Poxvirus infection of Steller sea lions (Eumetopias jubatus) in Alaska

Detection of Cetacean Poxvirus in Peruvian Common Bottlenose Dolphins (Tursiops truncatus) Using a Pan-Poxvirus PCR

Cetacean poxviruses (CePVs) cause ‘tattoo’ skin lesions in small and large cetaceans worldwide. Although the disease has been known for decades, genomic data for these poxviruses are very limited, with the exception of CePV-Tursiops aduncus, which was completely sequenced in 2020. Using a newly developed pan-pox real-time PCR system targeting a conserved nucleotide sequence located within the Monkeypox virus D6R gene, we rapidly detected the CePV genome in typical skin lesions collected from two Peruvian common bottlenose dolphins (Tursiops truncatus) by-caught off Peru in 1993. Phylogenetic analyses based on the sequencing of the DNA polymerase and DNA topoisomerase genes showed that the two viruses are very closely related to each other, although the dolphins they infected pertained to different ecotypes. The poxviruses described in this study belong to CePV-1, a heterogeneous clade that infects many species of dolphins (Delphinidae) and porpoises (Phocoenidae). Among this clade, the T. truncatus CePVs from Peru were more related to the viruses infecting Delphinidae than to those detected in Phocoenidae. This is the first time that CePVs were identified in free-ranging odontocetes from the Eastern Pacific, surprisingly in 30-year-old samples. These data further suggest a close and long-standing pathogen–host co-evolution, resulting in different lineages of CePVs.

Recovery of the first full-length genome sequence of a parapoxvirus directly from a clinical sample

We recovered the first full-length poxvirus genome, including the terminal hairpin region, directly from complex clinical material using a combination of second generation short read and third generation nanopore sequencing technologies. The complete viral genome sequence was directly recovered from a skin lesion of a grey seal thereby preventing sequence changes due to in vitro passaging of the virus. Subsequent analysis of the proteins encoded by this virus identified genes specific for skin adaptation and pathogenesis of parapoxviruses. These data warrant the classification of seal parapoxvirus, tentatively designated SePPV, as a new species within the genus Parapoxvirus.

Identification of Novel Cetacean Poxviruses in Cetaceans Stranded in South West England

Poxvirus infections in marine mammals have been mainly reported through their clinical lesions and electron microscopy (EM). Poxvirus particles in association with such lesions have been demonstrated by EM and were previously classified as two new viruses, cetacean poxvirus 1 (CePV-1) and cetacean poxvirus 2 (CePV-2). In this study, epidermal pox lesions in cetaceans stranded in South West England (Cornwall) between 2008 and 2012 were investigated by electron microscopy and molecular analysis. PCR and sequencing of a highly conserved region within the viral DNA polymerase gene ruled out both parapox- and orthopoxviruses. Moreover, phylogenetic analysis of the PCR product clustered the sequences with those previously described as cetacean poxviruses. However, taking the close genetic distance of this gene fragment across the family of poxviridae into account, it is reasonable to postulate further, novel cetacean poxvirus species. The nucleotide similarity within each cluster (tentative species) detected ranged from 98.6% to 100%, whilst the similarity between the clusters was no more than 95%. The detection of several species of poxvirus in different cetacean species confirms the likelihood of a heterogeneous cetacean poxvirus genus, comparable to the heterogeneity observed in other poxvirus genera.

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

Background

Herpesvirus and poxvirus can infect a wide range of species: herpesvirus genetic material has been detected and amplified in five species of the superfamily Pinnipedia; poxvirus genetic material, in eight species of Pinnipedia. To date, however, genetic material of these viruses has not been detected in walrus (Odobenus rosmarus), another marine mammal of the Pinnipedia clade, even though anti-herpesvirus antibodies have been detected in these animals.

Case presentation

In February 2013, a 9-year-old healthy captive female Pacific walrus died unexpectedly at L’Oceanografic (Valencia, Spain). Herpesvirus was detected in pharyngeal tonsil tissue by PCR. Phylogenetic analysis revealed that the virus belongs to the subfamily Gammaherpesvirinae. Poxvirus was also detected by PCR in skin, pre-scapular and tracheobronchial lymph nodes and tonsils. Gross lesions were not detected in any tissue, but histopathological analyses of pharyngeal tonsils and lymph nodes revealed remarkable lymphoid depletion and lymphocytolysis. Similar histopathological lesions have been previously described in bovine calves infected with an alphaherpesvirus, and in northern elephant seals infected with a gammaherpesvirus that is closely related to the herpesvirus found in this case. Intracytoplasmic eosinophilic inclusion bodies, consistent with poxviral infection, were also observed in the epithelium of the tonsilar mucosa.

Conclusion

To our knowledge, this is the first molecular identification of herpesvirus and poxvirus in a walrus. Neither virus was likely to have contributed directly to the death of our animal.

Molecular analysis of parapoxvirus from a spotted seal Phoca largha in Japan

A spotted seal Phoca largha with nodular and scab lesions on the whole body was brought to an aquarium in Nagoya, Japan. We extracted DNA from the lesions and used the polymerase chain reaction (PCR) method for detecting orthopoxvirus and parapoxvirus DNA. Parapoxvirus but not orthopoxvirus DNA was detected. The partial nucleotide sequence of the envelope gene was determined from the PCR product, and the sequence was seen to be closely related to 2 parapoxvirus strains from spotted seals in Alaska, showing 100% identity at the amino acid level, with one nucleotide substitution. Virus-neutralizing (VN) antibody against canine distemper virus (CDV) was not detected in the serum, indicating that this individual was not infected with CDV or phocine distemper virus (PDV), which both have a high mortality rate for marine mammals. These results suggest that the lesions were caused by infection with pinniped parapoxvirus, and that the viruses spread and are maintained within the habitat range or populations of spotted seals from the Bering Sea to the Japan Sea. This is the first report of molecular analysis of parapoxvirus in marine mammals in Japan.

Postnatal ontogeny of erythropoietin and hematology in free-ranging Steller sea lions (Eumetopias jubatus)

The hormone erythropoietin (EPO) is responsible for the increased production of red blood cells (RBC) in response to tissue hypoxia. While the role of EPO in hematological development has been established in humans and terrestrial mammals, this relationship has never been examined in marine mammals that rely heavily on stored oxygen to maintain aerobic metabolism while diving. Since blood is the major oxygen storage site in marine mammals, it was hypothesized that EPO may have a significant influence on the development of hematology parameters associated with the expansion of blood oxygen stores during development. To explore this hypothesis, serum EPO concentrations were determined by radioimmunoassay in 235 free-ranging Steller sea lions (Eumetopias jubatus), throughout their Alaskan range. Hematocrit (Hct), hemoglobin (Hb), and red blood cell (RBC) counts were also measured, and mean corpuscular hemoglobin content (MCHC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCV) values determined. Erythropoietin and most hematological parameters varied with age. Hematocrit, Hb, RBC, and MCHC decreased after birth, reached their lowest values at two to three months of age, and then increased to values similar to those of adults by five months of age. Since changes in Hct and Hb account for the majority of the changes in blood oxygen stores and EPO was negatively correlated with both, it appears that EPO may play an important role in blood development of Steller sea lions, similar to previous studies on terrestrial mammals.