Patterns and significance of bite wounds in Eurasian otters (Lutra lutra) in southern and south-west England

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.     

Pathological changes and organochlorine residues in tissues of wild otters (Lutra lutra)

In 1984 two adult, wild otters (Lutra lutra) from north Norfolk were subjected to full post mortem examinations. One was found dead and the other sick. Both were thin. No evidence of infectious disease was found, but there were organochlorine concentrations of 433 and 75 mg/kg of fat (69 per cent polychlorinated biphenyls in both) in skeletal muscle. Leiomyoma of the reproductive tract and adrenocortical hyperplasia in one otter were similar to age associated changes in other mammals. Integumentary, including pedal, lesions were present in both otters. The possibility that the pedal lesions were caused by the toxic effects of polychlorinated biphenyls is discussed.     

Cholecystitis in otters (Lutra lutra) and mink (Mustela vison) caused by the fluke Pseudamphistomum truncatum

Between 1988 and 2004, postmortem examinations were carried out on 445 otters found dead, mostly as a result of road traffic accidents, in southern and south-west England. Thickened, shrunken gall bladders were observed in 10 cases, the first in 2000 and the others between February 2002 and August 2004. A digenean fluke, Pseudamphistomum truncatum, was found in the gall bladders of three cases and also in three of seven American mink examined. Nine of the 10 otters and all the mink came from a localised area of Somerset, indicating that the fluke has become established in the local fish population. P. truncatum has not been recorded previously in Britain, and the results suggest that it has been introduced recently, possibly in imported fish.     

Retinal dysplasia in wild otters (Lutra lutra)

Eyes from 88 otters found dead in south-west England between 1990 and 2000, were collected as part of a larger pathological study. Histopathological examination of 131 eyes revealed dysplastic changes such as rosetting and folding in the retinas of 26 of the otters. In the eyes of 42 of the otters there were postmortem and fixation-induced retinal detachment which complicated the differentiation of dysplastic from normal retina, but 11 eyes had folds which probably indicated a dysplastic pathology. The eyes of 18 of the otters had inflammatory or autolytic changes which precluded a definitive evaluation of their dysplastic status. Liver samples from 55 of the otters were analysed for a range of polychlorinated hydrocarbons and for vitamin A. The otters with dysplastic retinas had significantly lower concentrations of vitamin A and higher concentrations of dieldrin than the otters with normal retinas.     

Evaluation of cardiac lesions and risk factors associated with myocarditis and dilated cardiomyopathy in southern sea otters (Enhydra lutris nereis)

OBJECTIVE: To describe cardiac lesions and identify risk factors associated with myocarditis and dilated cardiomyopathy (DCM) in beach-cast southern sea otters. ANIMALS: Free-ranging southern sea otters. PROCEDURE: Sea otters were necropsied at the Marine Wildlife Veterinary Care and Research Center from 1998 through 2001. Microscopic and gross necropsy findings were used to classify sea otters as myocarditis or DCM case otters or control otters. Univariate, multivariate, and spatial analytical techniques were used to evaluate associations among myocarditis; DCM; common sea otter pathogens; and potential infectious, toxic, and nutritional causes. RESULTS: Clusters of sea otters with myocarditis and DCM were identified in the southern aspect of the sea otter range from May to November 2000. Risk factors for myocarditis included age, good body condition, and exposure to domoic acid and Sarcocystis neurona. Myocarditis associated with domoic acid occurred predominantly in the southern part of the range, whereas myocarditis associated with S. neurona occurred in the northern part of the range. Age and suspected previous exposure to domoic acid were identified as major risk factors for DCM. A sample of otters with DCM had significantly lower concentrations of myocardial L-carnitine than control and myocarditis case otters. CONCLUSIONS AND CLINICAL RELEVANCE: Cardiac disease is an important cause of death in southern sea otters. Domoic acid toxicosis and infection with S. neurona are likely to be 2 important causes of myocarditis in sea otters. Domoic acid-induced myocarditis appears to progress to DCM, and depletion of myocardial L-carnitine may play a key role in this pathogenesis.     

