Literature DB >> 28407753

Genomic characterization of two novel pathogenic avipoxviruses isolated from pacific shearwaters (Ardenna spp.).

Subir Sarker1, Shubhagata Das2, Jennifer L Lavers3, Ian Hutton4, Karla Helbig5, Jacob Imbery6, Chris Upton6, Shane R Raidal2.   

Abstract

BACKGROUND: Over the past 20 years, many marine seabird populations have been gradually declining and the factors driving this ongoing deterioration are not always well understood. Avipoxvirus infections have been found in a wide range of bird species worldwide, however, very little is known about the disease ecology of avian poxviruses in seabirds. Here we present two novel avipoxviruses from pacific shearwaters (Ardenna spp), one from a Flesh-footed Shearwater (A. carneipes) (SWPV-1) and the other from a Wedge-tailed Shearwater (A. pacificus) (SWPV-2).
RESULTS: Epidermal pox lesions, liver, and blood samples were examined from A. carneipes and A. pacificus of breeding colonies in eastern Australia. After histopathological confirmation of the disease, PCR screening was conducted for avipoxvirus, circovirus, reticuloendotheliosis virus, and fungal agents. Two samples that were PCR positive for poxvirus were further assessed by next generation sequencing, which yielded complete Shearwaterpox virus (SWPV) genomes from A. pacificus and A. carneipes, both showing the highest degree of similarity with Canarypox virus (98% and 67%, respectively). The novel SWPV-1 complete genome from A. carneipes is missing 43 genes compared to CNPV and contains 4 predicted genes which are not found in any other poxvirus, whilst, SWPV-2 complete genome was deemed to be missing 18 genes compared to CNPV and a further 15 genes significantly fragmented as to probably cause them to be non-functional.
CONCLUSION: These are the first avipoxvirus complete genome sequences that infect marine seabirds. In the comparison of SWPV-1 and -2 to existing avipoxvirus sequences, our results indicate that the SWPV complete genome from A. carneipes (SWPV-1) described here is not closely related to any other avipoxvirus genome isolated from avian or other natural host species, and that it likely should be considered a separate species.

Entities:  

Keywords:  Ardenna; Avipoxvirus; Next generation sequencing; Poxvirus; Shearwater; dermatitis

Mesh:

Year:  2017        PMID: 28407753      PMCID: PMC5390406          DOI: 10.1186/s12864-017-3680-z

Source DB:  PubMed          Journal:  BMC Genomics        ISSN: 1471-2164            Impact factor:   3.969


Background

The Avipoxvirus genus includes a divergent group of viruses that cause diseases in more than 278 species of wild and domestic birds in terrestrial and marine environments worldwide [1, 2]. Relatively little is known about the origins, worldwide host distribution and genetic diversity of avipoxviruses [3]. In affected birds, avipoxviruses typically cause proliferative ‘wart-like’ growths that are most commonly restricted to the eyes, beak or unfeathered skin of the body (so-called ‘dry’ pox), but infections can also develop in the upper alimentary and respiratory tracts (‘wet’ or ‘diptheritic’ pox) [2]. The incubation period and magnitude of avipoxvirus infection is variable, and is rarely fatal although secondary bacterial or fungal infections are common and cause increased mortality [2]. Such conditions in naïve populations can reach a much higher prevalence with substantial fatality [4, 5]. Avipoxviruses belong to the subfamily Chordopoxvirinae (ChPV) of the Poxviridae family, which are relatively large double-stranded DNA (dsDNA) viruses that replicate in the cytoplasm of infected cells [6]. Although poxviruses have evolved to infect a wide range of host species, to date only six avipoxvirus genomes have been published; a pathogenic American strain of Fowlpox virus (FPVUS) [7], an attenuated European strain of Fowlpox virus (FP9) [8], a virulent Canarypox virus (CNPV) [9], a pathogenic South African strain of Pigeonpox virus (FeP2), a Penguinpox virus (PEPV) [3], and a pathogenic Hungarian strain of Turkeypox virus (TKPV) [10]. Although these genome sequences demonstrate that avipoxviruses have diverged considerably from the other chordopoxviruses (ChPVs), approximately 80 genes have been found to be conserved amongst all ChPVs and to comprise the minimum essential poxvirus genome [11]. These genes tend to be present in the central core of the linear genome with the remainder presumed to be immunomodulatory and host specific genes located towards the terminal regions of the genome [3]. With the exception of TKPV (188 kb), avipoxvirus genomes (266–360 kb) tend to be bigger than those of other ChPVs due in part to multiple families of genes. Over the past two decades, the status of the world’s bird populations have deteriorated with seabirds declining faster than any other group of birds [12]. On Lord Howe Island in eastern Australia, the Flesh-footed Shearwater Ardenna carneipes has been declining for many years and is therefore listed as Vulnerable in the state of New South Wales [13]. The ongoing threat of plastic pollution, and toxicity from the elevated concentration of trace elements such as mercury could be confounding drivers of this declining species [14]. Infectious diseases, including those caused by avipoxviruses, have also been identified as an important risk factor in the conservation of small and endangered populations, particularly in island species [15-18]. The impact of the introduction of avipoxviruses has been severe for the avifauna of various archipelagos [19]. The emergence of distinctive avipoxvirus with a high prevalence (88%) in Hawaiian Laysan Albatross (Phoebastria immutabilis) enabled one of the first detailed studies of the epidemiology and population-level impact of the disease in the seabirds [20]. However, relatively little is known about the general prevalence or effects of poxviruses in seabird species, including for shearwaters (Ardenna or Puffinus spp.). Therefore, the aim of the present study was to identify and characterize pathogens associated with clinical disease in breeding colonies of Flesh-footed Shearwater and Wedge-tailed Shearwater sourced from Lord Howe Island in 2015.

Results

Identification of fungal pathogens

In the sample from A. pacificus (15–1526, and 15–1527), there were multifocal areas of inflammation and exudation associated with serocellular surface crust that contained abundant branching fungal hyphae and aggregations of bacteria (Fig. 1c). A PCR screening was conducted for the presence of fungal pathogen using the ITS region to amplify a segment of approximately 550 bp. Two samples (out of 6) were positive for fungal pathogens, and direct Sanger sequencing of the purified gel bands resulted in a 550 bp sequence after trimming off primer sequences (data not shown). These sequences were further verified using high-throughput NGS, and generated con tigs of 3,430 bp (15–1526; GenBank accession KX857213) and 5,188 bp (15–1527; GenBank accession KX857212). A BLASTn search for the bird coinfected with fungal pathogen (15–1526) returned multiple hits to various fungal species, all with very similar scores; however, the best match (88%) was to the Phaeosphaeria nodorum (GenBank Accession EU053989.1, and value ≤ e-153), a major necrotrophic fungal pathogen of wheat [21]. Similar search model for the fungal pathogen of bird 15–1527, demonstrated a highest hit (96%) to the Metarhizium anisopliae var. anisopliae (GenBank Accession AY884128.1, and value ≤ e-173), an entomopathogenic fungus [22].
Fig. 1

Pathological evidence of characteristic pox and fungal lesions. a Grossly well circumscribed, popular, crusting pox lesions across the featherless skins (white arrows). b Feather skin demonstrating diffuse proliferation of the epidermis and follicular infundibula with keratinocytes containing eosinophilic intracytoplasmic inclusions (Bollinger bodies) and serocellular surface crust (double head arrow). c Inflammatory exudates associated with serocellular surface crust that contained abundant branching fungal hyphae and aggregations of bacteria

Pathological evidence of characteristic pox and fungal lesions. a Grossly well circumscribed, popular, crusting pox lesions across the featherless skins (white arrows). b Feather skin demonstrating diffuse proliferation of the epidermis and follicular infundibula with keratinocytes containing eosinophilic intracytoplasmic inclusions (Bollinger bodies) and serocellular surface crust (double head arrow). c Inflammatory exudates associated with serocellular surface crust that contained abundant branching fungal hyphae and aggregations of bacteria

Identification of virus

Samples from six shearwater chicks of two different species, A. carneipes and A. pacificus, with evidence of gross well circumscribed, popular, crusting lesions across the feather skins (Fig. 1a), were biopsied, with blood and liver samples also collected. Histological examinations of the skin demonstrated focal to diffuse full thickness necrosis of the epidermis and a thick serocellular surface crust. A marked heterophilic rich inflammatory cellular response and exudation was present alongside abundant macrophages and perifollicular fibroplasia. In some areas there was focal proliferation of the adjacent epidermis associated with ballooning degeneration of keratinocytes with eosinophilic intracytoplasmic inclusions (Fig. 1b). A PCR screening was conducted for the presence of poxvirus, circovirus and reticuloendotheliosis virus, which are likely to cause this type of skin lesions. Two birds (A. pacificus 15–1526 and A. carneipes 15–1528) were positive by PCR targeting the 4b gene that encodes a core protein of ChPV, however, there were no evidence of either circovirus or reticuloendotheliosis for any of the samples used in this study. Direct Sanger sequencing of the purified gel bands resulted in a 578 bp sequence after trimming off primer sequences (data not shown). A BLASTn search with these sequences returned multiple hits to the 4b core gene from a variety of poxviruses, all with very similar scores; however, the best match was to the Canarypox virus 4b core protein gene ((bird 15–1526; similarity with AY318871 was 99% and identity score ≤ e-162), and bird 15–1528; similarity with LK021654 was 99% and identity score ≤ e-157)).

