Abstract
Parasites of marine mammals have been documented for decades, and recent taxonomic and systematic revisions of many genera have helped our understanding of marine mammal biology, pathogenicity, and evolution. Parasitic infections can have direct or indirect effects on health, immune status, survival, recruitment, and population dynamics. Apparently benign parasites can become opportunistic, invasive, and highly pathogenic in susceptible or weakened animals, particularly in small isolated populations or species at risk.1-5
In human clinical radiology, specific and advanced imaging techniques like computed tomography, magnetic resonance, and positron emission tomography-computed tomography, can be helpful in solving the differential diagnosis, especially when parasitic disease mimics malignant neoplasms.6 To the best of our knowledge, the formal literature is devoid of any reference to the applicability of virtopsy in the diagnosis of parasitic infections in stranded cetaceans. This study aimed to evaluate the practicality of virtopsy techniques in stranded cetaceans and compared the findings obtained by conventional necropsy whenever possible.
Retrospective analysis of stranding cases in Hong Kong and adjacent waters between 2015 and 2019 with parasitic infections included as postmortem findings were undertaken, with both postmortem computed tomography (PMCT) and conventional necropsy performed. PMCT was useful in identifying sites of infection, including cranial sinuses, lung, liver, mammary glands and muscles, where extensive and profound destructions to the surrounding tissues like erosion of the carbon-rich bone fraction, might observe. PMCT also revealed broad variability in the morphological appearance and calcification pattern of parasite-induced lesions, which may potentially be associated with the course and type of the parasitic infections. Implementation of a grading system using PMCT might provide more detailed information than was typically described in the case record and has the added value of uniform designations of lesion classification and severity. Such records could therefore be helpful in future studies of pathophysiology and epidemiology of parasitic infections within the cetacean population in Hong Kong and adjacent waters.
Acknowledgements
The authors would like to thank the Agriculture, Fisheries, and Conservation Department of the Hong Kong SAR Government for the support in the virtopsy project. Sincere appreciation is also extended to veterinarians, staff, and volunteers from Ocean Park Hong Kong, Ocean Park Conservation Foundation Hong Kong, and City University of Hong Kong for paying great effort on the stranding response and necropsy in this project. Special gratitude is owed to radiographers from Veterinary Medical Centre, City University of Hong Kong for operating the CT units to collect volumetric data in the present study. This project was financially supported by the Marine Ecology Enhancement Fund (Grant number: MEEF2017014/L01 and MEEF2019010/L01) and the Open Collaborative Research Fund of the Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou). Any opinions, findings, conclusions, or recommendations expressed herein do not necessarily reflect the views of the Marine Ecology Enhancement Fund or the Trustee.
*Presenting author
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