Herpesvirus infection in marine mammals: A retrospective molecular survey of stranded cetaceans in the Portuguese coastline.

Herpesvirus (HVs) infection has already been reported in cetaceans, but available information on its epidemiology is scarce. In this study we surveyed a total of 179 cetaceans belonging to 6 different species. Samples were obtained from cetaceans stranded along the Portuguese coastline, belonging to populations that roam the north-east region of the Atlantic Ocean. Detection of HVs was performed by conventional nested PCR. Amplicons were sequenced by Sanger's method and sequences used to construct phylogenetic trees by Maximum Likelihood method. Our results show that prevalence of positive samples, among fresh carcasses, reached 14.3% (10/70) and both alpha and gammaherpesvirus were detected. Histopathology showed that herpesvirus infection varied from absence of signs compatible with disease, localized genital lesions and systemic disease. Phylogenetic analysis revealed three clusters within the alphaherpesvirus family; within the gammaherpesvirus no subdivision was detected. All clusters included animals from different species and geographic origins. In seven of the positive HVs samples, co-infections with other agents such as morbillivirus and toxoplasma gondii were detected. The viral nucleotide sequences were not assigned to a specific animal species, nor presented a given geographic distribution, which may imply a wider distribution of herpesvirus in these animal populations. Our results are also the first report of herpesvirus infection in common dolphins (Delphinus delphis), with both alpha and gammaherpesvirus detected.