Mycobacterium marinum dermatitis and panniculitis with chronic pleuritis in a captive white whale (Delphinapterus leucas) with aortic rupture.

A 16-year-old female white whale, Delphinapterus leucas, died after nearly 18 months of chronic lymphopenia and pyogranulomatous dermatitis. Necropsy revealed rupture of the aorta with hemorrhage into the cranial mediastinum and between fascial planes of the ventral neck musculature. Multiple foci of ulcerative dermatitis and panniculitis were present across the thorax and abdomen and surrounded the genital folds. In addition, there was a chronic proliferative pleuritis with over 20 liters of histiocytic exudate in the thoracic cavity. Acid-fast bacteria consistent with Mycobacterium sp. were identified in sections of skin lesions and in cytospins of pleural exudate. Cultures of pleura and 1 skin lesion collected at necropsy yielded sparse growth of an acid-fast bacillus with colony characteristics and morphology consistent with Mycobacterium marinum. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis confirmed the presence of M. marinum DNA in samples of skin. This is the first documented occurrence of mycobacteriosis in a white whale and is a unique presentation of mycobacterial dermatitis and panniculitis with chronic pleuritis in a cetacean. The improved PCR-RFLP protocol utilized in this case unifies techniques from several protocols to differentiate between species of Nocardia and rapidly growing mycobacteria clinically relevant to aquatic animals.

Humoral immune responses of black-footed penguins (Spheniscus demersus) after DNA-mediated immunization with a beta-galactosidase reporter gene.

Humoral immune responses of black-footed penguins (Spheniscus demersus) to DNA-mediated immunization with a beta-galactosidase reporter gene expression plasmid were evaluated. Six male and 6 female adult penguins received either test plasmid, pCMV-beta, containing the beta-galactosidase gene or control plasmid, pCI, lacking a gene for expression. Three birds from each group were used previously in a diluent control group and given one injection of sterile saline. All samples were screened for anti-beta-galactosidase antibodies by indirect enzyme-linked immunosorbent assay with anti-chicken immunoglobulin G as secondary antibody. Antibodies to beta-galactosidase were detected in the sera of pCMV-beta-inoculated penguins, with a peak response on day 21. Antibody titers of the test plasmid group versus both control groups on days 21, 28, and 42 differed significantly. These results demonstrate that black-footed penguins can be safely transfected with the gene encoding beta-galactosidase and will mount a humoral response against the in vivo-expressed protein. Knowledge from this initial study can be applied to the development of DNA-mediated vaccines against specific infectious diseases of penguins.

Gastric intramural hematoma and hemoperitoneum in a captive northern fur seal.

A 16-yr-old adult male northern fur seal (Callorhinus ursinus) was found dead in its outdoor pool in November 1995. The animal was maintained at Mystic Aquarium (Mystic, Connecticut, USA) from March 1980 to November 1995. Gross necropsy findings included hemoperitoneum and locally extensive gastric intramural hemorrhage that involved the posterior fundic, antral, and pyloric regions and extended into the duodenum. The gastric mural thickening grossly resembled hemangioma, and the gastric serosa was ruptured at the site of maximal mural expansion. In histologic sections of the stomach, a cribiform network of fibrin, which encompassed numerous variably-sized aggregates of closely packed erythrocytes, markedly expanded the submucosa. No vascular endothelium was identified in serial histologic sections of the expanded gastric submucosa stained with hematoxylin and eosin or immunohistochemically with antibodies to vimentin and Factor VIII-related antigen, establishing an absence of hemangioma. Carstairs' and Weigert's histochemical stains confirmed that the framework expanding the submucosa was fibrin. Although the appearance of the gastric wall resembled hemangioma, a population of neoplastic endothelial cells was not identified within the submucosal expansion of hemorrhage and fibrin, and microscopic evidence was most consistent with the diagnosis of gastric intramural hematoma. This lesion is a rare pathologic event that has not been reported in marine mammals, but one that should be included in diagnostic considerations of hemoperitoneum and gastric mural expansion.

Epizootiology of morbillivirus infection in harp, hooded, and ringed seals from the Canadian Arctic and western Atlantic.

Using a virus neutralization technique, we found phocine distemper virus (PDV) antibody in 130 (83% of 157) harp seals (Phoca groenlandica) from the western North Atlantic sampled between 1988 and 1993 inclusive. In contrast, only 44 (24% of 185) hooded seals (Cystophora cristata) had antibodies against PDV even though they were sympatric with harp seals and were sampled over a similar period, from 1989 to 1994 inclusive. Antibodies occurred in 106 (41%) of 259 ringed seals (Phoca hispida); this prevalence was higher than expected given the solitary behavior and territoriality characteristic of this species. Seropositive ringed seals were found at each of seven locations across Arctic Canada from Baffin Bay to Amundsen Gulf at which samples were collected between 1992 and 1994. However, the prevalence of infection was highest where ringed seals are sympatric with harp seals in the eastern Canadian Arctic.

