Small intestinal volvulus in a captive Steller sea lion (Eumetopias jubatus)

CAUSES OF MORBIDITY AND MORTALITY IN STELLER SEA LIONS (EUMETOPIAS JUBATUS) UNDER PROFESSIONAL CARE IN NORTH AMERICAN AQUARIUMS FROM 1979 TO 2021

To date, published comprehensive pathology investigations documented in Steller sea lions (SSL; Eumetopias jubatus) are from free-ranging populations, whereas health data from those under professional care in aquariums are currently lacking. A retrospective review of gross and histopathologic reports of SSL under human care in North American aquariums from 1979 to 2021 (n = 20) was performed. Associations between age, sex, or birth origin (born in aquariums versus the wild) with cause of death (COD) and comorbidities were explored. Age was significantly associated with development of endocrine organ pathology (P = 0.011). A relationship between age and both cardiovascular and ocular disease was suggested by the data, but did not reach significance (P = 0.058). Ocular disease was significantly associated with being born in aquariums (P = 0.022). The most common COD was neoplasia (n = 10), which was significantly associated with aged animals (P = 0.038). Less frequent COD included sepsis (confirmed, n = 2; suspected, n = 3), cardiomyopathy (n = 1), clostridial enteritis (n = 1), Sarcocystis spp. (n = 1), complication secondary to sedation (n = 1), and unknown (n = 1). This is the first report documenting the high prevalence of neoplasia in SSL, with tumors found incidentally in three individuals, frequent metastasis (10/13, 77%), and many cases of multiple primary malignancies (6/13, 46%). These data expand upon the current understanding of disease in SSL, highlight this species' predisposition to neoplasia with increasing longevity, and underscore the need for heightened screening in aged animals, which may ultimately serve to elevate the care of SSL under professional care in aquariums.

Intestinal displacements in older harbour and grey seals

Intestinal displacements including volvulus, torsion and invagination have been reported in various terrestrial and marine mammals. We conducted pathological investigations on 157 seals that had either stranded on the coasts of the North or Baltic Sea between 1996 and 2015 (115 harbour seals, >19 mo old; 21 grey seals, >13 mo old) or died while in human care (18 harbour seals, >19 mo old; 3 grey seals, >13 mo old). Intestinal displacements were found in 23% of the examined free-living harbour seals, in 5% of the stranded grey seals and in 17% of the harbour seals in human care. Intestinal volvulus, found in 24 cases, was characterized by twisting of the intestine along the mesenteric axis (180-540°) resulting in vascular obstruction and haemorrhagic infarction. In harbour seals, the sex ratio of individuals suffering from volvulus tended to be biased towards females during April to June, suggesting an elevated risk for pregnant females around birth time. Invagination was detected in 11 cases, 5 of which suffered from additional volvulus. Pathological findings associated with intestinal volvulus and invagination were sero-haemorrhagic effusions in the abdominal cavity. Enteritis, parasitic infection with gastric nematodes and intestinal acanthocephalans and bacterial infection with predominantly Clostridium perfringens and Escherichia coli were observed in most of the affected animals. In total, 30 investigated harbour and grey seals suffered from intestinal displacements. Pregnant females seemed to be more vulnerable around birth time. Causes of intestinal displacements remain undetermined, but are likely multifactorial.

Intestinal volvulus in cetaceans

Intestinal volvulus was recognized as the cause of death in 18 cetaceans, including 8 species of toothed whales (suborder Odontoceti). Cases originated from 11 institutions from around the world and included both captive (n = 9) and free-ranging (n = 9) animals. When the clinical history was available (n = 9), animals consistently demonstrated acute dullness 1 to 5 days prior to death. In 3 of these animals (33%), there was a history of chronic gastrointestinal illness. The pathological findings were similar to those described in other animal species and humans, and consisted of intestinal volvulus and a well-demarcated segment of distended, congested, and edematous intestine with gas and bloody fluid contents. Associated lesions included congested and edematous mesentery and mesenteric lymph nodes, and often serofibrinous or hemorrhagic abdominal effusion. The volvulus involved the cranial part of the intestines in 85% (11 of 13). Potential predisposing causes were recognized in most cases (13 of 18, 72%) but were variable. Further studies investigating predisposing factors are necessary to help prevent occurrence and enhance early clinical diagnosis and management of the condition.

Small intestinal volvulus in a free-ranging female dugong (Dugong dugon)

An adult female dugong (Dugong dugon) was found dead and floating in Moreton Bay, Queensland, Australia. This animal was found to have a 360° mesenteric volvulus with infarction of the associated segment of small intestine, and fibrinous peritonitis. Mortality was attributed to the volvulus and its sequelae. The cause was not apparent on gross or histological examination.