A model preventive medicine program for sea otters
Michael J. Murray, DVM,
Monterey Bay Aquarium
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Preventive medicine should be the basis for all animal health programs in zoos and aquariums. It is not only required by AZA and USDA, but it is also considered to be a best practice by the Association of Zoo Veterinarians and is an important component of any animal welfare program. Sea otters are no exception to this, yet they are frequently overlooked for a variety of reasons. The goal of this presentation is to provide a model for a preventive medicine program that has been used effectively for several years. A suggested program protocol:
• Sedation / physical restraint / behavioural control
• Physical examination
o Oral cavity
o Ophthalmic exam
o Abdominal palpation
• Clinical pathology
o Blood gases (ie, iStat)
o Serum chemistry panel
o Serum vitamin A
o Infectious disease titres
o Fecal microbiology
o Fecal parasite
Direct saline mount
• Ancillary imaging
o Thermal imaging
Thorax – 4 views
Abdomen – 2-3 views
Pelvic limb – 2 views
o Risk assessment
o Parasite (intestinal, heartworm)
o Dental prophylaxis
Pending Publishing Permission
The dead do tell tales! Investigating southern sea otter (Enhydra lutris nereis) mortality patterns (1998–2012)
Melissa A. Miller,
California Department of
Fish and Wildlife
The most recent comprehensive review of southern sea otter (SSO: Enhydra lutris neries) mortality patterns was completed >15 years ago2, and was limited to 105 cases. To address this knowledge gap, our multi-agency team compiled data from 560 SSO necropsies spanning 15 years. Enrolled animals were minimally decomposed, with detailed necropsy performed during 1998-2012, including all eligible subadult (1-4 years), adult (4-10 years), or aged adult (>10 years) SSO of either sex; younger animals were excluded due to more limited examination by veterinary pathologists, and lower probability of guiding key conservation decisions. Our sample population included all opportunistically collected animals within the SSO range in California, and all tagged otters that fit the above selection criteria. The primary and contributing cause(s) of death were determined based on gross lesions, histopathology and diagnostic tests, including systematic serology and biochemical testing. Standardized coding was established to distinguish between primary or contributing cause(s) of death, and sequelae such as secondary bacterial infection. In addition to updating collective knowledge regarding “classical” causes of SSO death, such as white shark (Carcharodon carcharias) predation6, protozoal infection and Profilicollis sp.-associated acanthocephalan peritonitis2,4, we also studied less well-characterized processes, such as domoic acid (DA) intoxication, cardiomyopathy3 and end-lactation syndrome (ELS)1,5 that could be impacting SSO population recovery. Spatial scan statistics and multivariate models were used to identify high or low-risk coastal locations for common diseases, and potential connections between common causes of SSO death. Our models also highlighted associations between risk of presenting with specific health conditions and SSO sex, age, stranding date, stranding season, stranding year, and other factors. Shark bite was the most common primary cause of death, followed by acanthocephalan peritonitis, probable DA intoxication, cardiomyopathy, ELS, and primary bacterial infection. When the primary and top three contributing cause(s) of mortality were pooled, the most common cause(s) of SSO death were cardiomyopathy, gastrointestinal erosions/melena, shark bite, protozoal infection, probable DA intoxication, possible DA intoxication, ELS, emaciation, and primary bacterial infection. Significant spatial, temporal, or space-time clustering was noted for several common causes of death, including shark bite, acanthocephalan peritonitis, protozoal disease, ELS, cardiomyopathy and coccidioidomycosis. Shark bite was significantly more common as a cause of death during later years, in subadults stranding in good nutritional condition, and for SSO stranding from August through January. Acanthocephalan peritonitis was significantly more common in emaciated subadults, and otters stranding near Moss Landing from 2002 through 2007. Although SSO stranding during the late wet and early dry season were nearly 1.6 times more likely to strand with acanthocephalan peritonitis, this finding was not statistically significant. Bacterial infections as sequelae were important contributors to death from shark bite and acanthocephalan peritonitis.
