A Retrospective Survey of Cetacean Morbillivirus Infection in Formalin Fixed Paraffin Embedded Samples of Stranded Cetaceans in Taiwan Using qRT-PCR and High Resolution Melting
Cetacean morbillivirus (CeMV) is considered one of the most important viral pathogens in cetaceans.1 In infected cetaceans, the virus causes serious respiratory, central nervous system disease and immunosuppression which lead to serious secondary bacterial and fungal infections. CeMV was shown to be associated with high-mortality events of the population of several cetacean species in Europe, the Americas, and Australia in the past three decades.2 To clarify the real distribution of CeMV and possible carriers, the retrospective study of CeMV is essential.3 Here we report a preliminary retrospective survey of CeMV infection in formalin fixed paraffin embedded (FFPE) samples of stranded cetaceans in Taiwan. The validated screening method using qRT-PCR and high resolution melting (HRM) was utilized. The CeMV-confirmed FFPE samples from previous studies were used as positive control. Twenty FFPE samples of stranded cetaceans from 2001 to 2015 were tested, and only two of them were positive. One is a male pygmy sperm whale (200 cm in length) found alive stranded in central Taiwan on May 25, 2015. It died after 2 days of medical care. Eosinophilic intranuclear inclusions in lymph nodes and purulent interstitial pneumonia were noticed. The second one was a male pygmy killer whale (228 cm in length) found alive stranded in north Taiwan on August 25, 2015. It died after 4 days of medical care. However, no typical morbillivirus lesions were detected in this case. To the authors' best knowledge, this is the first case of morbillivirus infection in pygmy killer whale detected by qPCR. In previous studies, some cetaceans were positive for CeMV by RT-PCR without typical pathological findings resulting from CeMV infection, indicating possible subclinical CeMV infection in certain species and areas. Future studies based on this method could elucidate the role of virus strains in disease susceptibility, resistance, and progression, and could lead to a greater understanding of not only the differing prevalence and outbreak conditions between Atlantic and Pacific oceans, but also the mechanisms of variable host response to pathogens.
Thanks for all researchers that have done me several favors to complete this study and I would like to give my gratitude especially to Dr. Yang and Miss Wu. Without their encouragement for me to learn and propel me to polish up my skills doing the experiments, I might still do some research in vain.
* Presenting author
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2. Van Bressem MF, Duignan PJ, Banyard A, et al. Cetacean morbillivirus: current knowledge and future directions. Viruses. 2014;6(12):5145–81.
3. Wu BJ, Chan KW, Sierra E, Fernandez A, Groch KR, Catão-Dias JL, West K, Yang WC. Simultaneous diagnosis and genotyping of cetacean morbillivirus from formalin-fixed paraffin-embedded sections using qRT-PCR and high-resolution melting assay. In: Proceedings from International Association for Aquatic Animal Medicine 46th Annual Conference; April 6–9, 2015; Chicago, IL.