Causes of death and pathogen prevalence in bottlenose dolphins Tursiops truncatus stranded in Alabama, USA, between 2015 and 2020, following the Deepwater Horizon oil spill.

Between 2010 and 2014, an unusual mortality event (UME) involving bottlenose dolphins Tursiops truncatus occurred in the northern Gulf of Mexico, associated with the Deepwater Horizon oil spill (DWHOS). Cause of death (COD) patterns in bottlenose dolphins since then have not been analyzed, and baseline prevalence data for Brucella ceti and cetacean morbillivirus, 2 pathogens previously reported in this region, are lacking. We analyzed records from bottlenose dolphins stranded in Alabama from 2015 to 2020 with necropsy and histological findings to determine COD (n = 108). This period included another UME in 2019 associated with prolonged freshwater exposure. A subset of individuals that stranded during this period were selected for molecular testing for Brucella spp. and Morbillivirus spp. Causes of death for all age classes were grouped into 6 categories, including (1) human interaction, (2) infectious disease, (3) noninfectious disease (prolonged freshwater exposure and degenerative), (4) trauma, (5) multifactorial, and (6) unknown. Two additional categories unique to perinates included fetal distress and in utero pneumonia. Human interaction was the most common primary COD (19.4%) followed closely by infectious disease (17.6%) and noninfectious disease (freshwater exposure; 13.9%). Brucella was detected in 18.4% of the 98 animals tested, but morbillivirus was not detected in any of the 66 animals tested. Brucella was detected in some moderately to severely decomposed carcasses, indicating that it may be beneficial to test a broad condition range of stranded animals. This study provides valuable information on COD in bottlenose dolphins in Alabama following the DWHOS and is the first to examine baseline prevalence of 2 common pathogens in stranded animals from this region.

Encephalitozoonosis in 2 South American Fur Seal (Arctocephalus australis) Pups.

Cerebral and disseminated encephalitozoonosis was diagnosed by histopathology, electron microscopy, and immunohistochemistry in 2 free-ranging South American fur seal pups found dead at Guafo Island (43°33'S 74°49'W) in southern Chile. In the brain, lesions were characterized by random foci of necrosis with large numbers of macrophages containing numerous microsporidial organisms within parasitophorous vacuoles. In addition, occasional histiocytes loaded with numerous mature and immature microsporidia spores consistent with Encephalitozoon sp were observed in pulmonary alveolar septa, splenic red pulp, glomerular capillaries, and proximal renal tubules by Gram and immunohistochemical stains. To our knowledge, microsporidial infection in a marine mammal species has not been previously reported.

Occlusive fungal tracheitis in 4 captive bottlenose dolphins (Tursiops truncatus).

Respiratory disease is common in dolphins, primarily affecting pulmonary parenchyma and sparing large airways. Over a 10-year period, 4 captive adult bottlenose dolphins succumbed to chronic, progressive respiratory disease with atypical recurrent upper respiratory signs. All dolphins had severe, segmental to circumferential fibrosing tracheitis that decreased luminal diameter. Histologically, tracheal cartilage, submucosa, and mucosa were distorted and replaced by extensive fibrosis and pyogranulomatous inflammation centered on fungal hyphae. In 3 of 4 cases, hyphae were morphologically compatible with Aspergillus spp and confirmed by culture in 2 cases. Amplification of fungal DNA from tracheal tissue was successful in one case, and sequences had approximately 98% homology to Aspergillus fumigatus. The remaining case had fungi compatible with zygomycetes; however, culture and polymerase chain reaction were unsuccessful. Lesions were evaluated immunohistochemically using antibodies specific to Aspergillus spp. Aspergillus-like hyphae labeled positively, while presumed zygomycetes did not. These cases represent a novel manifestation of respiratory mycoses in bottlenose dolphins.

Isolation of a novel adenovirus from California sea lions Zalophus californianus.

Viral hepatitis associated with adenoviral infection has been reported in California sea lions Zalophus californianus admitted to rehabilitation centers along the California coast since the 1970s. Canine adenovirus 1 (CAdV-1) causes viral hepatitis in dogs and infects a number of wildlife species. Attempts to isolate the virus from previous sea lion hepatitis cases were unsuccessful, but as the hepatitis had morphologic features resembling canine infectious hepatitis, and since the virus has a wide host range, it was thought that perhaps the etiologic agent was CAdV-1. Here, we identify a novel adenovirus in 2 stranded California sea lions and associate the infection with viral hepatitis and endothelial cell infection. Phylogenetic analysis confirmed the classification of the sea lion adenovirus in the Mastadenovirus genus with the most similarity to tree shrew adenovirus 1 (TSAdV-1, 77%). However, as the sea lion adenovirus appeared to be equally distant from the other Mastadenovirus species based on phylogenetic analysis, results indicate that it represents an independent lineage and species. Although sequences from this novel virus, otarine adenovirus 1 (OtAdV-1), show some similarity to CAdV-1 and 2, it is clearly distinct and likely the cause of the viral hepatitis in the stranded California sea lions.

Evidence of injury caused by gas bubbles in a live marine mammal: barotrauma in a California sea lion Zalophus californianus.