Pending Publishing Permission
Esophageal perforation in a southern sea otter
(Enhydra lutris nereis)
Lauren T. Michaels,
SeaWorld, San Diego
On September 19, 2016, a 4 year old female Southern sea otter (Enhydra lutris nereis) living at SeaWorld San Diego, became anorexic and exercise intolerant. The patient had no previous medical history, however, three weeks prior the staff observed an abrupt diet aversion to shrimp. A cursory exam was conducted at the exhibit under manual restraint. A blood sample was collected, and hematology and serum chemistry analytes were relatively unremarkable, showing a mild increase in white blood cells, mild dehydration and moderately increased muscle enzyme values. The patient was started on subcutaneous fluids, injectable broad-spectrum antibiotics and pain medication. The following day, a thorough physical exam, radiographs, ultrasound and blood sampling for fungal serology were performed under general anesthesia. On exam, the otter was noted to have good body condition, but increased respiratory effort and muffled lung sounds on auscultation. Initial thoracic radiographs revealed a severe, diffuse alveolar pattern suggestive of pneumonia. A trans-tracheal wash was performed, and the cultured sample grew a resistant Staphylococcus epidermidis. Fungal serology was negative. Supportive care and sensitivity-directed antibiotics were continued post-anesthesia. After a few days of treatment, the otter continued to have tachypnea after exercise, but showed mild improvement in her energy levels and appetite. On September 26, 2016, the patient began regurgitating. Follow-up radiographs, blood and gastric samples were performed and revealed mild improvement in her pulmonary pattern and static hematology and serum chemistry values. Toxoplasma testing was negative. Anti-emetics and a gastrointestinal pro-motility agent were added to her therapy. Despite mild improvement on this therapy, the patient spontaneously died 36 hours later. Necropsy revealed a small, chronic, distal, focal esophageal perforation (0.6 cm x 0.3 cm) that dissected 8 centimeters in length creating sacculation within the serosal layer. In addition, there was 1 liter of green brown fibrinous pleural fluid, as part of the diffuse pyothorax and pleuritis. It was suspected that the original insult (possible food source) had incited a partial esophageal tear creating an outpouching of the esophagus filled with purulent material. Eventually the outpouching ruptured and caused a secondary pyothorax and pleuritis resulting in the patient’s ultimate respiratory failure and demise. Microbial culture of the sacculation revealed growth of Staphylococcus lentus. Culture of the pleural effusion was negative for bacterial growth. It was hypothesized that the culture of the pleural fluid was negative for bacteria because the patient had been treated with broad-spectrum antibiotics for almost one week prior to death.
Ultimately, it was believed that a piece of the patient’s food, possibly shrimp, perforated through her esophagus resulting in a pyothorax and her eventual respiratory failure. When considering this case, a question is raised about what types of diets to feed sea otters under human care. Esophageal perforation and subsequent comorbidities associated with this insult should be considered in future sea otters, managed or wild, that present with similar clinical signs. This case illustrates the importance of monitoring subtle behavioral signs, like a specific food aversion, in sea otters under human care. In addition, this case serves as a teaching point for biologists, veterinarians and husbandry staff working with sea otters, that the natural crustacean diet of the Southern sea otter is not necessarily benign, and it can cause trauma to the gastrointestinal system of this species.
