Genetic Identification of Poxviruses in Cutaneous Lesions of Cetaceans and Pinnipeds
Poxviruses are widespread, successful pathogens known to infect a wide range of vertebrate and invertebrate species. Terrestrial poxviruses of vertebrates encompass a variety of well-known pathogens, including smallpox, lumpy skin disease, swinepox, fowlpox and orf, among others. Although significant advances have been made in sequencing full genomes of some terrestrial poxviruses, little genetic data have been published for marine poxviruses. Total DNA extracted from skin lesions of cetaceans from oceanaria and rehabilitation facilities, as well as from free-ranging cetaceans and pinnipeds, was assayed by polymerase chain reaction (PCR) using primers designed to target the DNA polymerase and DNA topoisomerase genes. Published primers were used to target the major envelope protein of parapoxviruses (Inoshima et al. 2000). Targeting the DNA polymerase gene of cetacean poxviruses yielded DNA fragments 546-bp in length shown to be 84% and 89% identical in their nucleotides and amino acid sequences, respectively. These findings have revealed the existence of at least two poxvirus species in cetaceans that we provisionally refer to as cetacean poxvirus-1 (CPV-1) and CPV-2. The same assay applied to total DNA from skin lesions of Steller sea lion (Eumetopias jubatus) poxvirus (SSLPV) yielded 543-bp DNA fragments that were, respectively, 76 and 77% identical to the nucleotide sequence of the homologue fragments from CPV-1 and CPV-2 and 74 and 78% identical at the amino acid level. Multiple sequence analyses of the CPV-1 and CPV-2 DNA polymerase gene fragments showed closest amino acid identity (81 and 83%) to members of the orthopoxvirus genus. DNA polymerase gene fragments amplified from pinniped parapoxviruses from three Steller sea lions, two spotted seals (Phoca largha) and one harbor seal (Phoca vitulina) were 536-bp in length and had closest amino acid identities to orf and bovine papular stomatitis viruses (87 and 89%). PCR targeting of the DNA topoisomerase gene of poxvirus generated DNA fragments 344-bp in length, when total DNA from poxvirus lesions from CPV-1, CPV-2 and SSLPV were used as templates. The predicted amino acid sequences from CPV-1, CPV-2 and SSLPV were closest in identity to the homologues from camelpox, swinepox, and vaccinia viruses (65 to 69%). DNA fragments amplified from the DNA topoisomerase gene of parapoxviruses of pinnipeds were 252-, 347- and 350-bp in length and showed closest identities to the homologous fragments of orf and bovine papular stomatitis virus. Amplification of 594-bp fragments of the major envelope protein gene of parapoxviruses of pinnipeds confirmed previous results. In summary, we have identified the existence of two poxviruses of cetaceans, namely, cetacean poxvirus-1 of dolphins (T. truncatus, T. aduncus, Steno bredanensis, Stenella coeruleoalba), and cetacean poxvirus-2 of whales (Balaena mysticetus). Similarly, we have genetically characterized a new poxvirus and parapoxviruses of Steller sea lions, and parapoxviruses of spotted and harbor seals.
This work was supported by a grant from Harbor Branch Oceangraphic Institution and Florida Fish and Wildlife Commission through the Marine Mammal Animal Health Program of the University of Florida. The work was also supported by the Alaska Department of Fish and Game under permit number 358-1564-03.
1. Inoshima Y, A Morooka, H Sentsui. 2000. Detection and diagnosis of parapoxvirus by the polymerase chain reaction. Journal of Virological Methods. 84: 201-208