Papillomaviruses (PVs) are double-stranded DNA viruses that are being isolated in a wide variety of animal hosts, where they cause papillomas (warts) or squamous carcinomas on the skin or on the mucosal oral and/or genital surfaces. More than 100 different HPVs have been characterized in humans. However, in most other species studied to date, only one or a few different PVs have been identified. The multitude of PV types in humans most likely reflects a greater medical research effort, rather than a special situation in humans. Most PVs appear to be species-specific or restricted to infection of closely related animals within the same genus. This has the implication that if all warm-blooded vertebrate species have their own set of species-specific papillomaviruses, there could be more than a million different papillomavirus genotypes. Because PVs use the high-fidelity host cell DNA polymerase for viral replication, PVs are remarkably stable genetic entities. Because of the global presence of diverse, genomically stable, species-specific spectra of PVs in numerous mammalian and avian species, it can be safely assumed that PVs are ancient viruses that originated early in vertebrate evolution, and have co-evolved and co-speciated in synchrony with their host-species. Based on co-evolution data for primate, artiodactyl, and feline species, we calculated a mutation rate for PVs to be 0.73 to 1.20 × 10-8 substitutions/site/years. The mutation rate for PVs is only 10 times faster than the mutation rate of their eukaryotic host species, and more than four orders of magnitude slower than the mutation rate of most RNA viruses.
Over the past years, our laboratories have described numerous novel PV-related lesions in animals, and cloned and sequenced their papillomaviral genomes. Our laboratories are also involved in the development of novel vaccines and antiviral drugs to prevent/treat PV-associated diseases. A wider variety of animal PV genomes is needed to produce a more precise picture of the evolution and origin of the papillomaviruses. Since veterinarians and animal handlers in zoos are the first to notice the appearance of warts in one of their animals, we would very much like to invite AAZV-members to bring wart-like lesions to our attention. We would welcome the opportunity to investigate these lesions, and where possible we would like to offer assistance with treatment. Such projects will always be performed as a collaborative effort, and with the utmost respect for the animal’s health, well-being and safety.