Mortality associated with melarsomine dihydrochloride administration in two North American river otters (Lontra canadensis) and a red panda (Ailurus fulgens fulgens).

Two adult North American river otters (Lontra canadensis) and an adult red panda (Ailurus fulgens fulgens) at three separate institutions died within 22 hr after receiving single 2.5- to 2.7-mg/kg doses of melarsomine dihydrochloride administered in the epaxial musculature as a treatment for filarid nematodes. One otter had a suspected Dirofilaria immitis infection, the other had a confirmed D. lutrae infection, and the red panda had a confirmed Dirofilaria sp. infection, presumably with D. immitis. Postmortem examinations revealed similar gross lesions, although they were less severe in the red panda. The trachea and primary bronchi contained abundant foamy fluid, the lungs were mottled with areas of consolidation, and the pulmonary parenchyma exuded abundant fluid at the cut section. Histologic evaluation revealed acute pulmonary edema, which resulted in respiratory failure and death. There may have been direct pulmonary cellular toxicity of melarsomine dihydrochloride or a severe systemic anaphylactic reaction to antigens released after parasite death. An idiosyncratic drug reaction or a low therapeutic index of melarsomine probably caused the death of the three individuals. Melarsomine dihydrochloride use should be avoided in North American river otters and red pandas.     

Clinical evaluation and prerelease management of American river otters in the second year of a reintroduction study

In the first year (1984) of a reintroduction study, 10 American river otters (Lutra canadensis) from Louisiana were transported to Oklahoma, held for 5 days for clinical evaluation, surgical implantation with intra-abdominal radiotelemetry devices, and then released in Oklahoma. Four of 10 otters released died within 32 days. Clinical evaluation indicated that respiratory tract disease, bacterial and parasitic infections, and inanition may have contributed to the death of these otters. In the second year (1985) of the study, an exotic feline diet was fed, and the holding period for 10 otters was increased to provide time for evaluation and treatment before surgery, postsurgical acclimation to Oklahoma, and reevaluation before release. Although the initial clinical findings on otters in the second year were similar to those found in the first year, otter body weights increased, and the prevalence and severity of clinical abnormalities decreased with treatment during the second-year holding period. Three of 10 second-year otters died during the holding period, and contributing causes of death were determined to be: trauma (hepatic hematoma), inanition, renal disease, pneumonia, salmonellosis (Salmonella anatum), and a retropharyngeal abscess (Klebsiella pneumoniae). Seven healthy otters were reintroduced into Oklahoma in 1985, and postrelease deaths were not experienced.     

Serologic evaluation of vaccinated American river otters

The Oklahoma Department of Wildlife Conservation acquired 20 American river otters (Lutra canadensis) between 1984 and 1985 for reintroduction into Oklahoma waterways. In 1985, 10 otters were evaluated for serum antibody titers after vaccination with canine distemper virus, canine adenovirus type 2, canine parvovirus (CPV), feline panleukopenia virus (FPV), feline rhinotracheitis virus (FRV), and feline calicivirus. Prevaccination serum-virus neutralization (SVN) antibody to feline rhinotracheitis virus was found in 2 otters and to feline calicivirus in 1 otter. Using an indirect fluorescent antibody (IFA) assay, prevaccination antibody to CPV and FPV was found in 2 otters. A significant increase in SVN antibody titers was found after vaccination of otters with canine adenovirus type 2 (6 of 8 animals) and feline calicivirus (1 of 8 animals). One of 8 otters developed significant antibody titers to CPV and FPV, as measured by IFA assay. Otters did not develop SVN antibody titers to canine distemper virus after vaccination. Antigens of feline leukemia virus, using ELISA, or antibodies to feline infectious peritonitis, using IFA assay, were not found in the 20 otters.     

Clinical anatomy of the North American river otter (Lontra canadensis).

