HERPESVIRUS-INFECTION IN STRANDED PACIFIC HARBOR SEALS OF COASTAL CALIFORNIA

Histopathological examination revealed multifocal acute to chronic adr enal necrosis in 74 of 162 (45%) Pacific harbor seal pups (Phoca vitul ina richardsi) crying during rehabilitation following live stranding a long the coast of central and northern California (USA). Necrotic adre nal cells contained amphophilic, smudgy intranuclear inclusion bodies that were stained positive for DNA. Fifty of these seals also had lesi ons typical of sepsis, bacterial omphalophlebitis, pneumonia or gastro enteritis. Twenty four seals had no lesions other than thymic atrophy and occasional multifocal hepatic necrosis. Prior to death, affected s eals had a marked lymphopenia. Electron microscopy revealed unenvelope d intranuclear hexagonal to round viral particles approximately 100 nm in diameter, and cytoplasmic enveloped virions approximately 160 nm i n diameter. These were morphologically consistent with herpesvirus. In oculation of phocine adrenal and kidney cell lines with an adrenal tis sue homogenate from affected animals produced a cytopathic effect in 5 days. Electron microscopy of cell cultures showing this cytopathic ef fect revealed similar viral particles to those observed in affected ad renal glands. Cases with characteristic inclusion bodies were observed in 42 of 95 (44%) male and 32 of 67 (47%) female seals. Affected anim als had been in rehabilitation 0 to 63 days and were below average bir th weight for this species.