First molecular detection and characterization of herpesvirus and poxvirus in a Pacific walrus (Odobenus rosmarus divergens)

Viral skin diseases in odontocete cetaceans: gross, histopathological, and molecular characterization of selected pathogens

Fifty-five skin lesions from 31 stranded cetaceans along the Canary coasts (2011-2021) were submitted to macroscopic, histological, and molecular analyses to confirm infection by cetacean poxvirus, herpesvirus and cetacean morbillivirus. They were macroscopically categorized into eight categories with respective subcategories according to their color, shape, size, and consistency. Cetacean poxvirus was detected in 54.54% of the skin lesions through real-time and conventional PCRs based on the DNA polymerase gene. Additionally, herpesvirus and morbillivirus were currently detected from 43.63 and 1.82% of the cutaneous lesions, respectively. Coinfection of poxvirus and herpesvirus was detected in nine of them (16.36%), which makes the present study the first to report coinfection by both pathogens in skin lesions in cetaceans. A plausible approach to histopathological characterization of poxvirus-and herpesvirus-positive skin lesions was established. Hyperkeratosis, acanthosis, ballooning degeneration, and intracytoplasmic inclusion bodies in vacuolized keratinocytes through the stratum spinosum were common findings in poxvirus skin lesions. Alphaherpesvirus was associated with a prominent acanthotic epidermis, moderate necrosis, multifocal dyskeratosis, and irregular keratinocytes with both cellular and nuclei pleomorphism. The common histopathological findings of both pathogens were observed in coinfection lesions. However, those associated with herpesvirus were considerably more remarkable. Relationships between molecular and microscopic findings were observed for the lesions that showed tattoo-like and tortuous patterns. Further multidisciplinary diagnostic studies of infected skin lesions are needed to understand the epidemiology of these emerging infectious diseases.

Novel alphaherpesvirus in a wild South American sea lion (Otaria byronia) with pulmonary tuberculosis

In 2017, an adult male South American sea lion (Otaria byronia), presenting emaciation and a cervical abscess, stranded alive in Florianópolis, southern Brazil. The animal was directed to a rehabilitation center, dying a few days later. On necropsy, the main gross findings were necrotizing lymphadenitis of the right prescapular lymph node and nodular bronchopneumonia. A novel alphaherpesvirus, tentatively named Otariid alphaherpesvirus 1, was amplified in several tissue samples. No histopathologic findings associated with viral infection were observed. Additionally, pulmonary tuberculosis by Mycobacterium pinnipedii was diagnosed by histopathological, immunohistochemical, and molecular techniques. Several bacteria were cultured from antemortem and postmortem samples, including Proteus mirabilis from the cervical abscess and cardiac blood, and Escherichia coli from the cervical abscess and pericardial effusion. Flavivirus, morbillivirus, and Apicomplexa were not detected by molecular techniques. Herein, we report a novel alphaherpesvirus in a pinniped species of the family Otariidae. Although previously described in Southern Hemisphere pinniped species, including South American sea lions, there is limited information regarding M. pinnipedii impact over this group. Further research is required to determine the associated pathogenesis of this novel herpesvirus, and prevalence of Otariid alphaherpesvirus 1 and M. pinnipedii in the reproductive colonies.

Systematic Determination of Herpesvirus in Free-Ranging Cetaceans Stranded in the Western Mediterranean: Tissue Tropism and Associated Lesions

