Diffuse large B cell lymphoma and a novel gammaherpesvirus in northern elephant seals Mirounga angustirostris.

Two emaciated male northern elephant seal (NES) Mirounga angustirostris pups were admitted to The Marine Mammal Center (Sausalito, California, USA) and treated for malnutrition. Complete blood counts showed a progressive moderate to marked leukocytosis characterized by a predominance of large monomorphic mononuclear cells of probable lymphoid origin, frequently with flower-shaped nuclei. Both seals were euthanized due to suspected lymphoid neoplasia. At necropsy, most lymph nodes in both pups were markedly enlarged, some with distinct white nodules, the spleens were diffusely enlarged, and the intestinal mucosae were thickened. Histopathologic features consistent with disseminated large cell lymphoma were identified to varying degrees of severity in lymph nodes, bone marrow, liver, tonsils, spleen, liver, intestines, kidneys, lower urinary tract, and several other organs. Immunohistochemical staining of neoplastic cells was most consistent with B lymphocyte origin, with most cells staining positively for Pax 5 and CD20 with admixed small CD3-positive T lymphocytes and CD204-positive macrophages. PCR and sequencing identified a novel gammaherpesvirus, herein called miroungine gammaherpesvirus 3, from affected tissues. This virus is in a clade outside of named genera that utilize hosts in the suborder Caniformia. The present study is the first description of diffuse large B cell lymphoma with leukemic manifestation and concomitant detection of a novel gammaherpesvirus in free-living NESs. Further research regarding the prevalence of this new gammaherpesvirus and its associated pathogenesis in this species is indicated.

THE USE OF EPHEDRINE TO TREAT ANESTHESIA-ASSOCIATED HYPOTENSION IN PINNIPEDS.

Hypotension is a common adverse effect of general anesthesia that has historically been difficult to measure in pinniped species due to technical challenges. A retrospective case review found seven pinniped cases that demonstrated anesthesia-associated hypotension diagnosed by direct blood pressure measurements during general anesthesia at The Marine Mammal Center (Sausalito, CA) between 2017 and 2019. Cases included five California sea lions (CSL: Zalophus californianus), one Hawaiian monk seal (HMS: Neomonachus schauinslandi), and one northern elephant seal (NES: Mirounga angustirostris). Patients were induced using injectable opioids, benzodiazepines, and anesthetics including propofol and alfaxalone. Excluding the HMS, all patients required supplemental isoflurane with a mask to achieve an anesthetic plane allowing for intubation. Each patient was maintained with inhalant isoflurane in oxygen for the duration of the anesthetic event. Each patient was concurrently administered continuous IV fluids and four patients received fluid boluses prior to administration of ephedrine. All hypotensive anesthetized patients were treated with IV ephedrine (0.05-0.2 mg/kg). The average initial systolic (SAP) and mean (MAP) arterial blood pressures for the CSL prior to ephedrine administration were 71 ± 14 mmHg and 48 ± 12 mmHg respectively. The average SAP and MAP for the CSL increased to 119 ± 32 mmHg and 90 ± 34 mmHg respectively within 5 m of ephedrine administration. The NES initial blood pressure measurement was 59/43 (50) (SAP/diastolic [MAP]) mmHg and increased to 80/51 (62) mmHg within 5 m. The initial HMS blood pressure was 79/68 (73) mmHg and increased to 99/78 (85) mmHg within 5 m following ephedrine administration. All patients recovered from anesthesia. These results support the efficacy of IV ephedrine for the treatment of anesthesia-associated hypotension in pinnipeds.

Use of potassium chloride for low-residue euthanasia of anesthetized California sea lions (Zalophus californianus) and northern elephant seals (Mirounga angustirostris) with life-threatening injury or disease.

OBJECTIVE: To demonstrate the efficacy of potassium chloride (KCl) for low-residue euthanasia of anesthetized pinnipeds in field settings for which carcass retrieval for disposal is not feasible. ANIMALS: Stranded, free-ranging California sea lions (CSLs; Zalophus californianus; n = 17) and northern elephant seals (NESs; Mirounga angustirostris; 6) with life-threatening injury or disease between May and August 2020. PROCEDURES: Each animal was anesthetized and then received a lethal dose of KCl solution administered by IV or intracardiac injection. The effective KCl dose; durations to cardiac arrest, respiratory arrest, and pupil dilation; and presence or absence of agonal breaths, muscle fasciculations, or skeletal movements were recorded. RESULTS: Mean effective dose of KCl was 207.4 mg/kg (94.3 mg/lb) for the 17 CSLs and 209.1 mg/kg (95.0 mg/lb) for 5 of 6 NESs (1 outlier NES was excluded). The range in duration from the beginning of KCl injection to cardiac arrest was 0 to 6 minutes, to pupil dilation was 0 to 5 minutes, and to respiratory arrest was 0 to 5 minutes. Muscle fasciculations, skeletal movements, and agonal breaths were observed in both species during and after KCl administration. CONCLUSIONS AND CLINICAL RELEVANCE: The use of KCl provides an effective, low-residue method of euthanasia in anesthetized CSLs and NESs. Our recommended dose for these species is 250 mg KCl/kg (113.6 mg KCl/lb) delivered by intracardiac injection. Compared with euthanasia by barbiturate overdose, the use of KCl reduces the potential for secondary intoxication of scavengers and is appropriate in field scenarios in which the carcass cannot be retrieved for disposal.

An MRI protocol for anatomical and functional evaluation of the California sea lion brain.

BACKGROUND: Domoic acid (DOM) is a neurotoxin produced by some harmful algae blooms in coastal waters. California sea lions (Zalophus californianus) exposed to DOM often strand on beaches where they exhibit a variety of symptoms, including seizures. These animals typically show hippocampal atrophy on MRI scans. NEW METHOD: We describe an MRI protocol for comprehensive evaluation of DOM toxicosis in the sea lion brain. We intend to study brain development in pups exposed in utero. The protocol depicts the hippocampal formation as the primary region of interest. We include scans for quantitative morphometry, functional and structural connectivity, and a cerebral blood flow map. RESULTS: High-resolution 3D anatomical scans facilitate post hoc slicing in arbitrary planes and accurate morphometry. We demonstrate the first cerebral blood flow map using MRI, and the first structural tractography from a live sea lion brain. COMPARISON WITH EXISTING METHODS: Scans were compared to prior anatomical and functional studies in live sea lions, and structural connectivity in post mortem specimens. Hippocampal volumes were broadly in line with prior studies, with differences likely attributable to the 3D approach used here. Functional connectivity of the dorsal left hippocampus matched that found in a prior study conducted at a lower magnetic field, while structural connectivity in the live brain agreed with findings observed in post mortem studies. CONCLUSIONS: Our protocol provides a comprehensive, longitudinal view of the functional and anatomical changes expected to result from DOM toxicosis. It can also screen for other common neurological pathologies and is suitable for any pinniped that can fit inside an MRI scanner.