A review of Brucella infection in marine mammals, with special emphasis on Brucella pinnipedialis in the hooded seal (Cystophora cristata)

ABSTRACT: Brucella spp. were isolated from marine mammals for the first time in 1994. Two novel species were later included in the genus; Brucella ceti and Brucella pinnipedialis, with cetaceans and seals as their preferred hosts, respectively. Brucella spp. have since been isolated from a variety of marine mammals. Pathological changes, including lesions of the reproductive organs and associated abortions, have only been registered in cetaceans. The zoonotic potential differs among the marine mammal Brucella strains. Many techniques, both classical typing and molecular microbiology, have been utilised for characterisation of the marine mammal Brucella spp. and the change from the band-based approaches to the sequence-based approaches has greatly increased our knowledge about these strains. Several clusters have been identified within the B. ceti and B. pinnipedialis species, and multiple studies have shown that the hooded seal isolates differ from other pinniped isolates. We describe how different molecular methods have contributed to species identification and differentiation of B. ceti and B. pinnipedialis, with special emphasis on the hooded seal isolates. We further discuss the potential role of B. pinnipedialis for the declining Northwest Atlantic hooded seal population.     

Prevalence of Brucella pinnipediae in healthy hooded seals (Cystophora cristata) from the North Atlantic Ocean and ringed seals (Phoca hispida) from Svalbard

Investigations for Brucella-infections were conducted in 29 hooded seals (Cystophora cristata) caught between Svalbard and Greenland (North Atlantic Ocean; Greenland Sea) autumn 2002, and from 20 ringed seals (Phoca hispida) caught in Billefjord, Svalbard, spring 2003. All animals were apparently healthy and were caught in their natural habitat. Bacteriology on tissue samples from ringed seals was negative, whereas Brucella sp. were recovered in tissues from 11 of the 29 hooded seals (38%), with the highest tissue prevalence in spleen (9/29) and lung lymph nodes (9/24). Anti-Brucella antibodies were detected in sera from 9 hooded seals (31%) (EDTA-modified Slow Agglutination test of Wright, Rose Bengal test, Complement Fixation Test, and Protein-A ELISA). The bacterial isolates all belonged to the genus Brucella according to classical biotyping and PCR analysis based on Insertion Sequence IS711, and were shown to be typical marine mammal strains, based on the occurrence of an IS711 element downstream of the bp26 gene. Their dependency on CO2 for growth, and the presence of one copy each of the omp2a and omp2b gene finally classified them as Brucella pinnipediae. Furthermore, all the hooded seal isolates showed an A+ M+ agglutination profile, which is different from the profile of reference seal strain 2/94 (harbour seal, Phoca vitulina). Thus, these results indicate that B. pinnipediae may contain different biovars. The present results suggest that infection with B. pinnipediae is enzootic in this population. Since the hooded seal is commercially hunted and consumed in Norway, the pathological impact of such infections and their zoonotic potential should be further addressed.     

Systemic aspergillosis and mucormycosis in 23 cats

The clinical and pathological features of 23 cats with systemic opportunistic mycosis--aspergillosis and mucormycosis--are described. The diagnoses were made post mortem by histology. The history and characteristics of the pathological lesions of the 29 cases of feline mycosis described in the literature are compared with this series. It appears that the incidence of such mycoses is increasing.     

Systemic mycosis caused by Scedosporium apiospermum in a stranded northern elephant seal (Mirounga angustirostris) undergoing rehabilitation.

A recently weaned, stranded, male northern elephant seal (Mirounga angustirostris) pup that had been undergoing rehabilitation was found severely obtunded with hyponatremia, hypokalemia, hypochloremia, and hypophosphatemia after a history of intermittent regurgitation. The animal was euthanatized, and gross postmortem findings included multifocal abscessation affecting brain, spleen, kidney, muscle, and subcutaneous tissue. Scedosporium apiospermum and mixed bacteria were cultured from brain, kidney, and subcutaneous tissue. Histopathologic examination revealed multiple fungal granulomas of variable size in the kidneys, brain, liver, and skeletal muscle. This is the first report of S. apiospermum infection associated with lesions in a marine mammal.     

