Abstract
Lungworm infestation is a relatively common finding in stranded cetaceans, and could be a major mortality factor for cetacean populations or presented as a self-limited lesion.4,8 Prenatal infection via transplacental pathway of the lungworm had been evident in bottlenose dolphin (Tursiops truncatus) and harbour porpoises (Phocoena phocoena).1,3 However, the impact of lungworm infestation on calf survival is still largely unknown. In this case report, we describe lungworm infestation in 2 cetacean calves, including a finless porpoise (Neophocaena phocaenoides) and a Fraser's dolphins (Lagenodelphis hosei). In addition, the differences in lesion severity and the possible mechanism are also discussed. The pulmonary lesions in the finless porpoise were multiple, bulged, irregularly-shaped, variably-sized, white to grey nodules, and the cut sections of these nodules showed cystic structures with abundant parasites and small amount of caseous material. Microscopically, normal architectures of pulmonary parenchyma were multifocally disrupted by pyogranulomatous inflammations with intralesional nematode parasites. The nematodes are morphologically consistent with Metastrongyles, which is characterized by the presence of coelom, cuticular sheath, hypodermal cords, lateral cords, coelomyarian muscularis, and multinucleated cell lined intestinal tract of adult worm.5 In contrast, the lung lobes of Fraser's dolphin calf were relatively normal and only small to moderate amount of parasite was found in the bronchus and bronchiole. Microscopically, only mild pulmonary edema and alveolitis were noted in the pulmonary parenchyma without the presence of parasites, suggesting the parasite infestation was confined in the bronchus and bronchiole. It is speculated the different severity of lungworm infestation between these 2 calves could be associated with the burden of immunosuppressive contaminants. Previous study had demonstrated the finless porpoise had higher burdens of contaminants.7 Furthermore, the maternal transfer of the immunosuppressive contaminants such as polychlorinated biphenyls (PCBs) had also been evident in previous studies.2,6 Therefore, it is speculated that the finless porpoise calf suffered from higher contaminant burden, which may impair the immune function and thereby increase susceptibility to parasite infestation. In contrast, the Fraser's dolphin inhabits pelagic and oceanic waters, which is extremely different form finless porpoise (costal habitat), and thus the contaminant burdens could be relatively low in the Fraser's dolphin calf. Further investigation of contaminant concentrations in these 2 dolphin calves is proposed.
Acknowledgements
The authors thank to Dr. Chiou-Ju Yao of the National Museum of Natural Science, Taiwan for specimen storage, veterinary students and professors in National Pingtung University of Science and Technology for assisting the necropsy procedures, and all the people in Taiwan Cetacean Stranding Network including the costal guards, laboratory of cetacean research in National Taiwan University, and Taiwan Cetacean Society for animal rescue and shipment.
* Presenting author
+ Student presenter
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