals did not show clinical signs of tick-borne diseases, evidence of infection with C. burnetii, spotted fever group Rickettsia sp., and A. phagocytophilum were found in 50%, 20%, and 10% of the lions, respectively. One of the lions tested positive for all three pathogens. This study is the first report of molecular evidence of infection with C. burnetii, Rickettsia sp., and A. phagocytophilum in lions and provides evidence that these felids become infected and serve as hosts for tick-transmitted bacteria.     

Presumed primary thiamine deficiency in a young African lion (Panthera leo).

A 1-yr-old intact male African lion (Panthera leo) fed only beef muscle meat was evaluated for episodes of hypermetric ataxia, generalized weakness and tonic-clonic front limb movements. A hemogram, biochemical profile, blood lead, electrocardiogram, survey radiographs, and brain computed tomography were normal. Cerebral spinal fluid analyses suggested mild inflammation. Acetylcholine receptor antibody and serologic tests for all infectious agents tested were negative. Clinical signs resolved completely 9 days after instituting oral thiamine (3 mg/kg/day) and a completely nutritional diet. This lion's pretreatment thiamine blood value (11 nmol/L) was markedly lower than that of a healthy lion (191 nmol/L) and a proposed reference range for adult African lions (160-350 nmol/L). The lion remained clinically normal 2 yr later when his blood thiamine value was 340 nmol/L. African lions can develop clinical primary thiamine deficiency and may respond favorably when thiamine treatment and adequate diet are instituted prior to irreversible neuronal necrosis.     

Seroepizootiological survey for selected viral infections in captive Asiatic lions (Panthera leo persica) from western India.

Infectious diseases have been responsible for large-scale declines in many endangered animals. Disease outbreaks in small populations have probably led to the eventual extinction of such endangered animals in the wild. The endangered Asiatic lion (Panthera leo persica) population may also face such threats. This was evident from this study on captive Asiatic lions from western India, which were sampled from December 1998 to March 1999. Fifty-six Asiatic lions, including 17 hybrid lions (Afro-Asian crosses) from six captive centers in western India, were tested for antibodies against canine distemper virus (CDV), feline parvovirus (FPV), feline immunodeficiency virus (FIV), and feline leukemia viral (FeLV) antigen. Agar gel immunodiffusion test and dot immunobinding assay were employed for CDV and FPV antibody detection. Commercial enzyme-linked immunosorbent assay kits were used for FIV antibody and FeLV antigen detection. Forty-nine of 56 lions (87.5%) were positive for CDV. All 56 (100%) lions were positive for FPV antibodies. There were no detectable levels of FIV antibodies and FeLV antigens. It was observed that CDV and FPV, two viruses known to cause high mortality in captive carnivores, were widely prevalent in these captive Asiatic lions. It is suggested that these seropositive animals will have the potential to pose a risk of infection to other seronegative animals. Hence, it is imperative to carefully consider any movement, translocation, or reintroduction of these animals to new regions. It is also recommended that these animals be required to undergo standard quarantine and disease screening protocols. The lack of exposure to pathogens, such as FIV and FeLV, would also be a risk, and, hence, identification of reservoirs and screening of in-contact animals is highly recommended. Vaccinations must be considered, using killed or other suitable viral vaccines, which have been proved to be safe, effective, and efficacious in endangered felids.     

Vitamin A deficiency in the captive African lion cub Panthera loe (Linnaeus, 1758).

Dietary, breeding and clinical histories and pathological findings are presented from 2 confirmed and 5 presumed cases of vitamin A deficiency in immature African lions. Five of the 7 animals were born in the wild while 2 were born in captivity. All animals were fed lean red meat sprinkled with a vitamin/mineral supplement. Salient clinical signs were incoordination, "star gazing", blindness and intermittent convulsions. Pathological lesions seen in 4 animals included severe thickening of the cranial bones, with consequent marked compression of the brain and partial herniation of the cerebellum. Vascular damage in the cerebellum and ensuing haemorrhages, resulting in acute increases of an already high intracranial pressure, were thought to be the cause of some of the clinical signs, particularly convulsions rather than direct pressure-necrosis and atrophy of nervous tissue.     