Genome sequence and annotation of viruses

The Shearwaterpox virus complete genomes were assembled using CLC Genomics workbench 9.5.2 under La Trobe University Genomics Platform. The assembled complete genomes of SWPV-1 and −2 were 326,929 and 351,108 nt, respectively. The SWPV-1 and −2 complete genomes were annotated as described in the methods using CNPV as a reference genome (Additional file 1: Table S1 and Additional file 2: Table S2). We took a conservative approach to the annotation in order to minimize the inclusion of ORFs that were unlikely to represent functional genes. Table 1 lists the 310 and 312 genes annotated for SWPV-1 and −2, respectively. For the most part, these two new complete genomes are collinear to CNPV although there are a number of rearrangements of blocks of 1–6 genes in addition to insertions and deletions with respect to CNPV (Table 1). Comparison of the predicted proteins of SWPV-2 to orthologs in CNPV reveal the vast majority are >98% identical (aa), with more than 80 being completely conserved. In contrast, the orthologs of SWPV-1 only have an average aa identity of 67% to CNPV. However, with the lower average identity, greater genetic distance, comes a much greater range of variation in the level of identity and a significant number of predicted proteins are 80 – 90% identical (aa) to CNPV orthologs.
Table 1

Shearwaterpox virus (SWPV) genome annotations and comparative analysis of ORFs relative to CNPV genomes