A yearling male California sea lion Zalophus californianus with hypermetric ataxia and bilateral negative menace reflexes was brought to The Marine Mammal Center, Sausalito, California, U.S.A., in late 2009 for medical assessment and treatment. The clinical signs were due to multiple gas bubbles within the cerebellum. These lesions were intraparenchymal, multifocal to coalescing, spherical to ovoid, and varied from 0.5 to 2.4 cm diameter. The gas composed 21.3% of the total cerebellum volume. Three rib fractures were also noted during diagnostic evaluation and were presumed to be associated with the gas bubbles in the brain. The progression of clinical signs and lesion appearance were monitored with magnetic resonance imaging, cognitive function testing and computed tomography. Gas filled voids in the cerebellum were filled with fluid on follow up images. Clinical signs resolved and the sea lion was released with a satellite tag attached. Post release the animal travelled approximately 75 km north and 80 km south of the release site and the tag recorded dives of over 150 m depth. The animal re-stranded 25 d following release and died of a subacute bronchopneumonia and pleuritis. This is the first instance of clinical injury due to gas bubble formation described in a living pinniped and the first sea lion with quantifiable cerebellar damage to take part in spatial learning and memory testing.

Tumor morphology and immunohistochemical expression of estrogen receptor, progesterone receptor, p53, and Ki67 in urogenital carcinomas of California sea lions (Zalophus californianus).

Metastatic carcinoma of urogenital origin is a common cause of mortality in free-ranging California sea lions (Zalophus californianus). The etiology of this cancer is likely multifactorial, with viral infection, genetic factors, and exposure to environmental organochlorine contaminants possible contributing factors. In this study, expression of estrogen receptor alpha (ER alpha), progesterone receptor (PR), p53, and Ki67 were evaluated by immunohistochemistry in 12 sea lions with metastatic carcinoma, genital epithelial dysplasia, and intraepithelial neoplasia; 4 with genital epithelial dysplasia and intraepithelial neoplasia without metastases; and 6 control animals. Dysplastic and neoplastic lesions were identified in multiple areas of the cervix, vagina, penis, prepuce, and urethra in affected animals, suggesting multicentric development. Lesions were graded according to degree of epithelial dysplasia and infiltration and lesions of different grades were evaluated separately. Estrogen receptor expression was lower in intraepithelial lesions compared with normal genital epithelium, and expression in metastatic lesions was completely absent. There was progesterone receptor expression in neoplastic cells in intraepithelial lesions of all grades and in metastases, with no significant difference between lesion grades or between control and affected epithelium. Ki67 index and p53 expression increased with lesion grade and were higher in lesions than normal epithelium. Metastatic tumors exhibited highly variable morphology; however, proliferation index, ER alpha, PR, and p53 expression were similar in tumors with different patterns of growth. These results suggest that endogenous hormones, environmental contaminants that interact with steroid hormone receptors, and alterations in p53 may play a role in urogenital carcinogenesis in California sea lions.

Novel symptomatology and changing epidemiology of domoic acid toxicosis in California sea lions (Zalophus californianus): an increasing risk to marine mammal health.

Harmful algal blooms are increasing worldwide, including those of Pseudo-nitzschia spp. producing domoic acid off the California coast. This neurotoxin was first shown to cause mortality of marine mammals in 1998. A decade of monitoring California sea lion (Zalophus californianus) health since then has indicated that changes in the symptomatology and epidemiology of domoic acid toxicosis in this species are associated with the increase in toxigenic blooms. Two separate clinical syndromes now exist: acute domoic acid toxicosis as has been previously documented, and a second novel neurological syndrome characterized by epilepsy described here associated with chronic consequences of previous sub-lethal exposure to the toxin. This study indicates that domoic acid causes chronic damage to California sea lions and that these health effects are increasing.

Multicentric T-cell lymphosarcoma in an alpaca.

A two-year-old female alpaca with multicentric lymphosarcoma presented because of progressive weakness and recumbency. The diagnosis of lymphosarcoma was based on the detection of immature and atypical lymphocytes in a lumbosacral CSF sample. Post mortem examination confirmed multicentric lymphosarcoma involving multiple organs. Immunophenotyping using cross reactive T- and B-cell antibodies characterized the tumour as a T-cell lymphosarcoma.

Pathological features of amyloidosis in stranded California sea lions (Zalophus californianus).

Amyloidosis was diagnosed in 26 stranded adult California sea lions between 1983 and 2006 by retrospective case analysis. The kidneys (92.3% of animals), blood vessels (80.7%) and thyroid glands (65.4%) were most commonly affected. Macroscopically, affected kidneys were swollen, with pale tan cortices and loss of corticomedullary differentiation. Amyloid deposits in the kidney were located in the glomeruli, blood vessels, and peritubular interstitium, most prominently in the outer stripe of the medulla. The amyloid deposits were identified as type amyloid A (AA) by potassium permanganate staining and immunolabelling with antibodies against AA protein. Concurrent diseases, including inflammatory processes and genital carcinoma, were common in affected animals. Serum amyloid A concentrations were high (>1200 microg/ml) in six of seven affected sea lions, while the median value in clinically healthy animals was <10 microg/ml. These findings suggest that renal amyloidosis contributes to morbidity and mortality in stranded adult California sea lions.