Papillomaviruses and herpesviruses: who is who in genital tumor development of free-ranging Atlantic bottlenose dolphins (Tursiops truncatus)?

The number of studies addressing neoplasia in marine mammals has recently increased, giving rise to concern whether such lesions could be reflective of an emerging infectious disease. Eight species-specific viruses, seven papillomaviruses (PVs) and two herpesviruses (HVs) have separately been shown to be associated with genital tumors in Atlantic bottlenose dolphins (Tursiops truncatus, Tt): TtPV1-6, as well as HVs provisionally assigned the names DeHV4 and -5 (Delphinid HVs). A definite causal role of these viruses in cell transformation remains to be demonstrated. Concurrent PV- and HV-infection has never been reported in marine mammals. DNA extractions from biopsies of genital tumors derived from 15 free-ranging Atlantic bottlenose dolphins were selected for molecular examination. Polymerase chain reaction (PCR) analyses revealed the presence of DeHV4, while a serological screening using an antibody-based TtPV enzyme-linked immunosorbent assay (ELISA) demonstrated previous and/or current infection of the HV-positive dolphins with at least one TtPV type. Therefore, care must be taken when drawing conclusions about viral causalities in tumor development, since the "hit and run" and other mechanisms have been described for types of both viral families. This study presents the first evidence of marine mammals having a history of PV- as well as HV-infection and discusses the disputed effects of viral co-infection.