SWPV1 syntenySWPV2 syntenyCNPV syntenyCNPV BLAST hitsSWPV1 % identitySWPV2 % identitySWPV1 AA sizeSWPV2 AA sizeReference AA sizenotes
CNPV001CNPV001 hypothetical protein72
SWPV2-001CNPV002CNPV002 hypothetical protein92.941171171
SWPV1-001SWPV2-002CNPV003CNPV003 C-type lectin-like protein32.04485.99181208204
SWPV1-002CNPV004CNPV004 ankyrin repeat protein56.458468514
SWPV1-003SWPV2-003CNPV005CNPV005 conserved hypothetical protein87.38799.55220222222
SWPV2-004CNPV006CNPV006 hypothetical protein88.71134182SWPV2: C-terminus fragment, not likely translated
CNPV007CNPV007 ankyrin repeat protein674
SWPV1-004SWPV2-005CNPV008CNPV008 C-type lectin-like protein5098.225174169169
SWPV2-006CNPV009CNPV009 ankyrin repeat protein99.564688688
CNPV010CNPV010 ankyrin repeat protein734
SWPV2-007CNPV011CNPV011 ankyrin repeat protein99.147586586
SWPV2-008CNPV012CNPV012 hypothetical protein100189189
SWPV2-009CNPV013CNPV013 hypothetical protein98.81168168
SWPV2-010CNPV014CNPV014 immunoglobulin-like domain protein99.184490490
SWPV2-011CNPV015CNPV015 ankyrin repeat protein97.538528528
SWPV1-005CNPV035 C-type lectin-like protein35.556138134
SWPV1-006CNPV318 ankyrin repeat protein58.932487514
SWPV1-007SWPV2-012CNPV016CNPV016 C-type lectin-like protein52.12898.81117168168
SWPV1-008SWPV2-013CNPV017CNPV017 ankyrin repeat protein64.47197.912425479486
SWPV1-009CNPV295 ankyrin repeat protein56.41277396
SWPV2-014CNPV018CNPV018 IL-10-like protein90.805190191
SWPV2-015CNPV019CNPV019 ankyrin repeat protein99.083436436
SWPV1-010SWPV2-016CNPV020CNPV020 ankyrin repeat protein56.31199.761412419419
SWPV1-011CNPV320 Ig-like domain protein31.656483469
SWPV1-012SWPV2-017CNPV021CNPV021 ankyrin repeat protein62.31399.626528535535
SWPV1-013SWPV2-018CNPV022CNPV022 putative serpin65.64298.324356358358
SWPV1-014PEPV260 ankyrin repeat protein53.158190192
SWPV1-015CNPV011 ankyrin repeat protein34530586
SWPV2-019CNPV023CNPV023 vaccinia C4L/C10L-like protein98.595424427
SWPV2-020CNPV024CNPV024 hypothetical protein96.629178178
SWPV1-016SWPV2-021CNPV025CNPV025 alpha-SNAP-like protein57.49198.667304300300
SWPV1-017SWPV2-022CNPV026CNPV026 ankyrin repeat protein54.27198.953397382382
SWPV1-018SWPV2-023CNPV027CNPV027 ankyrin repeat protein59.37598.722646626626
SWPV1-019SWPV2-024CNPV028CNPV028 ankyrin repeat protein57.61899.164408365362
SWPV1-020SWPV2-025CNPV029CNPV029 C-type lectin-like protein50.3599.296142142142
SWPV1-021SWPV2-026CNPV030CNPV030 ankyrin repeat protein63.7298.529345340340
SWPV1-022SWPV2-027CNPV031CNPV031 hypothetical protein60.33197.479120119119
SWPV1-023CNPV013 conserved hypothetical protein44.048168168
SWPV1-024SWPV2-028CNPV032CNPV032 Ig-like domain putative IFN-gamma binding protein51.83792.149242242242
SWPV1-025SWPV2-029CNPV033CNPV033 Ig-like domain protein48.09593.496238246246
SWPV2-030CNPV034CNPV034 ankyrin repeat protein99.848659659
SWPV2-031CNPV035CNPV035 C-type lectin-like protein94.776133134
SWPV1-026SWPV2-032CNPV036CNPV036 conserved hypothetical protein48.23598.947889595
SWPV1-027SWPV2-033CNPV037CNPV037 conserved hypothetical protein63.06899.441178179179
SWPV1-028SWPV2-034CNPV038CNPV038 vaccinia C4L/C10L-like protein54.52399.516411413413
SWPV1-029SWPV2-035CNPV039CNPV039 G protein-coupled receptor-like protein67.28497.859323327327
SWPV1-030SWPV2-036CNPV040CNPV040 ankyrin repeat protein57.3693.401589591591SWPV2: High SNP Density
SWPV1-031SWPV2-037CNPV041CNPV041 ankyrin repeat protein66.28498.605432430430
SWPV1-032SWPV2-038CNPV042CNPV042 ankyrin repeat protein72.71299.339608605605
SWPV1-033SWPV2-039CNPV043CNPV043 conserved hypothetical protein74.62799.005202201201
SWPV1-034SWPV2-040CNPV044CNPV044 ankyrin repeat protein67.31699.583470480480
SWPV1-035SWPV2-041CNPV045CNPV045 G protein-coupled receptor-like protein65.231100331332332
SWPV1-036SWPV2-042CNPV046CNPV046 ankyrin repeat protein68.0898.667452450450
SWPV1-037SWPV2-043CNPV047CNPV047 conserved hypothetical protein65.699.194125124124
SWPV1-038SWPV2-044CNPV048CNPV048 alkaline phosphodiesterase-like protein68.23898.502804801801
SWPV1-039SWPV2-045CNPV049CNPV049 hypothetical protein72.667100148150150
SWPV1-040SWPV2-046CNPV050CNPV050 ankyrin repeat protein67.42298.864352352352
SWPV1-041SWPV2-047CNPV051CNPV051 DNase II-like protein63.68396.75398408401
SWPV1-042SWPV2-048CNPV052CNPV052 C-type lectin-like protein50100182171171
SWPV1-043FWPV ankyrin repeat protein45329406
SWPV1-044SWPV2-049CNPV053CNPV053 conserved hypothetical protein68.148100135146146
SWPV1-045SWPV2-050CNPV054CNPV054 conserved hypothetical protein62.5999.286141140140
SWPV1-046SWPV2-051CNPV055CNPV055 conserved hypothetical protein74.534100162163163
SWPV1-047SWPV2-052CNPV056CNPV056 dUTPase80.98698.621155145145
SWPV1-048SWPV2-053CNPV057CNPV057 putative serpin63.10799.02301306306
SWPV1-049SWPV2-054CNPV058CNPV058 bcl-2 like protein51.74498.857174180175
SWPV1-050SWPV2-055CNPV059CNPV059 putative serpin71.30299.704338338338
SWPV1-051SWPV2-056CNPV060CNPV060 conserved hypothetical protein46.93995.098236206316SWPV2: Large internal deletion, Translated but not likely functional
SWPV1-052SWPV2-057CNPV061CNPV061 DNA ligase80.99598.761567565565
SWPV1-053SWPV2-058CNPV062CNPV062 putative serpin70.94100349350350
SWPV1-054SWPV2-059CNPV063CNPV063 hydroxysteroid dehydrogenase-like protein71.34899.441359358358
SWPV1-055SWPV2-060CNPV064CNPV064 TGF-beta-like protein56.89798.587272283282
SWPV1-056SWPV2-061CNPV065CNPV065 semaphorin-like protein69.73599.485573583583
SWPV1-057SWPV2-062CNPV066CNPV066 hypothetical protein37.34998.519139399405SWPV1: Low BLAST hits, possible unique ORF
SWPV2-063CNPV067CNPV067 hypothetical protein1005757
SWPV1-058no significant BLAST hits239SWPV1: Possible Unique ORF
SWPV1-059SWPV2-064CNPV068CNPV068 GNS1/SUR4-like protein84.82599.611257257257
SWPV1-060SWPV2-065CNPV069CNPV069 late transcription factor VLTF-287.5100154155155
SWPV1-061SWPV2-066CNPV070CNPV070 putative rifampicin resistance protein, IMV assembly88.065100553551551
SWPV1-062SWPV2-067CNPV071CNPV071 mRNA capping enzyme small subunit89.273100289289289
SWPV2-068CNPV072CNPV072 CC chemokine-like protein96.262132312SWPV2: N-terminus fragment
SWPV1-063SWPV2-069CNPV073CNPV073 hypothetical protein45.263100110109109
SWPV1-064SWPV2-070CNPV074CNPV074 NPH-I, transcription termination factor92.75699.685635635635
SWPV1-065SWPV2-071CNPV075CNPV075 mutT motif putative gene expression regulator79.295100226228230
SWPV1-066SWPV2-072CNPV076CNPV076 mutT motif84.54999.569233232232
CNPV077CNPV077 hypothetical protein78
SWPV1-067CNPV011 ankyrin repeat protein29.806435586
SWPV1-068SWPV2-073CNPV078CNPV078 RNA polymerase subunit RPO1882.39100161160160
SWPV2-074CNPV079CNPV079 Ig-like domain protein94.161274272
SWPV1-069SWPV2-075CNPV080CNPV080 early transcription factor small subunit VETFS96.682100633633633
SWPV2-076CNPV081CNPV081 Ig-like domain protein97.006334333
SWPV1-070SWPV2-077CNPV082CNPV082 NTPase, DNA replication88.81899.748790794794
SWPV1-071SWPV2-078CNPV083CNPV083 CC chemokine-like protein60.35291.855223221221
SWPV1-072CNPV215 CC chemokine-like protein30.994195204
SWPV1-073SWPV2-079CNPV084CNPV084 uracil DNA glycosylase86.36497.706220218218
SWPV1-074SWPV2-080CNPV085CNPV085 putative RNA phosphatase67.89574.312245303403SWPV2: High SNP Density
SWPV1-075CNPV216 conserved hypothetical protein39.225398404
SWPV1-076SWPV2-081CNPV086CNPV086 TNFR-like protein67.32771.569103112117
SWPV2-082CNPV087CNPV087 putative glutathione peroxidase98.473131198SWPV2: C-terminus fragment, not likely translated
SWPV1-077CNPV227 N1R/p28-like protein74.638256359
SWPV1-078SWPV2-083CNPV088CNPV088 conserved hypothetical protein55.76997104100100
SWPV1-079SWPV2-084CNPV089CNPV089 conserved hypothetical protein64.935100164159159
SWPV1-080SWPV2-085CNPV090CNPV090 conserved hypothetical protein62.393100124127127
SWPV1-081SWPV2-086CNPV091CNPV091 HT motif protein64.634100778383
SWPV1-082SWPV2-087CNPV092CNPV092 conserved hypothetical protein64.90197.945140146146
SWPV1-083SWPV2-088CNPV093CNPV093 virion protein60.3799.625270267267
SWPV1-084SWPV2-089CNPV094CNPV094 T10-like protein7598.909282275275
SWPV1-085SWPV2-090CNPV095CNPV095 conserved hypothetical protein71.111100474545
SWPV1-086SWPV2-091CNPV096CNPV096 ubiquitin100100778585
SWPV1-087SWPV2-092CNPV097CNPV097 conserved hypothetical protein70.03199.705298339339
SWPV1-088SWPV2-093CNPV098CNPV098 hypothetical protein67.44298.75618080
SWPV1-089SWPV2-094CNPV099CNPV099 beta-NGF-like protein62.16297.949186195195
SWPV1-090SWPV2-095CNPV100CNPV100 putative interleukin binding protein51.17698.225211168169
SWPV2-096CNPV101CNPV101 hypothetical protein98.8248585
SWPV1-091SWPV2-097CNPV102CNPV102 conserved hypothetical protein54.16799.048102105105
SWPV1-092SWPV2-098CNPV103CNPV103 N1R/p28-like protein62.30498.947188190190
SWPV1-093SWPV2-099CNPV104CNPV104 putative glutaredoxin 2, virion morphogenesis86.499.2125125125
SWPV1-094SWPV2-100CNPV105CNPV105 conserved hypothetical protein77.3598.718234234234
SWPV1-095SWPV2-101CNPV106CNPV106 putative elongation factor76.82998.039103102102
SWPV2-102CNPV107CNPV107 hypothetical protein1007777
SWPV1-096PEPV083 transforming growth factor B64444336
SWPV1-097SWPV2-103CNPV108CNPV108 putative metalloprotease, virion morphogenesis85.489100633632632
SWPV1-098SWPV2-104CNPV109CNPV109 NPH-II, RNA helicase86.0599.706681681681
SWPV1-099SWPV2-105CNPV110CNPV110 virion core proteinase87.44199.763421422422
SWPV1-100SWPV2-106CNPV111CNPV111 DNA-binding protein80.61299.488391391391
SWPV1-101SWPV2-107CNPV112CNPV112 putative IMV membrane protein81.481100818181
SWPV1-102SWPV2-108CNPV113CNPV113 thymidine kinase75.97899.441181179179
SWPV1-103SWPV2-109CNPV114CNPV114 HT motif protein69.62100798282
SWPV1-104SWPV2-110CNPV115CNPV115 DNA-binding phosphoprotein71.42982.353282289289SWPV2: High SNP density
SWPV1-105SWPV2-111CNPV116CNPV116 unnamed protein product73.91398.551666969
SWPV1-106SWPV2-112CNPV117CNPV117 DNA-binding virion protein88.85499.677314310310
SWPV1-107SWPV2-113CNPV118CNPV118 conserved hypothetical protein75.76299.387656652653