Pending Publishing Permission
Uterine leiomyoma, cystic endometrial hyperplasia and endometriosis in a northern sea otter (Enhydra lutris lutris)
Megan M. Strobel,
One 14-year-old female Northern sea otter (Enhydra lutris lutris) from the Vancouver Aquarium collection presented with non-painful caudal abdominal swelling in March 2018. Initial bloodwork and ultrasound were suggestive of early-term pregnancy. While the animal continued to behave clinically normal, monthly bloodwork monitoring revealed persistent elevations in progesterone. Ultrasonographic monitoring was consistent with mild fluid accumulation within the uterus and no evidence of progression in fetal development. Seven months later, a round soft tissue structure, measuring approximately 3-4 cm, surrounded by fluid within the uterus was noted on radiographs and ultrasound. Ovariohysterectomy performed in December 2018 revealed two firm, fibrous masses measuring approximately 4.5cm and 2.5cm within the right and left uterine horns, respectively. Histopathology revealed nonencapsulated moderately cellular nodules of large fusiform cells with variably distinct cell membranes, consistent with leiomyoma with a mitotic index of 0-1/10hpf. Marked cystic endometrial hyperplasia and endometriosis were also noted within the uterus. Subsequent staging revealed no abnormalities in the lungs, lymph nodes, liver or spleen. Leiomyoma, a benign soft tissue tumor, was previously described in two Northern sea otters (Enhydra lutris) from Alaska post-mortem and in three sea otters at the Shedd Aquarium.1,2 In humans, progesterone and estrogen receptors have been documented in 70-80% of these tumors, with the hormones encouraging growth.3 In humans, it is suspected that cases of leiomyosarcoma result from malignant transformation of leiomyomas.3 Cystic endometrial hyperplasia was noted in one otter at Shedd with leiomyoma, however has not been otherwise reported.2 Cystic endometrial hyperplasia, along with endometriosis, likely contributed to discomfort and reproductive failure in this animal.
Pending Publishing Permission
Validation of an animal-side serum amyloid A ELISA for the
systemic inflammation in sea otters (Enhydra lutris)
Kendal Harr and Carrie Goertz,
Urika, LLC and
Alaska Sealife Center
The United States is home to two subspecies of sea otter: southern sea otters (Enhydra lutris nereis), which inhabit the nearshore waters off California, and northern sea otters (Enhydra lutris kenyoni), which inhabit waters off the state of Washington and the entire southern coast of Alaska from the southeastern panhandle to the westernmost point of the Aleutian chain. While population numbers have rebounded in the past decades, otters still face significant threats (e.g., boat strike, disease) and the southwestern Alaskan stock of northern sea otter is currently listed as threatened under the International Union for Conservation of Nature (IUCN) guidelines (USFWS 2014; Doroff and Burdin 2015).
Otters strand for a variety of reasons which need to be differentiated for treatment. Major causes in Alaska include dependent pups found in absence of an adult female and mature animals battling infectious diseases, often a Streptococcus sp. Clinical signs exhibited by stranded otters may be generalized and while blood analysis may be consistent with a serious infection, hematology and clinical chemistry results may be equivocal. Systemic Streptococcal infection leads to various organ derangements based on the site of infection. Blood cultures often confirm bacteremia but results take 5-7 days or longer, especially in remote locations. Meanwhile, intensive care is required, which is time consuming, depletes funds, and may be painful to the patient; often with death or euthanasia prior to availability of microbiology results. An additional, point-of-care, diagnostic test to confirm serious, systemic inflammatory illness at admit would assist in a speedier, more informed decision to proceed with rehabilitation or, if it is the best course of action, humane euthanasia.
Serum amyloid A (SAA) is a major acute phase protein in many species that rapidly increases 2 to1000 fold in response to inflammatory stimuli. Acute phase response (APR) proteins are used as screening diagnostics in domestic and livestock species because APR proteins are sensitive measures of internal inflammation and infection. It is likely that APR proteins could be a valuable tool in the diagnosis of inflammatory disease in otters as they are in cattle and other domestic animals as well as other marine mammals such as manatee. (Harr et al., 2006) A previous evaluation in domestic ferrets (Mustela putorius furo) revealed increased SAA concentration in diseased ferrets, though the disease category was incompletely described, and reported a reference interval of trace to 34 mg/L. (Ravich et al., 2015)
This study utilized a competitive field ELISA (Equichek, Accuplex Diagnostics, Kildare, Ireland) that require 10uL of whole blood, plasma, or serum. Results are semi-quantitative line estimates for different concentrations of SAA, one to four lines representing >200 mg/L, 75-200 mg/L, 30-75 mg/L, and <30 mg/L respectively. Cross reactivity was confirmed with 5 samples from animals with known severe inflammatory disease. Precision analysis was completed by running the same sample 2-5 times on separate ELISA kits using whole blood and/or serum samples from 10 different animals. All replicates provided identical results. A brief accuracy comparison was performed with a human SAA assay (Eiken, Tokyo, Japan) and all results binned adequately. A total of 71 samples from 49 juvenile to adult, male and female sea otters representing 34 “normal” and 37 “abnormal” samples were analyzed. Normal and abnormal categories were assigned by the clinician based on history, physical exam, and final disposition. Based on initial evaluation of samples from animals categorized as healthy, evaluators assessed 4 lines as a decision threshold (result within normal limits). In this population, this assay produced an 89% diagnostic specificity and 85% diagnostic sensitivity. Positive and negative predictive value was 87 and 88% respectively. The positive likelihood ratio indicates that an animal with a positive test is 6 times as likely to have significant inflammatory disease as a negative test.