Epizootiology of morbillivirus infection in North American harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus).

A longitudinal study of morbillivirus infection among harbor (Phoca vitulina) and gray (Halichoerus grypus) seals on the Atlantic coast of North America was carried out between 1980 and 1994. Serology also was carried out on harbor seals from the Pacific northwest coast collected in 1992 and 1993. The prevalence of morbillivirus neutralizing antibodies was significantly (P < 0.0001) higher in gray (73%, n = 296) than in harbor seals (37%, n = 387) from the Atlantic. Titers were significantly (P < 0.0001) higher against phocine distemper (PDV) compared to any other morbillivirus. Antibodies were not detected in serum from Pacific harbor seals. During the winter of 1991 to 1992 an epizootic occurred among harbor seals on the northeast coast of the United States. The event was characterized by an increase in strandings and by a significant (P = 0.001) increase in PDV antibody prevalence to 83% (n = 36) in seals stranded that winter. Morbillivirus lesions and antigen were observed in six animals found stranded from southern Maine to Long Island, New York (USA), between November 1991 and April 1992. In addition, morbillivirus encephalitis was detected in tissues from a harbor seal that stranded in 1988. Enzootic infection appeared to be present in both seal species, although with a different prevalence of disease. We propose that enzootic infection among gray seals is facilitated by population size, high annual recruitment and innate resistance to clinical disease. Infection may be maintained in the smaller harbor seal population through casual contact with gray seals.

Morbillivirus infection in cetaceans of the western Atlantic.

We report serologic evidence of morbillivirus infection in eleven of fifteen species of odontocete cetaceans from the western Atlantic since 1986. Blood samples were obtained both from free-ranging and stranded animals. Virus neutralizing titers were higher against porpoise and dolphin morbilliviruses than against peste des petits ruminants virus, phocine distemper virus or canine distemper virus (CDV). Serum from five species, tested in a heterologous immunoprecipitation assay using radiolabelled CDV, precipitated the nucleocapsid (N) protein. Clinical morbillivirus infection may potentially impact already threatened species such as the harbour porpoise and precipitate mass strandings of socially cohesive odontocetes.

Neutralizing antibodies to phocine distemper virus in Atlantic walruses (Odobenus rosmarus rosmarus) from Arctic Canada.

The first evidence of phocine distemper virus (PDV) infection in Atlantic walruses (Odobenus rosmarus rosmarus) from Nottingham Island, Northwest Territories, Canada, is reported. Blood samples were collected from three male walruses killed by Inuit hunters in the fall of 1990. Differential virus neutralization test for each animal yielded higher titers against PDV than against other members of the Morbillivirus genus including canine distemper, peste des petits ruminants, rinderpest and measles viruses. Thus, PDV infection may be enzootic in walruses of the eastern Canadian Arctic.

Thyroid hormone balance in beluga whales, Delphinapterus leucas: dynamics after capture and influence of thyrotropin.

Ten beluga whales, Delphinapterus leucas, were captured in the Churchill River, Manitoba, held for up to five days, and then released. Blood samples were obtained immediately after capture and at 6-7 h intervals thereafter to monitor changes in circulating levels of thyroid hormones (TH). In six of the whales, total and free thyroxine (T4) and triiodothyronine (T3) declined steadily, whereas reverse-T3 (rT3) showed a transient increase during the first 24-36 h, followed by a decrease to below initial values. The changes in TH may have been due to glucocorticoid-mediated reduction in endogenous thyroid stimulating hormone (TSH), and inhibition of 5'-monodeiodinase in peripheral tissue. Two whales were given 10 IU of bovine TSH immediately after capture, and again one and two days later, resulting in successive increases in all TH, which remained elevated for at least 24 h after the last injection. Thereafter, circulating levels declined as in the untreated whales. Two whales receiving a single TSH injection on the fourth day responded with an increase in plasma TH comparable to that observed following the first TSH injection in the other two animals. Average (+/- SD) circulating level of rT3 at capture was 6.3 +/- 3.1 nmol/L, which is higher than reported for any other mammal and was significantly correlated with the naturally elevated levels of T4 that occur in belugas occupying estuaries during the summer.

Stimulation of thyroid hormone secretion by thyrotropin in beluga whales, Delphinapterus leucas.