SWPV1-108SWPV2-114CNPV119CNPV119 virion core protein83.969100131131131
SWPV1-109SWPV2-115CNPV120CNPV120 putative IMV redox protein, virus assembly80.851100949393
SWPV1-110SWPV2-116CNPV121CNPV121 DNA polymerase89.1799.899988988988
SWPV1-111CNPV122CNPV122 putative membrane protein83.088273274
SWPV1-112SWPV2-117CNPV123CNPV123 conserved hypothetical protein82.31285.336571502571SWPV2: High SNP density
SWPV1-113SWPV2-118CNPV124CNPV124 variola B22R-like protein6798.957190619161918
SWPV1-114SWPV2-119CNPV125CNPV125 variola B22R-like protein71.66999.66174217671767
SWPV1-115SWPV2-120CNPV126CNPV126 variola B22R-like protein64.45698.847190218391951SWPV2: N-terminus fragment
SWPV2-121CNPV126 variola B22R-like protein961531951SWPV2: C-terminus fragment, not likely translated
SWPV1-116SWPV2-122CNPV127CNPV127 RNA polymerase subunit RPO3096.154100182182182
SWPV1-117SWPV2-123CNPV128CNPV128 conserved hypothetical protein77.07298.752742721721SWPV2: High SNP Density
SWPV1-118SWPV2-124CNPV129CNPV129 poly(A) polymerase large subunit PAPL83.89899.788472472472
SWPV1-119SWPV2-125CNPV130CNPV130 DNA-binding virion core protein76.471100114119119
SWPV1-120SWPV2-126CNPV131CNPV131 conserved hypothetical protein64.11599.517212207207
SWPV1-121SWPV2-127CNPV132CNPV132 conserved hypothetical protein81.08199.324151148148
SWPV1-122SWPV2-128CNPV133CNPV133 conserved hypothetical protein73.737100909999
SWPV1-123SWPV2-129CNPV134CNPV134 variola B22R-like protein65.51799.001177418011801
SWPV1-124SWPV2-130CNPV135CNPV135 putative palmitylated EEV envelope lipase89.41899.735378378378
SWPV1-125SWPV2-131CNPV136CNPV136 putative EEV maturation protein75.60299.68622625625
SWPV1-126SWPV2-132CNPV137CNPV137 conserved hypothetical protein62.2698.925467462465
SWPV1-127SWPV2-133CNPV138CNPV138 putative serine/threonine protein kinase, virus assembly83.632100445444444
SWPV1-128SWPV2-134CNPV139CNPV139 conserved hypothetical protein81.69100213213213
SWPV1-129SWPV2-135CNPV140CNPV140 conserved hypothetical protein78.788100656666
SWPV1-130SWPV2-136CNPV141CNPV141 HAL3-like domain protein88.333100182184184
SWPV1-131no significant BLAST hits28101571SWPV1: Possible Unique ORF
SWPV1-132SWPV2-137CNPV142CNPV142 N1R/p28-like protein48.26698.442314321321
SWPV1-133SWPV2-138CNPV143CNPV143 ankyrin repeat protein54.10398.361634671671
SWPV1-134SWPV2-139CNPV144CNPV144 ankyrin repeat protein59.01199.281562556556
SWPV1-135SWPV2-140CNPV145CNPV145 conserved hypothetical protein75.814100439440440
SWPV1-136SWPV2-141CNPV146CNPV146 RNA polymerase subunit RPO788.525100666262
SWPV1-137SWPV2-142CNPV147CNPV147 conserved hypothetical protein80.851100188188188
SWPV1-138SWPV2-143CNPV148CNPV148 virion core protein86.533100347348348
SWPV2-144CNPV149CNPV149 putative thioredoxin binding protein99.673306306
CNPV150CNPV150 ankyrin repeat protein351
SWPV2-145CNPV151CNPV151 ankyrin repeat protein99.029412412
SWPV2-146CNPV152CNPV152 hypothetical protein98149187SWPV2: C-terminus fragment, not likely translated
SWPV2-147CNPV153CNPV153 Rep-like protein99.359312312
SWPV1-139CNPV159 N1R/p28-like protein78.488333337
SWPV1-140FWPV121 CC chemokine-like protein4693121
SWPV1-141SWPV2-148CNPV154CNPV154 variola B22R-like protein90.06798.28619398751928SWPV2: N-terminus fragment/SWPV1: Low SNP Density
SWPV1-142SWPV2-149CNPV155CNPV155 variola B22R-like protein82.42799.454181018311830
SWPV2-150CNPV156CNPV156 hypothetical protein96.287834832
SWPV2-151CNPV157CNPV157 TGF-beta-like protein87.679343349
CNPV158CNPV158 TGF-beta-like protein172
CNPV159CNPV159 N1R/p28-like protein337
CNPV160CNPV160 N1R/p28-like protein396
SWPV2-152CNPV161CNPV161 TGF-beta-like protein99.441358358
SWPV2-153CNPV162CNPV162 TGF-beta-like protein97.987149149
CNPV163CNPV163 hypothetical protein92
CNPV164CNPV164 hypothetical protein98
SWPV2-154CNPV165CNPV165 N1R/p28-like protein98.75320346SWPV2: C-terminus fragment, not likely translated
SWPV1-143SWPV2-155CNPV166CNPV166 Ig-like domain protein96.81295.652345345345SWPV1: Low SNP Density
SWPV1-144SWPV2-156CNPV167CNPV167 Ig-like domain protein94.76788.372172168171SWPV1: Low SNP Density
SWPV2-157CNPV168CNPV168 N1R/p28-like protein96350358
SWPV1-145CNPV169CNPV169 N1R/p28-like protein83.578337332SWPV1: CNPV-168/169 Fusion
SWPV1-146SWPV2-158CNPV170CNPV170 thymidylate kinase100100121212212SWPV1: N-terminus fragment
SWPV1-147SWPV2-159CNPV171CNPV171 late transcription factor VLTF-196.923100260260260
SWPV1-148SWPV2-160CNPV172CNPV172 putative myristylated protein83.12599.403336335335
SWPV1-149SWPV2-161CNPV173CNPV173 putative myristylated IMV envelope protein91.35898.354243243243
SWPV1-150SWPV2-162CNPV174CNPV174 conserved hypothetical protein47.917100969696
SWPV1-151SWPV2-163CNPV175CNPV175 conserved hypothetical protein84.158100303303303
SWPV1-152SWPV2-164CNPV176CNPV176 DNA-binding virion core protein87.747100253252252
SWPV1-153SWPV2-165CNPV177CNPV177 conserved hypothetical protein84.733100131130130
SWPV1-154SWPV2-166CNPV178CNPV178 putative IMV membrane protein85.135100148148148
SWPV1-155SWPV2-167CNPV179CNPV179 poly(A) polymerase small subunit PAPS88.667100300302302
SWPV1-156SWPV2-168CNPV180CNPV180 RNA polymerase subunit RPO2287.63499.462186186186
SWPV1-157SWPV2-169CNPV181CNPV181 conserved hypothetical protein82.353100136136136
SWPV1-158SWPV2-170CNPV182CNPV182 RNA polymerase subunit RPO14793.86699.922128812881288
SWPV1-159SWPV2-171CNPV183CNPV183 putative protein-tyrosine phosphatase, virus assembly85.542100166166166
SWPV1-160SWPV2-172CNPV184CNPV184 conserved hypothetical protein91.534100190189189
SWPV1-161SWPV2-173CNPV185CNPV185 ankyrin repeat protein32.63296.341337328328
SWPV1-162SWPV2-174CNPV186CNPV186 IMV envelope protein100100329330330
SWPV1-163SWPV2-175CNPV187CNPV187 RNA polymerase associated protein RAP9491.11499.75799799799
SWPV1-164SWPV2-176CNPV188CNPV188 late transcription factor VLTF-470.11592.941170170170
SWPV1-165SWPV2-177CNPV189CNPV189 DNA topoisomerase88.60899.684316316316
SWPV1-166SWPV2-178CNPV190CNPV190 conserved hypothetical protein77.12499.346153153153
SWPV1-167SWPV2-179CNPV191CNPV191 conserved hypothetical protein70.87499.029103103103
SWPV1-168SWPV2-180CNPV192CNPV192 mRNA capping enzyme large subunit88.22199.764848846846
SWPV1-169SWPV2-181CNPV193CNPV193 HT motif protein72.619100104106106
SWPV1-170SWPV2-182CNPV194CNPV194 virion protein71.223100139140140
SWPV1-171SWPV2-183CNPV195CNPV195 hypothetical protein51.298.611139144144
SWPV1-172SWPV2-184CNPV196CNPV196 conserved hypothetical protein62.963100189190190
SWPV1-173SWPV2-185CNPV197CNPV197 N1R/p28-like protein61.67997.818279275275
SWPV1-174SWPV2-186CNPV198CNPV198 C-type lectin-like protein55.84499.359159156156
SWPV1-175SWPV2-187CNPV199CNPV199 deoxycytidine kinase-like protein79.111100222225225
SWPV1-176SWPV2-188CNPV200CNPV200 Rep-like protein72.90397.59152166166
SWPV1-177SWPV2-189CNPV201CNPV201 conserved hypothetical protein6097.661197167192
SWPV1-178SWPV2-190CNPV202CNPV202 N1R/p28-like protein69.20399.638275276276
SWPV1-179SWPV2-191CNPV203CNPV203 N1R/p28-like protein64.93599.738380382382
SWPV1-180SWPV2-192CNPV204CNPV204 conserved hypothetical protein53.226100536161
SWPV1-181SWPV2-193CNPV205CNPV205 N1R/p28-like protein71.88599.371317318318
SWPV1-182SWPV2-194CNPV206CNPV206 putative photolyase84.98999.364464472472
SWPV1-183CNPV081 Ig-like domain protein53.988332333
SWPV1-184SWPV2-195CNPV207CNPV207 N1R/p28-like protein64.53598.235193173183
SWPV1-185SWPV2-196CNPV208CNPV208 conserved hypothetical protein52.23997.5172200200
SWPV1-186SWPV2-197CNPV209CNPV209 N1R/p28-like protein65.686100311310310
SWPV1-187SWPV2-198CNPV210CNPV210 N1R/p28-like protein74.41999.237130131131
SWPV1-188SWPV2-199CNPV211CNPV211 conserved hypothetical protein49.0298.148545454
SWPV1-189SWPV2-200CNPV212CNPV212 N1R/p28-like protein76.13698.295175176176
SWPV1-190no significant BLAST hits70SWPV1: Possible Unique ORF
SWPV1-191SWPV2-201CNPV213CNPV213 deoxycytidine kinase-like protein58.76899.539216216217
SWPV2-202CNPV214CNPV214 vaccinia C4L/C10L-like protein99.438356356
SWPV1-192CNPV012 conserved hypothetical protein37.41165189
SWPV1-193CNPV223 ankyrin repeat protein31.579674847
SWPV1-194SWPV2-203CNPV215CNPV215 CC chemokine-like protein49.75196.078202204204
SWPV2-204CNPV216CNPV216 conserved hypothetical protein98.762401404
SWPV2-205CNPV217CNPV217 N1R/p28-like protein95.152330330
SWPV1-195CNPV223 ankyrin repeat protein38.474729847SWPV1: N-terminus fragment
SWPV1-196SWPV2-206CNPV218CNPV218 N1R/p28-like protein66.66799.522318223437SWPV2: N-terminus fragment
SWPV1-197CNPV228 N1R/p28-like protein53161371SWPV1: N-terminus fragment
SWPV1-198CNPV160 N1R/p28-like protein79.293367396SWPV1: Fragment/CNPV-220/221 Fusion
SWPV1-199CNPV160 N1R/p28-like protein66.582360396SWPV1: Paralog to SWPV1-198?
SWPV1-200CNPV161 TGF-beta-like protein36.882256358
SWPV1-201CNPV162 TGF-beta-like protein50141149
SWPV1-202no significant BLAST hits98SWPV1: Possible Unique ORF
SWPV2-207CNPV219CNPV219 N1R/p28-like protein99.713349349
SWPV2-208CNPV220CNPV220 N1R/p28-like protein80.26385178SWPV2: N-terminus fragment
SWPV2-209CNPV221CNPV221 N1R/p28-like protein94.231213281SWPV2: N-terminus fragment
SWPV2-210CNPV222CNPV222 N1R/p28-like protein99.649285285
SWPV2-211CNPV223CNPV223 ankyrin repeat protein98.819847847
SWPV1-203SWPV2-212CNPV224CNPV224 hypothetical protein50.382100126239239
SWPV2-213CNPV225CNPV225 N1R/p28-like protein74.03894159SWPV2: N-terminus fragment
SWPV2-214CNPV226CNPV226 N1R/p28-like protein96.825126134
CNPV227CNPV227 N1R/p28-like protein359
CNPV228CNPV228 N1R/p28-like protein371
SWPV1-204SWPV2-215CNPV229CNPV229 ankyrin repeat protein44.49897.926423434434
SWPV2-216CNPV230CNPV230 hypothetical protein98.4626565
SWPV1-205SWPV2-217CNPV231CNPV231 MyD116-like domain protein72.22298.101100158158SWPV1: large in-frame deletions
SWPV1-206SWPV2-218CNPV232CNPV232 CC chemokine-like protein59.02493.137205204204
SWPV1-207SWPV2-219CNPV233CNPV233 ankyrin repeat protein56.93699.788476471471
SWPV2-220CNPV234CNPV234 ankyrin repeat protein100508508SWPV2: High SNP Density
