Abstract

Phocine herpesvirus type-1 (PHV-1) has been associated with morbidity and high mortality in neonatal harbor seals (Phoca vitulina) on both the Pacific coast of California and in Northern Europe. Adrenal necrosis or adrenalitis with herpes inclusion bodies are common findings on histopathological examination in Pacific seals dying with PHV-1 associated disease. There is little information regarding the prevalence, transmission and pathogenesis of PHV-1 infection. In this study we examine the seroprevalence of anti-PHV-1 antibodies in free ranging harbor seal populations around North America. Samples were collected from animals in multiple age classes (preweaned, weaned and sub adults/adults) from three large geographical locations (northeast, northwest and southwest) and were assayed by an indirect enzyme linked immunosorbent assay (ELISA). These samples were used to compare differences in PHV-1 exposure between these age groups and geographical areas. Results suggest anti-PHV-1 antibody levels are low in neonatal harbor seals, but rapidly increase around weaning age and remain high throughout sub adult and adult life. These findings provide evidence for the horizontal transmission of PHV-1 among weaned seals. Following this exposure, antibody levels remain high, suggesting recurrent exposure to this virus. Further work is ongoing to determine how this virus is transmitted to understand factors influencing the events occurring at weaning that contribute to this increase in herpes specific antibody levels.

Acknowledgements

This work was funded by a grant from the Office of Protected Resources, National Marine Fisheries Service.