Published anatomic studies of North American river otters (Lontra canadensis) include only comparative reviews of single anatomic systems, but this paper includes multiple clinically relevant anatomic features. Both captive and free-ranging North American river otters were studied by gross dissection of nine specimens, radiography of 18 live otters, and physical examination of 170 otters. Body fat in North American river otters is stored primarily subcutaneously at the base of the tail and in the axillae, so lack of visceral detail on abdominal radiographs is due to a lack of coelomic fat. The heart and great vessels are oriented as in the dog. The cardiac radiographic silhouette measures three intercostal spaces laterally between the fourth and sixth ribs and 4-4.5 intercostal spaces between the seventh through 11th ribs on the ventrodorsal projection. Subjective estimation of age by evaluation of tooth wear is confirmed by histologic examination of cementum annuli. Structures of the feet were imaged by high-resolution mammographic technique. The adult thymus was prominent, but the gland was small in the one juvenile animal studied. The spleen was unexpectedly large but consistent with findings in European otters (Lutra lutra). As in other otters and mammals, kidneys are reniculated.     

Glucosuria associated with renal calculi in Asian small-clawed otters

Urine from one female and 2 male Asian small-clawed otters (Aonyx cinerea) with bilateral renal calculi, one female with unilateral calculi, and one nonaffected male were evaluated for abnormal urinary crystalloid excretion. One otter with bilateral renal calculi had cystic calculi composed of calcium oxalate monohydrate and dihydrate. The 2 affected males were littermates, as were the 2 affected females, but the 2 litters were from different parents. At the time of the study, the otters did not have clinical signs of disease. Hematologic and serum biochemical, electrolyte, and enzyme values were normal. The urinary excretion of calcium, oxalate, uric acid, phosphate, citrate, and amino acids in otters with renal calculi was similar to that of the nonaffected otter. The 4 otters with renal calculi had glucosuria but the nonaffected otter did not have glucosuria. The glucosuria, in the absence of hyperglycemia, suggested a renal tubular transport defect for glucose. Other renal abnormalities were not found.     

Enteric bacterial pathogen detection in southern sea otters (Enhydra lutris nereis) is associated with coastal urbanization and freshwater runoff

Although protected for nearly a century, California’s sea otters have been slow to recover, in part due to exposure to fecally-associated protozoal pathogens like Toxoplasma gondii and Sarcocystis neurona. However, potential impacts from exposure to fecal bacteria have not been systematically explored. Using selective media, we examined feces from live and dead sea otters from California for specific enteric bacterial pathogens (Campylobacter, Salmonella, Clostridium perfringens, C. difficile and Escherichia coli O157:H7), and pathogens endemic to the marine environment (Vibrio cholerae, V. parahaemolyticus and Plesiomonas shigelloides). We evaluated statistical associations between detection of these pathogens in otter feces and demographic or environmental risk factors for otter exposure, and found that dead otters were more likely to test positive for C. perfringens, Campylobacter and V. parahaemolyticus than were live otters. Otters from more urbanized coastlines and areas with high freshwater runoff (near outflows of rivers or streams) were more likely to test positive for one or more of these bacterial pathogens. Other risk factors for bacterial detection in otters included male gender and fecal samples collected during the rainy season when surface runoff is maximal. Similar risk factors were reported in prior studies of pathogen exposure for California otters and their invertebrate prey, suggesting that land-sea transfer and/or facilitation of pathogen survival in degraded coastal marine habitat may be impacting sea otter recovery. Because otters and humans share many of the same foods, our findings may also have implications for human health.     

Evaluation of injury severity and hematologic and plasma biochemistry values for recently captured North American river otters (Lontra canadensis).

As part of a reintroduction program, blood samples from free-ranging, recently captured Nearctic river otters (Lontra canadensis) in eastern New York state were collected and analyzed to determine baseline hematology and plasma biochemistry values for the source population, and to determine whether these values were significant predictors of trap-injury status. Based on physical exam, each otter was classified as uninjured, moderately injured, or severely injured. Clinical pathology parameters were compared across sex, age class, and injury classification. The increase in likelihood of a change in each parameter in injured versus uninjured otters was determined using logistic regression. Baseline hematology and plasma biochemistry values did not differ significantly from published values for captive otters in zoos or other reintroduction programs. Plasma aspartate aminotransferase levels increased as time from capture to venipuncture decreased. Some otters in this study showed clinical signs consistent with exertional myopathy, possibly altering our calculation of baseline values. Our results suggest that the hematology and plasma biochemistry values obtained in this recently captured population of otters are generally not good predictors of capture-related injury. This could be due to disease processes that are not readily visible upon physical examination or because changes in these values may be associated with factors independent of capture-related injury.     

