Virus-associated papillomatous skin lesions in a giant guitarfish Rhynchobatus djiddensis: a case report

Abstract

Although elasmobranch species are increasingly displayed in public aquaria, knowledge of disease in wild and captive elasmobranchs, as well as the agents involved, remains limited, and descriptions are often incomplete. This report describes papillomatous skin lesions in a juvenile giant guitarfish Rhynchobatus djiddensis associated with intranuclear viral particles. Skin biopsies were collected from multiple, friable, raised, villonodular skin lesions affecting pigmented and non-pigmented skin of the caudal fin and ventrum, respectively. Microscopic examination revealed papillary proliferation of the epidermis, with widespread marked karyomegaly of squamous epithelial cells. In approximately 75% of nuclei, chromatin was marginated by one to multiple, large, amphophilic inclusions. Large numbers of unencapsulated, 75 nm, icosahedral viral particles were observed to form large arrays in affected nuclei using transmission electron microscopy. Based on intranuclear location, particle size and morphology, a consensus nested-PCR for adenovirus polymerase was attempted. However, no adenoviral gene sequence was amplified. The nature of the involved virus remains unknown and an ongoing area of investigation. Lesions regressed completely over a 6 mo period, during which time the animal showed no signs of systemic illness, and there has been no recrudescence for 6 mo following resolution. Two cohorts of similar age and in close contact with the case animal were unaffected. KEY WORDS: Virus · Skin lesion · Histopathology · Giant guitarfishResale or republication not permitted without written consent of the publisher

Microscopic and Molecular Evidence of the First Elasmobranch Adomavirus, the Cause of Skin Disease in a Giant Guitarfish, Rhynchobatus djiddensis

“…1B ). Presented in greater detail in a previous case report ( 17 ), these findings prompted an investigation using deep metagenomic sequencing that demonstrated the novel adomaviral genome.…”

“…Elasmobranch fishes, including the sharks, rays, guitarfishes, and others, evolved from ancestral species at least 419 MYA during the early Devonian period. Compared to bony teleost fish, such as eels, examples of viral diseases in elasmobranchs are rare ( 17 , 18 ). During an investigation into the etiology of a proliferative skin disease in a giant guitarfish ( 17 ), two viral genomes were identified.…”

“…Compared to bony teleost fish, such as eels, examples of viral diseases in elasmobranchs are rare ( 17 , 18 ). During an investigation into the etiology of a proliferative skin disease in a giant guitarfish ( 17 ), two viral genomes were identified. One, giant guitarfish polyomavirus 1, was the first viral genome described from an elasmobranch species and represents the smallest known polyomavirus genome ( 11 ).…”

“…1E ). Electron microscopy ( 17 ) revealed large arrays of icosahedral, ~75-nm virions within affected epithelial cell nuclei ( Fig. 1B ).…”

Complete Sequence of the Smallest Polyomavirus Genome, Giant Guitarfish ( Rhynchobatus djiddensis ) Polyomavirus 1

“…Here, a complete polyomavirus genome is reported from a cartilaginous fish, the giant guitarfish ( Rhynchobatus djiddensis ), a batoid elasmobranch (order Rajiformes ). The presence of proliferative skin lesions, characterized microscopically by large intranuclear inclusions containing 75 nm icosahedral viral particles, initiated an investigation of the causative agent ( 10 ). To circumvent the lack of known viral genetic information in elasmobranchs, a sequence-independent metagenomic approach was performed to identify viral sequences within the lesions ( 11 , 12 ).…”