Abstract
Cetacean morbillivirus (CeMV) is a major natural cause of morbidity and mortality in cetaceans worldwide and results in epidemic and endemic fatalities. The pathogenesis of CeMV has not been fully elucidated, and questions remain regarding tissue tropism and the mechanisms of immunosuppression. We compared the histopathologic and viral immunohistochemical features in molecularly confirmed CeMV-infected Guiana dolphins (Sotalia guianensis) from the Southwestern Atlantic (Brazil) and striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) from the Northeast-Central Atlantic (Canary Islands, Spain) and the Western Mediterranean Sea (Italy). Major emphasis was placed on the central nervous system (CNS), including neuroanatomical distribution of lesions, and the lymphoid system and lung were also examined. Eleven Guiana dolphins, 13 striped dolphins, and 3 bottlenose dolphins were selected by defined criteria. CeMV infections showed a remarkable neurotropism in striped dolphins and bottlenose dolphins, while this was a rare feature in CeMV-infected Guiana dolphins. Neuroanatomical distribution of lesions in dolphins stranded in the Canary Islands revealed a consistent involvement of the cerebrum, thalamus, and cerebellum, followed by caudal brainstem and spinal cord. In most cases, Guiana dolphins had more severe lung lesions. The lymphoid system was involved in all three species, with consistent lymphoid depletion. Multinucleate giant cells/syncytia and characteristic viral inclusion bodies were variably observed in these organs. Overall, there was widespread lymphohistiocytic, epithelial, and neuronal/neuroglial viral antigen immunolabeling with some individual, host species, and CeMV strain differences. Preexisting and opportunistic infections were common, particularly endoparasitism, followed by bacterial, fungal, and viral infections. These results contribute to understanding CeMV infections in susceptible cetacean hosts in relation to factors such as CeMV strains and geographic locations, thereby establishing the basis for future neuro- and immunopathological comparative investigations.
Highlights
Cetacean morbillivirus (CeMV; genus Morbillivirus, family Paramyxoviridae) is the most significant natural cause of morbidity and mortality in cetaceans worldwide, having caused multiple outbreaks of lethal disease in odontocetes and mysticetes [1]
Guiana dolphins were infected by GD-CeMV [6,8], while striped dolphins and bottlenose dolphins were infected by dolphin morbillivirus (DMV) [3,19,20,21]
We have provided a comprehensive and comparative analysis of the results of histopathologic and viral immunohistochemical investigations on CeMV-associated pathology in GDCeMV-infected Guiana dolphins from Southwestern Atlantic (Brazil) and DMV-infected striped dolphins and bottlenose dolphins from the Northeast-Central Atlantic (Canary Islands, Spain) and Western Mediterranean Sea (Italy)
Summary
Cetacean morbillivirus (CeMV; genus Morbillivirus, family Paramyxoviridae) is the most significant natural cause of morbidity and mortality in cetaceans worldwide, having caused multiple outbreaks of lethal disease in odontocetes and mysticetes [1]. CeMV includes three well characterized strains: porpoise morbillivirus, dolphin morbillivirus (DMV), and pilot whale morbillivirus, all of which have been reported primarily in the Northern Hemisphere. Three new strains have been reported, one of them detected in Brazil and considered the first description in South America, namely Guiana dolphin (Sotalia guianensis) (GD)-CeMV [6]. CeMV may cause severe respiratory, lymphoid, and neurologic disease in susceptible species, leading to strandings and death [1]. Studies suggest that some species are more susceptible to CeMV infection, including striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) [1,7]. The high susceptibility of Guiana dolphins to GD-CeMV was recently demonstrated in the first unusual mortality event (UME) in South American cetaceans, in which approximately 250 Guiana dolphins died [8]
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