Vitamin A deficiency and hepatic retinol levels in sea otters, Enhydra lutris

Vitamin A deficiency has rarely been reported in captive or free-ranging wildlife species. Necropsy findings in two captively housed southern sea otters (Enhydra lutris nereis) included irregular thickening of the calvaria characterized by diffuse hyperostoses on the internal surface. One animal also had moderate squamous metaplasia of the seromucinous glands of the nose. There was no measurable retinol in the liver of either sea otter. For comparison, hepatic retinol concentration was determined for 23 deceased free-ranging southern and northern (Enhydra lutris kenyoni) sea otters from California and Alaska. Free-ranging otters were found to have similar hepatic retinol concentrations (316 +/- 245 mg/kg wet weight) regardless of their location and subspecies. All of these values were significantly higher than the levels in the affected animals. Consumption of a diet with very low vitamin A concentrations and noncompliance in daily supplementation are hypothesized as the causes of vitamin A deficiency in these two sea otters.     

Hematology and serum biochemistry parameters of North American river otters (Lontra canadensis).

Blood samples were obtained from 155 North American river otters (Lontra canadensis; 94 adult males, 38 adult females, 10 juvenile males, and 13 juvenile females) to establish baseline hematology and from 50 adult river otters (40 males and 10 females) for baseline serum biochemistry parameters for the species. The otters were livetrapped from eastern North Carolina (USA) during a 4-yr period. Data for 14 routine hematologic parameters and 22 serum chemistry assays showed significant differences in total leukocyte count and absolute neutrophil and monocyte numbers for adults versus juveniles, red blood cell counts and hemoglobin between adult and juvenile males, and calcium and alkaline phosphatase values for adult males between years of the study and an increase in leukocyte counts and absolute neutrophils with increased degree of trap injury sustained.     

Renal calculi in wild Eurasian otters (Lutra lutra) in England

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.     

Evaluation of urinary and serum metabolites in Asian small-clawed otters (Aonyx cinerea) with calcium oxalate urolithiasis.

Baseline renal function data was collected during 24-hr periods of feeding and fasting from three male and three female adult Asian small-clawed otters (Aonyx cinerea) with calcium oxalate urolithiasis. Urine was analyzed for calcium, phosphorus, and oxalate, and urinalyses were performed. There was no evidence of glucosuria, which has been previously reported in Asian small-clawed otters with urolithiasis. Urinary oxalate levels were quite high when compared with those of dogs and humans without uroliths, and the ratio of urinary oxalate to calcium was close to 1:1 during periods of food consumption. There was no significant difference in urinary oxalate excretion between the fed and fasting states. Urinary calcium excretion was five times greater during feeding than during fasting. Calcium levels were higher in the otters than those reported for dogs without uroliths but were similar to those for normal humans. Water consumption and urine production were significantly higher during periods of food consumption. Serum chemistry analyses and electrolyte levels were also determined. There was no evidence of hypercalcemia. Fractional clearance of calcium and phosphorus and endogenous creatinine clearance were significantly higher during food consumption than during fasting. Parathyroid hormone levels were similar to those reported for dogs and cats. Serum 25-hydroxy-vitamin D was slightly lower in the otters than in dogs.     