SWPV1-208PEPV008 vaccinia C4L/C10L-like protein55420411
SWPV2-221CNPV235CNPV235 conserved hypothetical protein88.426432432
SWPV1-209SWPV2-222CNPV236CNPV236 ribonucleotide reductase small subunit83.28295.666324323323
SWPV2-223CNPV237CNPV237 ankyrin repeat protein97.732441441
SWPV1-210CNPV234 ankyrin repeat protein30.545559508
SWPV1-211SWPV2-224CNPV238CNPV238 late transcription factor VLTF-395.111100225225225
SWPV1-212SWPV2-225CNPV239CNPV239 virion redox protein80.282100727575
SWPV1-213SWPV2-226CNPV240CNPV240 virion core protein P4b88.78899.848660659659
SWPV1-214SWPV2-227CNPV241CNPV241 immunodominant virion protein47.36899.07242215215
SWPV1-215SWPV2-228CNPV242CNPV242 RNA polymerase subunit RPO1988.16698.817169169169
SWPV1-216SWPV2-229CNPV243CNPV243 conserved hypothetical protein81.50198.928373373373
SWPV1-217SWPV2-230CNPV244CNPV244 early transcription factor large subunit VETFL95.91100709709709
SWPV1-218SWPV2-231CNPV245CNPV245 intermediate transcription factor VITF-390.66799.667300300300
SWPV1-219SWPV2-232CNPV246CNPV246 putative IMV membrane protein8098.667767575
SWPV1-220SWPV2-233CNPV247CNPV247 virion core protein P4a81.49499.664897893893
SWPV1-221SWPV2-234CNPV248CNPV248 conserved hypothetical protein78.723100281279279
SWPV1-222SWPV2-235CNPV249CNPV249 virion protein74.26999.405167168168
SWPV1-223SWPV2-236CNPV250CNPV250 conserved hypothetical protein36.08294.595735699SWPV2: N-terminus fragment
SWPV1-224SWPV2-237CNPV251CNPV251 putative IMV membrane protein69.565100696969
SWPV1-225SWPV2-238CNPV252CNPV252 putative IMV membrane protein68.47898.913929292
SWPV1-226SWPV2-239CNPV253CNPV253 putative IMV membrane virulence factor73.58598.113535353
SWPV1-227SWPV2-240CNPV254CNPV254 conserved hypothetical protein7598.958969696
SWPV1-228SWPV2-241CNPV255CNPV255 predicted myristylated protein84.28299.728368368368
SWPV1-229SWPV2-242CNPV256CNPV256 putative phosphorylated IMV membrane protein81.006100188192192
SWPV1-230SWPV2-243CNPV257CNPV257 DNA helicase, transcriptional elongation87.22999.784462462462
SWPV1-231SWPV2-244CNPV258CNPV258 conserved hypothetical protein77.647100868989
SWPV1-232SWPV2-245CNPV259CNPV259 DNA polymerase processivity factor81.86100432112434
SWPV1-233SWPV2-246CNPV260CNPV260 conserved hypothetical protein91.07199.77112434112
SWPV1-234SWPV2-247CNPV261CNPV261 Holliday junction resolvase protein80.405100151152152
SWPV1-235SWPV2-248CNPV262CNPV262 intermediate transcription factor VITF-386.126100383383383
SWPV1-236SWPV2-249CNPV263CNPV263 RNA polymerase subunit RPO13294.301100115811571157
SWPV1-237SWPV2-250CNPV264CNPV264 A type inclusion-like protein81.01599.502602601603
SWPV1-238SWPV2-251CNPV265CNPV265 A type inclusion-like/fusion protein67.01599.789471475475
SWPV1-239SWPV2-252CNPV266CNPV266 conserved hypothetical protein89.28699.286140140140
SWPV1-240SWPV2-253CNPV267CNPV267 RNA polymerase subunit RPO3577.55899.016303305305
SWPV1-241SWPV2-254CNPV268CNPV268 conserved hypothetical protein73.529100727575
SWPV1-242SWPV2-255CNPV269CNPV269 conserved hypothetical protein70.796100113113113
SWPV1-243SWPV2-256CNPV270CNPV270 conserved hypothetical protein70.588100119120120
SWPV1-244SWPV2-257CNPV271CNPV271 DNA packaging protein89.96399.648272284284
SWPV1-245SWPV2-258CNPV272CNPV272 C-type lectin-like EEV protein76.13699.448182181181
SWPV1-246CNPV012 conserved hypothetical protein30.147172189
SWPV1-247SWPV2-259CNPV273CNPV273 conserved hypothetical protein62.81699.635276274274
SWPV1-248SWPV2-260CNPV274CNPV274 putative tyrosine protein kinase63.19799.628286269269
SWPV1-249SWPV2-261CNPV275CNPV275 putative serpin72.27199.408340338338
SWPV1-250SWPV2-262CNPV276CNPV276 conserved hypothetical protein56.667100227252252
SWPV1-251SWPV2-263CNPV277CNPV277 G protein-coupled receptor-like protein9099.677310310310
SWPV1-252SWPV2-264CNPV278CNPV278 conserved hypothetical protein89.69198.958979696
SWPV1-253SWPV2-265CNPV279CNPV279 beta-NGF-like protein63.415100167169169
SWPV1-254SWPV2-266CNPV280CNPV280 HT motif protein67.69299.231134130130
SWPV1-255SWPV2-267CNPV281CNPV281 conserved hypothetical protein71.72899.533192214214
SWPV1-256SWPV2-268CNPV282CNPV282 HT motif protein71.552100118120120
SWPV1-257SWPV2-269CNPV283CNPV283 CC chemokine-like protein63.208100110111111
SWPV1-258SWPV2-270CNPV284CNPV284 putative interleukin binding protein37.40590.769192193195
SWPV1-259SWPV2-271CNPV285CNPV285 EGF-like protein62.99299.206123126126
SWPV1-260SWPV2-272CNPV286CNPV286 putative serine/threonine protein kinase76.74499.672303305305
SWPV1-261SWPV2-273CNPV287CNPV287 conserved hypothetical protein73.24898.758165160161
SWPV1-262SWPV2-274CNPV288CNPV288 C-type lectin-like protein52.41488.435163147147
SWPV1-263SWPV2-275CNPV289CNPV289 putative interleukin binding protein58.99399.281132139139
SWPV1-264SWPV2-276CNPV290CNPV290 conserved hypothetical protein8483.784757575
SWPV1-265SWPV2-277CNPV291CNPV291 ankyrin repeat protein48.06798.99613594594
SWPV1-266SWPV2-278CNPV292CNPV292 hypothetical protein37.2091001017474
SWPV1-267SWPV2-279CNPV293CNPV293 ankyrin repeat protein55.63499.648305284284
SWPV1-268SWPV2-280CNPV294CNPV294 ankyrin repeat protein68.44799.07424430430
SWPV1-269PIPV223 host range protein51138143
SWPV1-270FWPV217 hypothetical protein50330328
SWPV1-271SWPV2-281CNPV295CNPV295 ankyrin repeat protein57.736100264396396
SWPV1-272SWPV2-282CNPV296CNPV296 ankyrin repeat protein67.19599.127438458458
SWPV1-273SWPV2-283CNPV297CNPV297 ankyrin repeat protein54.97299.457717737737
SWPV1-274SWPV2-284CNPV298CNPV298 ankyrin repeat protein64.59199.825573571571
SWPV1-275SWPV2-285CNPV299CNPV299 putative serine/threonine protein kinase67.89399.333303300300
SWPV1-276SWPV2-286CNPV300CNPV300 ankyrin repeat protein75.8298.77253244244
SWPV1-277CNPV219 N1R/p28-like protein28.467142349
SWPV1-278CNPV228 N1R/p28-like protein43.03887371
SWPV1-279TKPV163 ankyrin repeat protein40432434
SWPV1-280SWPV2-287CNPV301CNPV301 ankyrin repeat protein59.54699.241510527527
SWPV1-281SWPV2-288CNPV302CNPV302 conserved hypothetical protein45.026100175193193
SWPV1-282SWPV2-289CNPV303CNPV303 ankyrin repeat protein68.93899.4499500500
SWPV1-283SWPV2-290CNPV304CNPV304 ankyrin repeat protein62.10599.785476466466
SWPV1-284SWPV2-291CNPV305CNPV305 N1R/p28-like protein54.545100261262262
SWPV1-285SWPV2-292CNPV306CNPV306 hypothetical protein30.76998.611737272
SWPV1-286SWPV2-293CNPV307CNPV307 C-type lectin-like protein55.828100165154154
SWPV1-287SWPV2-294CNPV308CNPV308 ankyrin repeat protein58.75799.44359357357
SWPV1-288SWPV2-295CNPV309CNPV309 ankyrin repeat protein69.388100195196196
SWPV1-289SWPV2-296CNPV310CNPV310 ankyrin repeat protein47.35999.255540537537
SWPV1-290SWPV2-297CNPV311CNPV311 EFc-like protein54.499.194125124124
SWPV1-291SWPV2-298CNPV312CNPV312 conserved hypothetical protein53.70498.795168166166
SWPV1-292SWPV2-299CNPV313CNPV313 Ig-like domain protein69.4398.165213218218
SWPV1-293SWPV2-300CNPV314CNPV314 ankyrin repeat protein71.55299.829580629584
SWPV1-294CNPV011 ankyrin repeat protein32513586
SWPV1-295SWPV2-301CNPV315CNPV315 G protein-coupled receptor-like protein59.1799.365315315315
SWPV1-296CNPV014 Ig-like domain protein59.624230490
SWPV1-297CNPV014 Ig-like domain protein59.641240490
SWPV1-298CNPV015 ankyrin repeat protein45.45574528
SWPV1-299CNPV150 ankyrin repeat protein36.36484351
SWPV1-300SWPV2-302CNPV316CNPV316 ankyrin repeat protein35.29499.632162544544
SWPV2-303CNPV317CNPV317 hypothetical protein1005555
SWPV2-304CNPV318CNPV318 ankyrin repeat protein98.054514514
SWPV2-305CNPV319CNPV319 ankyrin repeat protein97.638637739SWPV2: C-terminus fragment, not likely translated
SWPV1-301PIPV253 EFc-like protein69124124
SWPV1-302CNPV015 ankyrin repeat protein45.276520528
SWPV1-303CNPV223 ankyrin repeat protein40480847
SWPV1-304SWPV2-306CNPV320CNPV320 Ig-like domain protein76.85899.787468469469
SWPV2-307CNPV321CNPV321 EFc-like protein99.194124124
SWPV2-308CNPV322CNPV322 ankyrin repeat protein98.408689690
SWPV1-305CNPV035 C-type lectin-like protein35.556138134
SWPV1-306CNPV008 C-type lectin-like protein50174169
SWPV1-307SWPV2-309CNPV323CNPV323 conserved hypothetical protein75.6193.65184186182
SWPV1-308SWPV2-310CNPV324CNPV324 conserved hypothetical protein87.38799.55220222222
SWPV1-309CNPV325CNPV325 ankyrin repeat protein56.458468514
SWPV1-310SWPV2-311CNPV326CNPV326 C-type lectin-like protein32.04485.99181208204
SWPV2-312CNPV327CNPV327 hypothetical protein92.941171171
CNPV328CNPV328 hypothetical protein72
Shearwaterpox virus (SWPV) genome annotations and comparative analysis of ORFs relative to CNPV genomes This difference in similarity between the new viruses and CNPV is easily visualized in complete genome dotplots (Fig. 2a and b). Significantly more indels are present in the SWPV-1 vs CNPV dotplot (Fig. 2a). However, when the phylogenetic relationships of these viruses were examined together with the other available complete genomes, SWPV-1 was still part of the CNPV clade (Fig. 3a). From this alignment, CNPV is 99.2%, 78.7%, 69.4%, 69.5%, 68.8% and 66.5% identical (nt) to SWPV-2, SWPV-1, FeP2, PEPV, FWPV and TKPV, respectively. A greater selection of viruses was included in the phylogenetic tree by using other fragments of incompletely sequenced avipoxvirus genomes. For example, Vultur gryphus poxvirus (VGPV), Flamingopox virus (FGPV) and Hawaiian goose poxvirus (HGPV) are all more similar to SWPV-2 and CNPV than SWPV-1 (Fig. 3b), this confirms that other poxviruses are as closely related to CNPV as SWPV-2. By also building phylogenetic trees with partial nucleotide sequences from the p4b gene (Fig. 4) and DNA polymerase gene (Fig. 5), we discovered that several other viruses are within the SWPV-1, SWPV-2 and CNPV clade. This includes a poxvirus isolated from Houbara Bustards (Chlamydotis undulata) in captive-breeding programs in Morocco [23], but named CNPV-morocco, and avipoxviruses isolated from American crow (Corvus brachyrhynchos) and American robin (Turdus migratorius) [24], which is almost identical to CPNV-1 within this relatively small fragment of the genome.
Fig. 2