The monitoring of herpesvirus infection provides useful information when assessing marine mammals’ health. This paper shows the prevalence of herpesvirus infection (80.85%) in 47 cetaceans stranded on the coast of the Valencian Community, Spain. Of the 966 tissues evaluated, 121 tested positive when employing nested-PCR (12.53%). The largest proportion of herpesvirus-positive tissue samples was in the reproductive system, nervous system, and tegument. Herpesvirus was more prevalent in females, juveniles, and calves. More than half the DNA PCR positive tissues contained herpesvirus RNA, indicating the presence of actively replicating virus. This RNA was most frequently found in neonates. Fourteen unique sequences were identified. Most amplified sequences belonged to the Gammaherpesvirinae subfamily, but a greater variation was found in Alphaherpesvirinae sequences. This is the first report of systematic herpesvirus DNA and RNA determination in free-ranging cetaceans. Nine (19.14%) were infected with cetacean morbillivirus and all of them (100%) were coinfected with herpesvirus. Lesions similar to those caused by herpesvirus in other species were observed, mainly in the skin, upper digestive tract, genitalia, and central nervous system. Other lesions were also attributable to concomitant etiologies or were nonspecific. It is necessary to investigate the possible role of herpesvirus infection in those cases.

Novel herpesvirus discovered in walrus liver

A walrus (Odobenus rosmarus) born in an aquarium and hand-reared in Japan died at the age of 11 months. The affected animal showed fever and anorexia and had high levels of AST and ALT. Necropsy showed multiple necroses in the liver and adrenal glands and histological examination revealed necrotic lesions of the liver and adrenal cortex, both of which contained intranuclear inclusions. Electron microscopic analysis of the liver sample showed herpesvirus-like particles. High-throughput sequencing analysis of the liver sample and phylogenetic analysis of herpesvirus polymerase genes identified a new virus, Walrus alphaherpesvirus 1 (WaHV-1), which belonged to the subfamily Alphaherpesvirinae and had high homology with Phocid alphaherpesvirus 1. Phylogenetic analysis of the UL30 gene encoding glycoprotein B revealed that WaHV-1 was closely related to a cluster of phocid herpesviruses, including one that caused high mortality rates in harbor seals during past outbreaks. The mother walrus of the dead animal showed evidence of herpesvirus infection in the past and potentially harbored WaHV-1. As a result of hand-rearing, the dead animal might have acquired WaHV-1 from its infected mother and succumbed to WaHV-1 due to lack of maternal IgG, including those that could neutralize WaHV-1.

Fatal pulmonary parafilaroidiasis in a free-ranging subantarctic fur seal (Arctocephalus tropicalis) coinfected with two gammaherpesviruses and Sarcocystis sp

A juvenile subantarctic fur seal (Arctocephalus tropicalis) found dead in Santa Catarina state, southern Brazil, presented with disseminated verminous pneumonia due to Parafilaroides sp. A concomitant infection with two different gammaherpesviruses was identified by PCR in different tissues; one of them possibly a novel species (tentatively named Otariid herpesvirus 7). Sarcocystis sp. DNA was identified molecularly in skeletal muscle samples with intrasarcoplasmic bradyzoites and no apparent tissue response. All analyzed samples (mandibular, laryngeal, tracheal, and mesenteric lymph nodes, and lung) were PCR-negative for Brucella spp. The most likely cause of death was severe pulmonary parafilaroidiasis. The pathogenic role of the gammaherpesviruses in several of the tissues was not evident. This study describes the pathogenicity of Parafilaroides sp. in a subantarctic fur seal, widens the host range of herpesvirus in pinnipeds, and reports the first molecular identification of Sarcocystis sp. in this species.

Contaminants in Atlantic walruses in Svalbard part 1: Relationships between exposure, diet and pathogen prevalence