Therapeutic and prognostic implications will be discussed during the session.
Pending Publishing Permission
Aging sea otters using
dental growth patterns, tooth wear patterns and growth plates
Reliable and noninvasive ageing metrics are an important conservation tool, especially when managing California sea otters. Ideally, metrics such as tooth eruption and decay timelines provide age-specific information necessary to calculate individual growth curves, predict gestation time and age at maturity, and identify vulnerable life-stages to mitigate potential threats to survival or range expansion. Defining these metrics requires examination of known-aged individuals, which is challenging when sampling only from the wild population. During wild sea otter studies, observers have traditionally estimated age using a combination of relative metrics, such as tooth condition, grizzle, and body length, which may be biased by several factors, including diet, resource availability, and genetic variability. Our solution is to incorporate observations from rehabilitation programs, or zoos and aquaria, where metrics may be repeatedly gathered from known-aged animals to boost sample size, reliably quantify age-specific measurements, and explore accuracy of metric types. As a first effort, we combine more than three decades of physical examination data from the Monterey Bay Aquarium Sea Otter program with California field studies to demonstrate feasibility of using noninvasive tooth eruption and decay schedules for ageing sea otters. These ageing metrics enabled us to reasonably estimate sea otter gestation time (t0) and asymptotic average length (L∞) by fitting von Bertalanffy growth functions to both age-specific length and girth data under different resource regimes. We also explore using x-rays of long bone growth plates to improve age estimation of sea otters between juvenile and adult stages. These tools may prove crucial for monitoring population structure, and age-specific reproduction and survival, which could be used to assess management strategies implemented to ensure sea otter recovery throughout California.
Investigating potential dietary links to changes in serum liver parameters in sea otters
David A. S. Rosen,
University of British Columbia, Vancouver Aquarium
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Changes in serum liver profiles indicative of impeded hepatic function was recently observed in a group of young, rehabilitated sea otters maintained on a diet containing a high proportion of shrimp. Unfortunately, the underlying pathology of the original observation was not clear. We investigated whether a diet high in shrimp induces changes in serum liver parameters in sea otters by conducting controlled diet manipulations with a group of 5 managed sea otters (ages 1-6 yrs) at the Vancouver Aquarium. The otters were fed diets that consisted of their normal food items, but with additional shrimp fed at levels equal to either 20% or 30% of their daily intake by mass. The diets were also manipulated to contain capelin or not, to further manipulate protein:lipid intake levels. Each sea otter was subject to 2 different experimental diets for 2 weeks each, interspersed with a minimum 4-week "recovery" period of their normal diet. Biological samples were obtained at the start and end of each 2-week trial under vet-supervised anesthesia. Blood samples were drawn for determination of standard blood profiles as well as liver function enzymes. Ultrasound and radiograph images were also taken of the liver to quantify any morphological changes attributable to each dietary treatment.
Initial analysis of the blood samples indicates recognizable changes in hematology, biochemistry, and protein C levels, although not all of the changes were directly related to liver function. Radiograph and ultrasound image analyses are pending. The results of this study will have direct applicability to the nutritional health and welfare of otters kept under human care. It may also shed light on whether diet specialization is an impediment to range expansion in wild sea otters.