An eleven-day-old little blue penguin (Eudyptula minor) was found acutely deceased. Nine days prior to hatching, the egg had experienced trauma with a small depression and several hairline fissures radiating over the egg. The egg had been incubated by surrogate conspecific birds at the time. The egg fissures were repaired with surgical glue and topical antiseptics were applied. The chick hatched without complication and was doing well prior to death. At necropsy, the penguin was mildly thin and had bilaterally congested lungs. Histologically, there was severe nonsuppurative encephalitis with focally extensive neuronal necrosis and intranuclear inclusions in neurons within necrotic foci. The penguin also had mild interstitial pneumonia with hemorrhage. Generic herpesvirus PCR targeting the polymerase gene was positive on paraffin embedded brain tissue. Sanger sequencing of the PCR product demonstrated 100% and 98% sequence homology to sphenicid alphaherpesvirus 1 and penguin herpesvirus 2, respectively. While the sequence data are most supportive of an infection with sphenicid alphaherpesvirus 1, there is only limited sequence data available for penguin herpesvirus 2 and the sequenced PCR product is relatively short. A newly designed oligoprobe, with 100% homology to both viruses, was used for in situ hybridization (ISH) and demonstrated large amounts of herpesvirus nucleic acid in the intranuclear inclusions and neuronal nuclei within necrotic areas. The combined histology, PCR, Sanger sequencing and ISH results are most consistent with a herpesviral encephalitis, most likely caused by sphenicid alphaherpesvirus 1. Previous reports have associated herpesvirus and herpesvirus-like infections in penguins with lesions in the respiratory and/or gastrointestinal tract.1-4 To the authors’ knowledge this is the first report of a herpesvirus infection causing encephalitis in a penguin and the first report of a herpesvirus infection in this species.
1. Kinkaid AL, Bunton TE, Cranfield M. 1988. Herpesvirus-like infection in black-footed penguins (Spheniscus demersus). J Wild Dis 24(1):173–175.
2. Niemeyer C, Favero CM, Shivaprasad HL, et al. 2017. Genetically diverse herpesviruses in South American Atlantic coast seabirds. PLOS One 12(6):e0178811. https://doi.org/10.1371/journal.pone.0178811.
3. Parsons NJ, Gous TA, van Wilpe E, et al. 2015. Herpesvirus-like respiratory infection in African penguins Spheniscus demersus admitted to a rehabilitation centre. Dis Aquat Org 116:149–155.
4. Pfaff F, Schulze C, König P, et al. 2017. A novel alphaherpesvirus associated with fatal diseases in banded penguins. J Gen Virol 98:89–95.