Brucella pinnipedialis hooded seal (Cystophora cristata) strain in the mouse model with concurrent exposure to PCB 153

Brucellosis, a worldwide zoonosis, is linked to reproductive problems in primary hosts. A high proportion of Brucella-positive hooded seals (Cystophora cristata) have been detected in the declined Northeast Atlantic stock. High concentrations of polychlorinated biphenyls (PCBs) have also been discovered in top predators in the Arctic, including the hooded seal, PCB 153 being most abundant. The aim of this study was to assess the pathogenicity of Brucella pinnipedialis hooded seal strain in the mouse model and to evaluate the outcome of Brucella spp. infection after exposure of mice to PCB 153. BALB/c mice were infected with B. pinnipedialis hooded seal strain or Brucella suis 1330, and half from each group was exposed to PCB 153 through the diet. B. pinnipedialis showed a reduced pathogenicity in the mouse model as compared to B. suis 1330. Exposure to PCB 153 affected neither the immunological parameters, nor the outcome of the infection. Altogether this indicates that it is unlikely that B. pinnipedialis contribute to the decline of hooded seals in the Northeast Atlantic.     

Gastric zygomycosis (mucormycosis) in 4 suckling pigs

Acute gastric zygomycosis (mucormycosis) was diagnosed in four 6- to 7-day-old pigs with large venous infarcts in the gastric fundus. Two pigs were from one farm where several dams had developed fever at parturition and most of their litters had died. The other 2 pigs, from separate farms, had diarrhea that was unresponsive to broad-spectrum antibiotic therapy. Histologically there was severe hemorrhagic, ulcerative gastritis associated with numerous transmurally invading, mucoraceous fungi. The discussion includes speculation on the pathogenesis of this lesion in neonatal pigs.     

A case of intestinal mucormycosis in a common marmoset (Callithrix jacchus)

A 3-year-old female common marmoset was euthanatized because of wasting. Grossly, a perforating lesion was present in the jejunum and hemorrhagic lesions in the cecum and colon. Histopathologically, these gross lesions were a perforated jejunal ulcer and necrotizing colitis, respectively. Necrotizing colitis was characterized by extensive mucosal necrosis along with numerous ribbon-shaped aseptate hyphae. These aseptate hyaline hyphae were positively stained with PAS and GMS, and reacted immunohistochemically with the antibody against the family Mucoraceae. This case was diagnosed as intestinal mucormycosis. This is the first report on mucormycosis in a common marmoset.     

Hiatal hernia in a harbor seal (Phoca vitulina) pup

A 2-wk-old stranded harbor seal (Phoca vitulina) rescued by Mystic Aquarium showed signs of the presence of a hiatal hernia during rehabilitation. Contrast radiographs of esophagus and stomach revealed an intrathoracic radiodensity that contains filling defects typical of stomach, consistent with gastric rugal folds. Mural thickening was observed at the level of the cardia consistent with a diagnosis of a hiatal hernia. Although clinical improvement was noted with medical therapy and tube feeding, surgical correction of the hiatal hernia was considered necessary for full resolution. However, owing to the animal's low body weight, the corrective hernia surgery was postponed until the body condition improved. The seal needed to be surgically treated for a corneal ulcer, and while anesthetized with isoflurane, the seal became dyspneic and developed cardiac arrhythmias; ultimately cardiac arrest ensued. Resuscitation was unsuccessfully attempted and the seal was euthanized. Necropsy confirmed the radiographic diagnosis and further characterized a paraesophageal hiatal hernia.     