Bovine thyroid stimulating hormone administered to three beluga whales, Delphinapterus leucas, was effective in producing an increase in circulating levels of triiodothyronine and thyroxine. A single dose of 10 I.U. of thyroid stimulating hormone resulted in a 145% increase in triiodothyronine and a 35% increase in thyroxine after nine hours in a whale tested within two hours after capture. The response was less pronounced in an animal tested with the same does on two occasions after four and eight weeks in captivity. In the third whale, 10 I.U. of thyroid stimulating hormone given on each of three consecutive days produced a marked increase in triiodothyronine and thyroxine. The elevation of thyroxine concentration persisted for at least two days after the last injection of thyroid stimulating hormone. A subsequent decrease in thyroxine to levels below baseline signalled the suppression of endogenous thyroid stimulating hormone. This preliminary study helps to establish a protocol for testing thyroid function in cetaceans.

Epidermal growth in the bottlenose dolphin, Tursiops truncatus.

Epidermal growth in two mature female bottlenose dolphins, Tursiops truncatus, was investigated by following the movement of a cohort of tritiated thymidine-labeled epidermal cells for 59 days. The majority of the cells migrated in a cluster which was estimated to reach the skin surface in 73 days. We calculate that the outermost cell layer is sloughed 12 times per day. Turnover time and sloughing rate are estimated to be 1.7 times longer and 8.5 times faster than the respective values for epidermal cell kinetics in humans. This apparent inconsistency of slow transit time and rapid sloughing rate is reconciled by the convoluted structure of the stratum germinativum in the dolphin which results in a ratio of germinatival to superficial cells of 876:1. The stratum germinativum of dolphin epidermis appears to lack morphologically distinct, spatially segregated subpopulations of anchoring and stem cells. Dolphin epidermis has a large capacity for cell population, relatively long turnover time, and rapid sloughing rate. The adaptive advantages of these characteristics are discussed.

Are seals frequently infected with avian influenza viruses?

Influenza A virus isolates of the H4N5 subtype (which has previously been detected only in birds) were recovered from harbor seals dying of viral pneumonia on the New England coast from June 1982 through March 1983. When these isolates were compared with other mammalian and avian viruses in serological assays and RNA-RNA competitive hybridization, it was found that the seal viruses were most closely related antigenically and genetically to recent avian virus strains and were readily distinguishable from mammalian viruses, including H7N7 isolates recovered from seals in 1980. Unlike any previous isolates from mammals, these recent seal viruses replicate in the intestinal tracts of ducks, a characteristic of avian viruses. The association of avian viruses with influenza outbreaks in seals suggests that transmission of avian viruses to seals is occurring in nature. Potentially, this may be an example of the adaptation of avian viruses to mammals, which would represent an intermediate step in the evolution of new mammalian strains.

Mass mortality of harbor seals: pneumonia associated with influenza A virus.

More than 400 harbor seals, most of them immature, died along the New England coast between December 1979 and October 1980 of acute pneumonia associated with influenza virus, A/Seal/Mass/1/180 (H7N7). The virus has avian characteristics, replicates principally in mammals, and causes mild respiratory disease in experimentally infected seals. Concurrent infection with a previously undescribed mycoplasma or adverse environmental conditions may have triggered the epizootic. The similarities between this epizootic and other seal mortalities in the past suggest that these events may be linked by common biological and environmental factors.

A safe method for repeatedly immobilizing seals.

Phocid seals were immobilized safely and repeatedly, using a combination of ketamine and diazepam at mean IM or IV dosages of 1.5 mg/kg and 0.05 mg/kg, respectively. Induction and recovery were smoother than with ketamine used alone. Experimentally induced pneumonia did not alter the effects of the drugs, thus attesting to the safety of the ketamine-diazepam combination.

Dolphin pox: a skin disease of cetaceans.

Poxvirus has been identified morphologically from skin lesions in captive and free-ranging bottlenosed dolphins, Tursiops truncatus and a stranded Atlantic white-sided dolphin, Lagenorhynchus acutus. The lesions, commonly referred to as ring or pinhole lesions, appear as solitary or coalesced circular grey blemishes. Advanced ring lesions may take the form of black punctiform stippled patterns known as "tattoo". Histologically, the stratum externum is thickened, and there is ballooning degeneration and eosinophilic intractyoplasmic inclusions in the stratum intermedium. These includions contain virus particles which exhibit typical poxvirus morphology. Stress, environmental conditions and general health appear to play a major role in the clinical manifestation of dolphin pox.

Effects of handling stress on plasma enzymes in harp seals, Phoca groenlandica.

Three harp seal pups, Phoca groenlandica, were captured on the ice of the Gulf of St. Lawrence, and subjected to 3 h of transportation and handling stress. The activities of creatine kinase (CK), aspartate aminotransferase (AspAT), aldolase, alanine aminotransferase, gamma glutamyl transpeptidase, and leucine aminopeptidase were determined in serial blood samples collected for 4 d following the stress episode. Marked elevation of plasma CK activity was observed 3 h after capture. Values returned to normal in 12 h in two seals, and by 24 h in the third. Slight elevations in AspAT were also noted; the remaining enzymes were unaffected. Plasma CK is recommended as a sensitive indicator of handling stress in seals.