Dotplots of Shearwaterpox viruses (SWPV-1 and 2) vs CNPV genomes. Horizontal sequence: SWPV-1 (a) and SWPV-2 (b), vertical sequence CNPV. Red and blue boxes represent genes transcribed to the right and left of the genome, respectively

Fig. 3

Phylogenetic relationship between Shearwaterpox viruses (SWPV-1 and 2) and other avipoxviruses. a Phylogenetic tree of 173 kbp core region (large gaps removed) from available complete avipoxvirus genomes. b Phylogenetic tree highlighting viruses closely related to CNPV. The sequences were aligned with ClustalO and MEGA7 was used to create a maximum likelihood tree based on the Tamura-Nei method and tested by bootstrapping with 1000 replicates. The abbreviations and GenBank accession details for poxviruses strains were used: Canarypox virus (CNPV; AY318871), Pigeonpox virus (FeP2; KJ801920), Penguinpox virus (PEPV; KJ859677) Fowlpox virus (FWPV; AF198100), Shearwaterpox virus 1 (SWPV-1; KX857216), Shearwaterpox virus 2 (SWPV-2; KX857215), Turkeypox virus (TKPV; NC_028238), Vultur Gryphus poxvirus (VGPV; AY246559), Flamingopox virus (FGPV; HQ875129 and KM974726), Hawaiian goose poxvirus (HGPV; AY255628)

Fig. 4

Maximum likelihood phylogenetic tree from partial DNA sequences of p4b gene of avipoxviruses. Novel Shearwaterpox viruses (SWPV-1 and SWPV-2) are highlighted by gray background

Fig. 5

Maximum likelihood phylogenetic tree from partial DNA sequences of DNA polymerase gene of avipoxviruses. Novel Shearwaterpox viruses (SWPV-1 and SWPV-2) are highlighted by gray background

Dotplots of Shearwaterpox viruses (SWPV-1 and 2) vs CNPV genomes. Horizontal sequence: SWPV-1 (a) and SWPV-2 (b), vertical sequence CNPV. Red and blue boxes represent genes transcribed to the right and left of the genome, respectively Phylogenetic relationship between Shearwaterpox viruses (SWPV-1 and 2) and other avipoxviruses. a Phylogenetic tree of 173 kbp core region (large gaps removed) from available complete avipoxvirus genomes. b Phylogenetic tree highlighting viruses closely related to CNPV. The sequences were aligned with ClustalO and MEGA7 was used to create a maximum likelihood tree based on the Tamura-Nei method and tested by bootstrapping with 1000 replicates. The abbreviations and GenBank accession details for poxviruses strains were used: Canarypox virus (CNPV; AY318871), Pigeonpox virus (FeP2; KJ801920), Penguinpox virus (PEPV; KJ859677) Fowlpox virus (FWPV; AF198100), Shearwaterpox virus 1 (SWPV-1; KX857216), Shearwaterpox virus 2 (SWPV-2; KX857215), Turkeypox virus (TKPV; NC_028238), Vultur Gryphus poxvirus (VGPV; AY246559), Flamingopox virus (FGPV; HQ875129 and KM974726), Hawaiian goose poxvirus (HGPV; AY255628) Maximum likelihood phylogenetic tree from partial DNA sequences of p4b gene of avipoxviruses. Novel Shearwaterpox viruses (SWPV-1 and SWPV-2) are highlighted by gray background Maximum likelihood phylogenetic tree from partial DNA sequences of DNA polymerase gene of avipoxviruses. Novel Shearwaterpox viruses (SWPV-1 and SWPV-2) are highlighted by gray background

Features of SWPV-2

As noted above, and displayed in the Dotplot (Fig. 2b), SWPV-2 is very similar to CNPV with almost 98% nt identity. However, a 1% difference still gives approximately 10 mutations in an average sized gene any of which could have drastic effects if an early STOP codon is introduced to the gene sequence. Similarly, small changes to promoter regions can significantly alter gene expressions that are impossible to predict in these viruses. With this annotation strategy, 18 CNPV genes were deemed to be missing from the SWPV-2 complete genome and a further 15 genes significantly fragmented as to probably cause them to be non-functional (Table 1). No novel genes were predicted in SWPV-2, and no rearrangement of genes compared to CNPV was observed.

