Herpesvirus Diversity in Atlantic Procellariiformes

Procellariiformes are among the most threatened seabirds globally, yet viral pathogens affecting this group remain poorly understood. Herpesviruses are widespread in birds and capable of establishing latency, reactivating under immunosuppression, and causing severe disease, particularly in cross-species transmission. We surveyed herpesvirus in 50 individuals (12 species) that stranded along the southeastern Brazilian coast (2017-2023). A nested pan-PCR protocol targeting the DNA polymerase gene detected herpesvirus DNA in 24% (12/50) of the birds. Seven distinct herpesvirus sequence types were identified, all clustering within the genus <i>Mardivirus</i>, including two previously known variants and novel lineages. To our best knowledge, this represents the first herpesvirus report in the Black-browed Albatross (<i>Thalassarche melanophris</i>), Cape Verde Shearwater (<i>Calonectris edwardsii</i>), Manx Shearwater (<i>Puffinus puffinus</i>), and Southern Giant-Petrel (<i>Macronectes giganteus</i>), as well as new host reports for the Yellow-nosed Albatross (<i>T. chlororhynchos</i>) and Cory's Shearwater (<i>C. borealis</i>). No associated lesions were observed in histopathology. Our findings expand the known host range of herpesviruses in Procellariiformes and reveal possible circulation among colonies and non-breeding areas across the Southern and Northern hemispheres. Our results underscore the need for integrative ecological-, virological-, and population-based studies to clarify how seabird ecology influences herpesvirus transmission dynamics and long-term persistence in this group.