Abstract
Herpesvirus infection causes disease of variable severity in many species, including cetaceans. However, little is known about herpesvirus infection in harbor porpoises (Phocoena phocoena), despite being widespread in temperate coastal waters of the Northern Hemisphere. Therefore, we examined harbor porpoises that stranded alive in the Netherlands, Belgium, and Germany between 2000 and 2014 for herpesvirus infection and associated disease. Porpoises that died or had to be euthanized were autopsied, and samples were collected for virological and pathological analyses. We found one known herpesvirus (Phocoena phocoena herpesvirus type 1, PPHV-1)—a gammaherpesvirus—and two novel herpesviruses (PPHV-2 and PPHV-3)—both alphaherpesviruses—in these porpoises. A genital plaque, in which PPHV-1 was detected, occurred in 1% (1/117) of porpoises. The plaque was characterized by epithelial hyperplasia and intranuclear inclusion bodies that contained herpesvirus-like particles, and that stained positive by a PPHV-1-specific in situ hybridization test. PPHV-2 occurred in the brain of 2% (1/74) of porpoises. This infection was associated with lymphocytic encephalitis, characterized by neuronal necrosis and intranuclear inclusion bodies containing herpesvirus-like particles. PPHV-3 had a prevalence of 5% (4/74) in brain tissue, 5% (2/43) in blowhole swabs, and 2% (1/43) in genital swabs, but was not associated with disease. Phylogenetically, PPHV-1 was identical to a previously reported herpesvirus from a harbor porpoise, PPHV-2 showed closest identity with two herpesviruses from dolphins, and PPHV-3 showed closest identity with a cervid herpesvirus. In conclusion, harbor porpoises may be infected with at least three different herpesviruses, one of which can cause clinically severe neurological disease.
Highlights
Herpesvirus infections can cause disease of variable severity in many species, including cetaceans [1]
The most important as a mortality factor for harbor porpoises was PPHV-2, which was associated with severe encephalitis in a juvenile female harbor porpoise
Evidence that PPHV-2 infection was the cause of encephalitis were: (1) detection of characteristic inclusion bodies (INIB) in neurons of the affected brain tissue by light microscopy, (2) demonstration of herpesvirus-like particles within these INIB by electron microscopy and (3) detection of PPHV-2-specific DNA in brain samples of the affected porpoise by polymerase chain reaction (PCR) and sequencing
Summary
Herpesvirus infections can cause disease of variable severity in many species, including cetaceans [1]. The most common small cetacean species in the North Sea is the harbor porpoise (Phocoena phocoena) [2, 3]. This population of harbor porpoises is still vulnerable, according to IUCN criteria [4]. Most mammalian species have at least one and frequently multiple herpesviruses, if they are looked for This includes cetaceans, in several species van Elk et al Vet Res (2016) 47:28 of which herpesvirus infections have been documented. Herpesvirus-associated lesions in cetaceans range from mucosal and/or cutaneous lesions [8–10] to encephalitis [11–13] and disseminated systemic disease [14]. Despite the fact that the harbor porpoise is a relatively common cetacean species and many stranded individuals in several countries have been autopsied [15–17], the only reported herpesvirus infections are a case of encephalitis associated with herpesviral antigen expression in affected neurons [12], and several cases of dermatitis, in which a gammaherpesvirus, tentatively named Phocoenid herpesvirus-1, was detected by PCR [10]
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