Features of SWPV-1

As expected from the much lower percent nt identity, SWPV-1 was found to be considerably more different to CNPV than SWPV-2 when compared at the level of genes present or absent. (Table 1). 43 CNPV genes are absent from SWPV-1 and a further 6 are significantly fragmented. There are 4 predicted genes in SWPV-1 that are not present in any other poxvirus, nor do they match any sequences in the NR protein database using BLASTP. However, they are all relatively short ORFs and it is possible that they are not functional genes. Additionally, SWPV-1 encodes nine polypeptides that do not match CNPV proteins, but do match proteins from other avipoxviruses (penguinpox, turkeypox, pigeonpox and fowlpox). This could be due to recombination among ancestral viruses, but could also result from the loss of the corresponding ortholog in CNPV leaving another virus to provide the “best match”. As might be expected given the greater distance between SWPV-1 and CPNV than between SWPV-2 and CNPV, there are more instances of minor rearrangements that created a loss of synteny (Table 1). However, since most of these involve the families of repeated genes, it is also possible that divergence of these sequences has led to the inability to distinguish between the orthologous and paralogous genes.

Evidence of recombination among avipoxviruses

When we reviewed a graph of nt identity between the 2 new complete genomes and CNPV using BBB (not shown), there were several relatively short syntenic regions where 1) SWPV-1 matched CNPV significantly better than the majority of the genome, and 2) SWPV-2 matched CNPV significantly worse than the majority of the genome. To examine these regions in more detail, the Visual Summary feature of BBB was used to display individual SNPs for these genome comparisons (Fig. 6a and b). This analysis revealed that SWPV-1 and SWPV-2 were unique in these regions and confirmed that the genome sequences of SWPV-1and SWPV-2 were not contaminated during their assembly. However, when these regions were used as query sequences in BLASTN searches of all poxvirus sequences the best match remained CNPV suggesting that these sequences originated from avipoxvirus genomes that are not represented in the public databases.
Fig. 6

Region of recombination in Shearwaterpox viruses (SWPV) detected in A. carneipes and A. pacificus. Nucleotide differences to CNPV are shown in blue (SNPs), green/red (indels). Figure 6a. Region of recombination in SWPV-2. On the middle track, SWPV-2 has very few differences to CNPV except for highly divergent block in the middle of this region. Figure 6b. Region of recombination in SWPV-1. On the bottom track, SWPV-1 is very different to CNPV except for highly similar block between nt 193,000 and 195,500

Region of recombination in Shearwaterpox viruses (SWPV) detected in A. carneipes and A. pacificus. Nucleotide differences to CNPV are shown in blue (SNPs), green/red (indels). Figure 6a. Region of recombination in SWPV-2. On the middle track, SWPV-2 has very few differences to CNPV except for highly divergent block in the middle of this region. Figure 6b. Region of recombination in SWPV-1. On the bottom track, SWPV-1 is very different to CNPV except for highly similar block between nt 193,000 and 195,500

Discussion

This paper describes the detection and characterization of two novel avipoxvirus complete genome sequences in a naturally occurring infections of avian pox in a naïve population of shearwaters. The DNA sequences of SWPV-1 and SWPV-2 are significantly different than each other but nevertheless had closest similarity with Canarypox virus (67% and 98%, respectively). Furthermore, the genetic distance and novel genome structure of SWPV-1 from A. carneipes considered to be missing 43 genes likened to CNPV and contained 4 predicted genes which are not found in any other poxvirus and is overall sufficiently genetically different to be considered a separate virus species. Whilst, the SWPV-2 complete genome was missing 18 genes compared to CNPV, with a further 15 genes significantly fragmented as to probably cause them to be non-functional. Furthermore, the phylogenetic distribution of SWPV-1 indicates that shearwaters and perhaps other long-lived, vagile marine birds could be important hosts for avipoxvirus dispersal around the globe. The natural hosts of these avipoxviruses maybe this population of shearwaters, other migratory birds that use Lord Howe Island for breeding or resident avian host reservoir species. Species such as the Lord Howe White-eye (Zosterops tephropleura) and Lord Howe Golden Whistler (Pachcephala petoralis contempta) are candidate passerine birds that might provide such function. Examining the phylogenetic relationship between the Shearwaterpox viruses and other avipoxviruses, it is evident that the SWPV-2 is most closely related to Canarypox virus. The SWPV-1 and SWPV-2 complete genomes both contain several genes that are more closely related to CNPV throughout their entire genome. As shown in Fig. 3 it is reasonable to postulate that these viruses originated from a common ancestor that diverged from a CNPV-like progenitor related to fowlpox, penguinpox and pigeonpox viruses. Finer resolution of the phylogenetic relationship using partial nucleotide sequences of p4b and DNA polymerase genes of avipoxviruses revealed that SWPV isolated from seabirds also clustered in global clade B consisting of avipoxviruses originating from Canary Morocco, Canarypox and poxviruses from American crow and American robin. Given their genetic diversity, it is perhaps not surprising that Shearwater species can be exposed to multiple avipoxviral infections. Studies such as those by Barnett et al. [25] suggest that the species specificity of poxviruses is variable. Some genera, such as Suipoxvirus are highly restricted to individual vertebrate hosts, swinepox for instance, whereas others, such as avipoxviruses demonstrate some evidence of cross-species infection within a predator–prey system [24]. This suggests that the avipoxviruses can infect a diverse range of bird species if they are within a close enough proximity to each other [26]. Thus far, there were no clear patterns regarding species-specificity in the Shearwaterpox viruses described here. While overt and systemic lesions and fatal disease can occur, avian pox tends to be a self-limiting localized infection of apterial skin with full recovery possible. Many bird species experience life-long immunity if the immune system is not weakened and or the birds are not infected by different strains [27, 28]. As shown in our example, secondary infections can occur and these may contribute to morbidity and mortality [29-31]. Similar to the example in shearwaters, Shivaprasad et al. [30] reported evidence of poxvirus infection and secondary fungal pathogens in canaries (Serinus canaria). Stressful conditions, poor nutrition, overt environmental contamination and other underlying causes of immunosuppression and ill health may contribute to the pathogenesis of such lesions. This was the primary reason we tested for avian circovirus and other potential pathogens. Avian pox has not been previously reported in shearwaters (Ardenna spp.) from Lord Howe Island, nor has it been documented for any other bird species in this region. So it is difficult to attribute the causality of this unique event in these species. The value of complete genome characterization and analysis is highlighted since a phylogenetic relationship based on single gene studies such as the polymerase gene may have falsely implicated Canarypox virus as a potential exotic introduced emerging disease from domesticated birds. Although we cannot trace the actual source of infection in the shearwater chicks, it is more likely that the infection in the birds resulted from parental feeding or arthropod mediated transmission from other island bird species [32]. While, the reservoir host of these novel Shearwaterpox viruses is unknown, mosquitoes are suspected to play a part in transmission within the island. Avipoxvirus infection appears to be relatively rare in seabirds, but it has been reported in several species when they occur on human-inhabited islands that harbor mosquito vectors [33]. According to the Lord Howe Island Board, ship rats, mice, cats, humans and other invasive pest species such as owls are implicated in the extinction of at least five endemic birds, two reptiles, 49 flowering plants, 12 vegetation communities and numerous threatened invertebrates [34]. These rodents and invasive pests have also been highlighted for the potential reservoir of poxvirus infections [3, 35]. Transmission of avipoxvirus by prey–predator and other migratory seabirds likely plays a prominent role; however, the mode of avipoxvirus transmission on Lord Howe Island is not completely understood. Studies by Gyuranecz et al. [24], for example, postulated that raptors may acquire poxvirus infection from their avian prey. This suggests that the poxvirus in shearwaters is likely to be transmitted from other island species such as other migratory seabirds and/or prey–predator, although, it is difficult to be certain without further studies. Interestingly, these new shearwaterpox virus complete genomes also provide evidence that supports the hypothesis that recombination may play an important role in the evolution of avipoxviruses. A number of genes in SWPV-1 appear to be rearranged compared to CNPV and blocks of unusual similarity scores were seen in both SWPVs. Software that is designed to look for gross recombination between two viruses, such as two strains of HIV, fails to detect this level of recombination and it is left to the investigator to observe such small events by eye after visualizing the distribution of SNPs between viruses. Such relatively small exchanges of DNA may still exert important influences on virus evolution, and has been predicted to have been a driver in the evolution of smallpox [36].