This study investigated relationships between organohalogen compound (OHC) exposure, feeding habits, and pathogen exposure in a recovering population of Atlantic walruses (Odobenus rosmarus rosmarus) from the Svalbard Archipelago, Norway. Various samples were collected from 39 free-living, apparently healthy, adult male walruses immobilised at three sampling locations during the summers of 2014 and 2015. Concentrations of lipophilic compounds (polychlorinated biphenyls, organochlorine pesticides and polybrominated diphenyl ethers) were analysed in blubber samples, and concentrations of perfluoroalkylated substances (PFASs) were determined in plasma samples. Stable isotopes of carbon and nitrogen were measured in seven tissue types and surveys for three infectious pathogens were conducted. Despite an overall decline in lipophilic compound concentrations since this population was last studied (2006), the contaminant pattern was similar, including extremely large inter-individual variation. Stable isotope ratios of carbon and nitrogen showed that the variation in OHC concentrations could not be explained by some walruses consuming higher trophic level diets, since all animals were found to feed at a similar trophic level. Antibodies against the bacteria Brucella spp. and the parasite Toxoplasma gondii were detected in 26% and 15% of the walruses, respectively. Given the absence of seal-predation, T. gondii exposure likely took place via the consumption of contaminated bivalves. The source of exposure to Brucella spp. in walruses is still unknown. Parapoxvirus DNA was detected in a single individual, representing the first documented evidence of parapoxvirus in wild walruses. Antibody prevalence was not related to contaminant exposure. Despite this, dynamic relationships between diet composition, contaminant bioaccumulation and pathogen exposure warrant continuing attention given the likelihood of climate change induced habitat and food web changes, and consequently OHC exposure, for Svalbard walruses in the coming decades.

Cetacean Poxvirus in Two Striped Dolphins (Stenella coeruleoalba) Stranded on the Tyrrhenian Coast of Italy: Histopathological, Ultrastructural, Biomolecular, and Ecotoxicological Findings

Tattoo skin disease (TSD) is a poxviral disease typical of cetaceans. Two juvenile and well-preserved male striped dolphins (Stenella coeruleoalba), found stranded along the Tuscany and Latium coasts of Italy in 2015 and 2016, respectively, showed typical skin lesions ascribable to TSD. Histological, ultrastructural and biomolecular investigations confirmed a poxviral aetiology for the aforementioned skin lesions. To our knowledge, this should be the first report of TSD in cetaceans stranded along the Italian coastline. As organochlorines like PCBs and DDTs are known to be highly immunotoxic, the tissue loads of these contaminants were evaluated, in order to increase our knowledge on their potential role as well as on the relationships between the level of exposure to these pollutants and poxviral infection's occurrence.

Identification of Novel Gammaherpesviruses in a South American Fur Seal ( Arctocephalus australis) with Ulcerative Skin Lesions

There are few studies on pathogens affecting free-ranging pinnipeds from South America. We employed molecular techniques to identify a gammaherpesvirus infection by two putative novel herpesvirus species: Otariid herpesvirus 5 (OtHV-5), possibly associated with ulcerative cutaneous lesions, and Otariid herpesvirus 6 (OtHV-6) in a wild South American fur seal ( Arctocephalus australis) that stranded alive in Santa Catarina state, southern Brazil. Here we provide new information regarding pinniped herpesviruses, important for the design of future disease surveillance studies.

First molecular determination of herpesvirus from two mysticete species stranded in the Mediterranean Sea

BACKGROUND

Herpesvirus can infect a wide range of animal species: mammals, birds, reptiles, fish, amphibians and bivalves. In marine mammals, several alpha- and gammaherpesvirus have been identified in some cetaceans and pinnipeds species. To date, however, this virus has not been detected in any member of the Balaenoptera genus.

CASE PRESENTATION

Herpesvirus was determined by molecular methods in tissue samples from a male fin whale juvenile (Balaenoptera physalus) and a female common minke whale calf (Balaenoptera acutorostrata) stranded on the Mediterranean coast of the Region of Valencia (Spain). Samples of skin and penile mucosa from the fin whale and samples of skin, muscle and central nervous system tissue from the common minke whale tested positive for herpesvirus based on sequences of the DNA polymerase gene. Sequences from fin whale were identical and belonged to the Alphaherpesvirinae subfamily. Only members of the Gammaherpesvirinae subfamily were amplified from the common minke whale, and sequences from the muscle and central nervous system were identical. Sequences in GenBank most closely related to these novel sequences were viruses isolated from other cetacean species, consistent with previous observations that herpesviruses show similar phylogenetic branching as their hosts.

CONCLUSIONS

To our knowledge, this is the first molecular determination of herpesvirus in the Balaenoptera genus. It shows that herpesvirus should be included in virological evaluation of these animals.