Evaluation of T lymphocytes in captive african lions (Panthera leo) infected with feline immunodeficiency virus

OBJECTIVE: To determine whether FIV infection in captive African lions is associated with changes in immune cell variables similar to those detected in domestic cats infected with FIV. ANIMALS: 5 captive African lions naturally infected with FIV (FIV+) and 5 lions not infected with FIV (FIV-). PROCEDURE: Peripheral blood samples were collected from FIV+ lions during annual examinations conducted during a 7-year period and at a single time point from the FIV- lions. From results of CBC and flow cytometry, lymphocyte subsets were characterized and compared. RESULTS: Flow cytometric analysis revealed that the percentage and absolute number of CD4+ and CD8+ T cells were significantly lower in FIV+ lions, compared with these values in FIV- lions. In FIV+ lions, severe depletion in the absolute number of CD4+ and CD8+ T cells was detected, although this did not correlate with clinical signs. Muscle wasting was the most consistent clinical sign of infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that FIV+ African lions develop lymphocyte deficiencies, including significant decreases in the absolute number of CD4+ and CD8+ T cells; these findings of immune dysfunction are similar to those defined for FIV+ domestic cats. It is important to monitor the number of CD4+ T cells in infected animals as a measure of disease progression.     

Prevalence of pituitary tumors among diabetic cats with insulin resistance

OBJECTIVE: To determine prevalence of pituitary tumors, detectable by means of computed tomography or magnetic resonance imaging, in cats with insulin resistance suspected to have acromegaly or hyperadrenocorticism versus cats with well-controlled diabetes mellitus. DESIGN: Case series. ANIMALS: 16 cats with insulin resistance that were also suspected to have acromegaly (n = 12) or pituitary-dependent hyperadrenocorticism (4) and 8 cats with well-controlled diabetes mellitus. PROCEDURE: Computed tomography was performed on all 16 cats with insulin resistance and 2 cats in which diabetes mellitus was well-controlled. The remaining 6 cats in which diabetes mellitus was well-controlled underwent magnetic resonance imaging. Images were obtained before and immediately after i.v. administration of contrast medium. RESULTS: Computed tomography revealed a mass in the region of the pituitary gland in all 16 cats with insulin resistance. Maximum width of the masses ranged from 4.4 to 12.7 mm; maximum height ranged from 3.1 to 12.6 mm. Results of computed tomography performed on 2 cats with well-controlled diabetes and magnetic resonance imaging performed on the remaining 6 cats were considered normal. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cats with insulin resistance suspected to have acromegaly or pituitary-dependent hyperadrenocorticism are likely to have a pituitary mass detectable by means of computed tomography or magnetic resonance imaging.     

Isoflurane anaesthesia in four sea lions (Otaria byronia and Zalophus californianus)

OBJECTIVE: To (1) evaluate a purpose-built chamber for inducing isoflurane anaesthesia in sea lions and (2) assess isoflurane as an anaesthetic for dental surgery in these species. STUDY DESIGN: Prospective case study. ANIMALS: Four sea lions, aged between 5 and 12 years and weighing 74-110 kg, with dental disease. METHODS: Sea lions were restrained in a custom-built acrylic chamber into which 5% isoflurane (vapourizer setting) was delivered in O(2) (30 L minute(-1)) from three anaesthetic machines. When the animals were recumbent, the chamber was opened and induction completed using a face mask. Anaesthesia was maintained with 1.5-3.0% isoflurane (vapourizer setting) for 10-15 minutes and after tracheal intubation, was maintained with 1.0-3.0% isoflurane (end-tidal) for 41-255 minutes, using a partial rebreathing system with CO(2) absorption. RESULTS: During induction, the sea lions attempted to support their weight on their thoracic limbs before slipping into sternal or lateral recumbency. Sea lions underwent either root canal surgery, 'crowning' or canine tooth extraction. The animals were completely unresponsive during these operations and apnoea was never encountered at any point during anaesthesia. After surgery, the sea lions were placed into transport cages and their tracheae extubated once they began to move their heads. Thereafter, recovery from anaesthesia was smooth and no signs of distress were observed. Animals were able to raise their forequarters using their flippers within 1 hour of the operation and were returned to the aquarium about 2 hours after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: The purpose-built induction chamber is safe for inducing isoflurane anaesthesia in spontaneously breathing sea lions and isoflurane is an effective anaesthetic in this species.     

Assessment of ultrasound imaging as a noninvasive measure of blubber thickness in pinnipeds.

Portable ultrasound imaging was examined as a noninvasive measure of skin including blubber thickness in captive subadult Steller sea lions (Eumetopias jubatus) and adult harbor seals (Phoca vitulina). This method was validated through comparison with blubber biopsy. Ultrasound images provided depth measurements that were accurate to 99.8% of the actual. This method allowed clear images of the epidermis, dermis, and blubber layer to be rapidly obtained, with minimal animal restraint, and allowed differentiation of phocid and otariid blubber structure.