A study of the lesions of beaked whales (BWs) in a recent mass stranding in the Canary Islands following naval exercises provides a possible explanation of the relationship between anthropogenic, acoustic (sonar) activities and the stranding and death of marine mammals. Fourteen BWs were stranded in the Canary Islands close to the site of an international naval exercise (Neo-Tapon 2002) held on 24 September 2002. Strandings began about 4 hours after the onset of midfrequency sonar activity. Eight Cuvier's BWs (Ziphius cavirostris), one Blainville's BW (Mesoplodon densirostris), and one Gervais' BW (Mesoplodon europaeus) were examined postmortem and studied histopathologically. No inflammatory or neoplastic processes were noted, and no pathogens were identified. Macroscopically, whales had severe, diffuse congestion and hemorrhage, especially around the acoustic jaw fat, ears, brain, and kidneys. Gas bubble-associated lesions and fat embolism were observed in the vessels and parenchyma of vital organs. In vivo bubble formation associated with sonar exposure that may have been exacerbated by modified diving behavior caused nitrogen supersaturation above a threshold value normally tolerated by the tissues (as occurs in decompression sickness). Alternatively, the effect that sonar has on tissues that have been supersaturated with nitrogen gas could be such that it lowers the threshold for the expansion of in vivo bubble precursors (gas nuclei). Exclusively or in combination, these mechanisms may enhance and maintain bubble growth or initiate embolism. Severely injured whales died or became stranded and died due to cardiovascular collapse during beaching. The present study demonstrates a new pathologic entity in cetaceans. The syndrome is apparently induced by exposure to mid-frequency sonar signals and particularly affects deep, long-duration, repetitive-diving species like BWs.

Between 1999 and 2005, 233 stranded cetaceans (comprising 19 species) were reported in the waters of the Canary Islands. Of these, 138/233 (59.2%) were subjected to a complete or partial standardized necropsy, including 4 Balaenopteridae, 9 Physeteridae, 8 Kogiidae, 27 Ziphiidae and 90 Delphinidae. Of these, 46/138 (33.3%) cetaceans were diagnosed with anthropogenic pathological categories (i.e. the cause of death was anthropogenic). These included fishing interaction (bycatch) (19 individuals), 'atypical' mass stranding events linked to naval exercises (13), ship collisions (8) and other anthropogenic-related pathology (6). 'Natural' (i.e. non-anthropogenic) causes of death accounted for another 82/138 (59.4%) cases, including infectious and non-infectious diseases (63), neonatal pathology (8), intra- and interspecific interactions (6) and mass strandings (5). The cause(s) of death could not be determined in 10/138 (7.3%) necropsied animals. The most common causes of death were ship collisions in 6/9 (66.6%) Physeteridae, 'atypical' mass stranding linked to naval exercises in 13/27 (48.1%) Ziphiidae, and 'natural' infectious and non-infectious diseases in 55/90 (61.1%) Delphinidae. Interaction with fishing activities was established as cause of death in 15/90 (16.7%) Delphinidae. These data show that a range of anthropogenic and natural single and mass mortality events occur in multiple cetacean species stranded in the Canary Islands.

Porcine enzootic pneumonia (PEN), caused by Mycoplasma hyopneumoniae (Mh), has been described in pigs in all geographic areas. The disease is characterized by high morbidity and low mortality rates in intensive swine production systems. A morphologic and immunohistochemical study was done to determine the cellular populations present in lung parenchyma of infected pigs, with special attention to the bronchus-associated lymphoid tissue (BALT). Polyclonal and monoclonal antibodies were used for the detection of antigens of Mh, T lymphocytes (CD3⁺, CD4⁺, and CD8⁺), IgG⁺ or IgA⁺ lymphocytes, and cells containing lysozyme, S-100 protein, major histocompatibility complex class II antigen or myeloid-histiocyte antigen. Findings in lung tissues associated with Mh infection were catarrhal bronchointerstitial pneumonia, with infiltration of inflammatory cells in the lamina propria of bronchi and bronchioles and alveolar septa. Hyperplasia of mononuclear cells in the BALT areas was the most significant histologic change. The BALT showed a high morphologic and cellular organization. Macrophages and B lymphocytes were the main cellular components of germinal centers. T lymphocytes were primarily located in perifollicular areas of the BALT, lamina propria and within the airway epithelium, and plasma cells containing IgG or IgA at the periphery of the BALT, in the lamina propria of bronchi and bronchioles, in alveolar septa, and around bronchial submucosal glands. The hyperplastic BALT in PEN cases consisted of macrophages, dendritic cells, T and B lymphocytes, and IgG⁺ and IgA⁺ plasma cells. CD4+ cells predominated over CD8+ cells. Local humoral immunity appears to play an important role in the infection.