Vibro sp. are not only common bacterial organisms existing in the gastrointestinal and respiratory tracts of marine mammals, but also potential pathogens involved in varying severity of disease in marine mammals.7 However, the factors converting the commensal bacteria into pathogenic bacteria causing fatal/severe diseases are still largely unknown.2 The present report described a stranded juvenile Fraser's dolphin (Lagenodelphis hosei) with antibiotic-resistant Vibrio parahaemolyticus (V. parahaemolyticus) septicemia, pre-existing lungworm infestation, and oropharyngeal foreign body in Taiwan. The animal showed imbalanced buoyancy with severe leukocytopenia, and blood sample for bacterial culture was also collected in the meantime. Unfortunately, the animal died after arriving at the temporary rehabilitation pool. Reduced blubber thickness was noted without external wounds. Both lung lobes showed dark-red and pink mottled appearance with meaty texture. Several 0.2 x 0.2 x 0.2 cm, white and firm nodules were found in lung parenchyma. A piece of plastic woven sheet was found in the oropharyngeal area with multiple strip-shaped sunk lesions. Samples for bacterial culture were taken from lung, liver, and kidney. Vibrio parahaemolyticus was isolated from all the blood/tissue samples and showed resistance to amikacin, amoxicillin/clavulanic acid, and cefmetazole. Microscopically, multifocal to coalescing suppurative bronchopneumonia with multifocal aggregates of coccobacilli was noted. The white nodules were pyogranulomatous inflammations with multiple intralesional circular calcifications, suggestive of previous lungworm infestation. The oropharyngeal mucosal epithelium was multifocally sloughed and covered by a layer of coccobacilli without marked tissue response, suggestive of a moribund lesion caused by the foreign body compression.
It is speculated the animal was stranded due to the discomfort related to the oropharyngeal foreign body and/or the pulmonary lesions. Subsequently, V. parahaemolyticus invaded into the bloodstream through the pulmonary and/or oropharyngeal lesions and caused acute septicemia, which is considered as the cause of death. For cetaceans, ingestion of plastic debris not only causes damage to digestive tract, but also compromises the health due to the released chemical compound.1,3 The present juvenile dolphin may suffer from the difficulty of early maternal separation, which leads to a wrong food choice and foreign body ingestion. The other possibility is the animal may play with the plastic debris and accidentally ingest it. As previous studies had indicated, bacteria can be harbored in parasites and transmitted through parasite infestation,5 the current V. parahaemolyticus infection can be also associated with previous lungworm infestation. Furthermore, the presence of antibiotic-resistant V. parahaemolyticus in stranded cetacean demonstrates the antibiotic-resistant bacteria/genes have existed in marine environment and cetacean populations around Taiwanese waters.4 The possibility of transmitting antibiotic-resistant pathogenic bacteria from marine mammal to human, especially coastal residents, tourists, and cetacean rescue personnel, should be considered.6,8
The authors thank all the people in Taiwan Cetacean Stranding Network (TCSN) who helped this animal.
* Presenting author
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