The venous drainage of the heart in porcupines (Hystrix cristata)

The venous drainage of the heart in porcupines (Hystrix cristata) was investigated. Each of the five adult porcupines (three males, two females) was injected with a coloured latex mixture via the V. cava caudalis for the demonstration of the cardiac veins. The dissection of the specimens revealed that the venous drainage of the heart in porcupines was made by the V. cordis magna, V. distalis ventriculi sinistri, V. proximalis ventriculi sinistri, V. cordis caudalis (the left marginal vein), V. cordis media and Vv. cordis dextrae. The cardiac veins were observed in a subepicardial course on the heart except for the R. interventricularis paraconalis. The R. interventricularis paraconalis showed an intramyocardial course until the middle of the sulcus interventricularis paraconalis, and a subepicardial course after this point. The V. cordis magna and V. distalis ventriculi sinistri opened to the sinus coronarius. The V. cordis caudalis and the V. cordis media drained into the V. cava caudalis. The venous drainage of the conus arteriosus was made by the left V. coni arteriosi opening to the R. interventricularis paraconalis, and by the right V. coni arteriosi which continued to the Vv. cordis dextrae.     

Morphology of the filiform lingual papillae in porcupine (Hystrix cristata)

The light and scanning electron microscopic structure of the filiform lingual papillae was studied in five adult porcupine (three males and two females). The tongue was characterised by a round tip, a rostral median sulcus and a deep lingual fossa which was situated just rostral to a prominent inter-molar eminence corresponding to a torus linguae. The filiform papillae were curved, enclosed a large connective tissue core and were separated by wide inter-papillary zones covered by a thick epithelium. Most filiform papillae had a cylindrical shape, but the rostral and central parts of the tongue contained a number of flat, comb-shaped papillae with rounded tips.     

Isolation of M. pneumoniae from monkeys (Presbitus cristata)

Monkeys of the species Presbitus cristata died of severe interstitial pneumonia 20-60 days after their transportation. The carcases were examined for the presence of mycoplasmas. Thirty-six out of 65 samples obtained from the liver, spleen, kidney, lung, lymph nodes, pharynx, bronchi and blood of 13 monkeys contained mycoplasmas biochemically and serologically identical with M. pneumoniae. The isolated strains were able to elicit a rise in body temperature and an elevation in the number of leucocytes in blood as well as development of interstitial pneumonia, colonization of the inner organs by the mycoplasmas and a serological response in the experimentally infected guinea-pigs.     

The macroanatomical investigations on the aortic arch in porcupines (Hystrix cristata)

The anatomy of aortic arch in porcupine was studied. Angiography was applied to each of the three adult porcupines (two males, one female) following the injection of latex from the abdominal aorta for the examination of aortic arch. The results indicated that three arteries arose from aortic arch in porcupine. These were truncus brachiocephalicus, arteria carotis communis sinistra and arteria subclavia sinistra. The truncus brachiocephalicus in porcupine yielded arteria subclavia dextra and arteria carotis communis dextra. Truncus bicaroticus was absent. The origin of truncus costocervicalis (right) and arteria vertebralis (right) arose from a common root. Left or right axillary arteries seemed to be a continuation of subclavian arteries. The results of this study may contribute to the data in this area of science.     

Seroprevalence of Toxoplasma gondii in North-eastern Atlantic harbor seal (Phoca vitulina vitulina) and grey seal (Halichoerus grypus)

Antibodies to Toxoplasma gondii were determined in serum samples from 47 grey seals (Halichoerus grypus) and 56 harbor seals (Phoca vitulina vitulina) from the Atlantic coasts of United Kingdom and France. Antibodies to T. gondii assayed by the modified agglutination test (MAT) were found in 14 (13.6%; IC(95%): 7.0-20.2) of 103 seals tested, with titres of 1:25 in 13 seals and 1:50 in 1 seal. Seroprevalence against T. gondii (MAT 1:25 or higher) was significantly higher in grey seals (23.4%) compared to harbor seals (5.4%). No significant differences were found between seroprevalence against T. gondii and sex, age or geographical locations. These results show natural exposure of European harbor and grey seals to T. gondii oocysts in the Atlantic Ocean. To the best of our knowledge, this is the first serological survey of T. gondii in European grey and harbor seals.