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We present a novel case of an intestinal cestode infection in a southern sea otter (Enhydra lutris nereis). The cestode species Diphyllobothrium tetrapterum (syn. Diplogonoporus tetrapterus) was confirmed genetically. Stable isotope analysis of whiskers collected from the sea otter did not confirm the consumption of fish as the route of exposure.

Recent studies have implicated beta-hemolytic streptococci as opportunistic pathogens of marine mammals, including southern sea otters (Enhydra lutris nereis), but little is known about their prevalence or pathophysiology. Herein, we focus on risk factors for sea otter infection by a single beta-hemolytic streptococcal species, Streptococcus phocae. Streptococcus phocae was first identified as a marine mammal pathogen in 1994, and the first report in southern sea otters was in 2009. Its broad host range encompasses fish, pinnipeds, cetaceans, and mustelids, with S. phocae now recognized as an important pathogen of marine species worldwide. We assessed risk factors and lesion patterns for S. phocae infection in southern sea otters. Using archival necropsy data, S. phocae prevalence was 40.5% in fresh dead otters examined 2004-10. Skin trauma of any type was identified as a significant risk factor for S. phocae infection. The risk of infection was similar regardless of the cause and relative severity of skin trauma, including mating or fight wounds, shark bite, and anthropogenic trauma. Streptococcus phocae-infected sea otters were also more likely to present with abscesses or bacterial septicemia. Our findings highlight the importance of S. phocae as an opportunistic pathogen of sea otters and suggest that the most likely portal of entry is damaged skin. Even tiny skin breaks appear to facilitate bacterial colonization, invasion, abscess formation, and systemic spread. Our data provide important insights for management and care of marine species.

Macroscopic renal calculi were seen in 50 of 492 (10.2 per cent) wild Eurasian otters found dead in England from 1988 to 2007. Forty-eight adults and two subadults were affected. Calculi were present in 15.7 per cent (31 of 197) of adult males and 12.7 per cent (17 of 134) of adult females. There was an increase in prevalence in the study population over time; no calculi were found in 73 otters examined between 1988 and 1996, but in most subsequent years they were observed with increased frequency. Calculi occurred in both kidneys but were more common in the right kidney. They varied greatly in shape and size; larger calculi were mostly seen in the calyces while the smallest ones were commonly found in the renal medulla. Calculi from 45 cases were examined by x-ray diffraction analysis; in 43 (96 per cent), they were composed solely of ammonium acid urate. Affected otters had heavier adrenal glands relative to their body size than unaffected otters (P<0.001). There was no significant association between body condition index and the presence of calculi (P>0.05). Many otters had fresh bite wounds consistent with intraspecific aggression. The proportion bitten increased over time and this coincided with the increased prevalence of renal calculi.

Stranding networks, in which carcasses are recovered and sent to diagnostic laboratories for necropsy and determination of cause of death, have been developed to monitor the health of marine mammal and bird populations. These programs typically accumulate comprehensive, long-term datasets on causes of death that can be used to identify important sources of mortality or changes in mortality patterns that lead to management actions. However, the utility of these data in determining cause-specific mortality rates has not been explored. We present a maximum likelihood-based approach that partitions total mortality rate, estimated by independent sources, into cause-specific mortality rates. We also demonstrate how variance estimates are derived for these rates. We present examples of the method using mortality data for California sea otters (Enhydra lutris nereis) and Florida manatees (Trichechus manatus latirostris).

Postmortem examinations were carried out on 379 otters found dead in southern and south-west England between 1988 and 2003. Most (81 per cent) were road casualties, but many had open bite wounds and in some cases these had proved fatal. Mortality was strongly seasonal and was positively correlated with night length. Although numbers decreased in the summer months, the prevalence of bite wounds in adults was highest in late summer. The number of otters examined annually and the prevalence of bite wounds increased markedly during the study period, and in 2003 more than half the otters of both sexes had recent bite wounds. The majority of the bites were considered to have been caused by other otters, but some were thought to have been inflicted by American mink (Mustela vison). Bites to cubs were mostly caused by domestic dogs. The overall mortality due to bite wounds was approximately 10 per cent.

Detailed postmortem examination of southern sea otters (Enhydra lutris nereis) found along the California (USA) coast has provided an exceptional opportunity to understand factors influencing survival in this threatened marine mammal species. In order to evaluate recent trends in causes of mortality, the demographic and geographic distribution of causes of death in freshly deceased beachcast sea otters necropsied from 1998-2001 were evaluated. Protozoal encephalitis, acanthocephalan-related disease, shark attack, and cardiac disease were identified as common causes of death in sea otters examined. While infection with acanthocephalan parasites was more likely to cause death in juvenile otters, Toxoplasma gondii encephalitis, shark attack, and cardiac disease were more common in prime-aged adult otters. Cardiac disease is a newly recognized cause of mortality in sea otters and T. gondii encephalitis was significantly associated with this condition. Otters with fatal shark bites were over three times more likely to have pre-existing T. gondii encephalitis suggesting that shark attack, which is a long-recognized source of mortality in otters, may be coupled with a recently recognized disease in otters. Spatial clusters of cause-specific mortality were detected for T. gondii encephalitis (in Estero Bay), acanthocephalan peritonitis (in southern Monterey Bay), and shark attack (from Santa Cruz to Point Año Nuevo). Diseases caused by parasites, bacteria, or fungi and diseases without a specified etiology were the primary cause of death in 63.8% of otters examined. Parasitic disease alone caused death in 38.1% of otters examined. This pattern of mortality, observed predominantly in juvenile and prime-aged adult southern sea otters, has negative implications for the overall health and recovery of this population.

In 1993 a reintroduction project for the Eurasian otter (Lutra lutra) was initiated in northeastern Spain (Girona, Catalonia) to restore extirpated populations. Between 1996 and 2000, 43 otters were captured from southwestern and northern Spain and from Portugal with modified foot-hold traps and transported to Barcelona Zoo. Lesions produced by capture were classified into four categories of increasing severity. Thirty four (79%) animals had category I, three (7%) had category II, five (12%) had category III, and only one (2%) had category IV injuries. During captivity five (11%) animals died, including one from a precapture problem. Radiotransmitter devices were implanted i.p. into 36 otters to monitor postrelease movement and survival. At least three radio-implanted otters have bred successfully in Girona province, Catalonia, after release in that area.