Herpesvirus Diversity in Stranded Mysticetes of Brazil, Southwestern Atlantic

Emerging and re-emerging pathogens have been increasingly investigated in cetaceans worldwide, particularly in odontocetes, whereas infectious diseases in mysticetes remain poorly understood. This study surveyed herpesvirus in 51 baleen whales stranded along the Brazilian coast, between 2008 and 2022: humpback whales (Megaptera novaeangliae, n = 46), Bryde’s whales (Balaenoptera brydei, n = 3), a southern right whale (Eubalaena australis, n = 1), and a common minke whale (Balaenoptera acutorostrata, n = 1). A total of 159 tissue samples were analyzed using nested PCR assays targeting the herpesviral DNA polymerase (DPOL) and glycoprotein B (gB) genes. Herpesvirus DNA was detected in 25.5% (13/51) of individuals, including 23.9% (11/46) of humpback whales, one Bryde’s whale, and one common minke whale. Positive animals included six calves, six juveniles, and one adult. All 13 cases were detected by DPOL PCR, yielding eight sequence types (five alphaherpesviruses and three gammaherpesviruses). Additionally, six of them were also positive for gB, identifying four gammaherpesvirus sequence types within the genus Rhadinovirus. Humpback whales showed both alpha- and gammaherpesviruses, including one coinfection, whereas gammaherpesviruses were detected in Bryde’s and minke whales. This study reports the first herpesvirus in Bryde’s whales and expands the geographic range of infection in minke whales. The high prevalence in calves suggests vertical transmission.