Conclusions

These are the first avipoxvirus complete genome sequences that infect marine bird species. The novel complete genome sequences of SWPV-1 and −2 have greatly enhanced the genomic information for the Avipoxvirus genus, which will contribute to our understanding of the avipoxvirus more generally, and track the evolution of poxvirus infection in such a non-model avian species. Together with the sequence similarities observed between SWPV and other avipoxviruses, this study concluded that the SWPV complete genome from A. carneipes (SWPV-1) described here is not closely related to any other avipoxvirus complete genome isolated from avian or other natural host species, and that it likely should be considered a separate species. Further investigations of Shearwaterpox viruses genetic and pathogenesis will provide a unique approach to better assess the risk associated to poxvirus transmission within and between marine bird species.

Methods

Source of sampling

A total of six samples were collected from two different species of shearwater, five were from Flesh-footed Shearwater (ID: 15-1527-31), and other one was from Wedge-tailed Shearwater (ID: 15–1526). Of size birds, two were recoded to have evidence of gross well circumscribed lesions in the beak (Fig. 1a) and ankle, and others had feather defects (fault lines across the vanes of feathers). Samples were collected from fledglings (approximately 80–90 days of age) of both species on Lord Howe Island, New South Wales (32.53̊S, 159.08̊E) located approximately 500 km off the east coast of Australia during April-May 2015. Samples were collected with the permission of the Lord Howe Island Board (permit no. LHIB 02/14) under the approval of the University of Tasmania and Charles Sturt University Animal Ethics Committees (permit no. A0010874, A0011586, and 09/046). Samples from one individual of each shearwater species were collected including skin lesions, liver and skin biopsies, as well as blood for identifying the causative agents. Depending on the samples, either 25 mg of skin tissue were cut out and chopped into small pieces or 50–100 μL of blood were aseptically transferred into clean 1.5 mL microcentrifuge tube (Eppendorf), and genomic DNA was isolated using the Qiagen blood and tissue mini kit (Qiagen, Germany). The extracted DNA has been stored at −20 °C for further testing. Histopathological examination of the skin was performed.

Archived viral and fungal pathogen testing

Initially, the extracted DNA was screened for detecting novel circoviruses [37, 38] and reticuloendotheliosis virus [39]. For poxvirus screening, the primers PoxP1 (5′-CAGCAGGTGCTAAACAACAA-3′) and PoxP2 (5′-CGGTAGCTTAACGCCGAATA-3′) were synthesized from published literature and used to amplify a segment of approximately 578 bp from the 4b core protein gene for all ChPV species [40]. Optimized PCR reactions mixture contained 3 μL of extracted genomic DNA, 25 pmol of each primer (GeneWorks, Australia), 1.5 mM MgCl2, 1.25 mM of each dNTP, 1xGoTaq® Green Flexi Reaction Buffer, 1 U of Go Taq DNA polymerase (Promega Corporation, USA) and DEPC distilled H2O (Invitrogen, USA) was added to a final volume of 25 μL. The PCR amplification was carried out in an iCycler thermal cycler (Bio-Rad) under the following conditions: denaturation at 94 °C for 2 min followed by 35 cycles of 94 °C for 1 min, 60 °C for 1 min and 72 °C for 1 min, and a final extension step of 2 min at 72 °C. The internal transcribed spacer (ITS) region was chosen for screening and identification of fungal pathogens [41]. A set of fungus-specific primers ITS1 (5′- TCCGTAGGTGAACCTGCGG -3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC -3′) were designed and used to amplify a segment of approximately 550 bp from the fungal ITS gene [42]. The PCR was standardized to amplify ITS genes, and the 25-μL reaction mixture contained 3 μL of extracted genomic DNA, 25 pmol of each primer (GeneWorks, Australia), 1.5 mM MgCl2, 1.25 mM of each dNTP, 1xGoTaq® Green Flexi Reaction Buffer, 1 U of Go Taq DNA polymerase (Promega Corporation, USA). The PCR reaction involved initial denaturation at 95 °C for 5 min, followed by 30 cycles of denaturation at 94 °C for 30 s, annealing at 58 °C for 30 s, and extension at 72 °C for 1 min, and with a final step of one cycle extension at 72 °C for 10 min. Amplified PCR products, together with a standard molecular mass marker (Sigma), were separated by electrophoresis in 2.0% agarose gel and stained with GelRed (Biotium, CA). Selected bands were excised and purified using the Wizard® SV Gel and PCR Clean-Up System (Promega, USA) according to the manufacturer’s instructions. Purified amplicons were sequenced with PCR primers by the Australian Genome Research Facility Ltd (Sydney) using an AB 3730xl unit (Applied Biosystems). For each amplicon, sequences were obtained at least twice in each direction for each isolate. The sequences were trimmed for primers and aligned to construct contigs (minimum overlap of 35 bp, minimum match percentage of 95%) using Geneious Pro (version 10.0.2).

High throughput sequencing

Next-generation sequencing (NGS) was used to sequence the poxvirus genomes. Virion enrichment was performed by centrifugation for 2 min at 800 × g to remove tissue debris, and the supernatants were subsequently filtered through 5 μm centrifuge filters (Millipore) [43]. The filtrates were nuclease treated to remove unprotected nucleic acids using 8 μL RNase Cocktail Enzyme Mix (Invitrogen). Viral nucleic acids were subsequently extracted using QIAamp DNA mini (Qiagen). The genomic libraries were prepared with an insert size of 150 paired-end. DNA sequencing (NGS) was performed on a HiSeq4000 sequencing platform (Illumina) by Novogene, China.

Bioinformatics

Assembly of the viral genome was conducted according to the established pipeline [44] in CLC Genomics workbench 9.5.2 under La Trobe University Genomics Platform. Briefly, the preliminary quality evaluation for each raw read was generated using quality control (QC) report. The raw data were preprocessed to remove ambiguous base calls, and bases or entire reads of poor quality using default parameters. The datasets were trimmed to pass the quality control based on PHRED score or per base sequence quality score. Trimmed sequence reads were mapped against closely available host genome (Albatross) to remove possible remaining host DNA contamination, and post-filtered reads were mapped against reference Canarypox virus complete genome sequence. Consensus sequences were used to generate the complete poxvirus genome. Avipoxvirus complete genome sequences were aligned using MAFFT [45]. Then the poxvirus specific bioinformatics analyses were performed using the Viral Bioinformatics Resource Centre (virology.uvic.ca) [46], and the further analyses were conducted using the following tools: Viral Orthologous Clusters Database for sequence management (VOCs) [11]; Base-By-Base for genome/gene/protein alignments [47, 48]; Viral Genome Organizer for genome organization comparisons (VGO) [11], and Genome Annotation Transfer Utility for annotation (GATU) [49]. Open reading frames (ORFs) longer than 60 amino acids with minimal overlapping (overlaps cannot exceed 25% of one of the genes) to other ORFs were captured using the CLC Genomics Workbench (CLC) ORF analysis tool as well as GATU [49], and other protein coding sequence and annotation software described in Geneious (version 10.0.2, Biomatters, New Zealand). These ORFs were subsequently extracted into a FASTA file, and similarity searches including nucleotide (BLASTN) and protein (BLASTP) were performed on annotated ORFs as potential genes if they shared significant sequence similarity to known viral or cellular genes (BLAST E value ≤ e-5) or contained a putative conserved domain as predicted by BLASTp [50]. The final SWPV annotation was further examined with other poxvirus ortholog alignments to determine the correct methionine start site, correct stop codons, signs of truncation, and validity of overlaps.

Phylogenetic analysis

Phylogenetic analyses were performed using full poxvirus genome sequences for Shearwater species determined in this study with related avipoxvirus genome sequences available in GenBank database. A selection of partial sequences from seven completely sequenced avipoxvirus genomes and fragments of incompletely sequenced avipoxvirus genomes from Vultur Gryphus poxvirus (VGPV), flamingopox virus (FGPV) and Hawaiian goose poxvirus (HGPV) were also used for phylogenetic analysis. To investigate closer evolutionary relationship among avipoxviruses, partial nucleotide sequences of p4b and DNA polymerase genes were selected. The avipoxvirus sequences were aligned using ClustalO, and then manually edited in Base-by-Base. MEGA7 was used to create a maximum likelihood tree based on the Tamura-Nei method and tested by bootstrapping with 1000 replicates. An additional analysis was performed using complete genome nucleotide sequences of Canarypox virus (CNPV; AY318871), Pigeonpox virus (FeP2; KJ801920), Fowlpox virus (FPV; AF198100), Turkeypox virus (TKPV; NC_028238), Shearwaterpox virus strain-1 (SWPV-1; KX857216), and Shearwaterpox virus strain-2 (SWPV-2; KX857215), which were aligned with MAFTT in Base-By-Base for genome/gene/protein alignments [48]. The program jModelTest 2.1.3 favoured a general-time-reversible model with gamma distribution rate variation and a proportion of invariable sites (GTR + I + G4) for the ML analysis [51]. Summary of SWPV1 genome annotations (DOCX 52 kb) Summary of SWPV2 genome annotations (DOCX 145 kb)
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