Abstract

Polyomaviruses (PyVs) are small double-stranded DNA viruses capable of infecting species across all animal taxa.¹ They are generally considered host-specific and responsible for subclinical infections in immunocompetent hosts.² In cetaceans, PyVs have only been reported in the common dolphin (Delphinus delphis) presenting with ulcerative tracheobronchitis and laryngeal epithelial intranuclear inclusion bodies and in the common bottlenose dolphin (Tursiops truncatus), and killer whale (Orcinus orca) without associated lesions.^3,4 To partially fill this knowledge gap, we surveyed for PyV in 120 cetaceans, comprising 18 species (27 mysticetes and 93 odontocetes) stranded along the Brazilian coast from 2002 to 2022.

Standardized necropsies were performed, and samples were collected for molecular assays and histopathology.⁵ Total DNA was extracted from lungs using a commercial kit, and a nested-PCR partially amplified the VP1 gene of PyV.⁶ In positive individuals, all frozen available samples were also tested for PyV, and formalin-fixed tissues were examined by histopathology. Out of the 24 tested Guiana dolphins (Sotalia guianensis) (8.3%), polyomavirus was detected in two juvenile females that stranded in Rio de Janeiro (Rio de Janeiro state) and Guriri (Espírito Santo state) in 2017 and 2018, respectively. Both retrieved sequences were identical and presented 90.3% nucleotide identity with dolphin polyomavirus 1 (DPyV-1) detected in a common dolphin (KC594077), suggesting a novel species. On histopathology, one of the positive individuals presented basophilic intranuclear inclusion bodies morphologically compatible with polyomavirus. Other available tissues from both cases were PyV-PCR-negative; however, both individuals tested positive for Guiana dolphin morbillivirus. Despite the concomitant infections and immunosuppression, in both cases, PyV was only amplified in the lungs, with no signs of systemic involvement. Our findings suggest that this novel PyV has a tropism for the respiratory system. To our knowledge, this is the first report of PyV infection in cetaceans of the Southern Hemisphere and the first description of a coinfection with morbillivirus. Ongoing studies will further characterize this PyV and investigate the pathogenicity and host-specificity of this novel virus in Guiana dolphins.

All procedures were performed in full compliance and approved by the Biodiversity Information and Authorization System (SISBIO 67766), Brazilian Ministry of Environment, and by the Ethical Committee of the School of Veterinary Medicine and Animal Sciences, University of São Paulo (Ceuavet n° 169829011), and by the National System for the Management of Genetic Heritage and Associated Traditional Knowledge (SISGEN A49250C).

Acknowledgments

The authors thank the Coordination for the Improvement of Higher Education Personnel (CAPES), the Brazilian National Council for Scientific and Technological Development (CNPQ; Processes numbers #304999/2018-0; #141868/2019-8), Juan de la Cierva Incorporación (fellowship IJC2020-046019-I) and formación (JDC2022/048632-I) granted by Agencia Estatal de Investigación-Ministerio de Ciencia, Innovación y Universidades, and the State of São Paulo Research Foundation (FAPESP 2018/20956–0; #2019/26794-0). PMP-BS is a project required by the Brazilian Institute of the Environment and Renewable Natural Resources (IBAMA) of the Brazilian Ministry of Environment for the environmental licensing process of the oil and natural gas production and transport by Petrobras at the Santos Basin. JLCD is a recipient of a CNPq professorship (# 304106/2022-4).

*Presenting author

Literature Cited

1.  Moens U, Krumbholz A, Ehlers B, et al. Biology, evolution, and medical importance of polyomaviruses: an update. Infect Genet Evol. 2017;54:18–38.

2.  Ehlers B, Anoh AE, Ben Salem N, et al. Novel polyomaviruses in mammals from multiple orders and reassessment of polyomavirus evolution and taxonomy. Viruses. 2019;11:930.

3.  Anthony SJ, St Leger JA, Navarrete-Macias I, et al. Identification of a novel cetacean polyomavirus from a common dolphin (Delphinus delphis) with tracheobronchitis. PloS One. 2013;8:e68239.

4.  Smith K, Fielding R, Schiavone K, et al. Circular DNA viruses identified in short-finned pilot whale and orca tissue samples. Virology. 2021;559:156–164.

5.  Geraci JR, Lounsbury VJ. Marine Mammals Ashore: A Field Guide for Strandings. 2nd ed. Baltimore, MD: National Aquarium in Baltimore; 2005

6.  Leendertz FH, Scuda N, Cameron KN, et al. African great apes are naturally infected with polyomaviruses closely related to Merkel cell polyomavirus. J Virol. 2011;85:916–924.