Virtopsy as a Revolutionary Tool for Cetacean Stranding Programs: Implementation and Management

Abstract

On top of conventional necropsy, virtopsy (postmortem computed tomography and postmortem magnetic resonance imaging) has been integrated into the Cetacean Stranding Response Programme in Hong Kong since March 2014. To date, 177 out of 240 local stranded cetaceans have been examined by virtopsy. This integration has modernised the characterisation and documentation of cetacean biological health and profiles, and causes of death. During this 6-year period, critical pitfalls regarding logistics, carcass recovery, handling, and preservation have been identified. A strategic management scheme is crucial for the successful incorporation of virtopsy into this pioneer programme. This study explains the workflow of the Cetacean Virtopsy Stranding Response Programme in Hong Kong waters. Difficulties encountered are highlighted and practical solutions to address management issues are proposed to consolidate the stranding response network.

Characterisation of Crassicauda fuelleborni nematode infection in Indo-Pacific finless porpoises (Neophocaena phocaenoides) using postmortem computed tomography

“…In this study, histopathological analysis was not performed owing to the high level of decomposition for all 13 cases (code 4; Geraci and Lounsbury, 2005 ). A high proportion of advanced decomposed cetacean carcasses has been established as one of the main difficulties that hindered stranding research in HK, as decomposition affects the interpretation of pathological findings ( Jefferson et al, 2006 ; Tsui et al, 2020 ). However, PMCT was able to effectively discern the differences in gross characteristics between Crassicauda -related lesions (i.e., fresher lesions with viable nematodes versus more chronic lesions with degenerated and caseous materials) due to the differences in attenuation values produced by the calcified materials within the lesions.…”

“…Another advantage of using virtopsy is that the images are stored digitally and can be retrospectively and repeatedly analysed ( Chan et al, 2017 ). Utilising the collected virtopsy datasets in the cetacean stranding response programme in HK since March 2014 ( Tsui et al, 2020 ), an updated study to analyse both retrospective and prospective data is necessary to understand the epidemiology and health impacts of crassicaudid infections on the residential cetaceans in HK waters.…”

“…This study was conducted between August 2020 and April 2021. During this period, 33 stranded NP cases were recovered by the local cetacean stranding response programme in HK waters ( Tsui et al, 2020 ). Eight cases with incomplete carcasses or undetermined sex were excluded, and the remaining 25 fully intact NP carcasses were included in this prospective study.…”

“…As part of the local cetacean stranding response programme, all recovered stranding cases undergo routine PMCT scanning prior to conventional necropsy ( Tsui et al, 2020 ). For all 25 stranded NP cases in this study, PMCT scans were conducted using a Siemens 64-row dual-source SOMATOM go.Up CT scanner (Siemens Healthineers, Erlangen, Germany) or a Philips 16-slice Brilliance Big Bore CT scanner (Philips Healthcare, Amsterdam, Netherlands), with the following scan parameters: 100–140 kV, 69–303 mA, 0.6–0.8 mm slice thickness, and scan field of view of 401–621 mm.…”

“…With the advantage of non-invasiveness, virtopsy, the postmortem use of imaging modalities including computed tomography (PMCT) and magnetic resonance imaging ( Thali et al, 2003a ), has been increasingly applied in the postmortem examination of cetaceans in recent years (e.g., Danil et al, 2014 ; Hamel et al, 2020 ; Kot et al, 2018 , 2019 , 2020a , 2020b , 2021 ; Tsui et al, 2020 ; Yuen et al, 2017 ; Zucca et al, 2004 ). One of the applications of virtopsy, particularly PMCT, is to detect pathological lesions, including parasitic infections, especially in cumbersome regions that are difficult and not routinely examined thoroughly during conventional necropsy (e.g., cranial sinuses or muscles across the entire body), and therefore allowing precise examination and targeted sampling ( Tsui et al, 2020 ). However, PMCT studies focusing on the detection of parasitic infection in cetaceans are currently limited.…”