Measurement of serum immunoglobulin concentration in killer whales and sea otters by radial immunodiffusion

Killer whales and sea otters maintained in captivity are the subjects of routine health monitoring programs, and interest in immunologic studies in sea otters has been rising recently in response to potential impacts from infectious disease and environmental pollution on the threatened southern sea otter population. Development of species-specific reagents for immunologic studies in these two marine mammals is currently in its infancy. In this study, killer whale and sea otter immunoglobulin-specific polyclonal antibodies were generated, and used to develop tests for serum Ig concentration in the killer whale (Orcinus orca) and the southern (Enhydra lutris nereis) and northern sea otter (Enhydra lutris lutris). Killer whale serum IgG was purified using caprylic acid/ammonium sulfate precipitation. Sea otter plasma IgG was purified using protein-A-agarose. Polyclonal anti-Ig antisera were produced in rabbits, and specificity confirmed by immunoelectrophoresis. Radial immunodiffusion was used to measure Ig concentration in serum or plasma samples derived from 21 captive killer whales, 18 wild and 4 captive southern sea otters and 15 wild and 4 captive northern sea otters grouped by age. Mean killer whale serum Ig concentration (+/-95% confidence interval) ranged from 15.04 +/- 3.97 g/l for animals aged 0-5 years to 26.65 +/- 9.8 g/l for animals aged >10 years. Mean sea otter serum Ig concentration (+/-95% confidence interval) ranged from 28.39 +/- 11.00 g/l for southern sub-adults to 32.76 +/- 11.58 g/l for southern adults. No significant difference in serum Ig concentration was found between southern and northern sea otters. Serum Ig concentrations in two northern sea otter pups were low compared to those of adult sea otters. The two serum Ig quantitation assays produced were highly specific and reproducible and will be useful additions to the limited number of tests available for immune function in these marine mammal species.     

Reversible anesthesia in wild marine otters (Lontra felina) using ketamine and medetomidine.

Nine marine otters (Lontra felina) were anesthetized 15 times with a combination of ketamine (5.3 +/- 0.9 [range: 4.5-8.0] mg/kg) and medetomidine (53 - 9 [range: 45-80] microg/kg) i.m. by hand syringe for the placement of radiotransmitters. Times to initial effect and induction period ranged from 1.1 to 5.0 min and 1.8 to 5.4 min, respectively. Minor complications did occur, including mild hypothermia in six otters and severe hypoxemia in one otter. After 34 and 63 min, anesthesia was antagonized with atipamezole (226 +/- 29 [range: 179-265] microg/kg) and all otters recovered within 3.3-26.8 min.     

Reintroduction of the Eurasian otter (Lutra lutra) in northeastern Spain: trapping, handling, and medical management.

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.     

Evaluation of changes in hematologic and clinical biochemical values after exposure to petroleum products in mink (Mustela vison) as a model for assessment of sea otters (Enhydra lutris)

OBJECTIVE: To determine the effects of petroleum exposure on hematologic and clinical biochemical results of mink and to identify variables that may be useful for making management decisions involving sea otters (Enhydra lutris) that have been exposed to oil in their environment. ANIMALS: 122 American mink (Mustela vison). PROCEDURES: Mink were exposed once to a slick of oil (Alaskan North Slope crude oil or bunker C fuel oil) on seawater or via low-level contamination of their daily rations. RESULTS: In the acute phase of exposure, petroleum directly affected RBC, WBC, neutrophil, and lymphocyte counts, fibrinogen, sodium, calcium, creatinine, total protein, and cholesterol concentrations, and alanine transaminase, creatine kinase, alkaline phosphatase, and gamma-glutamyltransferase activities. Aspartate transaminase, alkaline phosphatase, gamma-glutamyltransferase, and lactate dehydrogenase activities and cholesterol concentration also varied as a result of chronic low-level contamination of feed. CONCLUSIONS AND CLINICAL RELEVANCE: Our results are in agreement with reports that attribute increased alanine transaminase and alkaline phosphatase activities and decreased total protein concentration to petroleum exposure in sea otters during an oil spill. Sodium, calcium, creatinine, cholesterol, and lactate dehydrogenase may be valuable variables to assess for guidance during initial treatment of sea otters exposed to oil spills as well as for predicting which petroleum-exposed sea otters will reproduce following an oil spill. Measurement of these variables should aid wildlife professionals in making decisions regarding treatment of sea otters after oil spills.